27-Year Study Finds No Survival Benefit for Daily Multivitamin Use

Daily Multivitamin Use Shows No Mortality Benefit

Daily Multivitamin Use Shows No Mortality Benefit

Agnès Vernet | 11 July 2024

Taking multivitamins daily has no beneficial effect on mortality, according to a large cohort study from the U.S. National Institutes of Health (NIH).

Taking multivitamins is a common health practice, with many French people and one in three American adults, especially older individuals and those with higher education, incorporating them into their daily routines. But does this practise actually improve health or increase survival rates? This was the question addressed by the study, published in JAMA Network Open.

Certain supplements are known to have notable effects. For instance, beta-carotene, vitamins C and E, and zinc can slow age-related macular degeneration. Folic acid intake for women planning to conceive can prevent neural tube defects in unborn children. However, the benefits of multivitamin cocktails remain unclear.

A previous meta-analysis could not determine the cardiovascular benefits of multivitamins due to insufficient long-term follow-up in the studies analysed. However, data from the recent Cocoa Supplement and Multivitamin Outcomes Study suggested that daily multivitamins might protect the ageing brain.

Despite these findings, most available studies and meta-analyses have significant biases or small sample sizes, making it difficult to draw definitive conclusions.

27-Year Study Finds No Survival Benefit

Marie-Christine Boutron-Ruault, an epidemiologist at the Institut National de la Santé et de la Recherche Médicale (Inserm) in France, who did not participate in the study, highlighted the strength of the new study when speaking to Medscape’s French edition: "It includes a large number of people who take multivitamins every day and all year round, which is harder to find in Europe," she noted.

NIH scientists analysed data from three large prospective studies: the NIH–AARP Diet and Health Study (327,732 participants); the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (42,732 participants); and the Agricultural Health Study (19,660 participants). Conducted between 1993 and 2004, the follow-up period lasted 27 years and included 390,124 adults without a history of cancer or chronic diseases.

Participants were classified based on their self-reported multivitamin use as nonusers, occasional users, or daily users. During the follow-up, 164,762 deaths were recorded, including 18,327 who were occasional users and 70,677 who were daily users.

Statistical analysis revealed no survival benefit from regular multivitamin use.

Multivitamin use was not associated with a lower risk of all-cause mortality, both in the first half of the follow-up period (adjusted RR 1.04 [1.02-1.07]) or the second half (adjusted RR 1.04 [0.99-1.08]).

Comparing daily users with nonusers showed no significant effect, regardless of age, smoking status, ethnicity, body mass index, or dietary habits.

"These products have no benefit on mortality. This supports the recommendations from ANSES: multivitamin treatments should remain occasional. If a patient consults, biological tests should be prescribed to target the appropriate supplementation," commented Boutron-Ruault.

Risks of Excessive Supplementation

Excessive supplementation can sometimes be harmful. "We know that excessive doses of folic acid can boost malignant proliferation, and excess vitamin B12 can have neurotoxic effects," emphasised Boutron-Ruault.

Future studies should explore other confounding factors, such as healthcare access. "Two significant biases exist in these studies: the 'superhealthy' patient bias, where individuals with healthy lifestyles take supplements to be even healthier, and the 'sick' patient bias, where individuals start taking vitamins to feel better, but they are actually experiencing early symptoms of a disease," according to Boutron-Ruault. It is also difficult to draw conclusions for occasional users due to the heterogeneous nature of this group and potential memory biases in self-reporting.

The debate on the usefulness of multivitamins, therefore, remains open.

Marie-Christine Boutron-Ruault declared receiving payments from Mayoly Spindler Laboratories for a lecture in 2020 and from Gilead Sciences in 2020 and 2021.

Medscape

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