Supplement

Vitamin C

Vitamin C is an essential vitamin and antioxidant that the body uses to build collagen and keep immune cells working. People most often look at it for the common cold, but the evidence there is very limited: one large trial of about 1,700 people found no clear difference in cold symptoms. That rests on a single study, and the more encouraging findings, like blood flow going up, come from small trials.

Sources: PMID 4870463

Updated 30 September 2026
How we grade
100 studies cited

Best evidence: Grade B
Conditions studied: 42
Outcomes: 262
Graded outcomes: 01819

Evidence by condition

Strong
Moderate
Limited
Very limited

42 conditions

General Cardiovascular Health

General Cardiovascular Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood Flow Small Increase	Improves (the measure goes up)	Small effect	4 studies	83 people
Studies that measured blood flow Ascorbic acid prevents vascular dysfunction induced by oral glucose load in healthy subjectsEur J Intern Med · PMID 22153532 Vitamin C restores blood pressure and vasodilator response during mental stress in obese childrenArq Bras Cardiol · PMID 21552645 Pretreatment with intravenous ascorbic acid preserves endothelial function during acute hyperglycaemia (R1)Clin Exp Pharmacol Physiol · PMID 15854139 Oral administration of ascorbic acid attenuates endothelial dysfunction after short-term cigarette smokingInt J Vitam Nutr Res · PMID 14743545
	Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	56 people
Studies that measured oxidative stress biomarkers Vitamin C supplementation lowers urinary levels of 4-hydroperoxy-2-nonenal metabolites in humansFree Radic Biol Med · PMID 21236333 High dosage of ascorbic acid and alpha-tocopherol is not useful for diminishing oxidative stress and DNA damage in healthy elderly adultsAnn Nutr Metab · PMID 18446021 Orange juice ingestion and supplemental vitamin C are equally effective at reducing plasma lipid peroxidation in healthy adult womenJ Am Coll Nutr · PMID 14684757 Does vitamin C supplementation influence the levels of circulating oxidized LDL, sICAM-1, sVCAM-1 and vWF-antigen in healthy male smokersEur J Clin Nutr · PMID 15127090 Influence of vitamin C on markers of oxidative stress in the earliest period of ischemic strokePharmacol Rep · PMID 20885017
	Blood glucose	Improves (the measure goes down)		3 studies	10 people
Studies that measured blood glucose High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809 Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581 FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
	Heart Rate	Improves (the measure goes down)		1 study	9 people
Studies that measured heart rate High dose ascorbic acid does not reverse central sympathetic overactivity in chronic heart failureJ Clin Pharm Ther · PMID 21916906
	Plasma Vitamin C	Improves (the measure goes up)		1 study	19 people
Studies that measured plasma vitamin c Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trialDiabetologia · PMID 18769906
	Pre-Eclampsia Risk	Changes; see studies		1 study	50 people
	Protection from Smoking	Improves (the measure goes up)		1 study	83 people
	Blood Pressure	Improves (the measure goes down)			9 people
	Insulin	Changes; see studies			10 people
	LDL Oxidation	Improves (the measure goes down)			64 people
	Vascular Function	Improves (the measure goes up)			19 people

High Blood Pressure

High Blood Pressure: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood Flow Small Increase	Improves (the measure goes up)	Small effect	4 studies	37 people
Studies that measured blood flow Ascorbic acid prevents vascular dysfunction induced by oral glucose load in healthy subjectsEur J Intern Med · PMID 22153532 Vitamin C restores blood pressure and vasodilator response during mental stress in obese childrenArq Bras Cardiol · PMID 21552645 Pretreatment with intravenous ascorbic acid preserves endothelial function during acute hyperglycaemia (R1)Clin Exp Pharmacol Physiol · PMID 15854139 Oral administration of ascorbic acid attenuates endothelial dysfunction after short-term cigarette smokingInt J Vitam Nutr Res · PMID 14743545
	HbA1c	Improves (the measure goes down)		9 studies	65 people
Studies that measured hba1c Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled studyFree Radic Biol Med · PMID 26774673 Vitamin C may have similar beneficial effects to Gemfibrozil on serum high-density lipoprotein-cholesterol in type 2 diabetic patientsJ Res Pharm Pract · PMID 25328896 Supplementation of vitamin C reduces blood glucose and improves glycosylated hemoglobin in type 2 diabetes mellitus: a randomized, double-blind studyAdv Pharmacol Sci · PMID 22242019 The effect of vitamin C supplementation on diabetic hyperlipidaemia: a double blind, crossover studyDiabet Med · PMID 2952396 Unchanged renal haemodynamics following high dose ascorbic acid administration in normoalbuminuric IDDM patientsScand J Clin Lab Invest · PMID 7624737 Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: Findings of a randomized cross-over trialDiabetes Obes Metab · PMID 30394006 Effects of eicosapentaenoic acid and vitamin C on glycemic indices, blood pressure, and serum lipids in type 2 diabetic Iranian malesJ Res Med Sci · PMID 22247720 Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trialsEur J Clin Nutr · PMID 28294172 The effect of aspirin and vitamins C and E on HbA1c assaysClin Chim Acta · PMID 16698007
	Triglycerides	Improves (the measure goes down)		5 studies	137 people
Studies that measured triglycerides Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trialDrug Des Devel Ther · PMID 26170625 Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?Endocr Pract · PMID 23757614 Effects of atorvastatin and vitamin C on forearm hyperaemic blood flow, asymmentrical dimethylarginine levels and the inflammatory process in patients with type 2 diabetes mellitusHeart · PMID 16914485 Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patientsPak J Biol Sci · PMID 22518934 Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsBr J Nutr · PMID 14748940
	Blood glucose	Improves (the measure goes down)		3 studies	174 people
Studies that measured blood glucose High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809 Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581 FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
	Inflammation	Improves (the measure goes down)		2 studies	941 people
Studies that measured inflammation Prolonged vitamin C supplementation and recovery from eccentric exerciseEur J Appl Physiol · PMID 15024666 Effect of ascorbic acid on inflammatory markers after cardiothoracic surgeryAm J Health Syst Pharm · PMID 21856809
	Total cholesterol	Improves (the measure goes down)		2 studies	1,078 people
	Body Fat	Improves (the measure goes down)		1 study	31 people
	C-Reactive Protein (CRP)	Improves (the measure goes down)		1 study	72 people
	Glycemic Control	Improves (the measure goes up)		1 study	37 people
	Plasma Vitamin C	Improves (the measure goes up)		1 study	37 people
	Weight	Improves (the measure goes down)		1 study	31 people
	Blood Pressure	Improves (the measure goes down)			65 people
	High-density lipoprotein (HDL)	Improves (the measure goes up)			65 people
	Insulin	Changes; see studies			68 people
	Interleukin 6	Improves (the measure goes down)			72 people
	Kidney Function	Improves (the measure goes up)			31 people
	Liver Enzymes	Changes; see studies			31 people
	Low-density lipoprotein (LDL)	Improves (the measure goes down)			65 people

Postural Orthostatic Tachycardia syndrome (POTS)

Blood Flow: improves
Microcirculation: improves

Postural Orthostatic Tachycardia syndrome (POTS): outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood Flow Small Increase	Improves (the measure goes up)	Small effect	4 studies	19 people
Studies that measured blood flow Ascorbic acid prevents vascular dysfunction induced by oral glucose load in healthy subjectsEur J Intern Med · PMID 22153532 Vitamin C restores blood pressure and vasodilator response during mental stress in obese childrenArq Bras Cardiol · PMID 21552645 Pretreatment with intravenous ascorbic acid preserves endothelial function during acute hyperglycaemia (R1)Clin Exp Pharmacol Physiol · PMID 15854139 Oral administration of ascorbic acid attenuates endothelial dysfunction after short-term cigarette smokingInt J Vitam Nutr Res · PMID 14743545
	Microcirculation	Improves (the measure goes up)		1 study	19 people
Studies that measured microcirculation Ascorbate improves circulation in postural tachycardia syndromeAm J Physiol Heart Circ Physiol · PMID 21622825

