Guide to Vitamins

Should I Take Vitamin C?

What researchers now know about the classic cold antidote

Markham Heid
Published in
4 min readNov 11, 2019


Illustrations by Kieran Blakey

This story is a part of The Elemental Guide to Vitamins. Here are the vitamins and supplements that are covered: multivitamins, vitamin D, vitamin C, calcium, B vitamins, omega-3, vitamin E, fiber, protein, and probiotics.

DDuring the 1960s, noted biochemist and author Linus Pauling developed a novel theory of the human body, which he called “orthomolecular” medicine. In a nutshell, Pauling’s theory was that human health could be viewed as a complicated system of chemical reactions. Over time, he came to the conclusion that vitamin C plays an important role in many of these reactions and that heavy doses of it could help prevent ailments ranging from the common cold to cancer.

Pauling’s 1970 book Vitamin C and the Common Cold was an unexpected success, and it ushered in an era of widespread enthusiasm for vitamin C. While vitamin C was, and still is, among the most popular vitamin supplements in the U.S., the research in support of vitamin C pills or powders is less comprehensive and robust than Pauling’s work led many to believe.

According to the National Institutes of Health’s Office of Dietary Supplements, some animal and lab studies have found that high-dose injections of vitamin C may help shrink tumors, but the evidence there is mixed.

Recently, researchers have looked at the benefits of vitamin C supplementation for sick people at risk for sepsis. Sepsis is a life-threatening condition in which the body overreacts to an infection and causes damage to its own tissues and organs. Some lab evidence has found that vitamin C may help prevent or reduce the risk of sepsis. But so far, the research in humans has been underwhelming.

“Vitamin C seems to work a little better than placebo for the common cold — but it may just be a really great placebo.”

Some researchers have looked at vitamin C’s effects on heart health and cardiovascular disease risk. A 2012 review in the American Journal of Clinical Nutrition found that short-term supplementation of around 500 milligrams of vitamin C per day could lower blood pressure scores, especially among people with hypertension. But that finding has not translated to lower heart disease risks. “When we looked at vitamin C’s effects on cardiovascular disease risk, all the endpoints were flat,” says Dr. Edgar Miller III, coauthor of the promising review and a professor of medicine at Johns Hopkins University. In other words, any short-term blood pressure improvements associated with vitamin C pills don’t seem to offer people protection from heart trouble.

Of course, vitamin C is best known for its cold-fighting, immunity-strengthening properties. And while taking vitamin C doesn’t seem to prevent colds altogether, studies have found that people who regularly take a vitamin C supplement may experience shorter colds with milder symptoms. “Vitamin C seems to work a little better than placebo for the common cold — but it may just be a really great placebo,” says Dr. Mark Moyad, the Jenkins/Pokempner director of preventive and alternative medicine at the University of Michigan.

One of the most promising uses for vitamin C, Moyad says, involves people who are experiencing the early stages of macular degeneration, the leading cause of age-related blindness. In the early 2000s, the National Eye Institute-funded Age-Related Eye Disease Study found that taking a combination of 500 milligrams of vitamin C along with zinc and several other nutrients could lower a person’s risk for developing advanced macular degeneration by about 25%.

On the other hand, Moyad says vitamin C supplements can come with side effects. “You have to be careful of your dosage because too much of it can cause kidney stones,” he says. Also, as one would guess, ascorbic acid can be “pretty harsh” on a person’s gut. It can cause cramps, stomach pain, and diarrhea in some people, he says.

The bottom line: While some risks exist, most of the research on vitamin C suggests that taking 500 milligrams or less of it each day is unlikely to cause any unwanted side effects in adults and that it could provide some immune system benefits.

This story is a part of The Elemental Guide to Vitamins.



Markham Heid

I’m a frequent contributor at TIME, the New York Times, and other media orgs. I write mostly about health and science. I like long walks and the Grateful Dead.