{"url":"https://whatshealthyandwhy.com/supplement-basics/do-you-need-a-supplement","path":"/supplement-basics/do-you-need-a-supplement","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/supplement-basics/do-you-need-a-supplement.json","markdown":"https://whatshealthyandwhy.com/supplement-basics/do-you-need-a-supplement.md"},"topic":{"slug":"supplement-basics","name":"Supplement Basics","url":"https://whatshealthyandwhy.com/supplement-basics"},"slug":"do-you-need-a-supplement","order":1,"title":"Do You Need a Supplement?","question":"Do you need a vitamin or mineral supplement, and how can you tell?","answer":"Most healthy adults who eat varied food probably gain little from supplements; pregnancy, vegan diets, older age, breastfed infants and some medicines create real needs.","description":"How to decide whether a vitamin or mineral supplement is worth taking: food first, which blood test answers which question, the groups with a proven need, and what the big multivitamin trials found for everyone else.","confidence":4,"confidenceNote":"Long randomized trials found little or no benefit from multivitamins in well-fed adults; the needs of specific groups rest on task-force reviews, randomized trials and deficiency surveys.","evidenceSummary":{"rctCount":6,"observationalCount":5,"metaAnalysisCount":1,"totalParticipants":"390,000+","replicated":true,"newestStudyYear":2026},"category":{"categoryTitle":"What's Good For You","categorySlug":"good-for-you","subcategoryName":"Supplements & Vitamins","subcategorySlug":"supplements","url":"https://whatshealthyandwhy.com/explore/good-for-you/supplements"},"actions":["Could you become pregnant? The US Preventive Services Task Force recommends a daily supplement with 400 to 800 micrograms of folic acid [7].","Breastfeeding, fully or partly? Pediatricians advise 400 IU of vitamin D drops a day for the baby, starting soon after birth [10].","Vegan, or over 50? Get vitamin B12 from fortified foods or a supplement: plant foods lack it, and many older people absorb food B12 poorly [14][15]."],"cautions":["Taking metformin, or an acid-reducing medicine for two years or more? Ask about a B12 test, and magnesium with proton pump inhibitors, instead of guessing [22][24][26].","Pregnant or planning? Choose a prenatal with iodine, and keep preformed vitamin A (retinol) from supplements under 10,000 IU a day [8][28].","Thinking of iron for tiredness? Get ferritin checked first: iron helped tired women with low stores, but people with hemochromatosis must avoid it [20][21]."],"simpleText":"In healthy adults, the largest trials of daily multivitamins found little or no protection against heart disease, cancer or early death, and nutrients from food, not pills, went with longer life [1][3][5][6]. Supplements earn their place for a known gap: folic acid if you could become pregnant, vitamin D drops for breastfed babies, B12 for vegans and many older adults, iron when stores are low [7][10][15][16][21]. When unsure, the right blood test beats a guess.","mediumText":"How it works\n\nStart with food. In a study that followed 30,899 US adults for about six years, getting enough vitamin A, vitamin K, magnesium, zinc and copper went with lower death rates only when the nutrients came from food, and taking supplements did not go with longer life [1]. That study was observational, but it points the same way as the trials below.\n\nWhat the multivitamin trials found for everyone else. The US Preventive Services Task Force (USPSTF) found too little evidence to say whether a multivitamin prevents heart disease or cancer, and it advises against beta-carotene and vitamin E supplements for that purpose [2]. In the Physicians' Health Study II, 14,641 male doctors took a multivitamin or a placebo for a median of 11.2 years: heart attacks and strokes did not fall [3], and total cancer was 8% lower [4]. In COSMOS, 21,442 older adults saw no effect on cancer, heart disease or death [5], and among 390,124 adults followed for up to 27 years, multivitamin users did not live longer [6]. Our article on multivitamins goes further.