Immune Health

Blood glucose: improves
Upper Respiratory Tract Infection Symptoms: improves
Cortisol: improves

Immune Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood glucose Small Improvement	Improves (the measure goes down)	Small effect	3 studies	28 people
Studies that measured blood glucose High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809 Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581 FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
	Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	474 people
Studies that measured upper respiratory tract infection symptoms Vitamin C and the common cold: a double-blind trialCan Med Assoc J · PMID 5057006 Ascorbic acid and the common coldLancet · PMID 4113614 Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled surveyAdv Ther · PMID 12201356 Vitamin C and the common coldJ Soc Occup Med · PMID 162650 Winter illness and vitamin C: the effect of relatively low dosesCan Med Assoc J · PMID 1091343 Ascorbic acid for the common cold. A prophylactic and therapeutic trialJAMA · PMID 163386 Therapeutic effect of vitamin C. A co-twin control studyJAMA · PMID 318715 A randomized controlled trial of the therapeutic effect of vitamin C in the common coldPractitioner · PMID 319446 Vitamin C and the common cold: a second MZ Cotwin control studyActa Genet Med Gemellol · PMID 7048833 Trial of ascorbic acid in prevention of coldsBr Med J · PMID 4290259 and 14 more in the citations list
	Cortisol	Improves (the measure goes down)		5 studies	93 people
Studies that measured cortisol The effect of 2 weeks vitamin C supplementation on immunoendocrine responses to 2.5 h cycling exercise in manEur J Appl Physiol · PMID 16685547 Vitamin C supplementation and salivary immune function following exercise-heat stressInt J Sports Physiol Perform · PMID 19223675 Influence of vitamin C supplementation on oxidative and salivary IgA changes following an ultramarathonEur J Appl Physiol · PMID 12627313 Influence of acute vitamin C and/or carbohydrate ingestion on hormonal, cytokine, and immune responses to prolonged exerciseInt J Sport Nutr Exerc Metab · PMID 16327030 Effect of ascorbic acid on surgical stress response in gynecologic surgeryInt J Clin Pract · PMID 15587771
	Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	56 people
Studies that measured oxidative stress biomarkers Vitamin C supplementation lowers urinary levels of 4-hydroperoxy-2-nonenal metabolites in humansFree Radic Biol Med · PMID 21236333 High dosage of ascorbic acid and alpha-tocopherol is not useful for diminishing oxidative stress and DNA damage in healthy elderly adultsAnn Nutr Metab · PMID 18446021 Orange juice ingestion and supplemental vitamin C are equally effective at reducing plasma lipid peroxidation in healthy adult womenJ Am Coll Nutr · PMID 14684757 Does vitamin C supplementation influence the levels of circulating oxidized LDL, sICAM-1, sVCAM-1 and vWF-antigen in healthy male smokersEur J Clin Nutr · PMID 15127090 Influence of vitamin C on markers of oxidative stress in the earliest period of ischemic strokePharmacol Rep · PMID 20885017
	Upper Respiratory Tract Infection Risk	Changes; see studies		5 studies	1,159 people
Studies that measured upper respiratory tract infection risk Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trialBMJ Mil Health · PMID 32139409 The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common coldAm J Clin Nutr · PMID 463806 The clinical and biochemical effects of vitamin C supplementation in short-stay hospitalized geriatric patientsInt J Vitam Nutr Res · PMID 6376396 Megadosage of ascorbic acid in an Antarctic expeditionBr J Nutr · PMID 870023 Vitamin C prophylaxis in a boarding schoolN Engl J Med · PMID 4586102
	Exercise-Induced Oxidation	Changes; see studies		2 studies	16 people
	Inflammation	Improves (the measure goes down)		2 studies	30 people
	Muscle Damage	Changes; see studies		2 studies	30 people
	Uric Acid	Improves (the measure goes down)		2 studies	28 people
	Heart Rate	Improves (the measure goes down)		1 study	40 people
	Interferon Gamma	Improves (the measure goes up)		1 study	28 people
	Plasma Vitamin C	Improves (the measure goes up)		1 study	56 people
	Exercise-Induced Immune Suppression	Improves (the measure goes up)			93 people
	IL-1Ra	Improves (the measure goes down)			28 people
	Insulin	Changes; see studies			28 people
	Interleukin 10	Improves (the measure goes up)			28 people
	Interleukin 2	Improves (the measure goes up)			28 people
	Interleukin 6	Improves (the measure goes down)			28 people
	Interleukin 8	Changes; see studies			28 people
	Lymphocyte Count	Improves (the measure goes up)			28 people
	Monocyte Count	Improves (the measure goes up)			28 people
	Natural Killer Cell Content	Improves (the measure goes up)			28 people
	Neutrophil Count	Improves (the measure goes up)			28 people

High Cholesterol

Blood glucose: improves
HbA1c: improves
Triglycerides: improves

High Cholesterol: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood glucose Small Improvement	Improves (the measure goes down)	Small effect	3 studies	216 people
Studies that measured blood glucose High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809 Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581 FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
	HbA1c	Improves (the measure goes down)		9 studies	216 people
Studies that measured hba1c Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled studyFree Radic Biol Med · PMID 26774673 Vitamin C may have similar beneficial effects to Gemfibrozil on serum high-density lipoprotein-cholesterol in type 2 diabetic patientsJ Res Pharm Pract · PMID 25328896 Supplementation of vitamin C reduces blood glucose and improves glycosylated hemoglobin in type 2 diabetes mellitus: a randomized, double-blind studyAdv Pharmacol Sci · PMID 22242019 The effect of vitamin C supplementation on diabetic hyperlipidaemia: a double blind, crossover studyDiabet Med · PMID 2952396 Unchanged renal haemodynamics following high dose ascorbic acid administration in normoalbuminuric IDDM patientsScand J Clin Lab Invest · PMID 7624737 Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: Findings of a randomized cross-over trialDiabetes Obes Metab · PMID 30394006 Effects of eicosapentaenoic acid and vitamin C on glycemic indices, blood pressure, and serum lipids in type 2 diabetic Iranian malesJ Res Med Sci · PMID 22247720 Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trialsEur J Clin Nutr · PMID 28294172 The effect of aspirin and vitamins C and E on HbA1c assaysClin Chim Acta · PMID 16698007
	Triglycerides	Improves (the measure goes down)		5 studies	216 people
Studies that measured triglycerides Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trialDrug Des Devel Ther · PMID 26170625 Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?Endocr Pract · PMID 23757614 Effects of atorvastatin and vitamin C on forearm hyperaemic blood flow, asymmentrical dimethylarginine levels and the inflammatory process in patients with type 2 diabetes mellitusHeart · PMID 16914485 Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patientsPak J Biol Sci · PMID 22518934 Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsBr J Nutr · PMID 14748940
	Inflammation	Improves (the measure goes down)		2 studies	941 people
Studies that measured inflammation Prolonged vitamin C supplementation and recovery from eccentric exerciseEur J Appl Physiol · PMID 15024666 Effect of ascorbic acid on inflammatory markers after cardiothoracic surgeryAm J Health Syst Pharm · PMID 21856809
	Total cholesterol	Improves (the measure goes down)		2 studies	1,157 people
Studies that measured total cholesterol Influence of quercetin supplementation on disease risk factors in community-dwelling adultsJ Am Diet Assoc · PMID 21443986 Oral vitamin C supplementation decreased low-density lipoprotein in adults on hemodialysis: A systematic review and meta-analysis.Nutr Res · PMID 40532258
	Plasma Vitamin C	Improves (the measure goes up)		1 study	50 people
	Blood Pressure	Improves (the measure goes down)			99 people
	Creatinine	Improves (the measure goes up)			65 people
	High-density lipoprotein (HDL)	Improves (the measure goes up)			166 people
	Low-density lipoprotein (LDL)	Improves (the measure goes down)			166 people
	Urea	Improves (the measure goes up)			65 people

