Knowledge Base / Supplements
Supplements A to Z
What each supplement is used for, what the research shows, and who should avoid it.
A practical guide to 30 popular supplements, from 5-HTP to taurine. See the doses used in human studies, an honest rating of the evidence, common forms and the safety points that matter, then read our full guide for each one. Several of these change how prescription medicines work, so check the safety line before you start.
Quick reference
Compare the main use, studied dose and strength of evidence for every supplement at a glance.
| Supplement | Main use | Studied dose | Evidence | Forms |
|---|---|---|---|---|
| 5-HTP | Sleep quality and mood | 100 mg daily, as in the 2024 sleep trial | Limited | Vegan capsules (sourced from Griffonia simplicifolia seeds) |
| Activated Charcoal | Occasional gas; hospital poisoning care | No standard dose established; clinical poisoning use was 50 g | Limited | Capsules, toothpaste, face masks |
| Alpha-Lipoic Acid | Nerve comfort and blood sugar support | 300–600 mg daily; nerve trials used 600–1,800 mg, split doses | Moderate | Capsules (racemic ALA or R-ALA) |
| BCAAs | Muscle soreness after training | No standard dose established; trials ranged 1.5–82 g daily | Limited | Capsules, usually in a 2:1:1 ratio |
| Beet Root | Blood pressure and exercise efficiency | About 300–600 mg nitrate daily; 2–3 hours before exercise | Moderate | Capsules, powder, juice, shots |
| Betaine HCl | Adding stomach acid at meals | No standard dose established; usually 1 capsule with a protein meal | Very limited | Capsules, often combined with pepsin |
| Chlorella | Cholesterol and blood pressure markers | 1–5 g daily; effects mainly above 4 g | Moderate | Powder, tablets, capsules |
| Collagen | Skin elasticity, hair, nails, joints | 10–20 g daily; skin trials used 2.5–10 g | Moderate | Unflavored powder from bovine, marine or chicken sources |
| CoQ10 | Heart function, migraine, statin users | 100–300 mg daily with a fat-containing meal | Moderate | Softgels (ubiquinone or ubiquinol), tablets |
| Creatine | Strength, power and lean mass | 3–5 g daily; optional 20 g/day loading for 5–7 days | Strong | Powder, capsules, gummies |
| D-Mannose | Recurrent UTI support, mixed evidence | 2 g daily, in the evening or as 1 g twice | Limited | Powder, capsules |
| Diatomaceous Earth | Silica source, digestive bulking agent | One small trial used 250 mg three times daily; no standard dose established | Very limited | Powder |
| Fish Oil and Omega-3 | Lowering triglycerides | Depends on the goal; triglyceride treatment uses about 4 g EPA plus DHA daily under medical care | Strong | Fish oil softgels, krill oil, algae oil, flaxseed (ALA), omega 3-6-9 blends |
| Glucosamine | Knee osteoarthritis pain, sulfate form | 1500 mg daily (sulfate form), judged after 8–12 weeks | Moderate | Glucosamine sulfate or HCL capsules; combinations with chondroitin and MSM |
| Hyaluronic Acid | Skin hydration and fine wrinkles | 120–240 mg daily for 8–12 weeks (skin studies) | Moderate | Capsules, serums, eye drops, injections |
| Inositol | PCOS insulin and ovulation markers | 4 g/day myo- and D-chiro-inositol 40:1, split 2 g twice | Moderate | Myo-inositol, D-chiro-inositol, IP6; capsules, powder |
| L-Carnitine | Modest weight-loss support | No standard dose established | Moderate | Capsules, liquid |
| L-Leucine | Muscle protein synthesis signal | 2.5–3 g per meal; long trials used 7.5 g daily | Limited | Capsules; also supplied by protein foods such as whey |
| L-Lysine | Cold sores, weak evidence | 1,000–3,000 mg daily in trials; provisional ceiling 6,000 mg/day | Limited | Capsules (L-lysine hydrochloride) |
| L-Theanine | Acute stress and calm focus | 200 mg once or twice daily; 200–400 mg before bed | Moderate | Capsules, tablets, gummies; also green tea |
