Potential Benefits of Multivitamins

In 2018, 83 percent of adults, ages 18 to 34, who used supplements reported taking a multivitamin in a Council for Responsible Nutrition Consumer Survey on Dietary Supplements. That's a lot of people who are banking on the potential benefits of multivitamins, many of which are yet unproven. Multivitamins may be beneficial for certain populations, but most people won't benefit from taking them — and there may even be risks involved.

The U.S. supplement industry has exploded over the past 25 years and is now worth more than $40 billion, according to the AARP. With global growth projected to soon exceed $180 billion, reports the U.S. Pharmacopeial Convention, it's clear that multivitamin and mineral supplements are only increasing in popularity. But why?

According to the 2018 CRN survey, the top reason for taking a multivitamin among adults was overall health and wellness. The National Institutes of Health reports that many people look at multivitamins as a sort of "nutritional insurance," filling in any gaps in their daily diets that could lead to deficiencies in certain nutrients. Busy schedules and increased intake of refined grains and fast foods make it more likely that people aren't getting everything they need from a balanced diet.

Traditional multivitamins provide most or all of the essential vitamins and nutrients at levels close to the daily value (DV), recommended daily allowance (RDA) or adequate intake (AI), all of which are the amounts considered to be effective and safe for the general population. Other multivitamin and mineral supplements may contain more of certain nutrients targeted towards particular populations, such as extra calcium for women, or extra B vitamins to support men's heart health.

Specialized multivitamins may be aimed at athletes or people looking to lose weight, while others are promoted to improve immune function or provide relief for menopause symptoms. Some of these multivitamins may include herbal ingredients and come in packs containing several pills to be taken daily. Whether or not any of these supplements deliver their proposed benefits is yet to be determined.

The NIH reports that taking multivitamins increases daily intake of important nutrients, which may be helpful for people who do not have adequate dietary intakes. However, beyond that, the benefits are unclear. Some research has shown benefits of taking vitamins for some diseases, but not for others.

Overall Health

An analysis of survey data collected from more than 30,000 people found that dietary supplements had no effect on all-cause mortality over a period of six years. The NIH-funded study, published in the Annals of Internal Medicine in April 2019, concluded that certain nutrients, including vitamin A, vitamin K, magnesium, zinc and copper, were associated with lower risk of cardiovascular disease and all-cause mortality, but they were beneficial only when obtained from food.

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Cardiovascular Health

The Physicians' Health Study II examined the effects over an 11-year period of long-term multivitamin supplements on the cardiovascular health of 14,646 men over age 50, of whom 754 had a history of cardiovascular disease. The results, published in JAMA in November 2012, found that there were 1,732 major cardiovascular events, but no significant difference in risk among those who took the multivitamin and those who took a placebo.

The findings also found no effect of a daily multivitamin on myocardial infarction risk, stroke or cardiovascular disease mortality. Furthermore, multivitamin supplementation had no effect on the risk of cardiovascular events in men with a history of cardiovascular disease.

A later review of research published in the Journal of the American Heart Association in July 2018 examined results from 18 studies and found no multivitamin effect on risk of death from cardiovascular disease, coronary heart disease and stroke, and no effect on stroke incidence. The researchers concluded that multivitamins should not be taken for the purpose of reducing cardiovascular disease and mortality risk.

Cancer Risk

In another analysis of data from the Physicians' Health Study II published in JAMA, researchers found that a multivitamin had positive effects on cancer risk. Over the 11-year follow up period, 2,669 men had been diagnosed with cancer, half of whom had prostate cancer.

Overall, there was a statistically significant reduction in the risk of total cancers, but there was no effect on prostate cancer, colon cancer or other site-specific cancers. There was also no significant effect on risk of cancer mortality. The researchers concluded that daily multivitamin supplementation modestly but significantly reduced total cancer risk.

A study published in Breast Cancer Research and Treatment in October 2013 examined the effects of multivitamins on mortality in 7,729 women ages 50 to 79 with invasive breast cancer. After a seven-year period, breast cancer mortality was 30 percent lower in the women who took multivitamins compared to those who didn't. The researchers concluded that the findings may indicate a role for multivitamin supplements in attenuating breast cancer death, but that more research was needed.

Proving the benefits of taking vitamins for specific health concerns is problematic, reports NIH, because people who take dietary supplements tend to have healthier diets and lifestyles. In addition, the results can't be applied to all the multivitamin supplements available on the market due to the wide range of nutrients and amounts of nutrients in different supplements used in the studies, the different populations studied and the various follow-up periods.

The huge variety of multivitamin supplements also makes it difficult to say that all are safe. Because they are unregulated, many supplements provide far more of some nutrients than is recommended daily for the general population. When taken in excess, certain nutrients can be dangerous. For example, getting too much beta-carotene — a form of vitamin A — can increase the risk of cancer in smokers and other individuals with a higher risk for lung cancer, according to NIH.

Taking too much of another form of vitamin A called retinol during pregnancy can increase the risks of having a baby with birth defects. NIH also reports that men and postmenopausal women shouldn't take supplements containing the full DV for iron unless directed to do so by their doctors, because the DV far exceeds their daily needs.

For all other people, taking a basic multivitamin that contains nutrients close to the DV shouldn't pose any health risks. However, that depends on diet, as well. People who eat a lot of fortified foods and take a multivitamin could inadvertently be getting too much of some nutrients, even if their multivitamin contains conservative amounts.

The general consensus in the mainstream medical community is that individuals who eat a healthy, balanced diet do not need to take a multivitamin supplement. In the event of a diagnosed nutritional deficiency, a doctor may recommend a multivitamin or a specific nutritional supplement to repair the deficiency. However, according to a poll conducted by the American Osteopathic Association, less than a quarter of people who take vitamins or other supplements have a documented deficiency.

The others may just be throwing their money away, according to Johns Hopkins Medicine. Director of the Johns Hopkins Welch Center for Prevention, Epidemiology and Clinical Research, Larry Appel, MD, says there is much stronger evidence supporting the benefits of eating a healthy diet and maintaining other lifestyle habits such as regular exercise and maintaining a healthy weight.

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In a February 2013 article for Science-Based Medicine, pharmacist Scott Gavura reports observing people spend over $100 a month on supplements that most likely offer no benefit. However, many people cringe at the cost of fresh organic produce and grass-fed meat and dairy.

Instead of shelling out the bucks for expensive multivitamin and mineral supplements, consumers' money is probably better spent on nutritious food and a gym membership. Appel reports that he takes no supplements, instead focusing on eating three healthy meals each day, including two or more servings of fruits and vegetables at each meal, as well as low-fat dairy, whole grains and lean protein from fish or chicken.

If you are vegan or vegetarian, pregnant or have another health condition or diagnosed deficiency, you may need a supplement; however, it's wise to invest in supplements only after you have discussed it with your doctor.