This story is a part of The Elemental Guide to Vitamins. Here are the vitamins and supplements that are covered: multivitamins, vitamin D, vitamin C, calcium, B vitamins, omega-3, vitamin E, fiber, protein, and probiotics.
Multivitamins have been around since the 1930s. While it took Americans a while to warm up to the idea of swallowing a daily supplement, by the 1970s these products had become popular among both kids and adults. While specific ingredients and dosages vary a bit from one product to the next, most contain a cocktail of 25 or more essential vitamins and minerals, including vitamin C, Bs, A, and more.
The allure of these pills is obvious: Like a safety net, multivitamins are there to catch and address any nutrient requirements that your normal diet may miss. And some of the early research on multivitamins turned up evidence of benefits.
A large 1998 study published in the Annals of Internal Medicine found that long-term use of multivitamins could lower a woman’s risk for colon cancer. And research dating back to the 1980s found that pregnant women who take a multivitamin containing folic acid are less likely to give birth to children with neural tube defects.
More recently, a 2009 study in the American Journal of Clinical Nutrition found that women who took a multivitamin tended to have longer telomeres, which is a genetic marker of improved health. And a 2012 trial appearing in the Journal of the American Medical Association (JAMA) found that men age 50 and older who took a Centrum Silver multivitamin every day for 10 years or longer were a little less likely to develop cancer than men who took a placebo.
While many people assume that vitamins and nutrients are healthy — and so getting more of them is a good thing — the reality is more complicated than that.
Studies like these helped popularize the use of multivitamins. But in many cases, these findings have been questioned by experts or offset by newer and better experiments. For example, researchers immediately debated the validity of the JAMA study’s conclusions on cancer risk among older men. “The authors did not find that the supplement prevented any particular cancer preferentially, and there was no evidence of an association between adherence and the protective effect,” argued a JAMA editorial that accompanied the study’s publication.
While many people assume that vitamins and nutrients are healthy — and so getting more of them is a good thing — the reality is more complicated than that. Unless someone has a critical deficiency, more is not necessarily better, says Mark Moyad, MD, the Jenkins/Pokempner director of preventive and alternative medicine at the University of Michigan. In some cases, such as with vitamin E and certain antioxidants, consuming too much in supplement form can promote the development of medical issues, including risk for cancer, he says. At the same time, it’s not at all clear that the human body can take up and use nutrients from pills in the same way it uses nutrients from food, which are often ingested with fats or other molecules that aid absorption.
In 2018, a large meta-analysis of high-quality multivitamin trials concluded that these pills do not lower a person’s risk for cardiovascular disease, stroke, heart attack, or early death. More research has found that multivitamins do not help older adults avoid age-related mental declines. A 2006 “state-of-the-science” statement from the National Institutes of Health (NIH) concluded that the evidence “is insufficient to recommend either for or against the use of multivitamins by the American public to prevent chronic disease.”
Of course, not all multivitamins are created equal. From one product to the next, the types and amounts of included nutrients can vary widely, which may be one of the reasons the research on multivitamins is mixed. But depending on the makeup of a multivitamin, there may even be some risks associated with its use. During pregnancy, women who take too much vitamin A — a common ingredient in multivitamins — may be at greater risk for having kids with birth defects, according to an NIH fact sheet. Also, multivitamins containing beta carotene or vitamin A may increase lung cancer risks among smokers or former smokers. And a 2017 analysis from ConsumerLab.com, a private company that tests supplements for quality control issues, found 46% of multivitamin products failed to meet basic quality-control standards; while some multis didn’t break apart properly during digestion, others were short on their listed amounts of nutrients.
Long story short, the jury’s still out when it comes to the usefulness of multivitamins. The NIH recommends that pregnant women take supplements containing iron and folic acid to prevent birth defects or complications, but these do not necessarily have to come from a multivitamin tablet.
There’s some evidence that taking a multivitamin may help some people — particularly older adults — avoid cancer. But experts say people need to be careful about overdoing it when it comes to the specific nutrients in these products. “If you’re taking a multivitamin and also something for memory or eye health or skin health, a lot of these are just different combinations of many of the same ingredients,” says Zhaoping Li, MD, a professor of medicine and chief of the Division of Clinical Nutrition at UCLA. This overlap among products can lead to unintentional and potentially risky nutrient overdoses, Li says.
The bottom line: If you’re concerned about your nutrient intakes, Li recommends eating more whole fruits and vegetables. Compared to multivitamins, these healthy, nutrient-rich foods have a lot more evidence backing their benefits.
This story is a part of The Elemental Guide to Vitamins.