Supplement Database
Evidence-based information on 500+ vitamins, minerals, and herbal supplements including critical medicine interaction data.
Important: Supplements are NOT "harmless because they're natural." Many supplements interact significantly with prescription medications. Always inform your healthcare provider and pharmacist about all supplements you take.
28 supplements
22 supplements
120 supplements
18 supplements
35 supplements
40 supplements
St. John's Wort
Interacts with: SSRIs, Warfarin, Oral Contraceptives, HIV meds
Fish Oil (high dose)
Interacts with: Warfarin, Aspirin, Clopidogrel
Garlic supplements
Interacts with: Warfarin, Antiplatelet medicines
Vitamin E (high dose)
Interacts with: Warfarin, Aspirin
Kava
Interacts with: Benzodiazepines, Alcohol, CNS depressants
Ginkgo Biloba
Interacts with: Warfarin, NSAIDs, Antiplatelet medicines
The dietary supplement industry is a $50+ billion market in the United States, yet the regulatory requirements for supplements are fundamentally different from those for medicines. Unlike medications, supplements do not require FDA approval before being marketed — manufacturers are responsible for ensuring their products are safe and that label claims are truthful.
Under the Dietary Supplement Health and Education Act (DSHEA) of 1994, dietary supplements are regulated as a special category of food rather than as medicines. This means:
Supplement quality varies enormously. Third-party testing programs (USP, NSF International, ConsumerLab) test supplements for purity, potency, and absence of contaminants. Look for supplements with these certifications when quality matters.
Vitamin A (Retinol/Carotenoids): Essential for vision, immune function, and cell differentiation. Found in liver, dairy, and orange/yellow fruits and vegetables. Deficiency causes night blindness and immune impairment. Excessive intake (especially preformed vitamin A) causes liver toxicity and birth defects. RDA: 900 mcg (men), 700 mcg (women). Pregnancy: avoid high-dose vitamin A supplements due to teratogenic risk.
Vitamin B Complex: Eight B vitamins work together in energy metabolism. B1 (thiamine) prevents beriberi and Wernicke encephalopathy. B6 (pyridoxine) participates in amino acid metabolism; deficiency causes anemia and neuropathy, but excess (>200 mg/day) causes peripheral neuropathy. B12 (cobalamin) deficiency causes megaloblastic anemia and neurological damage; common in vegetarians/vegans, elderly, and patients on metformin or proton pump inhibitors. Folate (B9) is critical for DNA synthesis and pregnancy (prevents neural tube defects).
Vitamin C (Ascorbic Acid): Antioxidant and cofactor for collagen synthesis. Deficiency causes scurvy. Generally safe in high doses, though >2g/day causes diarrhea and may interact with chemotherapy. RDA: 90 mg (men), 75 mg (women). Smokers need 35 mg additional daily.
Vitamin D (Cholecalciferol): Essential for calcium absorption and bone health, plus emerging roles in immune function. Deficiency is widespread, especially in northern latitudes. Symptoms include muscle weakness, bone pain, and osteoporosis. Testing 25-hydroxyvitamin D levels guides supplementation. Most adults need 1000-2000 IU daily; deficiency states require higher therapeutic doses. Toxicity occurs above 50,000 IU daily for prolonged periods.
Vitamin E (Tocopherols): Fat-soluble antioxidant. Deficiency is rare. Routine supplementation may not provide benefits and high-dose vitamin E (>400 IU daily) has been associated with increased mortality and hemorrhagic stroke risk in some studies.
Vitamin K: Essential for blood clotting and bone health. Deficiency is rare in adults but common in newborns (treated with prophylactic injection). Vitamin K1 (phylloquinone) from green leafy vegetables. Vitamin K2 (menaquinones) from fermented foods and animal sources, with emerging research on bone and cardiovascular health.
Calcium: Critical for bone health, muscle function, and blood clotting. RDA varies by age and gender (1000-1300 mg/day). Best absorbed in doses ≤500 mg at a time. Supplements include calcium carbonate (cheap, requires stomach acid for absorption), calcium citrate (better absorption, no acid required), and various other forms. Excessive intake (>2000 mg daily) may increase cardiovascular risk and kidney stones.
