BooksVol. 12Available
Are All These Supplements Actually Doing Anything?
Stop Swallowing the Hype. Start Reading the Evidence.
by An Thanh Tùng
ASIN B0HNHZB22X · B0HNJ7MYMK
About this book
Every pill you take needs a reason, a measure and a review date.Chapter 13
A plain-language, evidence-labeled guide to which vitamins and supplements actually help, who needs them, which ones you can drop, and where they can do harm.
What you'll learn
- Ch. 1Ask a better questionNot “Is this vitamin good for you?” but “Am I low in it, and what can it actually do for me?”
- Ch. 3On sale doesn't mean checkedWith sexual-enhancement, weight-loss or muscle-building products, assume you don't know what's inside.
- Ch. 5The multivitamin policyReal insurance for people who could become pregnant. For healthy people with a decent diet, it pays out on almost nothing.
- Ch. 6Vitamin D has limitsIt helps people who are deficient. For those who already have enough, it doesn't prevent fractures, cancer or heart disease.
- Ch. 7Eat the fish, skip the pillFish twice a week has firmer support than fish oil capsules, and high-dose omega-3 can disturb your heart rhythm.
- Ch. 9Nothing “boosts” immunityNo bottle boosts the immune system of someone who isn't deficient. Sleep, vaccines and handwashing do more.
How the book is organized
- Part IBefore You Open the Bottle
- Part IIThe Usual Bottles
- Part IIIWhen "Harmless" Isn't
- Part IVYour Plan
Look inside
Pages from the book
- Chapter 1 opens
- Every claim carries a label
- Try it at home
- If you remember one thing
- A printable worksheet
- Notes and sources
Free with your email
Worksheets from this book
- Worksheet Four-Filter Worksheet Get the PDF
- Worksheet Am I in a Group at Risk? Get the PDF
- Worksheet What to Bring to Your Doctor or Pharmacist Get the PDF
- Worksheet 12-Week Trial Worksheet Get the PDF
- Safety card Safety Flags at a Glance Get the PDF
- Reference table If You Notice… Read… Get the PDF
- Reference table Supplement Dictionary Get the PDF
- Reference table Marketing Dictionary Get the PDF
92 references
Notes and sources
Ch. 1Are All These Supplements Actually Doing Anything?9
- How many adults take supplements Mishra S, Stierman B, Gahche JJ, Potischman N. Dietary supplement use among adults: United States, 2017–2018. NCHS Data Brief no. 399. Hyattsville, MD: National Center for Health Statistics; 2021. doi:10.15620/cdc:101131.
- Beta-carotene in male smokers (ATBC) Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med 1994;330(15):1029–1035.
- Beta-carotene and vitamin A (CARET) Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med 1996;334(18):1150–1155. Search PubMed
- Vitamin E and prostate cancer (SELECT) Klein EA, Thompson IM, Tangen CM, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2011;306(14):1549–1556. doi:10.1001/jama.2011.1437.
- USPSTF recommendation on vitamins and minerals US Preventive Services Task Force; Mangione CM, Barry MJ, Nicholson WK, et al. Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer: US Preventive Services Task Force recommendation statement. JAMA 2022;327(23):2326–2333. doi:10.1001/jama.2022.8970.
- Multivitamins and cancer (PHS II) Gaziano JM, Sesso HD, Christen WG, et al. Multivitamins in the prevention of cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA 2012;308(18):1871–1880. Search PubMed
- Multivitamins and heart disease (PHS II) Sesso HD, Christen WG, Bubes V, et al. Multivitamins in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA 2012;308(17):1751–1760. doi:10.1001/jama.2012.14805.
- Multivitamins and mortality Loftfield E, et al. Multivitamin use and mortality risk in 3 prospective US cohorts. JAMA Netw Open 2024;7(6):e2418729. doi:10.1001/jamanetworkopen.2024.18729.
