Condition
Flu
Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs, bringing fever, body aches, and deep tiredness. People most often look at vitamin D and elderberry, and a meta-analysis of elderberry examined upper respiratory symptoms, while two small analyses found asthma symptoms improved with vitamin D. Still, the vitamin D evidence is limited and neither result tested flu itself, so the picture remains unsettled.
Sources: PMID 30670267; PMID 39421966; PMID 41204244
- Supplements studied
- 3
- Graded outcomes
- 1
- Trials
- 7
- People studied
- 1,916
Evidence by supplement
- Strong
- Moderate
- Limited
- Very limited
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Asthma Symptoms Small Improvement | Improves (the measure goes down) | Small effect | 2 studies | 334 people | ||
Studies that measured asthma symptoms | ||||||
| Upper Respiratory Tract Infection Symptoms | Improves (the measure goes down) | 13 studies | 332 people | |||
Studies that measured upper respiratory tract infection symptoms
| ||||||
| Influenza Risk | Changes; see studies | 2 studies | 1,482 people | |||
Studies that measured influenza risk | ||||||
| Fever | Improves (the measure goes up) | 1 study | 334 people | |||
Studies that measured fever | ||||||
| Pneumonia Symptoms | Improves (the measure goes down) | 1 study | 334 people | |||
Studies that measured pneumonia symptoms | ||||||
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Upper Respiratory Tract Infection Symptoms | Improves (the measure goes down) | 3 studies | 87 people | |||
Studies that measured upper respiratory tract infection symptoms
| ||||||
| Grade | Outcome | Effect | Size | Studies | People | Studies list |
|---|---|---|---|---|---|---|
| Vaccine Augmentation | Improves (the measure goes up) | 1 study | 227 people | |||
Key findings
- Asthma SymptomsImproves (the measure goes down)
The Influenza (Flu) Prevention and Supportive Care protocol
2 primary supplements · 7 supporting supplements
- Vitamin D2,000–4,000 IU daily for prevention (target 40–60 ng/mL)
- Elderberry175–600 mg elderberry extract daily; higher dose (up to 1,200 mg) during acute illness
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Studies cited
100 studies from PubMed
- Effect of vitamin D supplementation for major adverse cardiovascular events: a meta-analysis based on randomised controlled trials.
- Optimal Vitamin D Status: Evidence and Guidelines
- Vitamin D and Cancer Prevention: A Comprehensive Review
- Effects of Vitamin D Supplementation on Musculoskeletal Health: A Systematic Review and Meta-Analysis
- Vitamin D and Prevention of Respiratory Tract Infections: A Systematic Review and Meta-Analysis
- Effects of Vitamin D Supplementation on Depression: A Systematic Review and Meta-Analysis
- Vitamin D and Immune Function: A Review
- Vitamin D Supplementation for Prevention of Mortality: A Meta-Analysis
- Vitamin D Supplementation During Pregnancy: Safety and Efficacy Review
- Vitamin D Supplementation: A Comprehensive Review of Efficacy for Various Health Outcomes
- Vitamin D Deficiency: Global Health Perspective
- Vitamin D and Cardiovascular Disease: A Review of Evidence
- Vitamin D and Bone Health in Adults: A Systematic Review
- Vitamin D3 supplementation does not modify cardiovascular risk profile of adults with inadequate vitamin D status
- Association of A1C levels with vitamin D status in U.S. adults: data from the National Health and Nutrition Examination Survey
- Serum 25-hydroxyvitamin D, ethnicity, and blood pressure in the Third National Health and Nutrition Examination Survey
- One-Week Elderberry Juice Treatment Increases Carbohydrate Oxidation after a Meal Tolerance Test and Is Well Tolerated in Adults: A Randomized Controlled Pilot Study.
- Effects of elderberry juice on fasting and postprandial serum lipids and low-density lipoprotein oxidation in healthy volunteers: a randomized, double-blind, placebo-controlled study.
- Elderberry Extract Outpatient Influenza Treatment for Emergency Room Patients Ages 5 and Above: a Randomized, Double-Blind, Placebo-Controlled Trial.
- A randomized, placebo-controlled clinical trial evaluating of a mouthwash containing Sambucus williamsii var. coreana extract for prevention of gingivitits.
- A Comparison of the Effect of Topical Preparation of L. and Hydrocortisone on Hand Eczema: A Double-Blind Randomized Controlled Trial.
- Cardiovascular disease risk biomarkers and liver and kidney function are not altered in postmenopausal women after ingesting an elderberry extract rich in anthocyanins for 12 weeks.
- Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review.
- Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials.
- Modulation of cognition and mood following administration of single doses of Ginkgo biloba, ginseng, and a ginkgo/ginseng combination to healthy young adults
- Acute, dose-dependent cognitive effects of Ginkgo biloba, Panax ginseng and their combination in healthy young volunteers: differential interactions with cognitive demand
- No ergogenic effect of ginseng ingestion
- No ergogenic effects of ginseng (Panax ginseng C.A. Meyer) during graded maximal aerobic exercise
- Ginseng supplementation does not enhance healthy young adults' peak aerobic exercise performance
- Effects of ginseng supplementation on supramaximal exercise performance and short-term recovery
- Panax ginseng Supplementation Increases Muscle Recruitment, Attenuates Perceived Effort, and Accelerates Muscle Force Recovery After an Eccentric-Based Exercise in Athletes
- Effects of ginseng on secretory IgA, performance, and recovery from interval exercise
- Effects of Panax ginseng, consumed with and without glucose, on blood glucose levels and cognitive performance during sustained 'mentally demanding' tasks
- Improvement of cognitive deficit in Alzheimer's disease patients by long term treatment with korean red ginseng
- Effects of Korean Red Ginseng on Cognitive and Motor Function: A Double-blind, Randomized, Placebo-controlled Trial
- Panax ginseng (G115) improves aspects of working memory performance and subjective ratings of calmness in healthy young adults
- Single doses of Panax ginseng (G115) reduce blood glucose levels and improve cognitive performance during sustained mental activity
- Panax ginseng enhances cognitive performance in Alzheimer disease
- Effects of Korean red ginseng on human gray matter volume and cognitive function: A voxel-based morphometry study
- Ginseng and Ginkgo Biloba Effects on Cognition as Modulated by Cardiovascular Reactivity: A Randomised Trial
- A double-blind, placebo-controlled clinical study on the effect of a standardized ginseng extract on psychomotor performance in healthy volunteers
- An open-label trial of Korean red ginseng as an adjuvant treatment for cognitive impairment in patients with Alzheimer's disease
- Improved cognitive performance in human volunteers following administration of guarana (Paullinia cupana) extract: comparison and interaction with Panax ginseng
- Efficacy of Panax ginseng Meyer Herbal Preparation HRG80 in Preventing and Mitigating Stress-Induced Failure of Cognitive Functions in Healthy Subjects: A Pilot, Randomized, Double-Blind, Placebo-Controlled Crossover Trial
- Anti-inflammatory and antifatigue effect of Korean Red Ginseng in patients with nonalcoholic fatty liver disease
- Effects of Korean Red Ginseng on Cardiovascular Risks in Subjects with Metabolic Syndrome: a Double-blind Randomized Controlled Study
- A double-blind crossover study evaluating the efficacy of korean red ginseng in patients with erectile dysfunction: a preliminary report
- Clinical efficacy of Korean red ginseng for erectile dysfunction
- Study of the efficacy of Korean Red Ginseng in the treatment of erectile dysfunction
- Effects of Panax ginseng on hyperglycemia, hypertension, and hyperlipidemia: A systematic review and meta-analysis.
- Panax ginseng has no effect on indices of glucose regulation following acute or chronic ingestion in healthy volunteers
- Antioxidant effects of Panax ginseng C.A. Meyer in healthy subjects: a randomized, placebo-controlled clinical trial
- Beneficial effects of Korean red ginseng on lymphocyte DNA damage, antioxidant enzyme activity, and LDL oxidation in healthy participants: a randomized, double-blind, placebo-controlled trial
- Effects of Panax ginseng supplementation on muscle damage and inflammation after uphill treadmill running in humans
- Korean red ginseng (Panax ginseng C.A. Meyer) root fractions: differential effects on postprandial glycemia in healthy individuals
- Ginseng and ginsenoside Re do not improve β-cell function or insulin sensitivity in overweight and obese subjects with impaired glucose tolerance or diabetes
- Ginseng therapy in non-insulin-dependent diabetic patients
- Red ginseng for type 2 diabetes mellitus: a systematic review of randomized controlled trials.
