Multivitamins Don't Do Much For Your Health, New Study Shows

The benefits of multivitamins may be all in the user's minds, new research has found. 

People who use multivitamins and multiminerals (MVM) self-report 30% overall better health, even though they have no apparent differences in measurable health outcomes than non-users, according to a study published in medical journal BMJ on November 4.  

Researchers based out of Boston, Massachusetts used data from nearly 5,000 adult MVM users and 16,670 non-users from the National Health Interview Survey to compare their health. They measured psychological and physical health, including 19 health conditions and 10 chronic diseases.

“We also looked at measures of mobility—so whether you can do daily activities by yourself—and with all of these health outcomes, there was no difference between multivitamins users and non-users,” Manish Paranjpe, an MD student at Harvard Medical School and lead author of the study, tells Verywell.

So why do MVM users say they’re healthier than their supplement-free Americans? Paranjpe says there’s two possible reasons.

“One is that people taking multivitamins have what’s called a ‘positive expectation effect.’ They expect that these multivitamins are going to help them somehow, and so people taking them tend to report better health,” Paranjpe says.

“Another possible explanation is that people taking multivitamins are just generally more positive people in general. And so they tend to rate their health better, when in reality, it probably isn't.”

Fang Fang Zhang, MD, PhD, a nutrition and cancer epidemiologist and associate professor at Tufts University, has also conducted research on supplement use. 

Zhang’s recent study found that dietary supplement use does not reduce the probability of death and/or cancer, and that supplement use itself likely does not have any direct health benefits. However, people who do take supplements tend to have healthier lifestyles and have higher socioeconomic status—which are both factors that affect mortality, she says.

“In addition, supplements users have higher levels of nutrient intake from foods alone compared to non-users,” Zhang tells Verywell. “Therefore, without any additional nutrients from supplements, those who use supplements already get enough nutrients from food to reduce their risk of death.”

Lifestyle Factors Matter

Like Zhang points out, lifestyle factors including a healthy diet and regular exercise have an effect on overall health. Research shows that a healthy, balanced, nutrient-rich diet is key to maintaining health and reducing the chance of conditions like diabetes and high blood pressure.

Paranjpe says that in the U.S., the multivitamin and supplement industry is very large and lucrative, and efforts from industry players can make consumers think there’s a benefit to taking their products. The power of the industry was one of the motivations behind his research team’s study; they wanted to understand why so many people take multivitamins, “when for the general population, there's not much reason to take them.”

“The main point that we want to drive home is that your money could be better spent on more evidence-based interventions, and things such as exercise and maintaining a healthy diet,” Paranjpe says. “We have a lot of evidence to show that those things will improve your health.”

What’s more, there’s a danger in taking too many vitamins or supplements. Zhang says her study suggests that high doses of calcium from supplements (1000 mg/day or higher) was associated with an increased risk of death due to cancer. 

For people with no signs of vitamin D deficiency, high doses of vitamin D supplements (400 IU/d or higher) was linked to an increased risk of all-cause and cancer mortality, she says. Further research is needed, Zhang says, but these results show that there’s risk of overdoing it with vitamins. 

That’s not to say that there’s no need for supplements or vitamins for certain segments of the population. Some people have real deficiencies and do need support. 

“This would apply to individuals with medical conditions that lead to malabsorption of nutrients from foods or those who have specific dietary practices that could cause nutritional deficiency,” Zhang says. 

“[But] the general population should aim to eat a healthy and balanced diet rather than relying on dietary supplements.”