| Melatonin | Sleep timing and jet lag | 0.5–3 mg, 30–60 minutes before bedtime | Strong | Tablets (immediate and extended release), capsules, sublingual liquid, gummies |
| Modified Citrus Pectin | Galectin-3 binding, heavy metal excretion | 5 g daily maintenance; up to 15 g daily in studies | Limited | Powder, capsules |
| NAC (N-Acetyl Cysteine) | Glutathione precursor, mucus thinning | 600–1200 mg daily, often split into 2 doses | Moderate | Capsules, tablets, effervescent powders |
| Nattokinase | Clotting markers, blood pressure research | 2000 FU (100 mg enzyme), the amount used in trials | Limited | Capsules; also eaten as natto (not standardized in FU) |
| Probiotics | Gut balance, antibiotic-associated diarrhea | 10–50 billion CFU daily; up to 100 billion for some uses | Moderate | Enteric-coated capsules, gummies, fermented foods |
| Protein | Muscle building with resistance training | Total 1.2–1.6 g per kg daily if active; RDA 0.8 g/kg | Strong | Whey concentrate powder, plant protein powder, whole foods |
| Pumpkin Seed | Prostate-related urinary symptoms | 10 g of seed daily, taken as 5 g twice daily | Limited | Ground seed capsules, oil softgels, ethanol extract, whole seeds (pepitas) |
| Quercetin | Allergy, inflammation, blood pressure markers | 500–1000 mg daily, often with bromelain | Moderate | Capsules, quercetin-bromelain combinations, phytosome form |
| Red Yeast Rice | LDL cholesterol reduction | No standard dose established; labels rarely state monacolin K content | Moderate | Capsules, tablets |
| Taurine | Blood pressure and cardiometabolic markers | 1.5–3 g daily in trials; 3 g/day observed safe level | Moderate | Capsules, powder |
Evidence ratings: Strong = consistent meta-analyses of many good trials for a specific use; Moderate = several human randomized trials or a meta-analysis; Limited = a few small human trials; Very limited = mostly lab, animal or traditional use. Studied doses are the amounts used in human trials described in our guides; the amount on a product label can be higher or lower.
Supplements are not a substitute for diagnosis or prescribed treatment. If you take prescription medicine, are pregnant or breastfeeding, or have surgery planned, check with your doctor or pharmacist first.
Explore the supplements
What it is used for, the dose used in studies, how strong the evidence is, and who should avoid it.
5-HTP
Serotonin precursor · Limited evidence
Taken for mood, sleep and appetite; the clearest recent trial looked at sleep quality in older adults, while mood evidence remains very thin.
- Studied dose
- 100 mg daily, as in the 2024 sleep trial
- Evidence
- Cochrane: 2 usable trials, 64 patients; 1 sleep trial of 30
- Forms
- Vegan capsules (sourced from Griffonia simplicifolia seeds)
Who should avoid: Anyone taking SSRIs, SNRIs, MAOIs, tricyclics, triptans, tramadol, linezolid or St John's wort; not a substitute for depression care.
Safety: Combining it with serotonergic drugs risks serotonin syndrome, which can be an emergency; nausea is the most commonly reported side effect.
Activated Charcoal
Adsorbent carbon · Limited evidence
Used occasionally for gas after a gas-producing meal; research mainly covers hospital use after certain poisonings, not blood or organ detox.
- Studied dose
- No standard dose established; clinical poisoning use was 50 g
- Evidence
- Proven only in hospital poisoning care; gas use rests on 1 1981 trial
- Forms
- Capsules, toothpaste, face masks
Who should avoid: Anyone drowsy or vomiting, with a possibly obstructed gut, or unable to keep a 2-hour gap from daily medication; ask first in pregnancy.
Safety: Binds medicines and nutrients non-selectively, including oral contraceptives; leave at least 2 hours either side of other medicines or supplements.