\n\nTest before you take. For several nutrients, a blood test can answer the question directly:\n\nWhat you want to know | The test | How it is read\n\nAm I low in vitamin D? | 25-hydroxyvitamin D, written 25(OH)D | 50 nmol/L (20 ng/mL) or more is enough for most people; under 30 nmol/L (12 ng/mL) raises the risk of deficiency; over 125 nmol/L (50 ng/mL) is linked to possible harm [11]\nAm I low in B12? | Serum B12, plus methylmalonic acid (MMA) when B12 is borderline | B12 under 200 to 250 pg/mL is usually called low; MMA is the most sensitive marker and confirms a deficiency when B12 is between 150 and 399 pg/mL [14]\nAre my iron stores low? | Ferritin, with a blood count | Ferritin measures stored iron, but inflammation can distort it, so it is read alongside other results [20]\nDo I get enough omega-3? | Omega-3 index: EPA plus DHA in red blood cells | Reflects roughly the last four months of intake [18]; researchers who proposed it linked 8% or more with the lowest risk of heart death and 4% or less with the highest [19]\n\nTwo limits. Guideline panels do not advise testing everyone for vitamin D: the Endocrine Society suggests against routine 25(OH)D tests in healthy people, including those with obesity or darker skin, and the USPSTF found too little evidence to screen adults without symptoms [12][13]. And some tests answer the question poorly: blood magnesium, for instance, says little about how much magnesium the body holds [26]. Your clinician can order these tests, and several are sold by the direct-to-consumer lab services we review, which we judge on the lab behind them and who reads your results.\n\nWho has a real need. The groups below have evidence behind them, not just marketing:\n\n- Planning a pregnancy, or could become pregnant: folic acid, 400 to 800 micrograms a day, which the USPSTF gives its top grade [7]; iodine, 150 micrograms a day as potassium iodide on American Thyroid Association advice, which not every prenatal contains [8]; and enough choline, which most prenatal supplements barely provide [9]. See eating well during pregnancy.\n- Breastfeeding: the same iodine advice applies [8], and vegan mothers need a reliable B12 source, because their babies can become deficient very early [14].\n- Breastfed babies: 400 IU (10 micrograms) of vitamin D a day from soon after birth, until the baby drinks at least 1,000 mL (about a quart) of fortified formula or whole milk a day; breast milk alone does not supply enough [10][11].\n- Over 50: many older people absorb the B12 in food poorly, so the National Academies advise getting it mainly from fortified foods or a supplement [15]. From 75, the Endocrine Society suggests vitamin D beyond the standard intake [12]. See who needs B12.\n- Vegans: B12 is not optional [16]; iodine can run short without dairy, seafood or eggs [8]; and an algae oil is the plant source of ready-made EPA and DHA, because the body converts little of the omega-3 in foods such as flaxseed [17][18]. See vegan and vegetarian diets.\n- Heavy periods, low ferritin or frequent blood donation: iron, after a test [20][21]. See iron basics.\n- Little sun: vitamin D intakes are set on the assumption of minimal sun, and people with little sun exposure or darker skin are more likely to run low [11]. See vitamin D supplementation.\n- Long-term metformin or acid-reducing medicine: B12 can fall, and so can magnesium with proton pump inhibitors [22][24][25]. See which medicines deplete nutrients.\n\nDecided you need something? Check how much is too much before you buy, read what to skip, then use the supplement schedule for when to take it.","deepText":"The evidence in detail\n\nMultivitamins in well-nourished adults\n\nThe Physicians' Health Study II randomized 14,641 male US physicians aged 50 or older (mean age 64.3) to a daily multivitamin or placebo. Over a median of 11.2 years there was no effect on major cardiovascular events (HR 1.01, 95% CI 0.91–1.10) or total mortality (HR 0.94, 95% CI 0.88–1.02) [3]. Total cancer was modestly lower (17.0 versus 18.3 cases per 1,000 person-years; HR 0.92, 95% CI 0.86–0.998), with no effect on prostate or colorectal cancer and no significant change in cancer deaths (HR 0.88, 95% CI 0.77–1.01) [4].