Is It Possible To Take Too Many Vitamins?

For decades, we were taught that vitamins and minerals in pill form could help make up for deficiencies in the typical diet or provide health and energy boosts that food alone couldn't. But some studies show no evidence that many popular supplements have real health benefits, leading many scientists to change some of their recommendations.

Yet data from the National Health and Nutrition Examination Survey (NHANES) indicates that people may be sticking with supplements. The survey data from 2017 to 2018 shows that almost 58% of people 20 years and older reported taking a dietary supplement in the last 30 days—an increase from 52% in 2011-2012.

Will all those supplements actually do you any good? And more importantly, is it possible to take too many vitamins? Health posed those questions to health and nutrition experts and dug into the research.

The Science on Supplements

Scientists know that people who eat lots of vitamin- and mineral-rich foods tend to live longer and healthier lives. But when those nutrients are served up in pill form, it's still unclear whether they have the same effect. For example, a major 2019 study in the Annals of Internal Medicine found that taking dietary supplements does not appear to reduce the risk of cancer.

Other research, including a 2018 study in the Journal of the American College of Cardiology, found that regular supplement use has no net effect on heart health or risk of early death.

"We found a surprising neutrality of effects," lead author David Jenkins, MD, professor of medicine and nutritional sciences at the University of Toronto, told Health. "In other words, it didn't seem to do anything." Their findings were accurate for multivitamins and for vitamin C, vitamin D, and calcium supplements—all nutrients that have been touted for heart health in the past.

In light of these and other studies, most experts say that dietary supplements aren't all they were once made out to be. "For the average healthy person, you probably don't need a multivitamin, multimineral supplement," said Beth Kitchin, PhD, assistant professor of nutrition studies at the University of Alabama at Birmingham. "And you certainly don't need a lot of additional supplements on top of that."

In Moderation, Most Won't Hurt, and Some Might Help

That being said, Kitchin said that a multivitamin can help make up for some deficiencies in a person's diet, especially if they avoid certain food groups like meat or dairy. Kitchin also recommended calcium and vitamin D supplements to some patients who are at risk of osteoporosis, "but I always look at their diet first before prescribing them."

Kitchin personally takes a daily multivitamin but only takes half a dose (one pill rather than a serving size of two): "I like to give myself a little extra insurance without overdoing it."

If people choose to take a multivitamin, it's best to look for one with no more than 100% of the daily value for any one nutrient—and to avoid spending a lot of money, Kitchin said. "There's no strong evidence that it will help you, but as long as you keep the dose reasonable, it's also not going to hurt you," she said.

Dr. David Jenkins also said that, when taken in moderation, most vitamin and mineral supplements won't cause harm. He also stressed that the 2018 study only looked at cardiovascular problems and early death and that supplements may still have benefits in other areas.

"We didn't look at overall health; we didn't look at whether people got beautiful hair or skin, or whether your bones got stronger," Dr. David Jenkins said. "I'm not going to say that some supplements can't be good for you in those ways."

There Is Such a Thing As Too Many

Just because supplements are safe in moderation doesn't mean that more is better. Combining multiple supplements or taking higher-than-recommended doses can increase the risk that they can cause harm, said Kitchin.

"You really can't get toxic doses of nutrients through food, but you can absolutely get toxic doses through supplements," Kitchin said.

According to the National Institutes of Health, taking high doses of vitamin C can lead to stomach cramping and diarrhea. High doses of vitamin A, vitamin D, and other nutrients can lead to more serious, long-term complications—like liver and kidney problems or a dangerous hardening of blood vessels.

"We've learned a very important lesson, in that when we isolate these nutrients out of food and put them in super-high doses, we may have some unintended consequences," Kitchin said.

Even if none of your supplements individually exceed the upper limit for a given nutrient, combining several pills—like a multivitamin and an additional vitamin D capsule, for example—may add up to higher-than-recommended doses. Supplements can also interact with each other, said Kitchin, or with medications you're already taking.

Always Run Things by Your Healthcare Provider

It's a good idea to talk with your healthcare provider about the supplements you're taking on a regular basis, said Kitchin, especially if you have a health condition, a dietary restriction, or you're on any type of medication. You should also run any new supplements you're considering by your provider or pharmacist before adding them to your regimen.

It's also important to focus on getting your nutrients from food first, said Dr. David Jenkins, and not from supplements. "Pills are not a substitute for a good diet—plant-based, fruit, veggies, whole grains, nuts, and seeds," Dr. David Jenkins said. "They are packed with what you need."

A Quick Review

The science shows that taking lots of supplements doesn't seem to have real health benefits and in some situations could be harmful. However, in moderation, there are some supplements that may be recommended if those vitamins or minerals are missing from your diet. People who eat lots of nutrient-rich foods live longer, healthier lives, so enjoy plenty of fruits, vegetables and whole grains and talk with a healthcare provider if you're unsure if you would benefit from taking supplements.