Obesity

Blood glucose: improves
Triglycerides: improves
Total cholesterol: improves

Obesity: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Blood glucose Small Improvement	Improves (the measure goes down)	Small effect	3 studies	72 people
Studies that measured blood glucose High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809 Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581 FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
	Triglycerides	Improves (the measure goes down)		5 studies	72 people
Studies that measured triglycerides Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trialDrug Des Devel Ther · PMID 26170625 Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?Endocr Pract · PMID 23757614 Effects of atorvastatin and vitamin C on forearm hyperaemic blood flow, asymmentrical dimethylarginine levels and the inflammatory process in patients with type 2 diabetes mellitusHeart · PMID 16914485 Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patientsPak J Biol Sci · PMID 22518934 Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsBr J Nutr · PMID 14748940
	Total cholesterol	Improves (the measure goes down)		2 studies	72 people
Studies that measured total cholesterol Influence of quercetin supplementation on disease risk factors in community-dwelling adultsJ Am Diet Assoc · PMID 21443986 Oral vitamin C supplementation decreased low-density lipoprotein in adults on hemodialysis: A systematic review and meta-analysis.Nutr Res · PMID 40532258
	C-Reactive Protein (CRP)	Improves (the measure goes down)		1 study	72 people
Studies that measured c-reactive protein (crp) Vitamin C treatment reduces elevated C-reactive proteinFree Radic Biol Med · PMID 18952164
	Heart Rate	Improves (the measure goes down)		1 study	20 people
Studies that measured heart rate High dose ascorbic acid does not reverse central sympathetic overactivity in chronic heart failureJ Clin Pharm Ther · PMID 21916906
	Weight	Improves (the measure goes down)		1 study	20 people
	Fat Oxidation	Improves (the measure goes up)			20 people
	Fatigue Symptoms	Improves (the measure goes down)			20 people
	Interleukin 6	Improves (the measure goes down)			72 people

Bone Health

Anti-Oxidant Enzyme Profile: improves
Bone Mineral Density: improves

Bone Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Anti-Oxidant Enzyme Profile Small Increase	Improves (the measure goes up)	Small effect	1 study	90 people
Studies that measured anti-oxidant enzyme profile Supplementation of ascorbic acid and alpha-tocopherol is useful to preventing bone loss linked to oxidative stress in elderlyJ Nutr Health Aging · PMID 20617290
	Bone Mineral Density	Improves (the measure goes up)		1 study	124 people
Studies that measured bone mineral density Effect of antioxidants combined to resistance training on BMD in elderly women: a pilot studyOsteoporos Int · PMID 19020919

Sexual Health

Depression Symptoms: improves
Plasma Vitamin C: improves
Frequency of Intercourse: improves

Sexual Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Depression Symptoms Small Improvement	Improves (the measure goes down)	Small effect	1 study	81 people
Studies that measured depression symptoms High-dose ascorbic acid increases intercourse frequency and improves mood: a randomized controlled clinical trialBiol Psychiatry · PMID 12208645
	Plasma Vitamin C	Improves (the measure goes up)		1 study	81 people
Studies that measured plasma vitamin c Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trialDiabetologia · PMID 18769906
	Frequency of Intercourse	Improves (the measure goes up)			81 people

Infertility

Seminal Motility: improves
Sperm Quality: improves

Infertility: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Seminal Motility Moderate Improvement	Improves (the measure goes up)	Moderate effect		120 people
	Sperm Quality	Improves (the measure goes up)		1 study	120 people
Studies that measured sperm quality Clinical relevance of vitamin C among lead-exposed infertile menGenet Test Mol Biomarkers · PMID 22731648

Common Cold

Upper Respiratory Tract Infection Risk
Common Cold Symptoms
Upper Respiratory Tract Infection Symptoms: improves

Common Cold: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Upper Respiratory Tract Infection Risk No effect		NoneNo effect	5 studies	21,620 people
Studies that measured upper respiratory tract infection risk Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trialBMJ Mil Health · PMID 32139409 The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common coldAm J Clin Nutr · PMID 463806 The clinical and biochemical effects of vitamin C supplementation in short-stay hospitalized geriatric patientsInt J Vitam Nutr Res · PMID 6376396 Megadosage of ascorbic acid in an Antarctic expeditionBr J Nutr · PMID 870023 Vitamin C prophylaxis in a boarding schoolN Engl J Med · PMID 4586102
	Common Cold Symptoms No effect		NoneNo effect	1 study	3,001 people
Studies that measured common cold symptoms Ineffectiveness of vitamin C in treating coryza.Practitioner · PMID 4870463
	Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	14,426 people
Studies that measured upper respiratory tract infection symptoms Vitamin C and the common cold: a double-blind trialCan Med Assoc J · PMID 5057006 Ascorbic acid and the common coldLancet · PMID 4113614 Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled surveyAdv Ther · PMID 12201356 Vitamin C and the common coldJ Soc Occup Med · PMID 162650 Winter illness and vitamin C: the effect of relatively low dosesCan Med Assoc J · PMID 1091343 Ascorbic acid for the common cold. A prophylactic and therapeutic trialJAMA · PMID 163386 Therapeutic effect of vitamin C. A co-twin control studyJAMA · PMID 318715 A randomized controlled trial of the therapeutic effect of vitamin C in the common coldPractitioner · PMID 319446 Vitamin C and the common cold: a second MZ Cotwin control studyActa Genet Med Gemellol · PMID 7048833 Trial of ascorbic acid in prevention of coldsBr Med J · PMID 4290259 and 14 more in the citations list

Acute Respiratory Infection (ARI)

Upper Respiratory Tract Infection Risk
Upper Respiratory Tract Infection Symptoms: improves

Acute Respiratory Infection (ARI): outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Upper Respiratory Tract Infection Risk No effect		NoneNo effect	5 studies	1,332 people
Studies that measured upper respiratory tract infection risk Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trialBMJ Mil Health · PMID 32139409 The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common coldAm J Clin Nutr · PMID 463806 The clinical and biochemical effects of vitamin C supplementation in short-stay hospitalized geriatric patientsInt J Vitam Nutr Res · PMID 6376396 Megadosage of ascorbic acid in an Antarctic expeditionBr J Nutr · PMID 870023 Vitamin C prophylaxis in a boarding schoolN Engl J Med · PMID 4586102
	Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	666 people
Studies that measured upper respiratory tract infection symptoms Vitamin C and the common cold: a double-blind trialCan Med Assoc J · PMID 5057006 Ascorbic acid and the common coldLancet · PMID 4113614 Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled surveyAdv Ther · PMID 12201356 Vitamin C and the common coldJ Soc Occup Med · PMID 162650 Winter illness and vitamin C: the effect of relatively low dosesCan Med Assoc J · PMID 1091343 Ascorbic acid for the common cold. A prophylactic and therapeutic trialJAMA · PMID 163386 Therapeutic effect of vitamin C. A co-twin control studyJAMA · PMID 318715 A randomized controlled trial of the therapeutic effect of vitamin C in the common coldPractitioner · PMID 319446 Vitamin C and the common cold: a second MZ Cotwin control studyActa Genet Med Gemellol · PMID 7048833 Trial of ascorbic acid in prevention of coldsBr Med J · PMID 4290259 and 14 more in the citations list