- Folic acid before pregnancy US Preventive Services Task Force; Barry MJ, Nicholson WK, Silverstein M, et al. Folic acid supplementation to prevent neural tube defects: US Preventive Services Task Force reaffirmation recommendation statement. JAMA 2023;330(5):454–459. Search PubMed
Ch. 2Check the Bucket First: When Are You Actually Low?9
- Metformin and B12 Aroda VR, Edelstein SL, Goldberg RB, et al. Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab 2016;101(4):1754–1761. doi:10.1210/jc.2015-3754.
- B12 monitoring with metformin American Diabetes Association. Standards of Care in Diabetes (updated annually).
- Acid reducers and B12 Lam JR, Schneider JL, Zhao W, Corley DA. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA 2013;310(22):2435–2442. Search PubMed
- B12 in older adults; nerve symptoms without anemia NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals.
- After weight-loss surgery Mechanick JI, Apovian C, Brethauer S, et al. Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures – 2019 update. Surg Obes Relat Dis 2020;16(2):175–247. doi:10.1016/j.soard.2019.10.025.
- Vitamin D screening Krist AH, Davidson KW, Mangione CM, et al. Screening for vitamin D deficiency in adults: US Preventive Services Task Force recommendation statement. JAMA 2021;325(14):1436–1442. Search PubMed
- Vitamin D guideline Demay MB, Pittas AG, Bikle DD, et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2024;109(8):1907–1947. doi:10.1210/clinem/dgae290.
- Hair mineral analysis Seidel S, Kreutzer R, Smith D, McNeel S, Gilliss D. Assessment of commercial laboratories performing hair mineral analysis. JAMA 2001;285(1):67–72. Search PubMed
- IV micronutrient therapy Ali A, Njike VY, Northrup V, et al. Intravenous micronutrient therapy (Myers' Cocktail) for fibromyalgia: a placebo-controlled pilot study. J Altern Complement Med 2009;15(3):247–257. Search PubMed
Ch. 3Is What's on the Label in the Bottle?6
- How supplements are regulated in the United States; quality seals NIH Office of Dietary Supplements. Dietary Supplements: What You Need to Know. Dietary Supplement Health and Education Act of 1994.
- Food supplements in the European Union Directive 2002/46/EC; Regulation (EC) No 1924/2006; Food Safety Authority of Ireland, Food Supplements.
- Melatonin gummies Cohen PA, Avula B, Wang YH, Katragunta K, Khan I. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA 2023;329(16):1401–1402. Search PubMed
- Undeclared drugs in supplements Tucker J, Fischer T, Upjohn L, Mazzera D, Kumar M. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open 2018;1(6):e183337. Search PubMed
- Banned drugs after recalls Cohen PA, Maller G, DeSouza R, Neal-Kababick J. Presence of banned drugs in dietary supplements following FDA recalls. JAMA 2014;312(16):1691–1693. doi:10.1001/jama.2014.10308.
- Emergency visits Geller AI, Shehab N, Weidle NJ, et al. Emergency department visits for adverse events related to dietary supplements. N Engl J Med 2015;373(16):1531–1540. doi:10.1056/NEJMsa1504267.
Ch. 4Decoding the Label4
- Structure/function claims US Food and Drug Administration. Structure/Function Claims. Code of Federal Regulations, 21 CFR 101.93.
- Proprietary blends; daily values US Food and Drug Administration. Small Entity Compliance Guide: Statement of Identity, Nutrition Labeling, and Ingredient Labeling of Dietary Supplements. 21 CFR 101.36.
- Health claims in Europe Regulation (EC) No 1924/2006.
- Detox products Klein AV, Kiat H. Detox diets for toxin elimination and weight management: a critical review of the evidence. J Hum Nutr Diet 2015;28(6):675–686. doi:10.1111/jhn.12286.
Ch. 5Multivitamins: Insurance or Wasted Money?6
- PHS II See Chapter 1 (Gaziano et al. 2012; Sesso et al. 2012).