Alpha-Lipoic Acid
Antioxidant compound · Moderate evidence
Used for nerve comfort and blood sugar support; most research studied people with diabetic nerve pain, and the strongest results used intravenous, not oral, doses.
- Studied dose
- 300–600 mg daily; nerve trials used 600–1,800 mg, split doses
- Evidence
- Several oral RCTs; 4-year NATHAN 1 missed its primary endpoint
- Forms
- Capsules (racemic ALA or R-ALA)
Who should avoid: People on insulin, other diabetes or thyroid medication, those with alcohol use disorder or malnutrition, and pregnant or breastfeeding women without physician guidance.
Safety: Can intensify the blood-sugar-lowering effect of insulin and other diabetes medication, raising hypoglycemia risk; monitor closely and never adjust prescribed medication alone.
BCAAs
Essential amino acids · Limited evidence
Used by people who train for muscle and recovery; reviews found negligible performance benefit, some reduced soreness, and no oral muscle-building data.
- Studied dose
- No standard dose established; trials ranged 1.5–82 g daily
- Evidence
- No oral muscle-building data; soreness reduced in 2022 review of 24 studies
- Forms
- Capsules, usually in a 2:1:1 ratio
Who should avoid: People with liver disease or cirrhosis, reduced kidney function or a raised creatinine result, or any diagnosed amino acid metabolism disorder.
Safety: Nausea and diarrhea affected 12% of people taking BCAAs versus 3% on control in liver-disease trials.
Beet Root
Food concentrate · Moderate evidence
Taken to support healthy blood pressure, circulation and exercise efficiency; trials studied dietary nitrate's effect on blood pressure and the oxygen cost of exercise.
- Studied dose
- About 300–600 mg nitrate daily; 2–3 hours before exercise
- Evidence
- Meta-analysis and RCTs: systolic down about 4–8 mmHg
- Forms
- Capsules, powder, juice, shots
Who should avoid: People on blood pressure medication, with very low blood pressure or a kidney stone history, and pregnant or breastfeeding women using concentrated supplements.
Safety: Combined with blood pressure medication it may lower pressure too far, causing dizziness; pink urine (beeturia) is common and harmless.
Betaine HCl
Acidifying salt · Very limited evidence
Taken with protein meals to add stomach acid; human studies only tested short-term re-acidification in drug-suppressed volunteers, not bloating or digestion.
- Studied dose
- No standard dose established; usually 1 capsule with a protein meal
- Evidence
- No human trials for digestion; 2 studies tested PPI-induced low acid
- Forms
- Capsules, often combined with pepsin
Who should avoid: Anyone with an ulcer, gastritis or H. pylori, or taking NSAIDs, corticosteroids, proton pump inhibitors or H2 blockers; never on an empty stomach.
Safety: Burning, heartburn, stomach pain and nausea are common reasons to stop; added acid can worsen an inflamed or eroded stomach lining, especially with NSAIDs.
Chlorella
Freshwater microalga · Moderate evidence
Taken as a nutrient-dense green food; trials looked at cholesterol, blood pressure and immune markers, while heavy-metal detox claims lack human evidence.
- Studied dose
- 1–5 g daily; effects mainly above 4 g
- Evidence
- Meta-analysis of 19 RCTs, 797 people; modest cholesterol and blood pressure drops
- Forms
- Powder, tablets, capsules
Who should avoid: People on warfarin (vitamin K content), on immunosuppressant therapy, or with autoimmune disease should check with a clinician first.
Safety: Supplies vitamin K, which interacts with warfarin; gas, bloating and green stools are common in the first 1 to 2 weeks.
Collagen
Protein peptides · Moderate evidence
Used for skin elasticity, hair, nails and joint comfort; trials mostly measured skin elasticity and hydration after 8 weeks or more of daily use.
- Studied dose
- 10–20 g daily; skin trials used 2.5–10 g
- Evidence
- Reviews report about 7% better skin elasticity after 8 weeks
- Forms
- Unflavored powder from bovine, marine or chicken sources
Who should avoid: People with kidney disease should ask a doctor first. Collagen always comes from animals, so it is not vegan.