\n\nCOSMOS randomized 21,442 US adults (women aged 65 or older, men aged 60 or older) to a multivitamin-multimineral or placebo. Over a median of 3.6 years, invasive cancer (HR 0.97, 95% CI 0.86–1.09), cardiovascular events (HR 0.98, 95% CI 0.86–1.12) and all-cause mortality (HR 0.93, 95% CI 0.81–1.08) did not differ. Lung cancer was lower (HR 0.62, 95% CI 0.42–0.92), a secondary finding [5].\n\nBecause the trials had limited follow-up, a 2024 cohort study pooled 390,124 adults without chronic disease from three US cohorts, with up to 27 years of follow-up and 164,762 deaths. Daily multivitamin use was not linked to lower mortality (HR 1.04, 95% CI 1.02–1.07 in the first half of follow-up; HR 1.04, 95% CI 0.99–1.08 in the second) [6]. Users were more often women and college educated and less often smokers, a reminder that people who take supplements differ from those who do not.\n\nThe USPSTF weighed this evidence in 2022. It issued an I statement (insufficient evidence) for multivitamins and for single or paired nutrients other than beta-carotene and vitamin E, and a D recommendation (against) for those two, for preventing cardiovascular disease or cancer. At the time, 52% of US adults reported using at least one supplement and 31% a multivitamin-mineral [2].\n\nThe food comparison comes from 30,899 adults in the National Health and Nutrition Examination Survey (NHANES), followed for a median of 6.1 years (3,613 deaths). Ever-use of supplements was not associated with mortality. Adequate intakes of vitamin A, vitamin K, magnesium, zinc and copper were associated with lower all-cause or cardiovascular mortality, but only when they came from food [1]. Calcium from supplements at 1,000 mg a day or more was associated with more cancer deaths (rate ratio 1.53, 95% CI 1.04–2.25) [1]. Residual confounding and recall bias are possible in a study like this. All of these studies enrolled mostly well-nourished US adults; none tested people with a known deficiency.\n\nWhat guideline panels say about testing\n\nThe 2024 Endocrine Society guideline found no trial evidence to support routine 25(OH)D screening in the general population, including people with obesity or a dark complexion, and no clear evidence for an optimal blood level, so it suggests against routine testing [12]. The same panel suggests vitamin D beyond the dietary reference intake for ages 1 to 18, adults over 75, pregnancy and high-risk prediabetes, and against it for healthy adults under 75; it calls the best doses unclear [12]. The USPSTF noted that no single blood level defines deficiency and gave screening of adults without symptoms an I statement [13].\n\nThe cut-offs in the table come from the Food and Nutrition Board for vitamin D [11], and from laboratory practice for B12 and MMA, where an MMA above 0.271 micromol/L suggests deficiency [14]. Ferritin reflects iron stores but can be affected by inflammation, and hemoglobin is neither sensitive nor specific, so clinicians often combine measures [20]. Red-cell fatty acids reflect about 120 days of intake, while plasma levels swing with the last meal [18]. The omega-3 index was proposed by its developers as a heart-risk marker: in their analysis an index of 8% or more went with the greatest protection and 4% or less with the least [19].\n\nPregnancy and infancy\n\nThe USPSTF concluded with high certainty that folic acid has a substantial net benefit and recommends 0.4 to 0.8 mg (400 to 800 micrograms) a day for anyone planning or able to become pregnant (grade A); about 3,000 US pregnancies a year are affected by neural tube defects [7]. For iodine, the American Thyroid Association advises 150 micrograms a day as potassium iodide for anyone planning a pregnancy, pregnant or breastfeeding, and the American Academy of Pediatrics advises at least 150 micrograms plus iodized salt; of 59 best-selling prenatal supplements in 2016 to 2017, only 34 contained iodine [8]. About 90% to 95% of pregnant women take in less choline than the adequate intake of 450 mg a day, and prenatal supplements typically contain little or none [9].