Metabolic Health

Aerobic Exercise Metrics
HbA1c: improves
Cortisol: improves

Metabolic Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People
	Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	7 people
Studies that measured aerobic exercise metrics Vitamin C consumption does not impair training-induced improvements in exercise performanceInt J Sports Physiol Perform · PMID 21487150 Effects of Applephenon and ascorbic acid on physical fatigueNutrition · PMID 17483009
	HbA1c	Improves (the measure goes down)		9 studies	488 people
Studies that measured hba1c Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled studyFree Radic Biol Med · PMID 26774673 Vitamin C may have similar beneficial effects to Gemfibrozil on serum high-density lipoprotein-cholesterol in type 2 diabetic patientsJ Res Pharm Pract · PMID 25328896 Supplementation of vitamin C reduces blood glucose and improves glycosylated hemoglobin in type 2 diabetes mellitus: a randomized, double-blind studyAdv Pharmacol Sci · PMID 22242019 The effect of vitamin C supplementation on diabetic hyperlipidaemia: a double blind, crossover studyDiabet Med · PMID 2952396 Unchanged renal haemodynamics following high dose ascorbic acid administration in normoalbuminuric IDDM patientsScand J Clin Lab Invest · PMID 7624737 Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: Findings of a randomized cross-over trialDiabetes Obes Metab · PMID 30394006 Effects of eicosapentaenoic acid and vitamin C on glycemic indices, blood pressure, and serum lipids in type 2 diabetic Iranian malesJ Res Med Sci · PMID 22247720 Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trialsEur J Clin Nutr · PMID 28294172 The effect of aspirin and vitamins C and E on HbA1c assaysClin Chim Acta · PMID 16698007
	Cortisol	Improves (the measure goes down)		5 studies	31 people
Studies that measured cortisol The effect of 2 weeks vitamin C supplementation on immunoendocrine responses to 2.5 h cycling exercise in manEur J Appl Physiol · PMID 16685547 Vitamin C supplementation and salivary immune function following exercise-heat stressInt J Sports Physiol Perform · PMID 19223675 Influence of vitamin C supplementation on oxidative and salivary IgA changes following an ultramarathonEur J Appl Physiol · PMID 12627313 Influence of acute vitamin C and/or carbohydrate ingestion on hormonal, cytokine, and immune responses to prolonged exerciseInt J Sport Nutr Exerc Metab · PMID 16327030 Effect of ascorbic acid on surgical stress response in gynecologic surgeryInt J Clin Pract · PMID 15587771
	Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	112 people
Studies that measured oxidative stress biomarkers Vitamin C supplementation lowers urinary levels of 4-hydroperoxy-2-nonenal metabolites in humansFree Radic Biol Med · PMID 21236333 High dosage of ascorbic acid and alpha-tocopherol is not useful for diminishing oxidative stress and DNA damage in healthy elderly adultsAnn Nutr Metab · PMID 18446021 Orange juice ingestion and supplemental vitamin C are equally effective at reducing plasma lipid peroxidation in healthy adult womenJ Am Coll Nutr · PMID 14684757 Does vitamin C supplementation influence the levels of circulating oxidized LDL, sICAM-1, sVCAM-1 and vWF-antigen in healthy male smokersEur J Clin Nutr · PMID 15127090 Influence of vitamin C on markers of oxidative stress in the earliest period of ischemic strokePharmacol Rep · PMID 20885017
	Triglycerides	Improves (the measure goes down)		5 studies	80 people
Studies that measured triglycerides Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trialDrug Des Devel Ther · PMID 26170625 Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?Endocr Pract · PMID 23757614 Effects of atorvastatin and vitamin C on forearm hyperaemic blood flow, asymmentrical dimethylarginine levels and the inflammatory process in patients with type 2 diabetes mellitusHeart · PMID 16914485 Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patientsPak J Biol Sci · PMID 22518934 Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsBr J Nutr · PMID 14748940
	Blood Flow	Improves (the measure goes up)		4 studies	34 people
	Blood glucose	Improves (the measure goes down)		3 studies	875 people
	Exercise-Induced Oxidation	Changes; see studies		2 studies	23 people
	Inflammation	Improves (the measure goes down)		2 studies	16 people
	Muscle Damage	Changes; see studies		2 studies	16 people
	Total cholesterol	Improves (the measure goes down)		2 studies	80 people
	C-Reactive Protein (CRP)	Improves (the measure goes down)		1 study	476 people
	DNA Damage	Changes; see studies		1 study	73 people
	Exercise Adaptations	Improves (the measure goes up)		1 study	39 people
	Glycemic Control	Improves (the measure goes up)		1 study	21 people
	Mineral Bioaccumulation	Improves (the measure goes up)		1 study	45 people
	Plasma Vitamin C	Improves (the measure goes up)		1 study	89 people
	Protection from Smoking	Improves (the measure goes up)		1 study	30 people
	Resistin	Improves (the measure goes up)		1 study	80 people
	Exercise-Induced Immune Suppression	Improves (the measure goes up)			31 people
	High-density lipoprotein (HDL)	Improves (the measure goes up)			80 people
	Insulin	Changes; see studies			233 people
	Interleukin 6	Improves (the measure goes down)			6 people
	LDL Oxidation	Improves (the measure goes down)			30 people
	Plasma Vitamin E	Improves (the measure goes up)			80 people

Aerobic Exercise Performance

Aerobic Exercise Metrics
Cortisol: improves
Oxidative Stress Biomarkers: improves

Aerobic Exercise Performance: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	68 people
Cortisol	Improves (the measure goes down)		5 studies	28 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	35 people
Blood glucose	Improves (the measure goes down)		3 studies	28 people
Exercise-Induced Oxidation	Changes; see studies		2 studies	7 people
Uric Acid	Improves (the measure goes down)		2 studies	28 people
Exercise Adaptations	Improves (the measure goes up)		1 study	15 people
Glycemic Control	Improves (the measure goes up)		1 study	21 people
Heart Rate	Improves (the measure goes down)		1 study	28 people
Interferon Gamma	Improves (the measure goes up)		1 study	28 people
Plasma Vitamin C	Improves (the measure goes up)		1 study	28 people
Exercise-Induced Immune Suppression	Improves (the measure goes up)			28 people
Insulin	Changes; see studies			28 people
Interleukin 10	Improves (the measure goes up)			28 people
Interleukin 2	Improves (the measure goes up)			28 people
Interleukin 6	Improves (the measure goes down)			28 people
Interleukin 8	Changes; see studies			28 people
Lymphocyte Count	Improves (the measure goes up)			28 people
Monocyte Count	Improves (the measure goes up)			28 people
Natural Killer Cell Content	Improves (the measure goes up)			28 people
Neutrophil Count	Improves (the measure goes up)			28 people
Oxygen Uptake	Improves (the measure goes up)			15 people
Rating of Perceived Exertion	Improves (the measure goes up)			28 people

Muscle Recovery

Aerobic Exercise Metrics
Cortisol: improves
Oxidative Stress Biomarkers: improves

Muscle Recovery: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	28 people
Cortisol	Improves (the measure goes down)		5 studies	44 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	28 people
Blood glucose	Improves (the measure goes down)		3 studies	28 people
Exercise-Induced Oxidation	Changes; see studies		2 studies	16 people
Inflammation	Improves (the measure goes down)		2 studies	30 people
Muscle Damage	Changes; see studies		2 studies	76 people
Uric Acid	Improves (the measure goes down)		2 studies	28 people
Heart Rate	Improves (the measure goes down)		1 study	28 people
Interferon Gamma	Improves (the measure goes up)		1 study	28 people
Plasma Vitamin C	Improves (the measure goes up)		1 study	28 people
Exercise-Induced Immune Suppression	Improves (the measure goes up)			44 people
IL-1Ra	Improves (the measure goes down)			28 people
Insulin	Changes; see studies			28 people
Interleukin 10	Improves (the measure goes up)			28 people
Interleukin 2	Improves (the measure goes up)			28 people
Interleukin 6	Improves (the measure goes down)			28 people
Interleukin 8	Changes; see studies			28 people
Lymphocyte Count	Improves (the measure goes up)			28 people
Monocyte Count	Improves (the measure goes up)			28 people
Muscle Soreness	Improves (the measure goes down)			18 people
Natural Killer Cell Content	Improves (the measure goes up)			28 people
Neutrophil Count	Improves (the measure goes up)			28 people
Rating of Perceived Exertion	Improves (the measure goes up)			28 people

