Evidence-graded supplement guide
Find a supplement for your goal. See the evidence first.
Choose what you want help with. We show the supplements with the strongest research, what the studies found in plain words, and where to buy them.
From the evidence ledger
- Vitamin D · Healthy aging
Consistent research shows a moderate benefit for lowering fall risk in older adults.
Grade A (strong) · 3 studies · 2,426 people - Peppermint · Gut comfort
Consistent research shows a moderate benefit for IBS symptoms.
Grade A (strong) · 7 studies · 392 people - Roselle · Heart health
Consistent research shows a moderate benefit for blood pressure.
Grade A (strong) · 5 studies · 291 people
From 4,914 graded outcomes and 10,895 citations. How we grade
Top picks by goal
The best-evidenced options, in plain language
We may earn a commission. Buy links to Fullscript, iHerb or Thorne carry our referral, at no extra cost to you. Grades come from the research and never change based on what we earn. Disclosures
Sleep · Falling asleep and staying asleep
All 23 supplements studied for Sleep HealthGrade A · Strong evidence
Melatonin
May help you fall asleep faster
What the evidence says: Consistent research shows a large benefit for insomnia symptoms.
A study behind this grade: The effect of prolonged-release melatonin on sleep measures and psychomotor performance in elderly patients with insomnia · Int Clin PsychopharmacolAll research on Melatonin
iHerb pickNature Made Melatonin, 90 Tablets
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Grade C · Limited evidence
Valerian
A traditional sleep herb with modest evidence
What the evidence says: Early, limited research hints at a small benefit for insomnia symptoms.
A study behind this grade: Effect of valerian on sleep quality in postmenopausal women: a randomized placebo-controlled clinical trial · MenopauseAll research on Valerian
Not stocked by our partners yetRead the research before you shop.
Read the research
Stress & calm · Everyday stress and a calmer mood
All 25 supplements studied for StressGrade B · Moderate evidence
Ashwagandha
May help take the edge off everyday stress
What the evidence says: Several studies suggest a moderate benefit for feelings of stress and anxiety.
A study behind this grade: A double-blind, placebo-controlled evaluation of the anxiolytic efficacy ff an ethanolic extract of withania somnifera · Indian J PsychiatryAll research on Ashwagandha
Thorne pickThorne Ashwagandha
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Grade B · Moderate evidence
Lavender
May support a calmer mood
What the evidence says: Several studies suggest a moderate benefit for feelings of anxiety.
A study behind this grade: How Strong is the Evidence for the Anxiolytic Efficacy of Lavender?: Systematic Review and Meta-analysis of Randomized Controlled Trials. · Asian Nurs ResAll research on Lavender
iHerb pickLife Extension Anxiety Soother™, Lavender, 1 fl oz (30 ml)
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Grade B · Moderate evidence
Lemon Balm
May support relaxation
What the evidence says: Several studies suggest a large benefit for feelings of anxiety.
A study behind this grade: Effects of lozenge containing lavender oil, extracts from hops, lemon balm and oat on electrical brain activity of volunteers · Eur J Med ResAll research on Lemon Balm
iHerb pickNOW Foods Lemon Balm Extract, 250 mg, 2 fl oz (60 ml)
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Focus & memory · Attention, memory and mental energy
All 55 supplements studied for Cognitive ImprovementGrade B · Moderate evidence
Bacopa Monnieri
May support memory with daily use over several weeks
What the evidence says: Several studies suggest a small benefit for memory.
A study behind this grade: Does Bacopa monnieri improve memory performance in older persons? Results of a randomized, placebo-controlled, double-blind trial · J Altern Complement MedAll research on Bacopa Monnieri
iHerb pickLife Extension Bacopa , 320 mg, 60 Veggie Caps
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Grade B · Moderate evidence
Panax Ginseng (Korean Ginseng)
May support attention
What the evidence says: Several studies suggest a small benefit for attention.
A study behind this grade: 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 · PharmaceuticalsAll research on Panax Ginseng (Korean Ginseng)
iHerb pickNature Made Korean Ginseng, 75 Quick Release Capsules (500 mg per ...
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Grade B · Moderate evidence
Rhodiola Rosea
May support focus when you are tired
What the evidence says: Several studies suggest a small benefit for attention.
Thorne pickThorne Rhodiola
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Joint comfort · Stiff, achy joints and mobility
All 32 supplements studied for Osteoarthritis (OA)Grade B · Moderate evidence
Pycnogenol
May support joint comfort
What the evidence says: Several studies suggest a moderate benefit for joint symptoms in people with osteoarthritis.
