Are Multivitamins Good for You? A Look at Whether They Actually Work

Many people take a multivitamin to make sure they’re getting all the vitamins and minerals they need. It seems like an easy way to fill in any potential gaps in nutrition — especially for people who can’t always eat a balanced diet. But do multivitamins really work? Scientists have looked at whether they actually make a difference in your health. And the research might surprise you.

What are the benefits of multivitamins?

Most studies on multivitamins are designed to look at their potential benefits in specific areas. 

Heart health

When it comes to multivitamins and heart health, the research findings are mixed. 

One large study looked at male doctors who were 40 years and older and who took a multivitamin for an average of 12 years. It made no difference in their risk for:

• Heart attack

• Stroke

• Death from heart disease 

If the doctors took the multivitamin for 20 years or more, however, they did start to see a lower risk of heart disease and stroke, according to the study.

But another study found that there may be more benefits for women. The results showed that women who took a daily multivitamin for more than 3 years had a lower rate of death from heart disease compared with those who didn’t take a multivitamin.

One large scale analysis of other studies concluded that multivitamins aren’t associated with decreased risk of heart attack, stroke, and dying from heart disease. And the United States Preventive Services Task Force does not recommend using multivitamins to prevent heart disease.

Brain health

Scientists have also looked at whether multivitamins help protect the brain — and the results are more encouraging. Several studies suggest that multivitamins may improve memory in older adults. 

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In one study, participants who took a daily multivitamin for 3 years had improved memory. The average age of people in this study was 73 years old. 

Another study saw similar results. The group that took a daily multivitamin were better able to recall things when tested 1 year and 3 years later. The average age in this study was 71 years old.

Eye health

The research in multivitamins for eye health is also promising. 

One study suggests that certain mineral supplements may help protect long-term vision. 

People ages 55 to 80 years who took a daily supplement for 6 years were better able to maintain their vision. More specifically, they were less likely to develop worsening age-related macular degeneration (AMD). This daily supplement included many ingredients in a multivitamin, such as: 

• Vitamin C

• Vitamin E

• Vitamin A (beta-carotene)

• Zinc 

• Copper

Of note, a later study found that beta-carotene wasn’t a required ingredient to achieve the effects. 

Research also suggests that a multivitamin can help decrease the risk of certain types of cataracts. In one study, people ages 43 to 86 years who took a daily multivitamin for more than 10 years had a lower risk of cataracts. And another study of 15,000 male physicians showed similar benefits.

Cancer

Overall, it’s not clear if a daily multivitamin increases or decreases the likelihood of developing cancer. 

One study looked at women ages 20 to 79 years who took a daily multivitamin for 10 years. The researchers found no difference in their risk of developing breast cancer. 

Another study looked at men who took a daily multivitamin for more than 10 years. The study found a very small decrease in risk for cancer in general. But when the researchers tried to break that down into specific types of cancers, they couldn’t find any benefit. 

One study of both men and women ages 50 to 71 years who took a daily multivitamin for 16 years showed a decreased risk of colon cancer. But the same study also found that men taking a daily multivitamin had a higher risk of prostate cancer, lung cancer, and leukemia. And women had a higher risk of head and neck cancer. 

So at the end of the day, a lot more research is needed to understand how multivitamins affect cancer risk.

Are there any multivitamin side effects?

For most people, especially those who eat a regular diet, a multivitamin won’t hurt or lead to any unwanted side effects.

But in some cases, taking a multivitamin may lead to side effects. This can happen if you’re combining a multivitamin with additional vitamin supplements. Or if you’re eating a lot of one food that’s high in a certain vitamin.

In these cases, you may unintentionally overdose on vitamins. A few to watch out for include:

• Vitamin D: Taking too much vitamin D can cause nausea, vomiting, loss of appetite, and dehydration from excessive urination.

• Vitamin C: Excess vitamin C can cause stomach cramps and diarrhea, and in some cases, kidney stones.

• Iron: Taking too much iron can lead to an upset stomach, constipation, and vomiting. It can also interfere with the absorption of zinc, another important mineral for your body.

• Vitamin A: Too much vitamin A (beta-carotene) can cause headaches, nausea, blurry vision, dizziness, and achy muscles. 

Vitamin A also has a few more potential health risks. Large amounts of vitamin A increases the likelihood of developing lung cancer in cigarette smokers, former smokers, and people who have been exposed to asbestos. And too much vitamin A during pregnancy has been linked to birth defects.

Should you take a multivitamin every day?

If you’re eating a healthy, balanced diet most of the time, you probably don’t need a multivitamin. Research is still very mixed on whether they work, so multivitamins may not be worth the cost or effort.

But if you’re at risk of not getting enough of a particular vitamin or nutrient, it may make sense. People who have restricted diets are at increased risk of nutrient deficiencies. For example, vegans and vegetarians who eat a plant-based diet often require extra vitamin B12. This is because B12 is mostly found in animal-source foods.

Older adults may also benefit from multivitamins because vitamin B12 absorption decreases as you age. It can also be harder for older adults to get enough vitamin D.

If you do decide that you’d like to take a multivitamin, be sure to read the label and choose one that makes sense based on your situation. For example, vitamins for older adults generally contain higher levels of vitamin B12. And prenatal supplements typically don’t contain vitamin A in its retinol form, which may be harmful during pregnancy.

When is the best time to take a multivitamin?

The best time to take a multivitamin is right before a meal or during a meal with water. This is because food helps your body absorb fat-soluble vitamins (A, D, E, and K vitamins). And water is needed to absorb water-soluble vitamins (B and C vitamins). 

It’s also best to take multivitamins during the daytime, because digestion slows while you sleep. So taking it at night could affect the way you absorb the nutrients from the multivitamin.

Why trust our experts?

Written by:

Cherilyn Davis, MD

Cherilyn Davis, MD, is a board-certified pediatrician in New York City. She has held local and national roles at the American Medical Women’s Association including board member of the physician division and physician chair of social media.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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