Safety: Generally well tolerated; doses above 30 grams daily may slightly upset the gut, and extra protein adds to kidney workload in kidney disease.
CoQ10
Vitamin-like antioxidant · Moderate evidence
Used for heart and cellular energy support, migraine prevention and statin-related muscle aches; research centers on heart failure patients and migraine frequency.
- Studied dose
- 100–300 mg daily with a fat-containing meal
- Evidence
- Q-SYMBIO: 420 heart failure patients; migraine RCTs; statin data mixed
- Forms
- Softgels (ubiquinone or ubiquinol), tablets
Who should avoid: People on warfarin, blood pressure medication or chemotherapy should involve their provider; ask your doctor first if pregnant or breastfeeding.
Safety: May modestly reduce warfarin's anticoagulant effect, so INR needs closer monitoring; mild stomach upset above 200 mg is the most common side effect.
Creatine
Amino acid derivative · Strong evidence
Used to increase strength, power and lean mass alongside resistance training; research also looks at older adults, women and memory under stress.
- Studied dose
- 3–5 g daily; optional 20 g/day loading for 5–7 days
- Evidence
- Meta-analyses: strength 5–15% above placebo with resistance training
- Forms
- Powder, capsules, gummies
Who should avoid: People with kidney disease, pregnant or breastfeeding women, teens under 18 without oversight, and anyone with liver or metabolic disease should consult a doctor.
Safety: Can raise blood creatinine on lab tests; use caution combining with NSAIDs, diuretics or nephrotoxic drugs, and avoid with kidney disease unless a nephrologist approves.
D-Mannose
Simple sugar · Limited evidence
Taken to help stop E. coli from gripping the bladder wall; trials looked at recurrent urinary tract infections in women, with mixed results.
- Studied dose
- 2 g daily, in the evening or as 1 g twice
- Evidence
- Largest placebo trial (598 women) found no benefit; pooled analyses inconclusive
- Forms
- Powder, capsules
Who should avoid: People with diabetes or reduced kidney function, pregnant or breastfeeding women, and children; men and anyone with fever need medical evaluation.
Safety: Loose stools and bloating, mainly above 3 g daily. It does not replace antibiotics once an infection is established.
Diatomaceous Earth
Fossil silica powder · Very limited evidence
Food-grade powder taken in water as a bulking agent and silica source; one small 1998 trial looked at blood cholesterol.
- Studied dose
- One small trial used 250 mg three times daily; no standard dose established
- Evidence
- One uncontrolled 1998 trial in 19 adults, no placebo group
- Forms
- Powder
Who should avoid: Pregnant or breastfeeding women, children under 12, people with asthma, COPD, bowel strictures or IBD; separate from medicines.
Safety: Can adsorb drugs in the gut, so separate from any prescription drug by 2 hours. Constipation is common; inhaled dust irritates airways.
Fish Oil and Omega-3
Omega-3 fatty acids · Strong evidence
Taken to raise EPA and DHA intake when little fish is eaten; research shows dose-dependent triglyceride lowering, while heart-attack trials were neutral.
- Studied dose
- Depends on the goal; triglyceride treatment uses about 4 g EPA plus DHA daily under medical care
- Evidence
- 2023 meta-analysis: dose-dependent triglyceride drop; heart-attack prevention trials neutral
- Forms
- Fish oil softgels, krill oil, algae oil, flaxseed (ALA), omega 3-6-9 blends
Who should avoid: People on blood thinners, and anyone allergic to fish or shellfish (fish and krill oil).
Safety: Above 3 g of EPA plus DHA a day may raise bleeding risk with blood thinners, and high doses are linked to atrial fibrillation. Fishy burps are common.
Glucosamine
Cartilage building block · Moderate evidence
Taken mainly for knee osteoarthritis comfort; trials studied pain, function and joint-space narrowing, mostly with glucosamine sulfate.