Type 1 Diabetes

Aerobic Exercise Metrics
HbA1c: improves
Oxidative Stress Biomarkers: improves

Type 1 Diabetes: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	26 people
HbA1c	Improves (the measure goes down)		9 studies	74 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	26 people
Triglycerides	Improves (the measure goes down)		5 studies	50 people
Blood glucose	Improves (the measure goes down)		3 studies	100 people
Total cholesterol	Improves (the measure goes down)		2 studies	50 people
Heart Rate	Improves (the measure goes down)		1 study	26 people
Plasma Vitamin C	Improves (the measure goes up)		1 study	76 people
Blood Pressure	Improves (the measure goes down)			24 people
Kidney Function	Improves (the measure goes up)			24 people

Running Performance

Aerobic Exercise Metrics
Cortisol: improves
Oxidative Stress Biomarkers: improves

Running Performance: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	15 people
Cortisol	Improves (the measure goes down)		5 studies	28 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	28 people
Exercise Adaptations	Improves (the measure goes up)		1 study	15 people
Plasma Vitamin C	Improves (the measure goes up)		1 study	28 people
Exercise-Induced Immune Suppression	Improves (the measure goes up)			28 people
Oxygen Uptake	Improves (the measure goes up)			15 people

Cycling Performance

Aerobic Exercise Metrics
Oxidative Stress Biomarkers: improves
Exercise-Induced Oxidation: changes; see studies

Cycling Performance: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Aerobic Exercise Metrics No effect		NoneNo effect	2 studies	7 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	7 people
Exercise-Induced Oxidation	Changes; see studies		2 studies	7 people

Upper Respiratory Tract Infection

Common Cold Symptoms
Upper Respiratory Tract Infection Symptoms: improves
Upper Respiratory Tract Infection Risk: changes; see studies

Upper Respiratory Tract Infection: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Common Cold Symptoms No effect		NoneNo effect	1 study	1,731 people
Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	4,935 people
Upper Respiratory Tract Infection Risk	Changes; see studies		5 studies	8,012 people

General Athletic Performance

Glycemic Control
Inflammation: improves
Muscle Damage: changes; see studies

General Athletic Performance: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Glycemic Control No effect		NoneNo effect	1 study	21 people
Inflammation	Improves (the measure goes down)		2 studies	14 people
Muscle Damage	Changes; see studies		2 studies	60 people
Muscle Soreness	Improves (the measure goes down)			18 people

Body Composition

Body Fat
Weight: improves

Body Composition: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Body Fat No effect		NoneNo effect	1 study	941 people
	Weight	Improves (the measure goes down)		1 study	941 people

Pneumonia

All-Cause Mortality
Length of hospitalization: improves
Need for mechanical ventilation: changes; see studies

Pneumonia: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
All-Cause Mortality No effect		NoneNo effect	1 study	366 people
Length of hospitalization	Improves (the measure goes down)			366 people
Need for mechanical ventilation	Changes; see studies			366 people

Weight Loss & Maintenance

Body Fat
Weight: improves

Weight Loss & Maintenance: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Body Fat No effect		NoneNo effect	1 study	941 people
	Weight	Improves (the measure goes down)		1 study	941 people

Type 2 Diabetes

Adiponectin
HbA1c: improves
Oxidative Stress Biomarkers: improves

Type 2 Diabetes: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Adiponectin No effect		NoneNo effect		8 people
HbA1c	Improves (the measure goes down)		9 studies	354 people
Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	43 people
Triglycerides	Improves (the measure goes down)		5 studies	396 people
Blood Flow	Improves (the measure goes up)		4 studies	63 people
Blood glucose	Improves (the measure goes down)		3 studies	537 people
Inflammation	Improves (the measure goes down)		2 studies	8 people
Total cholesterol	Improves (the measure goes down)		2 studies	406 people
Uric Acid	Improves (the measure goes down)		2 studies	13 people
Anti-Oxidant Enzyme Profile	Improves (the measure goes up)		1 study	13 people
Body Fat	Improves (the measure goes down)		1 study	44 people
C-Reactive Protein (CRP)	Improves (the measure goes down)		1 study	106 people
Glycemic Control	Improves (the measure goes up)		1 study	80 people
Plasma Vitamin C	Improves (the measure goes up)		1 study	157 people
Weight	Improves (the measure goes down)		1 study	44 people
Blood Pressure	Improves (the measure goes down)			154 people
Creatinine	Improves (the measure goes up)			65 people
Fat Oxidation	Improves (the measure goes up)			13 people
Fructosamine	Changes; see studies			13 people
High-density lipoprotein (HDL)	Improves (the measure goes up)			284 people
Insulin	Changes; see studies			129 people
Interleukin 6	Improves (the measure goes down)			98 people
Kidney Function	Improves (the measure goes up)			55 people
LDL Oxidation	Improves (the measure goes down)			8 people
Liver Enzymes	Changes; see studies			31 people
Low-density lipoprotein (LDL)	Improves (the measure goes down)			284 people
Muscle Mass	Improves (the measure goes up)			13 people
TNF-Alpha	Improves (the measure goes down)			26 people
Urea	Improves (the measure goes up)			65 people
Vascular Function	Improves (the measure goes up)			26 people

Chronic Kidney Disease (CKD)

High-density lipoprotein (HDL)
Triglycerides: improves
Inflammation: improves

Chronic Kidney Disease (CKD): outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
High-density lipoprotein (HDL) No effect		NoneNo effect		112 people
Triglycerides	Improves (the measure goes down)		5 studies	112 people
Inflammation	Improves (the measure goes down)		2 studies	941 people
Total cholesterol	Improves (the measure goes down)		2 studies	112 people
Low-density lipoprotein (LDL)	Improves (the measure goes down)			112 people

Mental Resilience

Adrenocorticotropic Hormone
Cortisol: improves
Blood Flow: improves

Mental Resilience: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Adrenocorticotropic Hormone No effect		NoneNo effect		22 people
Cortisol	Improves (the measure goes down)		5 studies	22 people
Blood Flow	Improves (the measure goes up)		4 studies	21 people
Blood glucose	Improves (the measure goes down)		3 studies	22 people
Insulin	Changes; see studies			22 people
Osteocalcin	Improves (the measure goes up)			22 people

Atherosclerosis

Adiponectin
Triglycerides: improves
Blood glucose: improves

Atherosclerosis: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
Adiponectin No effect		NoneNo effect		8 people
Triglycerides	Improves (the measure goes down)		5 studies	8 people
Blood glucose	Improves (the measure goes down)		3 studies	8 people
Inflammation	Improves (the measure goes down)		2 studies	8 people
Total cholesterol	Improves (the measure goes down)		2 studies	8 people
C-Reactive Protein (CRP)	Improves (the measure goes down)		1 study	8 people
High-density lipoprotein (HDL)	Improves (the measure goes up)			8 people
Insulin	Changes; see studies			8 people
LDL Oxidation	Improves (the measure goes down)			8 people
Low-density lipoprotein (LDL)	Improves (the measure goes down)			8 people

Dyslipidemia

High-density lipoprotein (HDL)
Triglycerides: improves
Total cholesterol: improves

Dyslipidemia: outcomes studied for Vitamin C
Outcome	Effect	Size	Studies	People
High-density lipoprotein (HDL) No effect		NoneNo effect		439 people
Triglycerides	Improves (the measure goes down)		5 studies	439 people
Total cholesterol	Improves (the measure goes down)		2 studies	439 people
Low-density lipoprotein (LDL)	Improves (the measure goes down)			439 people

