Multivitamins: Healthy or Dangerous?

The Multivitamin Paradox

Multivitamins are a staple for millions of people. As many as one in three use them daily. The idea is that by filling any unknown vitamin and mineral gaps, these do-it-all supplements can boost your overall health.

But do they work? Recent studies paint a mixed picture. While some show benefits—particularly for cognitive health in older adults—other research is less optimistic. It indicates that multivitamins have no benefit. Taking them may even do harm.

In a recent 20-year study of 390,000 people, researchers from the National Institutes of Health (NIH) found that daily multivitamin use had no impact on a person’s age of death. [1]

In a commentary paper, a second team of researchers explained that some of the nutrients in multivitamins can do real harm. For starters, they can interfere with medications like antibiotics and blood thinners. [2] They may also increase the risk of lung cancer for smokers, and some can increase the risk of cardiovascular disease, diabetes, and even dementia.

That last one, dementia, is particularly confusing. It's in conflict with other research showing that multivitamins protect the brain.

Related: Supplements to Slow Aging? Here’s What the Science Says.

It’s all hard to understand, right? How can multivitamins be beneficial in some cases and harmful in others?

The answer becomes clear when you understand how these supplements work. We’re going to explain that right here, and if you’re looking for a supplemental solution that works, scroll to the bottom of this article.

Understanding multivitamins

Multivitamins work by blending many vitamins and minerals into one pill. Manufacturers choose these nutrients based on a couple key factors:

Expert recommendations for daily nutritional intake
Assumptions about where the general population falls short

With these considerations, multivitamins often contain vitamins A, C, D, E, K, and various B vitamins. They also carry minerals like iron, magnesium, and zinc. It’s not uncommon to see 20 or more nutrients in a single pill.

The multivitamin strategy can be described as a “spray-and-pray” approach to nutrition.

Without knowing what your body needs, these pills deliver a broad array of nutrients in the hope that something will be helpful. And often, one or two of them are. If you’re low in vitamin K, for instance, your pill's vitamin K may provide some health benefits.

But at the same time, some of the nutrients can do harm. They may push you into the territory of nutrient excess. With vitamins and minerals, too much of a good thing can be bad.

The truth is, multivitamins are no nutritional slam dunk. In fact, the people who take them are often the ones who need them the least.

In one study, a researcher from the University of California San Diego found that, on average, people who use multivitamins eat healthier than those who don't. [3]

And the better you eat, the less likely it is that you'll benefit from a multivitamin.

The (confusing) case for multivitamins

The multivitamin news isn't all doom and gloom. A handful of recent studies suggest that multivitamins can actually reduce the risk of cognitive decline, particularly in older adults.

One recent study found that older adults taking multivitamins for one year were better at remembering specific events from the past—and the results held for the entire duration of the 3-year study. [4]

Another study found that older adults taking multivitamins for 2 years had better memory recall and better overall cognitive function. [5]

Notably, there are caveats to both studies. In the first, the researchers found no improvement to overall cognitive ability, and in the second, the results were small. They failed to reach statistical significance.

And despite the promising results, it remains unclear which specific vitamin or mineral (s) in the multivitamin is leading to the brain boost. It's also unclear if the results apply to a larger group on a longer timeline.

In one older study, researchers gave men multivitamins or placebos for 14 years. In the end, those taking multivitamins saw no cognitive benefit. [6] This study more closely resembles the NIH study, which found no impact on life expectancy for multivitamin users.

The Multivitamin Paradox-1

How can multivitamins do harm?

Despite the mixed research, it’s still reasonable to ask: What’s the harm in taking a multivitamin?

Let’s use an example. Imagine a guy named Rick who’s low in vitamin B12 but doesn’t know it. He just knows he struggles to find the energy he needs to get through the day.

Rick starts taking a multivitamin that contains a couple dozen nutrients. Fortunately, one of them is B12. Within a couple of weeks, his energy is up and he’s feeling great. He doesn’t know why, but the multivitamin appears to be working. So for the next decade, he takes the multivitamin daily.

But there’s something else Rick doesn’t know about his body: He’s high in iron. And his multivitamin essentially doubles his daily intake.

During the decade that Rick takes his supplement, his body packs iron into his liver, heart, pancreas, and joints. Eventually, he develops heart problems and a metabolic profile that puts him at risk for type 2 diabetes. His testosterone is dropping, he feels achy, and his energy is low—again.

This example illustrates how multivitamins can do harm even as they do good. While Rick benefits from the B12, the excess iron poses a risk.

If he’d taken a vitamin B12 supplement instead of a multivitamin, he could have avoided the downside of high iron. But he didn’t know what he needed.

The truth is that many nutrients can do harm when taken in excess. Here are a few examples:

Excessive vitamin A can increase the risk of liver damage.
Excessive iron and copper levels can increase the risk of cardiovascular disease, diabetes, and dementia.
Excessive beta-carotene can increase the risk of lung cancer for people who are already at risk.
Excessive calcium can lead to kidney stones and cardiovascular issues.
Some nutrients can make medication less effective. For instance, zinc can interfere with antibiotics, and vitamin K can interfere with blood thinners.

The Multivitamin Paradox-2

Understanding what your body needs

You, like all people, have unique nutritional needs. If you want to understand what your body needs, you need to test your blood. And InsideTracker makes it easy.

Our tests look at a broad spectrum of biomarkers, and we combine that with your DNA and fitness tracker data to form a complete picture of your health. From there, we can show you exactly which supplements you need—along with the foods, exercises, and lifestyle habits that will help your body the most.

Learn more: How an InsideTracker Membership Uses Data to Add Healthy Years to Your Life

Whether you’re trying to sleep better, improve your energy, or simply live longer, InsideTracker can show you the way.

Multivitamins are made for the masses, which means they’re ideal for nobody. If you’re serious about your health, you need a personal approach.

Click here to get started: Explore InsideTracker Membership options

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