- Studied dose
- 1500 mg daily (sulfate form), judged after 8–12 weeks
- Evidence
- Sulfate RCTs positive; 2010 meta-analysis of 3803 patients found no relevant effect
- Forms
- Glucosamine sulfate or HCL capsules; combinations with chondroitin and MSM
Who should avoid: People with shellfish allergy (most glucosamine comes from shellfish), people taking warfarin, and people managing diabetes should review safety first.
Safety: Mild stomach upset is the most common complaint at 1500 mg daily; check safety first if you take warfarin or manage diabetes.
Hyaluronic Acid
Glycosaminoglycan · Moderate evidence
Taken to support skin moisture from within; trials looked at skin hydration and wrinkle depth, with fewer studies on knee comfort.
- Studied dose
- 120–240 mg daily for 8–12 weeks (skin studies)
- Evidence
- Several placebo-controlled skin trials, one with 150 adults; many are small
- Forms
- Capsules, serums, eye drops, injections
Who should avoid: Pregnant or breastfeeding women, people with active cancer (consult an oncologist), and anyone with a known HA allergy.
Safety: Generally well tolerated; mild stomach upset is uncommon. Low-molecular-weight HA promoted tumor growth in lab models, so people with active cancer should consult an oncologist.
Inositol
Sugar alcohol · Moderate evidence
Used mainly by women with PCOS; trials looked at insulin sensitivity, ovulation and androgen markers, with smaller studies on panic and anxiety.
- Studied dose
- 4 g/day myo- and D-chiro-inositol 40:1, split 2 g twice
- Evidence
- Meta-analyses support PCOS markers; many trials under 100 women, under 6 months
- Forms
- Myo-inositol, D-chiro-inositol, IP6; capsules, powder
Who should avoid: People on diabetes medicines or insulin, people taking lithium, and pregnant women (only under OB guidance).
Safety: May add to the glucose-lowering effect of diabetes drugs and may blunt lithium; nausea, gas or loose stools above 12 g daily.
L-Carnitine
Amino acid derivative · Moderate evidence
Carries fatty acids into mitochondria; trials looked at weight and body composition, mostly alongside diet or exercise, plus sperm parameters in men.
- Studied dose
- No standard dose established
- Evidence
- 4 meta-analyses find a modest weight effect; findings called inconsistent
- Forms
- Capsules, liquid
Who should avoid: People with kidney disease or on dialysis, warfarin users, seizure disorders, underactive thyroid, pregnancy or breastfeeding.
Safety: Gut bacteria convert carnitine into TMAO, which accelerated atherosclerosis in mice; carnitine has also been reported to affect warfarin's action.
L-Leucine
Essential amino acid · Limited evidence
Used to boost a meal's leucine for muscle protein synthesis; short-term synthesis rises, but long trials mostly found no extra muscle.
- Studied dose
- 2.5–3 g per meal; long trials used 7.5 g daily
- Evidence
- 9 of 13 long trials found no added muscle or strength
- Forms
- Capsules; also supplied by protein foods such as whey
Who should avoid: People with maple syrup urine disease (must avoid), those on glucose-lowering medicines, kidney or liver disease, pregnancy, breastfeeding, children and teens.
Safety: Must not be used with maple syrup urine disease. Taken with glucose, leucine raised the insulin response by 66%, relevant for anyone on blood-sugar medicines.
L-Lysine
Essential amino acid · Limited evidence
Mainly bought for cold sores; trials from 1987 or earlier gave mixed results, and a 2015 Cochrane review found no evidence of efficacy.
- Studied dose
- 1,000–3,000 mg daily in trials; provisional ceiling 6,000 mg/day
- Evidence
- Few old trials, newest 1987; 2015 Cochrane review found no evidence
- Forms
- Capsules (L-lysine hydrochloride)
Who should avoid: People with kidney disease, pregnant or breastfeeding women, those taking high-dose calcium or aminoglycoside antibiotics, or with gallbladder or heart disease.
