It’s the season for sickness.

According to the CDC, “most of the time flu activity peaks between December and March.” Cold season is also pegged to start around September and end around April inside the United States. Maybe that’s why so many of your friends and family are fighting through an illness right now.

One of the most common weapons used to combat sickness? Vitamin C. Products like Emergen-C and Airborne offer vitamin C megadoses that many people believe can help them fight off illness. But does more vitamin C really equal a stronger immune system? STACK Investigates.

The Snake Oil Salesman

The connection between vitamin C and the common cold starts with an American chemist named Linus Pauling.

Pauling was born in 1901. At age 30, he published a paper entitled, “The Nature of the Chemical Bond,” which featured concepts so revolutionary that he was awarded the Nobel Prize in chemistry. In 1949, his findings on sickle cell anemia essentially birthed the field of molecular biology. In 1951, he published a paper on the structure of proteins that laid the groundwork for how we understand the structure of DNA. Among chemists, Pauling was a rockstar. In 1961, he was on the cover of TIME magazine’s Men of the Year issue.

As Pauling gave way to old age, his research took a different path. He became convinced by a chemist named Irwin Stone that a daily dose of 3,000 mg of vitamin C could help him live longer. Pauling did exactly that and stated he felt livelier and healthier. He also noticed that the severe colds he used to get throughout the year had become a thing of the past. Pauling eventually bumped up his vitamin C usage to an incredible 18,000 mg per day. In 1970, he published a book entitled Vitamin C and the Common Cold, in which he urged the public to take 3,000 mg of vitamin C daily. It quickly became a best seller, and a subsequent expanded edition, entitled Vitamin C, the Common Cold and the Flu, promised that consistent large doses of vitamin C could eventually eradicate both the common cold and the flu. Sales of vitamin C supplements went through the roof.

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By the mid-1970s, 50 million Americans were following Pauling’s advice. His claims were losing him credibility in the scientific community—the theory that vitamin C helped prevent colds had almost no research to support it—but Pauling was still popular with the media. He went on to claim that megadoses of vitamin C could help cure cancer—as long as the patient didn’t first receive chemotherapy. He then said megadoses of vitamin C combined with massive doses of a handful of other vitamins and minerals could treat virtually every disease known to man—including AIDs, mental illness and kidney failure. He even stated that with the help of megadoses of vitamin C, the average human lifespan could eventually be expanded to 150 years. Scientists were outraged, but many members of the public bought it.

Pauling later died of prostate cancer. The Atlantic has an excellent piece on his rise and fall and his impact on the national health consciousness, but for our purpose, the takeaway is this—Linus Pauling convinced almost every American that massive doses of vitamin C would help them avoid sickness and disease. Though he died over 20 years ago, it’s an idea that scientists are still actively combating.

The Facts

Here’s where the research stands today. According to the Mayo Clinic, “in most cases, vitamin C supplements won’t help prevent colds.” The National Institutes of Health states “the evidence to date suggests that regular intakes of vitamin C at doses of at least 200 mg per day do not reduce the incidence of common cold in the general population.” However, there might be a small effect in the length of your cold if you take a vitamin C supplement prior to the onset of symptoms. The NIH points to a study that found use of prophylactic vitamin C modestly reduced cold duration by 8 percent in adults and 14 percent in children. But vitamin C supplements have been found to have no effect on cold duration or symptom severity if taken after the onset of symptoms.

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Some key members of the population might benefit from vitamin C supplements. They are people who have either been exposed to periods of severe physical exercise or intense cold (or both). Why these two groups? According to EXOS, too much exercise can have a negative effect on immunity. One study found that 90 minutes or more of high-intensity exercise (such as marathons or endurance races) make a person more susceptible to illness for up to 72 hours after the conclusion of the workout. As for cold weather, scientists recently discovered that cold temperatures weaken our first line of immune defenses, making us more susceptible to infection.

That’s not to say vitamin C plays no role in preventing sickness and illness. Vitamin C is essential for normal growth and development. It’s a water-soluble vitamin, meaning it dissolves in water, and excess amounts of it leave the body through urine. Thus, a consistent supply of vitamin C is key to making sure your levels stay where they need to be. According to the University of Maryland Medical Center, vitamin C is needed “for the growth and repair of tissues in all parts of the body.” It helps form protein to make skin, tendons, ligaments and blood vessels. It helps repair bones, cartilage and teeth. It aids in the absorption of iron and it helps heal wounds and make scar tissue. Vitamin C is also an antioxidant, meaning it battles the internal damage caused by free radicals. Free radicals may play a role in heart disease, cancer and conditions like arthritis.

Several cells in the immune system (such as phagocytes and t-cells) accumulate vitamin C and need it to perform their tasks. So if you’re deficient in vitamin C, your immune system can certainly take a hit and make you more susceptible to infection.

The average recommended daily value of vitamin C for adult men is 90 mg. For adult women, 75 mg. For teens, the values are 75 and 65 mg, respectively. But there’s a big difference between getting enough vitamin C and taking a megadose of it. It’s a classic case of diminishing returns—yes, our bodies need a sufficient amount of vitamin C to be healthy. But taking massive amounts of it doesn’t necessarily make us healthier.

Unlike some other vitamins (such as vitamin D), it’s quite easy to get a sufficient amount of vitamin C through your diet. Here’s a list of fruits and vegetables that contain at least 12 mg or more of vitamin C per reference amount. Examples include potatoes, Brussels sprouts, broccoli, bell peppers, blackberries, tomatoes, watermelon, strawberries, pineapple and spinach. It’s totally possible to get the RDV of vitamin C in just one or two servings if you pick the right foods. One serving of broccoli, for example, contains 220 percent of the RDV.

Murky Marketing

If the research says there’s little connection between megadoses of vitamin C and reduced risk of cold or flu, why do products like Airborne and Emergen-C have that reputation?

As it turns out, both products used to market themselves in some form or another as a way to battle cold and flus. Airborne is classified as a “dietary supplement.” It was invented by a former school teacher in the early 1990s. In its current form, Airborne Effervescent Zesty Orange (perhaps the company’s most popular product) contains “a blast of vitamin C plus 13 vitamins, minerals and herbs.” In this case, a “blast of vitamin C” equates to 1,000 mg per serving—roughly 1,667 percent of the recommended daily value. Emergen-C is a “dietary supplement” that’s been manufactured by Alacer Corp. since 1978. Emergen-C is also quite high in Vitamin B6 and Vitamin B12, but the main selling point is certainly its extreme amount of vitamin C. Emergen-C Super Orange contains 1,000 mg of vitamin C per serving, just like Airborne.

Since both Airborne and Emergen-C are “dietary supplements,” neither had to pass safety and efficacy research before coming to market. As such, both products have gotten in hot water for false or deceptive marketing claims. A class action lawsuit was filed against the former owners of Airborne Health, Inc. on the grounds that their products used false advertising. Namely, Airborne was being marketed as a way to cure or prevent the common cold. The Center for Science in the Public Interest participated in this class action lawsuit.

In March of 2008, the former owner of Airborne Health, Inc. agreed to pay $23.3 million to settle the lawsuit. In August of 2008, they agreed to pay the Federal Trade Commission up to $30 million to settle the FTC’s charges of false advertising. The FTC’s complaint included a statement that the company’s former owners and founders “made false claims that Airborne products are clinically proven to treat colds.” Nowadays, Airborne packaging makes no direct references to the common cold or flu.

In 2013, the Alacer Corp. was hit with a class action lawsuit for deceptive marketing. The complaint alleged that Emergen-C was represented as a supplement that would provide health benefits (such as reducing risk of or preventing colds and flu) without sufficient scientific evidence to support those claims. A superior court judge gave final approval to a $6.45 million settlement in June of 2014. Nowadays, you’ll notice that Emergen-C packaging has very little reference (if any) to an ability to fight off illness.

The Verdict

No one wants to be sick. That’s exactly why vitamin C megadose products like Airborne and Emergen-C have become so popular. Vitamin C does play a role in immune system strength, but more isn’t necessarily better. If you’re getting enough vitamin C from your diet (which you should be if you’re eating enough fruits and veggies), you shouldn’t feel the need to consistently take Vitamin C supplements. However, there’s not much risk in giving them a try if you think they’ll help. According to the University of Maryland Medical Center, serious side effects from consuming too much vitamin C are “very rare, because the body cannot store the vitamin.” Consuming more than 2,000 mg a day (which,  admittedly, is a very high amount on a daily basis) can lead to upset stomach and diarrhea.

If you’re someone who uses Airborne or Emergen-C on a semi-daily basis, perhaps it’s worth considering cutting back a bit. Maybe focus on taking them during periods when you know you’re at a higher risk of illness—such as after a period of extra intense exercise or exposure to very cold temperatures.

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