\n\nIron needs rise in pregnancy (the RDA is 27 mg a day) [20]. Yet the USPSTF found the evidence insufficient to judge either screening or routine iron supplementation in pregnant people without symptoms, although iron deficiency affects about 18% of pregnancies and rises from 6.9% to 28.4% between the first and third trimesters [27]. That is a question for your prenatal care team rather than a reason to add iron on your own. Preformed vitamin A needs a ceiling. Among 22,748 pregnant women, those taking more than 10,000 IU a day from supplements had 4.8 times the rate of cranial-neural-crest birth defects seen with 5,000 IU or less (95% CI 2.2–10.5), mostly when exposure came before the seventh week; the authors estimated that about 1 in 57 exposed babies had a malformation caused by the supplement [28]. That was a single observational cohort; its apparent threshold, near 10,000 IU a day of supplemental vitamin A, is the same as the adult upper limit in how much is too much. …","deepTruncated":true,"references":[{"id":"1","title":"Association Among Dietary Supplement Use, Nutrient Intake, and Mortality Among U.S. Adults: A Cohort Study","authors":"Chen F, Du M, Blumberg JB, et al.","year":2019,"journal":"Annals of Internal Medicine","pmid":"30959527","url":"https://pubmed.ncbi.nlm.nih.gov/30959527/"},{"id":"2","title":"Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: US Preventive Services Task Force Recommendation Statement","authors":"Mangione CM, Barry MJ, Nicholson WK, et al.","year":2022,"journal":"JAMA","pmid":"35727271","url":"https://pubmed.ncbi.nlm.nih.gov/35727271/"},{"id":"3","title":"Multivitamins in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial","authors":"Sesso HD, Christen WG, Bubes V, et al.","year":2012,"journal":"JAMA","pmid":"23117775","url":"https://pubmed.ncbi.nlm.nih.gov/23117775/"},{"id":"4","title":"Multivitamins in the prevention of cancer in men: the Physicians' Health Study II randomized controlled trial","authors":"Gaziano JM, Sesso HD, Christen WG, et al.","year":2012,"journal":"JAMA","pmid":"23162860","url":"https://pubmed.ncbi.nlm.nih.gov/23162860/"},{"id":"5","title":"Multivitamins in the prevention of cancer and cardiovascular disease: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial","authors":"Sesso HD, Rist PM, Aragaki AK, et al.","year":2022,"journal":"American Journal of Clinical Nutrition","pmid":"35294969","url":"https://pubmed.ncbi.nlm.nih.gov/35294969/"},{"id":"6","title":"Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts","authors":"Loftfield E, O'Connell CP, Abnet CC, et al.","year":2024,"journal":"JAMA Network Open","pmid":"38922615","url":"https://pubmed.ncbi.nlm.nih.gov/38922615/"},{"id":"7","title":"Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement","authors":"Barry MJ, Nicholson WK, Silverstein M, et al.","year":2023,"journal":"JAMA","pmid":"37526713","url":"https://pubmed.ncbi.nlm.nih.gov/37526713/"},{"id":"8","title":"Iodine: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2024,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/"},{"id":"9","title":"Choline: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2022,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/Choline-HealthProfessional/"},{"id":"10","title":"Prevention of rickets and vitamin D deficiency in infants, children, and adolescents","authors":"Wagner CL, Greer FR","year":2008,"journal":"Pediatrics","pmid":"18977996","url":"https://pubmed.ncbi.nlm.nih.gov/18977996/"},{"id":"11","title":"Vitamin D: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2025,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/"},{"id":"12","title":"Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline","authors":"Demay MB, Pittas AG, Bikle DD, et al.","year":2024,"journal":"Journal of Clinical Endocrinology and Metabolism","pmid":"38828931","url":"https://pubmed.ncbi.nlm.nih.gov/38828931/"},{"id":"13","title":"Screening for Vitamin D Deficiency in Adults: US Preventive Services Task Force Recommendation Statement","authors":"Krist AH, Davidson