The truth about multivitamins

“I know I don’t eat very well, so I’ll just take a multivitamin to get my nutrition.”

“I eat pretty healthy, but I take vitamins just to cover the bases.”

Can you identify with either of those statements? If so, you’re not alone. More than one third of Americans take supplements, and it is a $37 billion a year business. There’s a never-ending variety: women’s, men’s, over 50, children’s, prenatal, eye health, heart health, chewables, and gummies, to name a few. Whatever you need, the industry provides. But do you really need it? Do they even work? Might they be harmful? These are important questions! Let’s take a look.

What do multivitamin/mineral supplements have in them?

Multivitamin/mineral supplements (MVMs) have a combination of vitamins and minerals that are determined by the manufacturer. There are usually other ingredients, too, like binders, colors, and flavors. Some of the most common MVMs are once-daily products that usually contain all or most essential vitamins and minerals (essential means we need to eat these for good health — our bodies can’t make them) in amounts close to the recommendations.

Higher potency MVMs are also available, and are usually marketed for specific conditions like eye health, pregnancy, or improved immunity.

That sounds really good! What’s the downside?

Supplements are not regulated by the U.S. Food and Drug Administration (FDA) in the same way medications are. That means there is no guarantee the claim on the bottle is accurate, that the supplement will do what it says it does, or even that the supplement contains what the bottle says it contains. And considering how long MVMs have been on the market, there are surprisingly few clinical trials testing them. The ones that have been conducted, however, are not as promising as we hoped.

Probably the most studied supplement is calcium. As we know, calcium is important for bone health and several other vital functions, and many people don’t get enough. In fact, osteoporosis occurs at almost epidemic levels in older adults. However, recent studies suggest calcium supplements do little to improve bone density, and at high doses can increase the risk of heart disease and kidney stones.

While it is rare to overdose on vitamins or minerals from food, it’s easy to take too many vitamins or minerals in supplement form. Even if you don’t overdose on your supplement, many foods and beverages, like cereal, vitamin water, sports drinks, and even orange juice, may be fortified, increasing the risk of overdosing. Vitamin/mineral toxicity can be as benign as a bout of diarrhea and as severe as irreversible damage to the heart, kidneys, or liver. Always follow your doctor’s advice if you take supplements, and make sure you’re not routinely consuming more than 100 percent of the recommendation from all sources.

The people who are most likely to take MVMs are people who are already eating a healthy diet. There is no documented advantage to taking supplements if you’re already healthy. For instance, studies have shown that people who are healthy and taking MVMs are not at a lower risk for cancer, heart disease, or diabetes.

Supplements are also not a substitute for a healthy diet. Food contains hundreds of substances that just aren’t in supplements. Many of those substances work in ways we don’t yet fully understand to improve absorption, help us feel more satisfied after eating, or otherwise improve overall health and prevent disease. We discover more all the time. Taking a MVM instead of eating healthy means missing out on these vital substances. And some studies show supplemental vitamins/minerals may not be absorbed as well as nutrients from food.

Should anyone take multivitamins?

While taking a MVM will probably not be beneficial for people who are already healthy, doing so may be beneficial for people who have certain health problems. Your doctor will recommend an appropriate supplement if you fall into that category.

There are some populations who also may need more of certain nutrients, as outlined in the Dietary Guidelines for Americans. If you fall into one of these categories, you may want to talk to your doctor or a registered dietitian about how to increase these nutrients in your diet or an individual nutrient supplement:

People older than 50 years old may need more vitamin B12 in crystalline form.
Women of childbearing age and adolescent females should consume foods that are a source of heme-iron (like meats) and/or iron-rich plant foods (like cooked dry beans or spinach) along with a vitamin C source.
Women of childbearing age and who are pregnant should consume adequate folic acid from a varied diet every day, in addition to a supplement if recommended.
Older adults, people with dark skin, and people who get insufficient exposure to sunlight should consume extra vitamin D from fortified foods and/or supplements.

If you really can’t get your nutrition from the foods you eat, supplements of individual nutrients (rather than a catch-all multivitamin) can help fill in the gaps. However, you should talk to your doctor or registered dietitian. These health professionals can help you pinpoint what specific nutrients you may be lacking, and recommend a trusted brand and safe dose.

The bottom line

MVMs can be beneficial to some people who have certain health problems. But for most people who are already healthy, they are probably a waste of money at best — and potentially harmful at worst. Always get all the nutrition you can through your food. If you absolutely can’t, talk to a qualified health professional about individual nutrient supplements rather than a MVM to avoid toxicity and other health problems.