- COSMOS, cancer and heart disease Sesso HD, Rist PM, Aragaki AK, et al. Multivitamins in the prevention of cancer and cardiovascular disease: the COSMOS randomized clinical trial. Am J Clin Nutr 2022;115(6):1501–1510. doi:10.1093/ajcn/nqac056.
- COSMOS, memory Vyas CM, Manson JE, Sesso HD, et al. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COSMOS randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS. Am J Clin Nutr 2024;119(3):692–701. Baker LD, Manson JE, Rapp SR, et al. Alzheimers Dement 2023;19(4):1308–1319. Search PubMed
- Folic acid and neural tube defects See Chapter 8 (MRC Vitamin Study 1991; USPSTF 2023).
- After weight-loss surgery See Chapter 2 (Mechanick et al. 2020).
- Vitamin A in pregnancy Rothman KJ, Moore LL, Singer MR, et al. Teratogenicity of high vitamin A intake. N Engl J Med 1995;333(21):1369–1373. Search PubMed
Ch. 6Vitamin D on Trial9
- VITAL, cancer and heart disease Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. N Engl J Med 2019;380(1):33–44. Search PubMed
- VITAL, fractures LeBoff MS, Chou SH, Ratliff KA, et al. Supplemental vitamin D and incident fractures in midlife and older adults. N Engl J Med 2022;387(4):299–309. Search PubMed
- D-Health Neale RE, Baxter C, Romero BD, et al. The D-Health Trial: a randomised controlled trial of the effect of vitamin D on mortality. Lancet Diabetes Endocrinol 2022;10(2):120–128. Search PubMed
- Vitamin D and bone health Bolland MJ, Grey A, Avenell A. Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis. Lancet Diabetes Endocrinol 2018;6(11):847–858. Search PubMed
- Vitamin D with calcium, fractures Avenell A, Mak JCS, O'Connell DL. Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database Syst Rev 2014;(4):CD000227. Search PubMed
- Very high yearly dose Sanders KM, Stuart AL, Williamson EJ, et al. Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA 2010;303(18):1815–1822. Search PubMed
- Cancer incidence and mortality Keum N, Lee DH, Greenwood DC, Manson JE, Giovannucci E. Vitamin D supplementation and total cancer incidence and mortality: a meta-analysis of randomized controlled trials. Ann Oncol 2019;30(5):733–743. doi:10.1093/annonc/mdz059.
- Respiratory infections Jolliffe DA, Camargo CA, Sluyter JD, et al. Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of stratified aggregate data. Lancet Diabetes Endocrinol 2025;13(4):307–320. doi:10.1016/S2213-8587(24)00348-600348-6).
- Guideline, doses and adults 75 and over See Chapter 2 (Demay et al. 2024).
Ch. 7Fish Oil: Heart, Brain, and a Surprise9
- Eating fish Rimm EB, Appel LJ, Chiuve SE, et al. Seafood long-chain n-3 polyunsaturated fatty acids and cardiovascular disease: a science advisory from the American Heart Association. Circulation 2018;138(1):e35–e47. doi:10.1161/CIR.0000000000000574.
- VITAL, omega-3 Manson JE, Cook NR, Lee IM, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer. N Engl J Med 2019;380(1):23–32. Search PubMed
- ASCEND ASCEND Study Collaborative Group. Effects of n−3 fatty acid supplements in diabetes mellitus. N Engl J Med 2018;379(16):1540–1550.
- Cochrane review Abdelhamid AS, Brown TJ, Brainard JS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev 2020;3(3):CD003177. Search PubMed
- REDUCE-IT Bhatt DL, Steg PG, Miller M, et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia. N Engl J Med 2019;380(1):11–22. Search PubMed
- STRENGTH Nicholls SJ, Lincoff AM, Garcia M, et al. Effect of high-dose omega-3 fatty acids vs corn oil on major adverse cardiovascular events in patients at high cardiovascular risk: the STRENGTH randomized clinical trial. JAMA 2020;324(22):2268–2280. Search PubMed
- Atrial fibrillation Gencer B, Djousse L, Al-Ramady OT, Cook NR, Manson JE, Albert CM. Effect of long-term marine omega-3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes: a systematic review and meta-analysis. Circulation 2021;144(25):1981–1990. doi:10.1161/CIRCULATIONAHA.121.055654.
