Many adults take multivitamins in the hope of improving their health. However, the benefits and harms of regular multivitamin use remain unclear. Previous studies of multivitamin use and mortality have yielded mixed results and been limited by short follow-up times.
A large analysis of data from nearly 400,000 U.S. adults followed for more than 20 years was published June 26, 2024, in JAMA. The participants included in this analysis were generally healthy, with no history of cancer, other chronic diseases, or even vitamin deficiencies!
This study looked at the use of multivitamins containing vitamins A, B3, B6, B12, C, D, and E; beta carotene; folic acid; calcium; magnesium; selenium; and zinc. It found no association between regular multivitamin use and longer life.
Because the study population was so large and included lengthy follow-up and extensive information on demographics and lifestyle factors, the research was less subject to the possible biases that may have influenced the findings of other studies. For example, people who use multivitamins may have healthier lifestyles in general, and sicker patients may be more likely to increase their use of multivitamins.
The study was particularly focussed on mortality from cancer, heart disease, and cerebrovascular diseases. The results were adjusted for factors such as race, ethnicity, and level of education, although the researchers did remark that most of the participants in the study were white.
In population-based research there are always concerns about the accuracy of self-reporting. First, multivitamin users tend to eat healthier diets, exercise more, and smoke cigarettes less; this phenomenon has been referred to as the healthy user effect. Second, it is unclear if multivitamin use changes over time. Patients with diagnosed disease may increase their multivitamin intake seeking health benefits; this has been termed the sick user effect.
This large study indicates that there is virtually no difference in the risk for heart disease, cancer, and cerebrovascular disease mortality between those who use multivitamins and those who do not.
Our Take: there’s more to this story
Although this cohort study doesn’t support using multivitamins as “health insurance” for everyone, that doesn’t mean they are “mostly useless” as stated in the National Post headline: we consider that a gross oversimplification!
These results assessed the effects of multivitamins on the quantity of life, but they didn’t look at the quality of life. In many specific circumstances there are trials that show positive effects on quality of life, especially as we age. We SHINE doctors would like our vision and memories to remain as good as possible for as long as possible, even if we don’t live longer!
Some of the benefits from multivitamins are:
Pregnancy: multivitamins with folate decrease obstetric complications, congenital anomalies, and are associated with prevention of pediatric cancers
Age-related macular degeneration: probably slows progression from early or intermediate to late stage disease
Memory: improves memory in older adults. Researchers estimated improved memory performance by the equivalent of 3.1 years of age-related memory change
Dementia risk reduction later in life: slowed cognitive decline by 2 years
Hip fractures from osteoporosis: multivitamins are significantly protective
Better behaviour in prisons: 39% fewer rule violations in young male prison inmates on multivitamins
Also note that the study excluded people in institutions, so the benefits to prisoners were not included. We don’t think prisoners are likely getting the best fresh nutrient-dense foods, so they’ll benefit more from supplementation than fit foodies do. But then what about folk in retirement homes, also eating institutional food? Might they need more than, say, a young adult? They are the ones trying to stave off macular degeneration and the effects of age-related and other dementias.
We have always advocated for a clean, minimally processed, high vegetable content diet as the foundation of good health. If asked whether we would budget for a multivitamin versus high quality organic food, we would always opt for the food!
Naturopathic doctors prefer to use vitamins and minerals as indicated for individual needs. Do you have low ferritin? You need iron. Do you have migraine headaches? You will likely benefit from magnesium. Are you deficient in B12 or Vitamin D? Better to supplement to get into the optimum range.
Some people take multivitamins to cover gaps on days when they may not eat as well as they would like.
This study reinforces the knowledge that it is good to personalise what supplementation you are using, according to your circumstances, and what you are trying to achieve. This advice extends to the use of multivitamins, as well as targeted nutritional healing.
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