Lower Respiratory Tract Infection

Upper Respiratory Tract Infection Symptoms: improves

Lower Respiratory Tract Infection: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	57 people

Respiratory Health

Upper Respiratory Tract Infection Symptoms: improves

Respiratory Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Upper Respiratory Tract Infection Symptoms	Improves (the measure goes down)		24 studies	252 people

Stroke

Oxidative Stress Biomarkers: improves

Stroke: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Oxidative Stress Biomarkers	Improves (the measure goes down)		5 studies	60 people

COVID-19

COVID-19 Severity: improves

COVID-19: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	COVID-19 Severity	Improves (the measure goes down)		2 studies	274 people

Kidney Health

Uric Acid: improves

Kidney Health: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Uric Acid	Improves (the measure goes down)		2 studies	1,013 people

Cardiovascular Disease

Inflammation: improves

Cardiovascular Disease: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Inflammation	Improves (the measure goes down)		2 studies	24 people

Fatigue

Aerobic Exercise Metrics: improves

Fatigue: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Aerobic Exercise Metrics	Improves (the measure goes up)		2 studies	18 people

Hyperuricemia

Uric Acid: improves

Hyperuricemia: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Uric Acid	Improves (the measure goes down)		2 studies	184 people

Gout

Gout Symptoms: improves

Gout: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Gout Symptoms	Improves (the measure goes down)		1 study	14,641 people

Bacterial Vaginosis (BV)

Bacterial Vaginosis Symptoms: improves

Bacterial Vaginosis (BV): outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Bacterial Vaginosis Symptoms	Improves (the measure goes down)		1 study	277 people

Cataracts

Cataract Risk: changes; see studies

Cataracts: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Cataract Risk	Changes; see studies		1 study	11,545 people

Charcot-Marie-Tooth Disease Type 1A (CMT1A)

Charcot Marie Tooth Disease Symptoms: improves

Charcot-Marie-Tooth Disease Type 1A (CMT1A): outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Charcot Marie Tooth Disease Symptoms	Improves (the measure goes down)		1 study	271 people

Heart Failure

Heart Rate: improves

Heart Failure: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Heart Rate	Improves (the measure goes down)		1 study	11 people

Mood Improvement

Subjective Well-Being: improves

Mood Improvement: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Subjective Well-Being	Improves (the measure goes up)		1 study	55 people

Premature Birth

Preterm Birth Risk: changes; see studies

Premature Birth: outcomes studied for Vitamin C
Grade	Outcome	Effect	Size	Studies	People	Studies list
	Preterm Birth Risk	Changes; see studies		1 study	9,968 people

What the published studies found

5 automated readings

Automated reading of the published studies (Decosa evidence engine), for outcomes Dr. Grey has not graded yet. It is not a Dr. Grey grade and does not change one. How it is read

LDL cholesterol
The studies disagree. The best available review (2021, 15 studies, 872 people) found little or no difference in LDL cholesterol, while 3 of the 9 studies read found an improvement. The evidence is very weak.
9 studies counted of 11 read: 5 reviews and 4 trials (543 people in the trials).
1. Meta-analysis, 2021; 15 studies, 872 people; patients with type 2 diabetes: no clear difference (the review the verdict rests on). vitamin C supplementation failed to improve LDL Does vitamin C supplementation exert profitable effects on serum lipid profile in patients with type 2 diabetes? A systematic review and dose-response meta-analysisPubMed 33984490
2. Meta-analysis, 2021: no clear difference. The effect of vitamin C supplementation on lipid profile of type 2 diabetic patients: a systematic review and meta-analysis of clinical trialsPubMed 33653396
3. Systematic review, 2019; 10 studies, 6,409 people: improves. significant improvement for each of the following risk factors Limited evidence for a beneficial effect of vitamin C supplementation on biomarkers of cardiovascular diseases: an umbrella review of systematic reviews and meta-analysesPubMed 30683434
4. Meta-analysis, 2016: mixed results. LDL-C in healthy participants (-0.32 mmol/L, 95% CI: -0.57, -0.07) Systematic review and meta-analysis of randomised controlled trials testing the effects of vitamin C supplementation on blood lipidsPubMed 26164552
5. Meta-analysis, 2008; 13 studies; patients with hypercholesterolemia: improves. The pooled estimate of effect for vitamin C supplementation on LDL and HDL cholesterol was … Vitamin C supplementation lowers serum low-density lipoprotein cholesterol and triglycerides: a meta-analysis of 13 randomized controlled trialsPubMed 19674720
6. Randomised trial, 2007; 84 people; patients with type 2 diabetes: improves. significant decrease in FBS, TG, LDL Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patientsPubMed 18160753
7. Randomised trial, 2004; 305 people: no clear difference. Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsPubMed 14748940
8. Randomised trial, 2001; 16 people; obese male volunteers: no clear difference. not significant differences in both groups [Effect of oral administration of ascorbic acid on insulin sensitivity and lipid profile in obese individuals]PubMed 11926203
9. Randomised trial, 1995; 138 people; adults aged 20 to 65 years: no clear difference. no overall effect of supplementation on plasma concentrations of HDL, LDL Effect of vitamin C supplementation on lipoprotein cholesterol, apolipoprotein, and triglyceride concentrationsPubMed 7728285
Automated reading of the published studies (Decosa evidence engine), run 30 Sep 2026. It reads abstracts, can miss studies, and a repeat run can differ.
Fatigue
The studies disagree. A Cochrane review (2014, 3 studies, 530 people) found little or no difference in fatigue, while 3 of the 5 studies read found an improvement. The evidence is very weak.
Side effects: 1 of the 4 studies that reported on them found more with Vitamin C (gastrointestinal side effects).
5 studies counted of 11 read: 3 reviews and 1 trial (36 people in the trials).
1. Meta-analysis, 2014; 3 studies, 530 people; adults with peripheral neuropathy: no clear difference (the review the verdict rests on). effects of ascorbic acid at either dose are probably small Interventions for fatigue in peripheral neuropathyPubMed 25519471
2. Systematic review, 2021; 9 studies, 720 people; patients with fatigue from various diseases: improves. significant decrease in fatigue scores in the vitamin C group Feasibility of Vitamin C in the Treatment of Post Viral Fatigue with Focus on Long COVID, Based on a Systematic Review of IV Vitamin C on FatiguePubMed 33807280
3. Systematic review, 2014; 37 studies: improves. Intravenous Vitamin C and Cancer: A Systematic ReviewPubMed 24867961
4. Crossover trial, 2020; 36 people; volunteers with low vitamin C or glutathione levels: no clear difference. but not after vitamin C treatment Antioxidant supplementation, redox deficiencies and exercise performance: A falsification designPubMed 32682929
5. Study, 2019; 47 people; patients undergoing alcohol detoxification: improves. 89% of the patients reported a decrease of tiredness Alcohol Withdrawal: Possible Risk of Latent Scurvy Appearing as Tiredness: A STROBE-Compliant StudyPubMed 30627275
Automated reading of the published studies (Decosa evidence engine), run 30 Sep 2026. It reads abstracts, can miss studies, and a repeat run can differ.
Respiratory infections
A Cochrane review (2013, 29 studies, 11,306 people) found little or no difference in respiratory infections. 1 of the 3 studies read agree; 1 found an improvement, 1 found no clear answer. The evidence is moderate.
3 studies counted of 6 read: 3 reviews.
1. Meta-analysis, 2013; 29 studies, 11,306 people: no clear difference (the review the verdict rests on). pooled RR was 0.97 (95% confidence interval (CI) 0.94 to 1.00) Vitamin C for preventing and treating the common coldPubMed 23440782
2. Meta-analysis, 2022; 10 studies: improves. shorter duration of respiratory infection (SMD -0.36 Effect of Vitamin C Supplements on Respiratory Tract Infections: A Systematic Review and Meta-AnalysisPubMed 34967304
3. Meta-analysis, 2013; 6 studies, 2,532 people: unclear: evidence too weak to tell. statistically significant (80% or greater) reduction in pneumonia incidence Vitamin C for preventing and treating pneumoniaPubMed 23925826
Automated reading of the published studies (Decosa evidence engine), run 30 Sep 2026. It reads abstracts, can miss studies, and a repeat run can differ.
Skin aging
The best available review (2024, 32 studies, 1,236 people) found an improvement in skin aging. That review studied patients using cosmeceuticals for antiaging. All 4 studies read agree. The evidence is moderate.
4 studies counted of 10 read: 2 reviews and 2 trials (28 people in the trials).
1. Systematic review, 2024; 32 studies, 1,236 people; patients using cosmeceuticals for antiaging: improves (the review the verdict rests on). Retinol and vitamin C for antiaging received a Grade A Cosmeceuticals for antiaging: a systematic review of safety and efficacyPubMed 38758222
2. Systematic review, 2023; 7 studies, 139 people; patients with melasma or photodamage: improves. Efficacy of topical vitamin C in melasma and photoaging: A systematic reviewPubMed 37128827
3. Crossover trial, 2018; 18 people; patients with Bateman purpura aged over 60: improves. significant improvement on the vitamin C-treated side Bateman purpura (dermatoporosis): a localized scurvy treated by topical vitamin C - double-blind randomized placebo-controlled clinical trialPubMed 28833652
4. Crossover trial, 2002; 10 people; ten patients with photodamage: improves. decreased photoaging scores of the cheeks (P = 0.006) Double-blind, half-face study comparing topical vitamin C and vehicle for rejuvenation of photodamagePubMed 11896774
Automated reading of the published studies (Decosa evidence engine), run 30 Sep 2026. It reads abstracts, can miss studies, and a repeat run can differ.
Stress
The studies read are too weak to tell whether Vitamin C changes stress. The strongest review read studied adults exposed to different exercise protocols. The evidence is very weak.
Side effects: 2 of the 4 studies that reported on them found more with Vitamin C (increased gamma glutamyl transpeptidase activity).
2 studies counted of 11 read: 1 review and 1 trial (40 people in the trials).
1. Meta-analysis, 2026; 12 studies, 124 people; adults exposed to different exercise protocols: unclear: evidence too weak to tell (the review the verdict rests on). no significant effects of vitamin C supplementation on IL-6 Effect of vitamin C supplementation on post-exercise recovery: A systematic review and meta-analysis of randomized double-blind placebo trialsPubMed 41687812
2. Randomised trial, 2022; 40 people; critically ill patients with septic shock: no clear difference. did not affect their 8-isoprostane F2α concentrations Critically ill septic patients have elevated oxidative stress biomarkers: lack of attenuation by parenteral vitamin CPubMed 36401921
Automated reading of the published studies (Decosa evidence engine), run 30 Sep 2026. It reads abstracts, can miss studies, and a repeat run can differ.

