According to the National Health and Nutrition Examination Survey, 52% of surveyed adults in the US use at least one dietary supplement per month, and 31% use a multivitamin supplement. The most popular reason to use supplements was to 'improve overall health'.
As eating fruits and vegetables is linked to reduced cardiovascular disease and cancer risk, many suppose it is reasonable to take supplements that contain the same vitamins as in fruits and vegetables. However, researchers say that it may not be so simple: the effects of individual micronutrients act differently in the body than when packaged with other dietary components.
In the current review, a group of independent researchers conducted a systematic review of 84 studies investigating the evidence for the efficacy of supplementation of single nutrients, nutrient pairs, and multivitamins in reducing cardiovascular disease, cancer, and mortality, alongside their potential harms.
From their analysis, they concluded with moderate certainty that the harms of beta carotene supplementation outweigh the benefits for preventing cardiovascular disease and cancer. They also noted that vitamin E supplements produce no net benefit for either condition.
They added, however, that there is insufficient evidence to determine the balance of benefits and harms in taking other supplements and multivitamins to prevent cardiovascular disease and cancer.
As such, the USPSTF recommends that healthy individuals who are not pregnant should not use supplements of beta carotene or vitamin E to prevent cardiovascular disease or cancer. They note, however, that these recommendations don't apply to individuals who are, or are trying to, get pregnant, or those with vitamin deficiencies.
"Pregnant individuals should keep in mind that these guidelines don't apply to them," said Dr. Natalie Cameron, an instructor of general internal medicine at Northwestern University and co-author of a JAMA editorial discussing the new guidelines.
"Certain vitamins, such as folic acid, are essential for pregnant women to support healthy fetal development. The most common way to meet these needs is to take a prenatal vitamin. More data is needed to understand how specific vitamin supplementation may modify risk of adverse pregnancy outcomes and cardiovascular complications during pregnancy," she continued.
In the JAMA editorial discussing the guidelines, Dr. Cameron and colleagues wrote: "Rather than focusing money, time, and attention on supplements, it would be better to emphasize lower-risk, higher-benefit activities. Individual, public health, public policy, and civic efforts should focus on supporting people in regular preventive care, following a healthful diet, getting exercise, maintaining a healthy weight, and avoiding smoking."
Sources: Science Daily, JAMA Network a, JAMA Network b