Iron: Required for hemoglobin and oxygen transport. Deficiency causes iron deficiency anemia. Common in menstruating women, pregnant women, vegetarians, and those with chronic blood loss. Ferrous sulfate is standard supplementation. Side effects include constipation and stomach upset. Excessive intake causes serious toxicity; iron overdose is a leading cause of fatal poisoning in children.
Magnesium: Involved in 300+ enzymatic reactions. Deficiency causes muscle cramps, fatigue, arrhythmias, and may contribute to migraines. Supplementation forms vary in absorption: magnesium glycinate (well-absorbed, low GI effects), magnesium citrate (good absorption, may cause diarrhea), magnesium oxide (poor absorption, used for constipation). RDA: 400-420 mg (men), 310-320 mg (women).
Zinc: Important for immune function, wound healing, and protein synthesis. Deficiency causes impaired immunity and growth retardation. High-dose zinc can cause copper deficiency and may suppress immune function. RDA: 11 mg (men), 8 mg (women).
Potassium: Critical for muscle and nerve function, particularly cardiac. Excessive supplementation can cause dangerous hyperkalemia, especially in patients with kidney disease or taking ACE inhibitors, ARBs, or potassium-sparing diuretics. Generally obtained from diet (fruits, vegetables) rather than supplements except in documented deficiency.
Echinacea: Used for cold and immune support. Meta-analyses show modest reduction in cold severity and duration when started at symptom onset. Generally safe but may cause allergic reactions in those allergic to ragweed family plants.
Garlic (Allium sativum): Has modest blood pressure and lipid effects. Multiple meta-analyses show small but significant reductions in systolic blood pressure. May increase bleeding risk, particularly when combined with anticoagulants.
Ginkgo Biloba: Used for memory and cognitive function. Evidence for benefit in dementia or memory enhancement is weak. Increases bleeding risk significantly, particularly concerning when combined with antiplatelet drugs.
Ginseng: Multiple varieties (Asian/Korean, American, Siberian) have different effects. Used for energy, immune support, and various other purposes. Quality varies enormously between products. May interact with diabetes medications, blood pressure medications, and anticoagulants.
Saw Palmetto: Used for benign prostatic hyperplasia symptoms. Recent high-quality trials show no significant benefit over placebo, though some men report subjective improvement. Generally safe.
St. John's Wort: Used for mild-to-moderate depression. Meta-analyses show modest efficacy comparable to standard antidepressants in mild depression. Major concern: induces CYP3A4 enzymes, reducing effectiveness of many medications including birth control pills, blood thinners, HIV medications, and chemotherapy.
Turmeric/Curcumin: Has anti-inflammatory effects. Some evidence for benefit in osteoarthritis, ulcerative colitis. Poor oral bioavailability; piperine (black pepper extract) enhances absorption. May increase bleeding risk.
Valerian: Used for sleep. Modest evidence for sleep quality improvement. May cause daytime drowsiness. Should not be combined with alcohol or sedatives.
The sports nutrition industry promotes numerous supplements claiming performance benefits. Most have limited evidence, but a few have demonstrated value:
Creatine Monohydrate: Extensively studied with consistent evidence for improving short-burst, high-intensity performance and increasing muscle mass during resistance training. Safe at recommended doses (3-5 grams daily) for healthy adults.
Protein Supplements: Whey, casein, soy, and other protein supplements help athletes meet elevated protein needs (1.6-2.2 g/kg/day for resistance training). Whole foods generally preferred when feasible.
Caffeine: Well-documented performance enhancer for endurance and high-intensity exercise. Effective doses 3-6 mg/kg, 30-60 minutes before exercise. Excessive intake causes jitteriness, palpitations, sleep disturbance.
Beta-Alanine: May improve high-intensity exercise lasting 60-240 seconds. Causes harmless tingling sensation (paresthesia) in some users.
Given the unregulated nature of the supplement industry, quality verification is essential. Independent testing organizations include:
Look for these certifications on supplement labels. Choose established manufacturers with reputations for quality control. Be wary of "miracle" claims, products promising rapid weight loss, or supplements claiming to cure diseases.
Generally beneficial situations:
Generally inadvisable situations: