I’m A Nutrition Scientist—Here’s Why I Take A Multivitamin

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Sarah Davis Editor
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Peek into my kitchen cabinets, and you’ll learn a few things about me. You might find fresh fruits and vegetables, 100% whole wheat bread, extra cheesy Cheez-Its…and a men’s multivitamin.

The latter might be surprising—with contrasting views on multivitamins ranging from them being “a nutrition insurance plan” to “flushing money down the drain,” people are often curious where I stand.

Why? Because I’m a scientist, professor and lead researcher in the field of nutrition science. I’m known for happily skewering food and nutrition myths for media outlets like Forbes Health and the Dr. Oz Show. This means people (correctly) assume I’ve dug into the data and drawn my own conclusions about what’s helpful—and what’s hype.

So, why do I take a multivitamin? It’s simple. Research shows the risks are low, and there are real benefits for most people[1]. Taking a daily multivitamin is a cost-effective way to insure against hidden micronutrient insufficiencies that can sap your immunity, health and long-term vitality.

Now, let’s dig into that.

What Is a Multivitamin?

Introduced in the 20th century, multivitamins are the most popular dietary supplements in the U.S., with over 50% of Americans reporting at least occasional use, according to a study I conducted alongside colleagues[2]. While there isn’t a concrete definition for what constitutes a multivitamin, my fellow researchers—and even Congress per the Older Americans Act Amendment of 2006—generally define them as containing 100% of the Daily Value (DV) of at least two-thirds of the required vitamins and minerals for a given life stage.

The ingredient lists of multivitamins range from brand to brand, but commonly include:

  • Fat-soluble vitamins: vitamins A (and beta-carotene), D, E and K
  • Water-soluble B-vitamins: thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, folic acid and vitamin B12
  • Minerals: iron, iodine, selenium and zinc

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Benefits of Multivitamins

While classic nutrient deficiency diseases like rickets and scurvy are now rare in the U.S., inadequate levels of certain micronutrients can still impair a wide range of biological functions.

For example, you’ve probably heard that inadequate intake of calcium and vitamin D over time can contribute to osteoporosis later in life, or that low folic acid intake among pregnant women increases the risk of neural tube defects in newborns.

What you may not have considered, though, is that micronutrient inadequacies can also increase susceptibility to illness and chronic diseases, such as cancer, heart disease, type 2 diabetes, age-related macular degeneration and cognitive dysfunction. Not getting enough of certain micronutrients can also lead to impaired immune function, making you increasingly susceptible to infection. I recently even argued that inadequate magnesium status may increase the risk of COVID-19 infection and severity, due to its various roles like activating vitamin D in the body.

To date, though, there’s only two large, long-term clinical trials of multivitamins. The Physicians Health Study II was the first to assess the long-term efficacy of multivitamins in preventing chronic disease. It tested four supplements (including a multivitamin) on the prevention of certain diseases among nearly 15,000 male physicians over the age of 50. Over an average of 11 years, the study found multivitamin use decreased risk of cancer by 8% and cataracts by 9%, with no effects on cardiovascular disease, cognitive decline or age-related macular degeneration. Not exactly a slam dunk, but remember this study didn’t find any noteworthy drawbacks to taking a multivitamin, either.  

The more recent  COSMOS randomized clinical trial in The American Journal of Clinical Nutrition assessed shorter-term efficacy of multivitamins on prevention of cancer and cardiovascular disease in over 21,000 participants.  Over an average of 3.6 years, the study failed to show effects of multivitamin use on total cancer or cardiovascular disease, although the relatively short duration of the study likely limits its ability to detect any small to moderate effects on cancer incidence. COSMOS did show a statistically significant reduction in lung cancer incidence.  

The study provides consistent evidence with the Physician’s Health II study that a daily multivitamin likely has little to no influence on development of cardiovascular disease, but also lacks any drawbacks to health (note that the multivitamin tested in both clinical trials was Centrum).

Although more research is needed, many researchers in the field (including myself) speculate that when micronutrient intakes are lower than recommended levels, immediate short-term requirements for micronutrients in metabolic reactions take precedence over long-term needs—which could lead to irreversible, long-term damage in exchange for keeping your short-term needs met. Think of it like only ever replying to the newest three emails in your inbox. For these reasons, taking a daily multivitamin makes practical sense to me.

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Are There Risks of Multivitamins?

One of the biggest arguments against the use of multivitamins is that it can lead to slightly excessive intake of certain nutrients. Indeed, a recent study I conducted alongside colleagues shows that consistent multivitamin use results in slightly excessive intakes for calcium, folic acid, selenium and zinc in a small portion of middle-age to older adults; however blood levels of these nutrients remained within clinically acceptable ranges[5].

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While excessive intake of certain nutrients through multivitamins has been documented, it underscores the importance of reading the label and talking with a registered dietitian nutritionist about your supplement regimen. For me, on days I’m eating healthy, I take half of my multivitamin.

Be wary of products that provide far more than the daily value for various micronutrients (notably the fat-soluble vitamins A, D, E and K and iron), and be sure to examine the ingredients in other supplements you’re taking to prevent excessive intakes. Multivitamins won’t contain the full daily value for all micronutrients, such as calcium, magnesium and choline, because you’d end up with a pill too big to swallow.

If you’re worried about getting too much of a good thing, data shows that frequent multivitamin use virtually eliminates many micronutrient inadequacies and rarely causes excessive intakes (or the level above which the risk of adverse health effects begin to increase)[6]. However, data also shows multivitamin users are more likely to take other dietary supplement products—and excessive intakes occur more easily when two or more dietary supplements contain the same nutrient.

Who Might Benefit from a Multivitamin?

For many of us, our diets are more indulgent than they are nutritious. Americans, on average, consume about 30% of their caloric needs from high-energy, nutrient-poor foods like desserts, snacks and alcohol, according to data from the National Health and Nutrition Examination Survey[7]. As a result, these foods are crowding out more nutritious options and causing less intake of essential micronutrients.

In fact, most Americans don’t consume enough dietary fiber, calcium, magnesium, potassium, choline and vitamins A, C, D, E and K, according to the 2020 Dietary Guidelines Advisory Committee. Other commonly, under-consumed nutrients for certain populations include iron, folate, protein and vitamin B12.

The Linus Pauling Institute, a molecular nutrition research institute at Oregon State University, offers a comprehensive list of people who may be at increased risk of micronutrient deficiencies. Those who could potentially benefit the most from taking a multivitamin include:

  • Women who are of childbearing age, pregnant or lactating.
  • Obese individuals who have increased requirements for some nutrients.
  • Infants, children, and adolescents who are growing and developing.
  • Older adults who can experience reduced nutrient absorption and appetite.
  • People with nutrient absorption issues, including heavy alcohol users, people who had bariatric surgery and those on certain medications.
  • People with lower nutrient intakes, including those not consuming a healthy diet, those facing food insecurity and potentially vegans or vegetarians.
  • Those likely to be low in vitamin D, including people who use sunscreen, cover all exposed skin when outside or have darker skin pigmentation.

How to Choose the Right Multivitamin

When it comes to multivitamins, there’s a dizzying array of options, from pills to powders to liquids to gummies, touting a multitude of benefits. Sometimes, those claims are unsubstantiated, making it even harder to select the right one.

My best advice is to stick with trusted national brands. When it comes to quality, products that are third-party certified by groups like NSF International or the U.S. Pharmacopeia Corporation (USP) can provide added reassurance.

Because micronutrient needs vary based on age, gender, amount of physical activity and other factors, many manufacturers offer targeted formulations for specific subpopulations, including prenatal, women, men, seniors, children and even athletes. These products can be a smart choice for meeting specialized micronutrient needs while avoiding excess intake.

Taking a supplement every day will not let you off the hook when it comes to eating well, and multivitamins aren’t a magic pill nor a substitute for a healthy lifestyle. Their purpose is to fill nutritional gaps that you may not know exist. That’s why I take one every day—just in case.

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