Question 1

Do healthy UK adults need a multivitamin?

Accepted Answer

NHS guidance is that most people get the vitamins and minerals they need from a varied, balanced diet, with two specific exceptions: all UK adults are advised to consider a 10 mcg vitamin D supplement in autumn and winter (because UK latitude means cutaneous synthesis is negligible October–March), and women who could become pregnant or are pregnant are advised to take 400 mcg folic acid daily until 12 weeks of gestation. SACN reviews of NDNS data confirm pockets of inadequacy — vitamin D, iron in menstruating women, magnesium, selenium, folate — but stop short of a population-wide multivitamin recommendation. A multivitamin is reasonable insurance for those with restrictive diets, older adults, or anyone with a documented gap.

Question 2

What does the largest RCT say about multivitamins and disease prevention?

Accepted Answer

The Physicians' Health Study II (n=14,641 male physicians aged 50+, median 11.2 years follow-up) is the largest and longest RCT of multivitamins in healthy adults. It found no reduction in major cardiovascular events (HR 1.01) but a small 8% reduction in total cancer incidence (HR 0.92). The 2022 US Preventive Services Task Force concluded the evidence was insufficient to recommend multivitamins for cardiovascular disease or cancer prevention in healthy adults, and explicitly recommended against beta-carotene and vitamin E for chronic disease prevention.

Question 3

What dietary gaps does NDNS identify in UK adults?

Accepted Answer

The UK National Diet and Nutrition Survey (NDNS) consistently shows mean intakes below the Lower Reference Nutrient Intake (LRNI) for several micronutrients in subgroups: vitamin D across the whole population, iron in girls and menstruating women, magnesium, selenium, potassium, and zinc in adolescents and some adults. SACN reports based on NDNS data have led to the universal vitamin D recommendation but have generally favoured targeted single-nutrient interventions over multivitamins. A multivitamin can act as a safety net but is not a substitute for addressing the underlying dietary pattern.

Question 4

What are the risks of taking a multivitamin?

Accepted Answer

Risks are dose-dependent. Standard formulas providing approximately 100% NRV are very safe. Mega-dose products risk exceeding EFSA tolerable upper intake levels — particularly for vitamin A (teratogenic in pregnancy at high doses), iron (oxidative damage), zinc (induces copper deficiency above 25 mg/day), B6 (peripheral neuropathy above 200 mg/day) and selenium. Beta-carotene at high doses increases lung cancer risk in smokers (CARET, ATBC trials). Pregnancy formulas use beta-carotene, not retinol, for this reason. People taking warfarin (vitamin K interaction) or thyroxine (calcium/iron interaction) should review their supplement with a pharmacist.

Question 5

Should pregnant women take a multivitamin?

Accepted Answer

NHS recommends 400 mcg folic acid daily from before conception until 12 weeks pregnant (or 5 mg in higher-risk groups including obesity, diabetes, family history of neural tube defects). All UK adults including pregnant women are advised 10 mcg vitamin D daily. Many women find a pregnancy-specific multivitamin a convenient way to deliver these alongside iron and other nutrients, but the evidence-based core is folic acid plus vitamin D. Pregnancy multis must avoid retinol-form vitamin A — large doses are teratogenic. Standard adult multivitamins are not appropriate in pregnancy.

Question 6

Does a multivitamin help cognitive function?

Accepted Answer

The COSMOS-Mind sub-study (n=2,262, 3 years, adults aged 65+) reported a small but statistically significant benefit on global cognition with daily multivitamin versus placebo — equivalent to slowing age-related decline by roughly 60% over the trial period. This is the strongest cognitive signal to date, but it has not been replicated in younger or independent populations and the absolute effect size is modest. The trial does not support multivitamin use for cognitive enhancement in healthy younger adults, but it adds to the case for multivitamins as reasonable insurance in older adults.

Grade	Health Outcome	Studies	Participants	Effect
B	Cardiovascular Events in Healthy Adults3 studies	3	27,000	Long-term multivitamin use in healthy adults does not reduce major cardiovascular events. Largest RCT (Physicians' Health Study II) reported no benefit over 11 years of follow-up.
B	Cancer Incidence and Mortality2 studies	2	30,000	PHS II reported a small reduction in total cancer incidence (8% relative risk reduction) but no effect on cancer mortality. Effect size is modest and not yet replicated in independent large RCTs.
B	All-Cause Mortality5 studies	5	90,000	Pooled analyses of multivitamin RCTs show no reduction in all-cause mortality. A 2022 USPSTF systematic review concluded evidence was insufficient to recommend multivitamins for chronic disease prevention.
C	Cognitive Function in Older Adults2 studies	2	5,500	COSMOS-Mind sub-study reported a small benefit on global cognition in older adults (~3 years), equivalent to slowing age-related decline by approximately 60%. Effect requires replication.

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