Safety: Mainly nausea, stomach ache or diarrhea; one published kidney-damage case (1996). Use caution with high-dose calcium or aminoglycoside antibiotics such as gentamicin.
L-Theanine
Non-protein amino acid · Moderate evidence
Taken for calm focus and stress; trials looked at acute stress, attention when paired with caffeine, and subjective sleep quality.
- Studied dose
- 200 mg once or twice daily; 200–400 mg before bed
- Evidence
- Consistent acute-stress effects in small RCTs, mostly 30–100 participants
- Forms
- Capsules, tablets, gummies; also green tea
Who should avoid: Pregnant or breastfeeding women, children without physician supervision, people with low blood pressure, or on blood-pressure, sedative or stimulant medicines.
Safety: May add to blood-pressure lowering from antihypertensives and to sedation with benzodiazepines or other sedatives; headache and nausea are the usual mild effects.
Melatonin
Hormone · Strong evidence
People use it to fall asleep sooner and to adjust to jet lag or shift work; trials looked at sleep onset and circadian timing.
- Studied dose
- 0.5–3 mg, 30–60 minutes before bedtime
- Evidence
- 30+ RCTs and Cochrane jet lag review; sleep onset only 7–11 minutes faster
- Forms
- Tablets (immediate and extended release), capsules, sublingual liquid, gummies
Who should avoid: Children, pregnant women, people with autoimmune conditions, and anyone on sedatives, SSRIs, anticoagulants, immunosuppressants or diabetes medications should check with a doctor first.
Safety: Fluvoxamine can raise melatonin levels 17-fold, and sedatives or alcohol add to drowsiness. Common side effects are daytime drowsiness, headache, dizziness and vivid dreams, mostly above 5 mg.
Modified Citrus Pectin
Modified plant fiber · Limited evidence
People use this low-molecular-weight citrus fiber for galectin-3 and heavy metal support; research is mostly lab and animal work plus small human studies.
- Studied dose
- 5 g daily maintenance; up to 15 g daily in studies
- Evidence
- Mostly preclinical; key human studies enrolled only 10 and 8 people
- Forms
- Powder, capsules
Who should avoid: Pregnant or breastfeeding women, people with citrus allergy, children under 12 without supervision, and stage 4-5 kidney disease without nephrologist clearance.
Safety: Mild bloating, gas or loose stools; it may slow absorption of medicines, so space it 2 hours from prescription drugs and monitor INR on warfarin.
NAC (N-Acetyl Cysteine)
Amino acid derivative · Moderate evidence
People use it to support glutathione, the body's main antioxidant; research looked at mucus thinning, liver enzymes, PCOS and mood, with mixed results.
- Studied dose
- 600–1200 mg daily, often split into 2 doses
- Evidence
- Multiple RCTs for mucus thinning; many trials enroll under 100 people
- Forms
- Capsules, tablets, effervescent powders
Who should avoid: Avoid with cystinuria; people taking nitroglycerin or chemotherapy, those with asthma, and pregnant or breastfeeding people should ask a clinician first.
Safety: Not a home treatment for acetaminophen overdose, which is an emergency. Usually mild nausea, mostly above 1200 mg; use with nitroglycerin only under a doctor.
Nattokinase
Enzyme · Limited evidence
An enzyme from fermented soybeans that breaks down fibrin; trials measured clotting markers, blood pressure and cholesterol, not heart attacks or strokes.
- Studied dose
- 2000 FU (100 mg enzyme), the amount used in trials
- Evidence
- 10 trials, mostly blood markers; 2024 meta-analysis calls evidence 'various'
- Forms
- Capsules; also eaten as natto (not standardized in FU)
Who should avoid: People on warfarin, DOACs, aspirin, clopidogrel or other blood thinners, with bleeding disorders, heart valves or stents, upcoming surgery, pregnancy, or soy allergy.
Safety: Bleeding risk: 7 case reports describe harms, including a fatal bleed and a brain bleed in someone also on aspirin. Never combine with or substitute for prescribed blood thinners.
