Can Emergen-C Actually Prevent a Cold?

If you reach 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 and other nutrients—has become a mainstay of medicine cabinets, winter-weather survival kits, travel packing lists, and even wedding weekend goodie bags. But is Emergen-C good for you?

"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 medicine at the University of Alabama at Birmingham, told 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 making health claims without actual evidence. 

But Emergen-C promises to offer "everyday immune support." Devotees swear by its ability to keep them healthy through the cold-and-flu season or even shorten the duration of a cold once it starts.

But is there any objective evidence of those supposed benefits? Not really, noted Dr. Curry. In fact, as of November 2022, there are zero published clinical trials on Emergen-C. However, there have been many studies on its main ingredient, vitamin C. 

A Look at Emergen-C’s Ingredients

The iconic orange Emergen-C powder offers many flavors and colors of its original "immune support" product. It also provides chewable and gummy varieties. And other additional products target hydration, better sleep, electrolyte replenishment, and gut health. 

The brand's flagship immune support formula's main ingredient is vitamin C. Each packet of powder has about 1,000 milligrams. There are approximately 500 milligrams per gummy and 1,000 milligrams per chewable. For comparison, many other OTC vitamin C supplements contain only 500 milligrams per dose. And multivitamins may contain only around 60 milligrams.

The Emergen-C immune support also contains the following ingredients:

• Antioxidants like zinc, vitamin E, and manganese
• Electrolytes like sodium, calcium, phorsphorus, magnesium, and potassium 
• Seven B vitamins—thiamin, riboflavin, niacin, vitamin B6, folic acid, vitamin B12, and pantothenic acid
• Caffeine
• Melatonin
• Ginseng
• Vitamin D
• Probiotics
• Superfoods
• Plant-based proteins

What Evidence Suggests About Emergen-C

Emergen-C's claim to fame is the high dose of vitamin C. But studies on the effectiveness of vitamin C at preventing or treating colds have been inconclusive at best, noted Dr. Curry. "The research has not been very high quality, and the results have been mixed," said Dr. Curry.

In 2013, the Cochrane Database of Systematic Reviews published a study that found that 1,000 milligrams of vitamin C daily helped prevent colds in physically active people, like marathon runners and skiers. However, those benefits didn't translate to other studies on the general population.

"That was a little surprising, and we still don't really know why this was the case," noted Dr. Curry. "But there seems to be something about the combination of being really physically active and taking vitamin C that may be protective." 

Dr. Curry added that the study could only show an association between high vitamin C doses and fewer colds, not a cause-and-effect relationship.

So, the relationship is inconclusive. But given vitamin C's low cost and relative safety, the researchers wrote that it doesn't hurt to try.

As for zinc, according to Dr. Curry, some studies have also suggested that this mineral may speed up recovery for common-cold patients. But a packet of Emergen-C only contains two milligrams of zinc, which may not be enough to fight colds.

The other ingredients in Emergen-C may have antioxidant or electrolyte properties. But Dr. Curry noted that there's no evidence they can directly protect against colds or other viruses.

What Are the Risks?

The tolerable upper limit for vitamin C 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," explained Dr. Curry. Excess vitamin C may also cause diarrhea, nausea, and abdominal cramps.

Dr. Curry cautioned patients who want to take Emergen-C or similar products to pay attention to their dosage and not exceed the upper limit. So, steer clear of several doses of Emergen-C in a day. Also, be careful when taking it alongside other supplements containing vitamin C. Emergen-C recommends one packet, one chew, or three gummies daily.

Some studies have also suggested that vitamin C can interact with certain medicines, including statins and chemotherapy drugs. And it likely won't protect you if you're coming down with a more severe illness, like influenza. If you're unsure whether vitamin C might affect your current medication regimen, consult your healthcare provider. 

Daily Recommended Value of Vitamin C

The recommended daily vitamin C intake for average adult women and men is 75 and 90 milligrams per day.

Obviously, you don't need a daily Emergen-C to achieve those levels. Eating the recommended minimum of two daily cups of fruit and three daily cups of vegetables will get you at least 200 milligrams of vitamin C, said Cynthia Sass, MPH, RD, Health's contributing nutrition editor. 

That's "enough to keep your immune system well supported every day so you won't need to play catch-up," wrote Sass.

So, should you spend your money on mega-doses of vitamin C 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," noted Dr. Curry. "If your experience is that it's helpful for you, then that's great."

If you choose to take Emergen-C 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," added Sass.

According to Sass, citrus fruits like oranges and grapefruit are excellent sources of vitamin C. Other sources of vitamin C include:

• Red and green peppers
• Kiwi
• Broccoli
• Strawberries
• Brussels sprouts
• Cantaloupe

A Quick Review

Although many people take Emergen-C to prevent or shorten a cold, the scientific evidence showing it works is minimal. 

If you're an athlete or physically active, this supplement's vitamin C may help prevent a cold. Still, there's inconclusive research about vitamin C's effectiveness in preventing or treating colds in the general population. 

And the amount of zinc in one serving of Emergen-C isn't enough to shorten a cold. If you still decide to take Emergen-C, keep it to one serving daily. If you're taking statins or chemotherapy medications, talk with your healthcare provider before using the supplement.