Vitamin Myths and Misconceptions: What the Evidence Says

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Each belief below is a claim to check, not a fact. We say what the sources found, for which people and which vitamin, and how strong the evidence is. Labels: established nutritional role, mixed, insufficient evidence, no good evidence of benefit, evidence of harm, marketing claim. Findings for one vitamin, form or group do not automatically carry over to another. A clinician or pharmacist can say what is right for a person.

"Vitamins give you energy"

The NHS says several B vitamins help the body release energy from food. [1] That is a normal role, and a shortage such as vitamin B12 deficiency anaemia can cause problems. [1] It does not show that extra vitamins add energy in a person who is not short of them. A 2021 review of 16 randomized trials (6,276 people) of B12 in people without overt deficiency or advanced neurological disorders found no effect on cognitive function or depression, and only one study reported on unexplained fatigue, so no analysis was possible. [2] A 2013 meta-analysis of eight placebo-controlled multivitamin/mineral trials in apparently healthy people found lower perceived stress, anxiety and fatigue; the trials lasted at least 28 days, and the authors themselves raised questions about doses and active ingredients. [3] So the honest summary is mixed or insufficient evidence, not a proven lift. Fatigue that does not go away deserves a medical check; see Energy supplements compared.

"Natural vitamins are better and safer"

A 2013 review of human studies noted that synthetic and food-derived vitamin C is chemically identical, and that all steady-state human studies found no difference in bioavailability between them, with only small, transient differences in some other human studies. [4] That is about vitamin C only; forms of other vitamins (for example folate, B12, vitamin E) need their own check. NCCIH adds that "natural" does not always mean "safe." [5] See Natural vs synthetic vitamins.

"Water-soluble vitamins are harmless"

MedlinePlus says leftover water-soluble vitamins leave the body in urine, [6] but the NHS says taking 200 mg or more a day of vitamin B6 can lead to loss of feeling in the arms and legs (peripheral neuropathy), [1] and more than 1,000 mg of vitamin C a day can cause diarrhoea. [7] Both are UK statements about supplements, not food. Details: Vitamin B6 toxicity.

"More is better"

MedlinePlus: many people think that if some is good, a lot is better, but this is not always the case. [6] The US Preventive Services Task Force (2022) concluded with moderate certainty that harms of beta-carotene supplements outweigh benefits for preventing cardiovascular disease or cancer, and that vitamin E has no net benefit for that purpose, in nonpregnant adults. [8] The NHS says more than an average of 1.5 mg (1,500 mcg) a day of vitamin A over many years may affect bones. [9] The NIA advises older adults to avoid megadoses. [10]

"A multivitamin prevents heart disease and cancer"

The USPSTF (2022) found the evidence insufficient to judge benefits and harms of multivitamins for preventing cardiovascular disease or cancer. [8] In the Physicians' Health Study II, 14,641 male US physicians aged 50 or older had a small reduction in total cancer (hazard ratio 0.92) over a median 11.2 years, but not in prostate or colorectal cancer. [11] In COSMOS-Mind, 2,262 older adults showed a small cognitive benefit over 3 years (mean z 0.07), [12] and a meta-analysis of three COSMOS substudies agreed. [13] These are single-product trials in older adults and do not show that any multivitamin prevents disease. See Multivitamins.

"Vitamin C prevents colds"

The 2013 Cochrane review found that regular vitamin C did not reduce the number of colds in the general community (risk ratio 0.97, 95% CI 0.94 to 1.00), though in 598 marathon runners, skiers and soldiers on subarctic exercises the ratio was 0.48. It shortened colds by 8% in adults and 14% in children, and starting it after symptoms began showed no consistent effect. [14] More: Vitamin C, vitamin D and zinc for immune health.

"A pill can replace a good diet"

The NIA says it is usually better to get nutrients from food than a pill, because nutrient-dense foods contain other good things like fibre. [10] The NHS says most people should get what they need from a varied and balanced diet. [16] See Food vs supplement sources.