Probiotics
Probiotic bacteria · Moderate evidence
Live bacteria and yeasts taken to support gut balance; research looked at antibiotic-associated diarrhea, IBS symptoms, respiratory and stomach bugs, and vaginal balance.
- Studied dose
- 10–50 billion CFU daily; up to 100 billion for some uses
- Evidence
- 63-trial meta-analysis: 42% less antibiotic-associated diarrhea; effects are strain-specific
- Forms
- Enteric-coated capsules, gummies, fermented foods
Who should avoid: Check with a doctor if immunity is weakened (chemo, transplant, HIV), after major abdominal surgery, or if critically ill; not recommended in severe acute pancreatitis.
Safety: Some people get mild gas in the first week as the gut adjusts; take it 2-4 hours after an antibiotic dose so the bacteria survive.
Protein
Macronutrient · Strong evidence
People use protein powder to close gaps in daily protein intake; trials looked at muscle mass and strength when combined with resistance training.
- Studied dose
- Total 1.2–1.6 g per kg daily if active; RDA 0.8 g/kg
- Evidence
- 49-study meta-analysis: gains with training, plateau near 1.6 g/kg
- Forms
- Whey concentrate powder, plant protein powder, whole foods
Who should avoid: People with kidney or liver disease need an individually prescribed intake; whey concentrate often does not suit lactose intolerance.
Safety: Intakes near 2 g per kg are considered safe with healthy kidneys; existing kidney disease needs a doctor-set intake. Rapid increases can cause bloating or constipation if fluids stay low.
Pumpkin Seed
Food concentrate · Limited evidence
Ground seed, oil and extract are used for men's urinary comfort; one 12-month trial tested seed in men with prostate-related urinary symptoms.
- Studied dose
- 10 g of seed daily, taken as 5 g twice daily
- Evidence
- 1 large 12-month trial: seed beat placebo 58.5% vs 47.3%; extract did not
- Forms
- Ground seed capsules, oil softgels, ethanol extract, whole seeds (pepitas)
Who should avoid: See a doctor if: blood in urine, fever or urinary retention, pregnancy, breastfeeding, under 18, or past reaction to pumpkin seed, sesame or tree nuts.
Safety: Generally well tolerated; mild stomach upset in about 4% of users. Allergy, including anaphylaxis, is rare, and large amounts of whole seeds with hulls can block the rectum.
Quercetin
Plant flavonoid · Moderate evidence
A flavonoid found in onions, apples and capers; research looked at histamine response, inflammation markers, blood pressure and respiratory infections in athletes.
- Studied dose
- 500–1000 mg daily, often with bromelain
- Evidence
- Meta-analyses of 7 and 9 trials on blood pressure and CRP
- Forms
- Capsules, quercetin-bromelain combinations, phytosome form
Who should avoid: People taking prescription medicines, because quercetin can change how some drugs are broken down; pregnant or breastfeeding women, as safety data are lacking.
Safety: Short-term use up to 1,000 mg a day appears generally well tolerated; higher doses are more likely to upset the stomach.
Red Yeast Rice
Fermented rice product · Moderate evidence
Rice fermented with a mold that makes monacolin K; trials of products with known monacolin content measured LDL cholesterol, and shelf products vary widely.
- Studied dose
- No standard dose established; labels rarely state monacolin K content
- Evidence
- Pooled trials: LDL down 34–39 mg/dL, only with standardized products
- Forms
- Capsules, tablets
Who should avoid: People on statins, other cholesterol drugs or cyclosporine; pregnancy or breastfeeding; liver or kidney disease, heavy drinking, or past muscle pain on a statin.
Safety: Monacolin K is chemically identical to the statin lovastatin: never combine with a prescribed statin. Statin-type risks include muscle aches, rare liver injury, and statin-like interactions, including grapefruit juice.
Taurine
Amino sulfonic acid · Moderate evidence
A sulfur-containing compound from meat and seafood, not a stimulant; trials looked at blood pressure, blood sugar and exercise, finding modest effects.