Key findings

Blood FlowImproves (the measure goes up)
Blood glucoseImmune HealthImproves (the measure goes down)
Anti-Oxidant Enzyme ProfileBone HealthImproves (the measure goes up)

Shop the evidence-backed picks

Third-party tested Vitamin C products, in the forms the graded studies used where we can match them.

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Studies cited

100 studies from PubMed

Influence of vitamin C supplementation on oxidative and immune changes after an ultramarathonJ Appl Physiol, 1985 · PMID 11960947
Ascorbic acid supplementation improves skeletal muscle oxidative stress and insulin sensitivity in people with type 2 diabetes: Findings of a randomized controlled studyFree Radic Biol Med · PMID 26774673
Vitamin C may have similar beneficial effects to Gemfibrozil on serum high-density lipoprotein-cholesterol in type 2 diabetic patientsJ Res Pharm Pract · PMID 25328896
Supplementation of vitamin C reduces blood glucose and improves glycosylated hemoglobin in type 2 diabetes mellitus: a randomized, double-blind studyAdv Pharmacol Sci · PMID 22242019
The effect of vitamin C supplementation on diabetic hyperlipidaemia: a double blind, crossover studyDiabet Med · PMID 2952396
Unchanged renal haemodynamics following high dose ascorbic acid administration in normoalbuminuric IDDM patientsScand J Clin Lab Invest · PMID 7624737
Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: Findings of a randomized cross-over trialDiabetes Obes Metab · PMID 30394006
Effects of eicosapentaenoic acid and vitamin C on glycemic indices, blood pressure, and serum lipids in type 2 diabetic Iranian malesJ Res Med Sci · PMID 22247720
Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trialDrug Des Devel Ther · PMID 26170625
Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?Endocr Pract · PMID 23757614
Effects of atorvastatin and vitamin C on forearm hyperaemic blood flow, asymmentrical dimethylarginine levels and the inflammatory process in patients with type 2 diabetes mellitusHeart · PMID 16914485
Effect of vitamin C supplementation on postprandial oxidative stress and lipid profile in type 2 diabetic patientsPak J Biol Sci · PMID 22518934
High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistanceAm J Physiol Heart Circ Physiol · PMID 16126809
Vitamin C and the common cold: a double-blind trialCan Med Assoc J · PMID 5057006
Ascorbic acid and the common coldLancet · PMID 4113614
Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled surveyAdv Ther · PMID 12201356
Vitamin C and the common coldJ Soc Occup Med · PMID 162650
Winter illness and vitamin C: the effect of relatively low dosesCan Med Assoc J · PMID 1091343
Ascorbic acid for the common cold. A prophylactic and therapeutic trialJAMA · PMID 163386
Therapeutic effect of vitamin C. A co-twin control studyJAMA · PMID 318715
A randomized controlled trial of the therapeutic effect of vitamin C in the common coldPractitioner · PMID 319446
Vitamin C and the common cold: a second MZ Cotwin control studyActa Genet Med Gemellol · PMID 7048833
Trial of ascorbic acid in prevention of coldsBr Med J · PMID 4290259
Mega-dose vitamin C in treatment of the common cold: a randomised controlled trialMed J Aust · PMID 11700812
A controlled clinical trial of ascorbic acid for the common coldAnn N Y Acad Sci · PMID 1106302
The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infectionsJ Manipulative Physiol Ther · PMID 10543583
Vitamin C prophylaxis in marine recruitsJAMA · PMID 368370
L-Ascorbic acid and D-isoascorbic acid in a common cold surveyAm J Clin Nutr · PMID 1099894
A randomized controlled trial of vitamin C in the prevention and amelioration of the common coldBr J Prev Soc Med · PMID 788820
Evaluation of the efficacy of ascorbic acid in prophylaxis of induced rhinovirus 44 infection in manJ Infect Dis · PMID 4355208
Vitamin C as a preventive medicine against common colds in childrenScand J Infect Dis · PMID 897573
Blood ascorbic acid level in bioflavonoid and ascorbic acid therapy of common coldJ Am Med Assoc · PMID 13366735
A trial of ascorbic acid in the treatment of the common coldBr J Prev Soc Med · PMID 338079
Ineffectiveness of vitamin C in treating coryza.Practitioner · PMID 4870463
Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trialBMJ Mil Health · PMID 32139409
Influence of quercetin supplementation on disease risk factors in community-dwelling adultsJ Am Diet Assoc · PMID 21443986
Effect of vitamin C supplementation on lipid peroxidation, muscle damage and inflammation after 30-min exercise at 75% VO2maxJ Sports Med Phys Fitness · PMID 18427418
The effect of 2 weeks vitamin C supplementation on immunoendocrine responses to 2.5 h cycling exercise in manEur J Appl Physiol · PMID 16685547
Vitamin C supplementation and salivary immune function following exercise-heat stressInt J Sports Physiol Perform · PMID 19223675
Influence of vitamin C supplementation on oxidative and salivary IgA changes following an ultramarathonEur J Appl Physiol · PMID 12627313
The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common coldAm J Clin Nutr · PMID 463806
The clinical and biochemical effects of vitamin C supplementation in short-stay hospitalized geriatric patientsInt J Vitam Nutr Res · PMID 6376396
Prolonged vitamin C supplementation and recovery from eccentric exerciseEur J Appl Physiol · PMID 15024666
Effects of vitamin E and C supplementation either alone or in combination on exercise-induced lipid peroxidation in trained cyclistsJ Strength Cond Res · PMID 14666945
Influence of acute vitamin C and/or carbohydrate ingestion on hormonal, cytokine, and immune responses to prolonged exerciseInt J Sport Nutr Exerc Metab · PMID 16327030
Efficacy of antioxidant treatment in reducing resistin serum levels: a randomized studyPLoS Clin Trials · PMID 17479165
Ascorbic acid prevents vascular dysfunction induced by oral glucose load in healthy subjectsEur J Intern Med · PMID 22153532
Vitamin C supplementation lowers urinary levels of 4-hydroperoxy-2-nonenal metabolites in humansFree Radic Biol Med · PMID 21236333
High dosage of ascorbic acid and alpha-tocopherol is not useful for diminishing oxidative stress and DNA damage in healthy elderly adultsAnn Nutr Metab · PMID 18446021
Orange juice ingestion and supplemental vitamin C are equally effective at reducing plasma lipid peroxidation in healthy adult womenJ Am Coll Nutr · PMID 14684757
