You’re on the Verge of Getting a Cold: Can You Stop It in Its Tracks?

Illustration: Tess Smith-Roberts

GGetting those first signs of a cold? You’re probably wondering if it might be worth taking some form of vitamin C, or trusting a handful of other remedies touted as helping to nip a cold in the bud, such as working up a big sweat at the gym or taking steam. But do any of these approaches actually help?

The myths

According to studies, “sweating out” a cold right at its start (or later) isn’t likely to do anything to reduce its impact, no matter how you do it — via exercise, steam, or sitting in a hot, dry sauna. Many people in the studies swore they felt a little better, at least temporarily, but by all objective measures, there wasn’t any improvement in their colds.

And then there’s nasal washing or irrigation, which involves spraying or otherwise propelling water up through your nose into your nasal passages via a “neti pot” or other implements in the theory that it washes out mucus harboring the cold virus. Those, too, have been found ineffective against curtailing colds (and can cause infections if you use tap water instead of bottled saline solution).

The maybes

Research on two supplements—vitamin C and zinc — indicates they could have a bit of benefit.

The notion that vitamin C can help prevent and fight off colds has been around for the better part of a century — plenty long enough for researchers to have put the notion to the test in numerous ways, many of them rigorous. The evidence that it sometimes works to snuff out or at least moderate a cold that’s starting to take hold has gone back and forth over these studies. But the argument is mostly considered over, thanks largely to an exhaustive 2005 review study that looked at 55 previous studies, and a 2017 follow-up review.

None of these behaviors will do much for you with a cold if you take engage in them after you’ve been hit.

The verdict from those studies is that for most people, grabbing vitamin C at the first sign of a cold won’t help in any way. But those who regularly take a daily dose of 200 milligrams of vitamin C (about four times the amount found in a glass of orange juice) can slightly reduce the length of a cold — from about a week on average to about six days — as well as slightly reduce the severity of symptoms. That’s a far cry from stopping a cold in its tracks, but it does imply that vitamin C can have a small but real impact on the course of the illness, rather than just temporarily ease the symptoms, like what you get from taking a pain reliever or decongestant. In addition, the study found even stronger evidence that marathoners and other extreme exercisers seem to as much as halve their risks of getting a cold at all if they take vitamin C regularly. Researchers theorize that it may be because the intense exercise can weaken the immune system, and the extra C helps bring it back up to snuff.

Research on whether taking zinc at the onset of cold symptoms can shorten or ease the illness has also been somewhat mixed. Harri Hemilä, MD and PhD, and the author of that 2017 study and co-author of the 2005 study on vitamin C, also recently tried to settle the question on zinc, in this case with a randomized controlled trial that he carried out with colleagues on 88 people who came down with colds. The results, just published in January, were surprising and a bit confusing, Hemilä confesses: Those taking zinc lozenges for five days starting at the first signs of a cold saw no benefits — but after they stopped, their colds lasted a bit longer than for those people who didn’t take the lozenges. Hemila thinks this could be because of a “rebound effect,” a well-known issue in pharmacology. “What the studies into zinc and vitamin C have really shown is that the questions are complex,” Hemilä notes. “We still don’t have consistent findings.”

FFor those who want to give vitamin C or zinc (or both) a shot, it’s easy enough to find supplements of either. One popular zinc supplement, for example, is Zicam, which provides quick-dissolving tablets specifically marketed as shortening cold duration. Perhaps the best known (and reached for) product is Emergen-C, which provides 1000 milligrams of vitamin C in a packet of flavored powder which you dissolve in a glass of water. (There are other ingredients in Emergen-C, none of which have been convincingly linked to any cold-related benefits.)

But according to David Dildine, MD, an urgent-care physician with Atrius Health in Boston, there are no particular advantages or disadvantages to taking C and zinc via these sorts of products, other than it may be more convenient, and possibly more expensive, than other forms of the supplements.

And William Curry, MD, a professor of internal medicine at the University of Alabama at Birmingham, warns that any supplements, including vitamin C and zinc, can cause problems for some people if taken in high enough doses. If zinc is taken orally for much longer than a week or two, it can lead to a potentially dangerous shortage of copper in the body. “It’s always worth talking to your doctor before taking any supplement,” says Curry. “If an ingredient can provide some benefit, it can provide some risk of harm, too.”

Taking more vitamin C than the recommended daily maximum of 2000 milligrams is generally believed to carry at least a mild risk of nausea and diarrhea. (Emergen-C has 1000 milligrams of vitamin C, so you should be fine.)

So what does help to nip a cold in the bud?

The best strategy for anyone hoping to improve their odds with colds, according to research, is to adopt the same healthy habits recommended for general health: Regular exercise, a healthy diet with plenty of vegetables, good stress management, and plenty of restful sleep.

None of these behaviors will do much for you if you engage in them after you’ve been hit with a cold. But they’re all associated with at least a slightly lower risk of getting a cold in the first place, most likely because they can strengthen the immune system. “I see it all the time in the clinic,” says Dildine. “People who don’t take care of themselves, or who are stressed out, get colds and other illnesses more often.”

Even if a supplement or remedy ultimately offers nothing but a placebo effect on a cold, that doesn’t mean people should outright avoid it.

And there’s one other behavior that can help fend off colds: Staying warm. Studies have shown that cold viruses tend to replicate more robustly at colder temperatures, and people exposed to colder temperatures are more likely to get colds. In animal studies, colder temperatures have also been shown to reduce the immune system’s ability to fight off colds. Putting this insight to work probably requires staying inside more during cold weather — dressing more warmly outside wouldn’t likely do the trick, because you’d still be breathing the colder air that seems to cause the problem. Of course, if staying inside ends up limiting your exercise or keeping you in closer contact with people who may have colds, you’d face a trade-off in risks.

As for fighting off a cold that’s coming on, even if a supplement or remedy ultimately offers nothing but a placebo effect on a cold, that doesn’t mean people should outright avoid it, says Dildine. “The placebo effect can be pretty powerful,” he notes. “In studies, the placebo effect often comes out to be a 20% improvement in symptoms.” Whether that’s all in a patient’s mind, or perhaps might be linked to a strengthening of the immune system as a result of a positive attitude remains an open question, he says.

Either way, Dildine adds that a little judicious personal experimentation isn’t unreasonable. “Just because the evidence isn’t good that something works, it doesn’t absolutely mean it won’t work for you. If there’s no harm, why should I, as a doctor, be a jerk about telling you not to try it?”

David is a Boston-based science writer. The most recent of his five books is WRONG, about the problems with medical research and other expertise.