KW, Mangione CM, et al.","year":2021,"journal":"JAMA","pmid":"33847711","url":"https://pubmed.ncbi.nlm.nih.gov/33847711/"},{"id":"14","title":"Vitamin B12: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2025,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/"},{"id":"15","title":"Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline: Chapter 9, Vitamin B12","authors":"Institute of Medicine, Food and Nutrition Board","year":1998,"journal":"National Academies Press","url":"https://nap.nationalacademies.org/read/6015/chapter/11"},{"id":"16","title":"How prevalent is vitamin B(12) deficiency among vegetarians?","authors":"Pawlak R, Parrott SJ, Raj S, et al.","year":2013,"journal":"Nutrition Reviews","pmid":"23356638","url":"https://pubmed.ncbi.nlm.nih.gov/23356638/"},{"id":"17","title":"Blood docosahexaenoic acid and eicosapentaenoic acid in vegans: Associations with age and gender and effects of an algal-derived omega-3 fatty acid supplement","authors":"Sarter B, Kelsey KS, Schwartz TA, Harris WS","year":2015,"journal":"Clinical Nutrition","pmid":"24679552","url":"https://pubmed.ncbi.nlm.nih.gov/24679552/"},{"id":"18","title":"Omega-3 Fatty Acids: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2025,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/"},{"id":"19","title":"The Omega-3 Index: a new risk factor for death from coronary heart disease?","authors":"Harris WS, Von Schacky C","year":2004,"journal":"Preventive Medicine","pmid":"15208005","url":"https://pubmed.ncbi.nlm.nih.gov/15208005/"},{"id":"20","title":"Iron: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2025,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/"},{"id":"21","title":"Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial","authors":"Vaucher P, Druais PL, Waldvogel S, Favrat B","year":2012,"journal":"CMAJ","pmid":"22777991","url":"https://pubmed.ncbi.nlm.nih.gov/22777991/"},{"id":"22","title":"Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study","authors":"Aroda VR, Edelstein SL, Goldberg RB, et al.","year":2016,"journal":"Journal of Clinical Endocrinology and Metabolism","pmid":"26900641","url":"https://pubmed.ncbi.nlm.nih.gov/26900641/"},{"id":"23","title":"Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial","authors":"de Jager J, Kooy A, Lehert P, et al.","year":2010,"journal":"BMJ","pmid":"20488910","url":"https://pubmed.ncbi.nlm.nih.gov/20488910/"},{"id":"24","title":"Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency","authors":"Lam JR, Schneider JL, Zhao W, Corley DA","year":2013,"journal":"JAMA","pmid":"24327038","url":"https://pubmed.ncbi.nlm.nih.gov/24327038/"},{"id":"25","title":"Proton pump inhibitors linked to hypomagnesemia: a systematic review and meta-analysis of observational studies","authors":"Cheungpasitporn W, Thongprayoon C, Kittanamongkolchai W, et al.","year":2015,"journal":"Renal Failure","pmid":"26108134","url":"https://pubmed.ncbi.nlm.nih.gov/26108134/"},{"id":"26","title":"Magnesium: Fact Sheet for Health Professionals","authors":"NIH Office of Dietary Supplements","year":2026,"journal":"NIH Office of Dietary Supplements","url":"https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/"},{"id":"27","title":"Screening and Supplementation for Iron Deficiency and Iron Deficiency Anemia During Pregnancy: US Preventive Services Task Force Recommendation Statement","authors":"Nicholson WK, Silverstein M, Wong JB, et al.","year":2024,"journal":"JAMA","pmid":"39163015","url":"https://pubmed.ncbi.nlm.nih.gov/39163015/"},{"id":"28","title":"Teratogenicity of high vitamin A intake","authors":"Rothman KJ, Moore LL, Singer MR, et al.","year":1995,"journal":"New England Journal of Medicine","pmid":"7477116","url":"https://pubmed.ncbi.nlm.nih.gov/7477116/"}],"wordCount":2558,"source":{"path":"src/content/topics/supplement-basics/do-you-need-a-supplement.md"},"citeAs":"“Do you need a vitamin or mineral supplement, and how can you tell?.” What's Healthy and Why. https://whatshealthyandwhy.com/supplement-basics/do-you-need-a-supplement","notice":"General information backed by peer-reviewed research, not medical advice."}