Effects of vitamin C supplementation on glycaemic control: a systematic review and meta-analysis of randomised controlled trialsEur J Clin Nutr · PMID 28294172
The effect of aspirin and vitamins C and E on HbA1c assaysClin Chim Acta · PMID 16698007
Megadose of vitamin C delays insulin response to a glucose challenge in normoglycemic adultsAm J Clin Nutr · PMID 7942581
The effect of vitamin E and vitamin C supplementation on LDL oxidizability and neutrophil respiratory burst in young smokersJ Am Coll Nutr · PMID 10872898
Antioxidants prevent health-promoting effects of physical exercise in humansProc Natl Acad Sci U S A · PMID 19433800
Orange juice vs vitamin C: effect on hydrogen peroxide-induced DNA damage in mononuclear blood cellsBr J Nutr · PMID 17349075
The effects of vitamin C supplementation on blood and hair levels of cadmium, lead, and mercuryAnn N Y Acad Sci · PMID 3476002
Vitamin C treatment reduces elevated C-reactive proteinFree Radic Biol Med · PMID 18952164
Effect of antioxidant supplementation on insulin sensitivity in response to endurance exercise trainingAm J Physiol Endocrinol Metab · PMID 21325105
Effect of high dose vitamin C supplementation on muscle soreness, damage, function, and oxidative stress to eccentric exerciseInt J Sport Nutr Exerc Metab · PMID 16948483
No effect of antioxidant supplementation on muscle performance and blood redox status adaptations to eccentric trainingAm J Clin Nutr · PMID 21508092
Vitamin C consumption does not impair training-induced improvements in exercise performanceInt J Sports Physiol Perform · PMID 21487150
Effects of Applephenon and ascorbic acid on physical fatigueNutrition · PMID 17483009
The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trialEur J Pediatr · PMID 20689965
Vitamin C and acute illness in Navajo school childrenN Engl J Med · PMID 787788
Vitamin C supplementation reduces the incidence of postrace symptoms of upper-respiratory-tract infection in ultramarathon runnersAm J Clin Nutr · PMID 8185726
Megadosage of ascorbic acid in an Antarctic expeditionBr J Nutr · PMID 870023
Effect of ascorbic acid on surgical stress response in gynecologic surgeryInt J Clin Pract · PMID 15587771
Vitamin C restores blood pressure and vasodilator response during mental stress in obese childrenArq Bras Cardiol · PMID 21552645
Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trialDiabetologia · PMID 18769906
Does vitamin C supplementation influence the levels of circulating oxidized LDL, sICAM-1, sVCAM-1 and vWF-antigen in healthy male smokersEur J Clin Nutr · PMID 15127090
Pretreatment with intravenous ascorbic acid preserves endothelial function during acute hyperglycaemia (R1)Clin Exp Pharmacol Physiol · PMID 15854139
Oral administration of ascorbic acid attenuates endothelial dysfunction after short-term cigarette smokingInt J Vitam Nutr Res · PMID 14743545
FFA-induced endothelial dysfunction can be corrected by vitamin CJ Clin Endocrinol Metab · PMID 12050273
Vitamin C and E supplementation does not reduce the risk of superimposed PE in pregnancyHypertens Pregnancy · PMID 21174586
Effect of ascorbic acid on inflammatory markers after cardiothoracic surgeryAm J Health Syst Pharm · PMID 21856809
Supplementation of ascorbic acid and alpha-tocopherol is useful to preventing bone loss linked to oxidative stress in elderlyJ Nutr Health Aging · PMID 20617290
Effect of antioxidants combined to resistance training on BMD in elderly women: a pilot studyOsteoporos Int · PMID 19020919
Quercetin with vitamin C and niacin does not affect body mass or compositionAppl Physiol Nutr Metab · PMID 21574787
Efficacy of vitamin C vaginal tablets in the treatment of bacterial vaginosis: a randomised, double blind, placebo controlled clinical trialArzneimittelforschung · PMID 21650086
Influence of vitamin C on markers of oxidative stress in the earliest period of ischemic strokePharmacol Rep · PMID 20885017
Vitamin C prophylaxis in a boarding schoolN Engl J Med · PMID 4586102
Vitamin C status and perception of effort during exercise in obese adults adhering to a calorie-reduced dietNutrition · PMID 22677357
High-dose ascorbic acid increases intercourse frequency and improves mood: a randomized controlled clinical trialBiol Psychiatry · PMID 12208645
Age-related cataract in a randomized trial of vitamins E and C in menArch Ophthalmol · PMID 21060040
Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjectsBr J Nutr · PMID 14748940
Ascorbic acid in Charcot-Marie-Tooth disease type 1A (CMT-TRIAAL and CMT-TRAUK): a double-blind randomised trialLancet Neurol · PMID 21393063
The effects of vitamin C supplementation on serum concentrations of uric acid: results of a randomized controlled trialArthritis Rheum · PMID 15934094
Association between Oral vitamin C supplementation and serum uric acid: A meta-analysis of randomized controlled trialsComplement Ther Med · PMID 34280483
Oral vitamin C supplementation decreased low-density lipoprotein in adults on hemodialysis: A systematic review and meta-analysis.Nutr Res · PMID 40532258
Safety and effectiveness of high-dose vitamin C in patients with COVID-19: a randomized open-label clinical trialEur J Med Res · PMID 33573699
Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical TrialJAMA Netw Open · PMID 33576820
Vitamin C provision improves mood in acutely hospitalized patientsNutrition · PMID 20688474
Clinical relevance of vitamin C among lead-exposed infertile menGenet Test Mol Biomarkers · PMID 22731648
Ascorbate improves circulation in postural tachycardia syndromeAm J Physiol Heart Circ Physiol · PMID 21622825
The clinical effects of vitamin C supplementation in elderly hospitalised patients with acute respiratory infectionsInt J Vitam Nutr Res · PMID 7814237
Vitamin C and E supplementation to prevent spontaneous preterm birth: a randomized controlled trialObstet Gynecol · PMID 20733448
High dose ascorbic acid does not reverse central sympathetic overactivity in chronic heart failureJ Clin Pharm Ther · PMID 21916906
Effects of vitamin C supplementation on gout risk: results from the physicians' health study II trialAm J Clin Nutr · PMID 35575611
Efficacy and safety of vitamin C supplementation in the treatment of community-acquired pneumonia: a systematic review and meta-analysis with trial sequential analysis.Sci Rep · PMID 38783029

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