A study behind this grade: Treatment of osteoarthritis with Pycnogenol. The SVOS (San Valentino Osteo-arthrosis Study). Evaluation of signs, symptoms, physical performance and vascular aspects · Phytother ResAll research on Pycnogenol
iHerb pickLife Extension Pycnogenol, French Maritime Pine Bark Extract, 100 mg ...
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Grade B · Moderate evidence
Glucosamine
The classic joint supplement; effects are modest
What the evidence says: Several studies suggest a small benefit for joint symptoms in people with osteoarthritis.
A study behind this grade: Glucosamine therapy for treating osteoarthritis · Cochrane Database Syst RevAll research on Glucosamine
Not stocked by our partners yetRead the research before you shop.
Read the researchGrade B · Moderate evidence
Chondroitin
May support joint comfort
What the evidence says: Several studies suggest a small benefit for joint pain in people with osteoarthritis.
A study behind this grade: Efficacy of Chondroitin Sulfate in Patients with Knee Osteoarthritis: A Comprehensive Meta-Analysis Exploring Inconsistencies in Randomized, Placebo-Controlled Trials. · Adv TherAll research on Chondroitin
Not stocked by our partners yetRead the research before you shop.
Read the research
Heart health · Blood pressure and circulation
All 68 supplements studied for High Blood PressureGrade A · Strong evidence
Roselle
May support healthy blood pressure
What the evidence says: Consistent research shows a moderate benefit for blood pressure.
A study behind this grade: The effects of sour tea (Hibiscus sabdariffa) on hypertension in patients with type II diabetes · J Hum HypertensAll research on Roselle
iHerb pickNutricost Vital Extracts, Hibiscus, 60 VegCaps
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Grade B · Moderate evidence
Magnesium
May support healthy blood pressure
What the evidence says: Several studies suggest a moderate benefit for blood pressure.
A study behind this grade: Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. · HypertensionAll research on Magnesium
iHerb pickNature Made Magnesium, 250 mg, 100 Tablets
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Grade B · Moderate evidence
Nitrate
May support healthy blood flow
What the evidence says: Several studies suggest a small benefit for blood pressure.
A study behind this grade: Effect of inorganic nitrate supplementation on blood pressure in older adults: A systematic review and meta-analysis · Nitric OxideAll research on Nitrate
Not stocked by our partners yetRead the research before you shop.
Read the research
Gut comfort · Digestion, nausea and regularity
All 16 supplements studied for Digestive HealthGrade A · Strong evidence
Peppermint
May ease occasional digestive discomfort
What the evidence says: Consistent research shows a moderate benefit for IBS symptoms.
A study behind this grade: The effect of enteric-coated, delayed-release peppermint oil on irritable bowel syndrome · Dig Dis SciAll research on Peppermint
iHerb pickNutricost Peppermint Oil, 50 mg, 240 Softgels
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Grade A · Strong evidence
Ginger (Zingiber officinale)
May ease occasional nausea
What the evidence says: Consistent research shows a moderate benefit for nausea.
A study behind this grade: Ginger syrup as an antiemetic in early pregnancy · Altern Ther Health MedAll research on Ginger (Zingiber officinale)
iHerb pickNutricost Ginger Root Extract, 250 mg, 90 Veg Capsules
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Grade B · Moderate evidence
Probiotics
May support digestive regularity
What the evidence says: Several studies suggest a moderate benefit for diarrhea.
A study behind this grade: Oral probiotic supplementation to alleviate diarrhea induced by fluoropyrimidines or irinotecan-based chemotherapy: A systematic review and meta-analysis. · Complement Ther MedAll research on Probiotics
Thorne pickThorne Women's Daily Probiotic
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Immune support · Colds, flu season and resilience
All 55 supplements studied for Immune HealthGrade B · Moderate evidence
Zinc
May support normal immune function
What the evidence says: Several studies suggest a small benefit for cold symptoms.
iHerb pickNature Made Zinc, 30 mg, 100 Tablets
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Grade B · Moderate evidence
Vitamin D
May support immune health, especially if your levels are low
What the evidence says: Several studies suggest a small benefit for lowering flu risk.
A study behind this grade: Vitamin D supplementation did not prevent influenza-like illness as diagnosed retrospectively by questionnaires in subjects participating in randomized clinical trials · Scand J Infect DisAll research on Vitamin D
iHerb pickNature Made Vitamin D3, 25 mcg (1000 IU), 100 Softgels
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Grade B · Moderate evidence
Elderberry
May support recovery from seasonal colds
What the evidence says: Several studies suggest a small benefit for cold and flu symptoms.
A study behind this grade: Elderberry Extract Outpatient Influenza Treatment for Emergency Room Patients Ages 5 and Above: a Randomized, Double-Blind, Placebo-Controlled Trial. · J Gen Intern MedAll research on Elderberry
Not stocked by our partners yetRead the research before you shop.
Read the research
Training · Strength, power and endurance
All 45 supplements studied for Muscle Size & StrengthGrade B · Moderate evidence
Creatine
May support strength and power training
What the evidence says: Several studies suggest a small benefit for high-intensity exercise capacity.
A study behind this grade: Short-term creatine supplementation does not improve muscle activation or sprint performance in humans · Eur J Appl PhysiolAll research on Creatine
Thorne pickThorne Creatine - 90 Servings
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Grade B · Moderate evidence
Beta-Alanine
May support high-intensity performance
What the evidence says: Several studies suggest a small benefit for high-intensity exercise capacity.
A study behind this grade: The effect of beta-alanine supplementation on power performance during repeated sprint activity · J Strength Cond ResAll research on Beta-Alanine
Thorne pickThorne Beta Alanine-SR
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Healthy aging · Bones, muscle and longevity
All 4 supplements studied for Aging & LongevityGrade A · Strong evidence
Vitamin D
May support bone and muscle health with age
What the evidence says: Consistent research shows a moderate benefit for lowering fall risk in older adults.
A study behind this grade: Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials · BMJAll research on Vitamin D
iHerb pickNature Made Vitamin D3, 25 mcg (1000 IU), 100 Softgels
Buy on iHerbOur referral is applied: no code needed, same price for you.
Grade B · Moderate evidence
Vitamin K
May support bone health
What the evidence says: Several studies suggest a moderate benefit for bone density.
A study behind this grade: Effect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trials · J Bone Miner MetabAll research on Vitamin K
iHerb pickNature Made Vitamin K2, 100 mcg, 30 Softgels
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Not medical advice. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant, nursing or take medication.
How we grade
A grade belongs to an outcome, not a supplement
- Strong evidence
Multiple good-quality studies agree.
- Moderate evidence
Supporting studies, with open questions.
- Limited evidence
Early or small studies; treat as a hint.
- Very limited evidence
Very preliminary; not a conclusion.
- Research first. Picks are chosen from study outcomes, and supplements we cannot link to still appear.
- Sources one click away. Every pick links to a study behind its grade and to the full research page.
- No paid placement, no reviews. Retailers cannot buy a spot or a grade, and we do not publish testimonials.
Best evidence
Strongest results on this page
- Vitamin DHealthy aging · Fall Risk · 3 studies · 2,426 peopleiHerb
- PeppermintGut comfort · Irritable Bowel Syndrome Symptoms · 7 studies · 392 peopleiHerb
- RoselleHeart health · Blood Pressure · 5 studies · 291 peopleiHerb
- Ginger (Zingiber officinale)Gut comfort · Nausea Symptoms · 9 studies · 268 peopleiHerb
- MelatoninSleep · Insomnia Signs and Symptoms · 5 studies · 259 peopleiHerb
- Vitamin KHealthy aging · Bone Mineral Density · 18 studies · 4,800 peopleiHerb
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Most researched
Popular supplements, by amount of research
- L-Carnitine558 outcomes
- Curcumin502 outcomes
- Fish Oil448 outcomes
- Creatine433 outcomes
- Saffron390 outcomes
- Ashwagandha318 outcomes
- Resveratrol318 outcomes
- Vitamin D308 outcomes
- Spirulina304 outcomes
- Chromium300 outcomes
Browse everything: Supplements · Conditions · Protocols · Peptides · All Grade A evidence
Still deciding?
Search the evidence
Ask about a supplement or a goal: we show what the studies in our database found, with the grade behind each record and a link to its page. Keep it general; do not share personal health details.
How do you pick the supplements shown for each goal?
We start from the outcome you care about (for example insomnia symptoms or blood pressure) and show supplements whose studies reported a benefit for that outcome, ranked by evidence grade. Every number on the card comes from our research database, and each card links to a study and to the full research page.
What do the A–D evidence grades mean?
A means strong, consistent evidence from multiple good-quality studies; B moderate; C limited; D very limited. A grade describes the research for one specific outcome, not the supplement as a whole, and it is not a safety rating or a guarantee that it will work for you.
Do you earn money from the buy links?
Yes. Buy links to iHerb, Thorne and Fullscript carry our referral, so we may earn a commission if you purchase. You pay the retailer’s normal price. Commissions never change a grade or which supplements appear for a goal; products we cannot link to are still shown.
Is this medical advice?
No. Dr. Grey AI is an educational research guide. Supplements can interact with medications and are not right for everyone. Talk to your doctor or pharmacist before starting one, especially if you are pregnant, nursing, taking medication or managing a health condition.
Do you publish customer reviews or testimonials?
No. We do not publish reviews or testimonials. We summarize published research and link to the studies so you can check them yourself.