Can Emergen-C Actually Prevent a Cold?
The popular supplement has a cult following—but not much scientific evidence backing it up.
If you find yourself reaching for a packet of Emergen-C every time you feel a tickle in your throat, you’re certainly not alone. The fizzy orange power—a mix of vitamins C and B, along with other nutrients—has become a mainstay of medicine cabinets, winter-weather survival kits, travel packing lists, and even wedding weekend goodie bags.
“A lot of patients ask me about these products, and many of them can be very adamant about how certain they are that it helps them,” William Curry, MD, professor of internal medicine at the University of Alabama at Birmingham, tells Health.
Because Emergen-C is a supplement, it can’t make specific health claims. (In fact, its manufacturer settled a lawsuit in 2014 after it was accused of doing just that, without any real evidence.) But it does promise to offer “everyday immune support,” and devotees swear by its ability to keep them healthy through cold-and-flu season, or even shorten the duration of a cold once it starts.
But is there any real evidence of these supposed benefits? Not really, says Dr. Curry. In fact, there are exactly zero published clinical trials on Emergen-C itself, although there have been lots studies on its main ingredient, vitamin C. Here’s what we know, and what we still don’t, about this popular over-the-counter remedy.
A look at Emergen-C's ingredients
The company behind the iconic orange Emergen-C powder has expanded in recent years and now offers many different flavors and colors of its original “immune support” product. It also offers chewables and gummy varieties, as well as additional products aimed at hydration, better sleep, electrolyte replenishment, and gut health.
For now, let’s focus on the brand’s flagship “immune support” formula. The product’s main ingredient is vitamin C—1,000 milligrams per packet of powder, 500 milligrams per gummy, and 1,000 milligrams per chewable. (For comparison, many other over-the-counter vitamin C supplements contain only 500 milligrams per dose, while multivitamins may contain only around 60.)
Emergen-C immune support also contains antioxidants like zinc and manganese, electrolytes like sodium and potassium, and seven B vitamins—thiamin, riboflavin, niacin, vitamin B6, folic acid, vitamin B12, and pantothenic acid—“to enhance energy naturally,” according to the product’s website.
The ingredient list also contains calcium, phosphorus, magnesium, and chromium, along with sugar, flavorings, and other additives to preserve texture and freshness.
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What the evidence suggests
Emergen-C’s claim to fame is a high dose of vitamin C. But studies on this topic have been inconclusive at best, says Dr. Curry. “The research has not been very high quality, and the results have been mixed,” he says.
A 2013 Cochrane Review found that 1,000 milligrams a day of vitamin C seemed to help prevent colds in people who were very physically active—marathon runners and skiers, for example. But those benefits didn’t translate to other studies on more general populations.
“That was a little surprising, and we still don’t really know why this was the case,” says Dr. Curry. “But there seems to be something about the combination of being really physically active and taking vitamin C that may be protective.” He adds that the study was only able to show an association between high doses of vitamin C and fewer colds, and not a cause-and-effect relationship.
The review also noted that while some studies have shown a link between vitamin C and shorter cold duration, others have shown no benefit. Given vitamin C’s low cost and relative safety, the authors wrote, “it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them.”
As for zinc, says Dr. Curry, some studies have also suggested that this mineral may speed up recovery time for common-cold patients. But a packet of Emergen-C only contains 2 milligrams of zinc, which some experts say isn’t enough to be effective against colds. And while the other ingredients in Emergen-C may have antioxidant or electrolyte properties, Dr. Curry says there’s no evidence that they can directly protect against colds or other viruses.
Are there downsides to taking Emergen-C?
The tolerable upper limit for vitamin C, as set by the Institute of Medicine, is 2,000 milligrams a day. “Beyond that you run the risk of getting kidney stones, and you’re probably beyond the point where there’s going to be any benefit anyway,” says Dr. Curry. Excess vitamin C has also been shown to cause diarrhea, nausea, and abdominal cramps.
Dr. Curry cautions patients who want to take Emergen-C or similar products to pay attention to their dosage and to not exceed this upper limit. That means don’t take several doses of Emergen-C in a day, and be careful when taking it alongside other supplements that may also contain vitamin C. (The recommended dose for Emergen-C is one packet, one chew, or three gummies per day.)
Some studies have also suggested that vitamin C can interact with certain medicines, including some statins and chemotherapy drugs—and it likely won’t protect you if you’re coming down with a more serious illness like the flu. If you’re unsure about whether vitamin C might affect your current medication regimen (or if you’re having serious symptoms and think you might need real medical attention) it’s always a good idea to check with your doctor.
So how much vitamin C should you get—and where should you get it?
The recommended daily intake of vitamin C for adult women and men is 75 and 90 milligrams per day, respectively; smokers and women who are pregnant or lactating should get more than that, according to the Institute of Medicine.
Obviously, you don’t need a daily Emergen-C to achieve those levels; in fact, it’s not difficult to reach that amount from food alone. Eating the recommended minimum two daily cups of fruit and three daily cups of vegetables will get you at least 200 milligrams of vitamin C, says Health Contributing Nutrition Editor Cynthia Sass, MPH, RD. That’s “enough to keep your immune system well supported every day so you won’t need to play catch-up,” she wrote in a previous column.
So does it make sense to spend your money on mega-doses of vitamin C on top of that—at least during cold and flu season? “As long as you’re not taking enough to hurt yourself, and you recognize that the benefit is unclear, I don’t have a problem with patients who use these products,” says Dr. Curry. “If your experience is that it’s helpful for you, then that’s great.”
If you do choose to take Emergen-C, however—or any other supplement—don’t let it be an excuse to skimp on food-based sources of vitamins and minerals. “The best way to keep your immune system strong is to eat healthfully, including vitamin C-rich produce, all the time,” says Sass.
Citrus fruits (like oranges and grapefruit) may be the most famous source of vitamin C, but you can also find the nutrient in broccoli, Brussels sprouts, kiwi, strawberries, papaya, and pineapple, Sass says. And topping the list of vitamin C-rich foods is red bell pepper, which contains around 200 milligrams in just one chopped cup.
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