- Pregnancy Middleton P, Gomersall JC, Gould JF, et al. Omega-3 fatty acid addition during pregnancy. Cochrane Database Syst Rev 2018;11:CD003402. doi:10.1002/14651858.CD003402.pub3.
- Memory Sydenham E, Dangour AD, Lim WS. Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database Syst Rev 2012;(6):CD005379. Search PubMed
Ch. 8Four That Can Save You: Folate, Iron, B12, Calcium10
- Folic acid trial Wald N, Sneddon J; MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet 1991;338(8760):131–137.
- Folic acid recommendation See Chapter 1 (USPSTF 2023).
- Iron deficiency anemia Snook J, Bhala N, Beales ILP, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70(11):2030–2051. doi:10.1136/gutjnl-2021-325210.
- Alternate-day iron Stoffel NU, Zeder C, Brittenham GM, Moretti D, Zimmermann MB. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica 2020;105(5):1232–1239. doi:10.3324/haematol.2019.220830.
- Iron and young children US Food and Drug Administration. Dietary Supplement Labeling Guide, Chapter VIII. 21 CFR 101.17(e).
- B12 for vegans Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: vegetarian diets. J Acad Nutr Diet 2016;116(12):1970–1980. doi:10.1016/j.jand.2016.09.025.
- B12 safety See Chapter 2 (NIH Office of Dietary Supplements).
- Calcium and fractures Bolland MJ, Leung W, Tai V, et al. Calcium intake and risk of fracture: systematic review. BMJ 2015;351:h4580. Tai V, Leung W, Grey A, Reid IR, Bolland MJ. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ 2015;351:h4183. Search PubMed
- Calcium and heart attack Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ 2010;341:c3691. doi:10.1136/bmj.c3691.
- Calcium with vitamin D and kidney stones (WHI) Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006;354(7):669–683. Search PubMed
Ch. 9"Immune Boosters": Vitamin C, Zinc, and the Common Cold8
- Vitamin C Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2013;(1):CD000980. Search PubMed
- Zinc Nault D, Machingo TA, Shipper AG, et al. Zinc for prevention and treatment of the common cold. Cochrane Database Syst Rev 2024;5(5):CD014914. doi:10.1002/14651858.CD014914.pub2.
- Zinc safety NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals.
- Zinc nasal products US Food and Drug Administration warning on intranasal zinc products, June 2009.
- Echinacea Karsch-Völk M, Barrett B, Kiefer D, Bauer R, Ardjomand-Woelkart K, Linde K. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev 2014;(2):CD000530. doi:10.1002/14651858.CD000530.pub3.
- Elderberry Wieland LS, Piechotta V, Feinberg T, et al. Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review. BMC Complement Med Ther 2021;21(1):112. Search PubMed
- Sleep and colds Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally assessed sleep and susceptibility to the common cold. Sleep 2015;38(9):1353–1359. Search PubMed
- Vitamin D and respiratory infections See Chapter 6 (Jolliffe et al. 2025).
Ch. 10Natural Isn't Safe by Default: Herbal Pills6
- Liver injury from supplements Navarro VJ, Barnhart H, Bonkovsky HL, et al. Liver injury from herbals and dietary supplements in the U.S. Drug-Induced Liver Injury Network. Hepatology 2014;60(4):1399–1408. doi:10.1002/hep.27317.
- Green tea extract EFSA Panel on Food Additives and Nutrient Sources added to Food. Scientific opinion on the safety of green tea catechins. EFSA Journal 2018;16(4):5239. Commission Regulation (EU) 2022/2340.
