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No benefit from taking multivitamins daily

No benefit from taking multivitamins daily
No benefit from taking multivitamins daily

Nearly one in three Americans takes a daily multivitamin supplement, with the primary reason being to maintain or improve health. Studying the effectiveness of multivitamin supplements in the “real world” is complicated by the “healthy user effect” – people who take vitamin supplements tend to eat healthier, exercise more, and smoke less. The “sick user effect” may also play a role – patients with a diagnosed illness may increase their multivitamin intake due to the perceived benefits.

A new study examines the risk of death associated with daily multivitamin use by analyzing three different U.S. populations whose use was repeatedly assessed over time and health-related outcomes were tracked. This is a large study of over 390,000 adults, with 164,000 deaths reported.

The study

This was not a new clinical trial. It was led by Erikka Loftfield and researchers at the National Cancer Institute of the National Institutes of Health and published on June 26, 2024. JAMA Network open. Participants in this analysis were from the National Institutes of Health–AARP Diet and Health Study (NIH-AARP) cohort (initially 550,596 AARP members ages 50–71), the PLCO Cancer Screening Trial cohort (65,577 participants ages 55–74), and the Agricultural Health Study (AHS) cohort (57,333 participants ages 18+). After exclusions due to data quality, further exclusions included individuals with extreme caloric intake or those with chronic diseases. The final population available for analysis consisted of 390,124 adults who entered the study as early as 1993! The average age was 61 years and the cohort was 55% male.

In all three studies, participants were asked about their use of dietary supplements at baseline and follow-up. Those who answered “yes” were asked about the frequency of multivitamin use using predefined categories. Categories of multivitamin use were harmonized into three groups: non-users, non-daily users, and daily users of multivitamins.

As I noted above, there are many potential confounders that the authors attempted to harmonize across studies. These include age, gender, race/ethnicity, education level, smoking behavior/intensity, BMI, marital status, physical activity, alcohol consumption, coffee consumption, use of other dietary supplements, Healthy Eating Index, and family history of cancer.

Participants were followed from baseline until the date of death, loss to follow-up, or the end of the study period. Cause-specific mortality was determined from death certificates. Baseline results from the three different studies were similar, so the pooled analysis formed the basis for the overall conclusions. Although confounding factors were minimized because these were observational data, it is possible that there are unmeasured/unadjusted confounders that were not accounted for.

Results

In the three cohorts, daily multivitamin users were comparable to those who did not take them, except for a few differences:

Participants who took multivitamin supplements were more likely to use individual supplements, had a lower BMI, and had better diets than non-users. Multivitamin supplement use did not differ significantly by race/ethnicity or family history of cancer.

And as for effectiveness, daily multivitamin intake was associated with higher Risk of death compared to non-users (hazard ratio 1.04, 95% confidence interval 1.02-1.07). That is, mortality was 4% higher in multivitamin users. There were no differences in mortality for heart disease, cancer and cerebrovascular mortality:

No justification for daily multivitamin supplements

There is no doubt that vitamins play a crucial role in health. Supplementation is justified and evidence-based in certain circumstances, such as folic acid supplementation during pregnancy. However, supplementation is not always beneficial – just think of the damage caused by beta-carotene supplements or vitamin E supplements. The benefits of Multivitamin supplements have also been questioned for years. While many take multivitamin supplements as “insurance” against a potentially suboptimal diet, there is no evidence that general multivitamin supplements provide any meaningful benefit.

Given the frequency with which Americans take multivitamin supplements, it is important to understand their health effects. This large study with 20 years of follow-up has shown that there is no clear justification for routine multivitamin use in healthy adults. Rather, multivitamin users appear to slightly higher probability of death than their counterparts who do not use them. An accompanying editorial points out that mortality effects such as those examined in this study may overlook other health-related benefits, such as age-related macular degeneration, with certain supplements. While this is true, it underscores the need for targeted, science-based supplementation when the evidence supports it, rather than indiscriminate multivitamins.

The dietary supplement industry has deceived consumers tremendously by promoting the idea that vitamin and mineral supplements are beneficial to health and that more = better. None of this has been definitively proven when it comes to longevity. It is now very obvious that multivitamins as a form of nutritional “insurance” are a strategy that is useless at best and shortens life expectancy at worst.




  • Scott Gavura, BScPhm, MBA, RPh, is committed to improving medication utilization and views the pharmacy profession from the perspective of science-based medicine. His professional interest is in improving cost-effective medication utilization at the population level. Scott holds a Bachelor of Science in Pharmacy and a Master of Business Administration from the University of Toronto and has completed an accredited Canadian hospital pharmacy residency program. His professional background includes working as a pharmacist in community and hospital settings. He is a registered pharmacist in Ontario, Canada. Scott has no conflicts of interest to disclose. Disclaimer: All views expressed by Scott are solely his personal views and do not represent the opinions of any current or former employers or organizations with which he may be affiliated. All information is provided for discussion purposes only and should not be used as a substitute for consultation with a licensed and accredited healthcare professional.



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