- Studied dose
- 1.5–3 g daily in trials; 3 g/day observed safe level
- Evidence
- 34-trial meta-analysis: systolic pressure down 4.38 mmHg; lifespan shown only in animals
- Forms
- Capsules, powder
Who should avoid: Check with a clinician if on blood pressure or glucose-lowering medicine, pregnant or breastfeeding, for children, or with kidney disease or blood cancer treatment.
Safety: No adverse effects found up to 3 g a day in healthy adults; people on blood pressure or glucose-lowering medicines should check with a clinician first.
No supplement matches your search. Try a use (sleep), a form (powder) or a name (creatine).
Using supplements wisely
Three things worth checking before you buy or combine supplements.
What the Evidence Ratings Mean
Strong means consistent meta-analyses of many good trials for one use; Moderate means several human trials agree; Limited means a few small trials; Very limited means mostly lab or animal data. Only 4 of the 30 supplements here reach Strong.
Supplements and Medicines
Some supplements act like drugs. Red yeast rice contains the same compound as the statin lovastatin, nattokinase adds to blood thinners, 5-HTP can cause serotonin syndrome with antidepressants, and fluvoxamine raises melatonin levels about 17-fold.
Label Dose vs Study Dose
The amount in a capsule is often different from the dose tested in trials, sometimes far higher and sometimes far lower. Compare the label with the studied dose on each card before deciding how much to take, and never exceed the label without medical advice.
Common questions
Are dietary supplements approved by the FDA?
No. In the US, supplements are regulated under a 1994 law: makers must follow good manufacturing practices, but products do not need FDA approval for safety or effectiveness before sale. Third-party seals such as USP or NSF confirm that the bottle contains what the label says.
Which supplements interact with common medications?
Red yeast rice must never be combined with a statin, nattokinase adds to blood thinners such as warfarin, 5-HTP can cause serotonin syndrome with SSRIs, and alpha-lipoic acid can push blood sugar too low with insulin. Show your full supplement list to your pharmacist.
Is creatine bad for your kidneys?
Studies in healthy adults taking 3 to 5 g a day have not shown kidney harm. Creatine does raise blood creatinine, which can look like a kidney problem on a routine lab test, so tell your doctor you take it. People with kidney disease should avoid it unless a nephrologist approves.
How much melatonin should I take?
Studies use 0.5 to 3 mg taken 30 to 60 minutes before bed. More is not better: side effects such as morning drowsiness, headache and vivid dreams show up mostly above 5 mg. For jet lag, timing matters more than dose.
Should I take probiotics with antibiotics?
Yes, if you want to lower the chance of antibiotic-associated diarrhea: a meta-analysis of 63 trials found 42% fewer cases. Take the probiotic 2 to 4 hours after each antibiotic dose so more bacteria survive, and keep going for about a week after the course.
Is red yeast rice a natural statin?
Effectively yes. Its active compound, monacolin K, is chemically identical to lovastatin, and standardized products lowered LDL by 34 to 39 mg/dL in pooled trials. Shelf products vary widely and rarely state their monacolin K content, and it carries statin-type risks.
Can fish oil replace eating fish?
It raises EPA and DHA when you eat little fish, and it lowers triglycerides in a dose-dependent way. Large trials of fish oil for preventing heart attacks were neutral, though, so it is not a substitute for a heart-healthy diet. Doses above 3 g a day need a doctor's advice.
When is the best time to take supplements?
Take fat-soluble ones such as CoQ10 with a meal that contains fat, melatonin 30 to 60 minutes before bed, and probiotics 2 to 4 hours away from antibiotics. For creatine, taking 3 to 5 g every day matters more than the hour.
Do I need supplements if I eat well?
Many people do not. Most of the supplements here address specific goals, such as training, sleep timing or a diagnosed condition, rather than general health. Start with diet, sleep and activity, and use supplements to fill a defined gap.
Can supplements replace my prescription medicine?
No. Never stop or swap a prescribed medicine for a supplement without your doctor. Several supplements also change how medicines work, which can make treatment less effective or less safe.