- St John's wort National Center for Complementary and Integrative Health (NIH). St. John's Wort.
- Turmeric National Center for Complementary and Integrative Health (NIH). Turmeric.
- Ashwagandha National Center for Complementary and Integrative Health (NIH). Ashwagandha.
- Ginkgo (GEM trial) National Center for Complementary and Integrative Health (NIH). Ginkgo. DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA 2008;300(19):2253–2262. Search PubMed
Ch. 11The New Wave: NAD+, Creatine, Protein Powder and "Smart Pills"5
- NMN in humans Song Q, Zhou X, Xu K, et al. The safety and antiaging effects of nicotinamide mononucleotide in human clinical trials: an update. Adv Nutr 2023;14(6):1416–1435. Search PubMed
- Creatine in older adults Chilibeck PD, Kaviani M, Candow DG, Zello GA. Effect of creatine supplementation during resistance training on lean tissue mass and muscular strength in older adults: a meta-analysis. Open Access J Sports Med 2017;8:213–226. doi:10.2147/OAJSM.S123529.
- Creatine safety Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr 2017;14:18. doi:10.1186/s12970-017-0173-z.
- Protein supplements Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018;52(6):376–384. Search PubMed
- "Smart pills" Cohen PA, Avula B, Wang YH, Zakharevich I, Khan I. Five unapproved drugs found in cognitive enhancement supplements. Neurol Clin Pract 2021;11(3):e303–e307. doi:10.1212/CPJ.0000000000000960.
Ch. 12Stacking, Megadoses and Drug Interactions7
- Medicines and supplements in older adults Qato DM, Wilder J, Schumm LP, Gillet V, Alexander GC. Changes in prescription and over-the-counter medication and dietary supplement use among older adults in the United States, 2005 vs 2011. JAMA Intern Med 2016;176(4):473–482. Search PubMed
- Vitamin B6 upper safe level Turck D, Bohn T, Castenmiller J, et al. (EFSA Panel on Nutrition, Novel Foods and Food Allergens). Scientific opinion on the tolerable upper intake level for vitamin B6. EFSA Journal 2023;21(5):8006. doi:10.2903/j.efsa.2023.8006.
- Vitamin B6 in Australia Therapeutic Goods Administration (Australia). Health supplements containing vitamin B6 can cause peripheral neuropathy (safety alert).
- Vitamin K and warfarin See Chapter 3 (NIH Office of Dietary Supplements).
- Ginkgo and blood thinners See Chapter 10 (NCCIH, Ginkgo).
- Biotin and lab tests US Food and Drug Administration. The FDA warns that biotin may interfere with lab tests: FDA safety communication, November 28, 2017.
- Upper safe levels NIH Office of Dietary Supplements fact sheets: Vitamin A and Carotenoids; Vitamin D; Vitamin B6; Zinc; Iron.
Ch. 13Keep, Drop, or Ask1
- The ten key claims See the sources for Chapters 1, 2, 5, 6, 7, 8, 9, 10 and 12.
BackWorksheets at the back of the book3
- Groups at risk of running low See Chapters 2 and 8 (Aroda et al. 2016; Lam et al. 2013; Mechanick et al. 2020; Melina et al. 2016; Snook et al. 2021).
- Upper safe levels on the Four-Filter Worksheet See Chapter 12 (NIH Office of Dietary Supplements fact sheets; Turck et al., EFSA 2023).
- Drug interactions on the checklist for your doctor or pharmacist See Chapters 10 and 12 (NCCIH; US Food and Drug Administration, biotin safety communication 2017).
Updates and corrections
Evidence last reviewed October 16, 2026
Each evidence label shows how solid the evidence was on the day it was last reviewed. Corrections are posted here with the date they were made, and included in the next printing.
No corrections have been posted for this edition. Spotted an error, or a study that should change a label? Email [email protected]
