The Truth About Vitamins

Jamie Santa Cruz

We Americans love our vitamin and mineral supplements.

Approximately 50 percent of Americans take vitamins, including a daily multivitamin. We’re also big consumers of individual vitamins and minerals: Over 1 in 4 Americans 60 and older takes vitamin D. Significant percentages of Americans also take omega-3 supplements, B complex and B vitamins, calcium, and vitamin C.

In theory, popping a daily supplement seems like a no-brainer. After all, vitamin and mineral deficiencies are known to raise the risk of various types of cancer, heart disease, and a whole host of other illnesses. So taking your daily vitamins should be a great way to boost your health and provide “insurance” against those chronic diseases.

But are those supplements effective?

Surprisingly, the answer in many cases is no. Substantial research in the previous few decades has shown that vitamins and minerals tend to be more effective when they come from food sources, and taking them in supplement form doesn’t provide as much benefit as researchers once hoped. In fact, in some cases, supplements might even have a negative health impact.

Do vitamins prevent disease?

A look at the research

There are certain people who can’t get enough of particular vitamins and minerals from food who may genuinely benefit from supplements. But growing research suggests that many common supplements may not be providing clear benefits to the majority of people.

Consider chronic diseases like heart disease and cancer, for instance. Many people take supplements specifically to ward off these conditions, but a 2013 study that focused on adults with no nutritional deficiencies suggests supplements likely don’t work for that purpose. The study, conducted on behalf of the U.S. Preventive Services Task Force, reviewed 27 different trials that had been conducted on a range of vitamin and mineral supplements and found that in adults with good nutrition, there was no clear evidence that any of the supplements were effective at preventing cancer or heart disease, or for preventing premature death.

Last year, Canadian researchers came to a similar conclusion. After systematically reviewing an array of previous studies on the effects of common vitamin and mineral supplements, they found that none of the most common supplements (including multivitamins, vitamin D, calcium, and vitamin C) had any benefit for the prevention of heart disease or premature death. According to David Jenkins, M.D., the lead author of the study and a professor of medicine and natural sciences at the University of Toronto and a researcher at St. Michael’s Hospital, the supplements weren’t harmful, but they just didn’t offer advantages—at least for heart health or prevention of early death.

On vitamin C, in particular, it’s common to see claims that it can help lower blood pressure and reduce other heart disease risk factors. But a 2016 review from researchers at the University of Connecticut found that much of the evidence about its effectiveness is contradictory, with some studies showing that vitamin C supplements actually increase the risk of heart disease. The authors concluded that vitamin C supplements might provide a benefit for specific subgroups of people, but that current evidence doesn’t justify the general public taking vitamin C to improve heart health.

Of course, many people take supplements for reasons other than warding off heart disease and cancer. For instance, vitamin D, the “sunshine vitamin,” is one of the most common individual vitamin supplements, in part because vitamin D is known to contribute to good bone health and protect against osteoporosis. But an Australian study in 2018 systematically reviewed dozens of previous studies on vitamin D and concluded that, in supplement form, the vitamin doesn’t actually prevent fractures or falls, and it doesn’t have an impact on bone density. Calcium supplements, too, are popular for promoting bone health, but according to the U.S. Preventive Services Task Force, there’s not currently enough evidence to know whether they actually work for that purpose.

Ironically, high doses of certain vitamins may, in some cases, increase the risk for specific diseases. For example, antioxidants—which include beta-carotene and vitamin E—have received much hype in recent decades for their power to prevent a variety of chronic conditions, especially cancer and heart disease. Thus, many studies have examined the potential benefits of supplemental forms of these vitamins and minerals—but the results have not been promising. Here’s the most famous example. At one time, researchers believed that supplementation with beta-carotene might help reduce the risk of lung cancer in smokers—but then trials of the supplement in groups at high risk for lung cancer showed that it actually increased the risk by as much as 36 percent. Similarly, vitamin E supplements have received significant attention as a potential weapon against cancer, heart disease, and cognitive decline. But the majority of evidence suggests that not only are they not beneficial, they might increase the risk of prostate cancer.

In sum, vitamins and minerals may be crucial for good health, but in supplement form, they often don’t provide the benefits we might expect.

Food Sources vs. Supplements:

What’s the Difference?

One potential reason why supplements often produce lackluster results is that vitamins in supplement form aren’t completely equivalent to the vitamins we get from food sources.

“There are a lot of examples in research studies where we give individuals vitamin supplements and don’t see any benefit. And then when it’s provided through a food source, we do see an effect,” says Jamie Erskine, Ph.D., professor of nutrition and dietetics at the University of Northern Colorado.

According to Jenkins, the author of one of the studies mentioned earlier, a key difference between vitamins we get from food and vitamins we get from supplements is the speed with which the vitamin is delivered—supplements get absorbed much more rapidly than vitamins consumed as part of our diets. Vitamins in supplement form cause a quick, sharp spike in blood levels of that nutrient, whereas the same nutrient consumed in a food source will cause a less intense but more prolonged rise in blood levels. The slow, sustained rise in blood levels may make for better assimilation of the nutrient, says Jenkins, and therefore may produce different physiological effects.

Another key difference between supplements and vitamins from food sources is their context. According to Erskine, when we consume vitamins and minerals in food sources, the foods contain other components—such as polyphenols, carotenoids, and flavonoids—that may work with the vitamins and minerals, affecting how they are absorbed and how they are metabolized by the body. In other words, to get health benefits from vitamins and minerals, it’s not just the vitamins and minerals themselves that matter, but also the other compounds that surround them in our food sources.

The upshot? “It’s better to get the vitamins and minerals through diet,” says Erskine.

Jamie Santa Cruz is a writer, mother, and wife based in Colorado.

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