Can Emergen-C Actually Prevent a Cold?

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Emergen-C is available as a fizzy powder—and also gummies and chewables—that includes a mix of nutrients such as B vitamins and vitamin C. The packets of powder promise to offer "everyday immune support." Anecdotally, the supplement helps keep people healthy throughout the cold and flu season—but exactly how effective is Emergen-C? Unfortunately, the answer remains unknown.

There isn't any objective evidence of its benefits, but there have been many studies on its main ingredient, vitamin C, with mixed results. Because Emergen-C is a supplement, it can't make specific health claims. Its manufacturer settled a lawsuit in 2014 after it was accused of making health claims without actual evidence. Here's what you need to know.

Emergen-C Ingredients

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

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

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

What the Research Says

Emergen-C's claim to fame is the high dose of vitamin C, but the link between vitamin C and colds has been inconclusive. "The research has not been very high quality, and the results have been mixed," William Curry, MD, professor of medicine at the University of Alabama at Birmingham, told Health.

Some studies have found that vitamin C can help reduce how severe cold symptoms are. At the same time, the vitamin may not have much more of a benefit. For example, vitamin C doesn't prevent colds and may only have a slight effect on shortening how long you have a cold.

Adults need a daily amount of 8mg to 11mg of zinc—a mineral that's helpful for the immune system—and some studies have suggested zinc may speed up recovery for common-cold patients. However, Emergen-C may not be enough to fight a cold. One packet only contains 2mg of zinc.

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

Risks and Side Effects

Dietary supplements, like Emergen-C, receive minimal regulation by the FDA and can affect people differently. Its effects depend on factors like frequency of use and dosage.

For example, 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 gastrointestinal problems like diarrhea, nausea, and stomach cramps.

Keep some things in mind if you decide to take Emergen-C. Pay attention to the dosage and don't exceed the upper limit of the supplement. Also, it's best to limit Emergen-C to fewer daily doses. 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. Consult a healthcare provider if you're unsure whether vitamin C might affect your current medication regimen. Additionally, it likely won't protect you if you're coming down with a more severe illness, like influenza.

Daily Recommended Value of Vitamin C

The recommended daily vitamin C intake is as follows:

  • Adult males: 90mg
  • Adult females: 75mg
  • Lactating individuals: 120mg
  • Pregnant individuals: 85mg
  • Smokers: 35mg more daily than nonsmokers

You don't need a daily Emergen-C to achieve those levels. You can get vitamin C naturally from different foods, including:

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

How Else to Support Your Immune System

If you choose to take Emergen-C or any other supplement, don't let it be an excuse to avoid 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," Cynthia Sass, MPH, RD, contributing nutrition editor, told Health.

There are also other ways to support your immune system. You can ensure you're:

  • Being physically active regularly
  • Getting enough quality sleep
  • Limiting alcohol use
  • Maintaining a healthy weight
  • Quitting, or not starting, smoking

Also, you can purchase and take mega-doses of vitamin C during cold and flu season but keep some things in mind. "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."

A Quick Review

Although many people take Emergen-C to prevent or shorten a cold, the scientific evidence showing it works is minimal. There's also mixed research about vitamin C's effectiveness in preventing or treating colds in the general population. 

If you still decide to take Emergen-C, keep it to one serving daily. To ensure it's appropriate for you to take, especially if you're taking other medications, talk with a healthcare provider before using the supplement.

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12 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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