- Effects of red ginseng supplementation on menopausal symptoms and cardiovascular risk factors in postmenopausal women: a double-blind randomized controlled trial
- Effects of a standardized ginseng extract on quality of life and physiological parameters in symptomatic postmenopausal women: a double-blind, placebo-controlled trial. Swedish Alternative Medicine Group
- Effects of Korean red ginseng on sexual arousal in menopausal women: placebo-controlled, double-blind crossover clinical study
- Ginseng treatment improves psychomotor performance at rest and during graded exercise in young athletes
- Six weeks of Jilin ginseng root supplementation attenuates drop jump-related muscle injury markers in healthy female college students
- Effect of Korean red ginseng on arterial stiffness in subjects with hypertension
- Heat-processed ginseng enhances the cognitive function in patients with moderately severe Alzheimer's disease
- Preventive effect of ginseng intake against various human cancers: a case-control study on 1987 pairs
- Non-organ-specific preventive effect of long-term administration of Korean red ginseng extract on incidence of human cancers
- Effects of tissue-cultured mountain ginseng (Panax ginseng CA Meyer) extract on male patients with erectile dysfunction
- Effects of acute supplementation of Panax ginseng on endurance running in a hot & humid environment
- Effects of Panax Ginseng C.A. Meyer saponins on male fertility
- Effects of Korean red ginseng extract on behavior in children with symptoms of inattention and hyperactivity/impulsivity: a double-blind randomized placebo-controlled trial
- Effects of Korean red ginseng (Panax ginseng C.A. Mayer) and its isolated ginsenosides and polysaccharides on arterial stiffness in healthy individuals
- Red ginseng extract improves coronary flow reserve and increases absolute numbers of various circulating angiogenic cells in patients with first ST-segment elevation acute myocardial infarction
- Efficacy and safety of the standardised Ginseng extract G115 for potentiating vaccination against the influenza syndrome and protection against the common cold corrected
- Efficacy of Korean red ginseng (Panax ginseng) for middle-aged and moderate level of chronic fatigue patients: A randomized, double-blind, placebo-controlled trial
- HT1001, a proprietary North American ginseng extract, improves working memory in schizophrenia: a double-blind, placebo-controlled study
- Ginseng does not enhance psychological well-being in healthy, young adults: results of a double-blind, placebo-controlled, randomized clinical trial
- Effects of Panax ginseng on quality of life
- Ginseng in the treatment of fatigue in multiple sclerosis: a randomized, placebo-controlled, double-blind pilot study
- Fermented ginseng improves the first-night effect in humans
- Cognition enhancing effect of panax ginseng in Korean volunteers with mild cognitive impairment: a randomized, double-blind, placebo-controlled clinical trial
- Anti-Fatigue Effects of Enzyme-Modified Ginseng Extract: A Randomized, Double-Blind, Placebo-Controlled Trial
- Safety and antifatigue effect of Korean Red Ginseng: a randomized, double-blind, and placebo-controlled clinical trial
- Effects of selected dietary supplements on migraine prophylaxis: A systematic review and dose-response meta-analysis of randomized controlled trials.
- Safety, tolerability, and efficacy of orally administered cannabinoids in MS
- Smoked cannabis for spasticity in multiple sclerosis: a randomized, placebo-controlled trial
- The effect of cannabis on tremor in patients with multiple sclerosis
- Supplementation with vitamin D or ω-3 fatty acids in adolescent girls and young women with endometriosis (SAGE): a double-blind, randomized, placebo-controlled trial
- Double-blind randomised placebo-controlled trial of bolus-dose vitamin D3 supplementation in adults with asthma (ViDiAs)
- Vitamin D Supplementation and the Risk of Colds in Patients with Asthma
- Association between prenatal vitamin D supplementation and respiratory diseases in children: a systematic review and meta-analysis.
- Vitamin D supplementation decrease asthma exacerbations in children: a systematic review and meta-analysis of randomized controlled trials.
- The effects of prenatal vitamin D supplementation on respiratory and allergy-related outcomes in children: A systematic review and meta-analysis of randomized controlled trials.
- Effects of Vitamin D on Endometriosis-Related Pain: A Double-Blind Clinical Trial
- The effect of vitamin D supplementation on clinical symptoms and metabolic profiles in patients with endometriosis
- Vitamin D for primary dysmenorrhea and endometriosis-related pain - A systematic review of registered RCTs.
- High-Dose Monthly Vitamin D for Prevention of Acute Respiratory Infection in Older Long-Term Care Residents: A Randomized Clinical Trial
- Randomized trial of vitamin D supplementation and risk of acute respiratory infection in Mongolia
- Reduced primary care respiratory infection visits following pregnancy and infancy vitamin D supplementation: a randomised controlled trial
- Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis