Taking vitamin C at the first sign of illness won’t help fight a cold

As cold and flu season is in full swing, many people turn to home remedies in hopes of curing or preventing stuffy noses, coughs and sore throats. A commonly used product is vitamin C supplements. Manufacturers often claim these pills, lozenges, drink mixes or gummies will “support” or “protect” your immune system. That’s led many people to believe these supplements will fight off their colds. 

But a recent tweet called this long-held belief into question and sparked a conversation online about how effective vitamin C supplements are for fighting colds. 

THE QUESTION

Will taking vitamin C supplements at the first sign of illness help fight a cold?

THE SOURCES

• Harvard Health
• National Institute of Health 
• “Vitamin C for preventing and treating the common cold,” a study published in Cochrane Library
• The Linus Pauling Institute at Oregon State University
• Registered dietitian Mary-Eve Brown
• Yale Scientific

THE ANSWER

No, taking vitamin C supplements at the first sign of illness won’t help fight a cold.

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WHAT WE FOUND:

Years of research show that taking vitamin C supplements when you’re sick won’t make a cold go away. And for most people, taking daily vitamin C supplements before symptoms start also won’t prevent illness, though it could make future colds slightly shorter and less severe. 

Vitamin C is an antioxidant that helps our bodies make connective tissue and hormones, heal wounds and neutralize damaging free radicals. 

U.S. health officials recommend that men get 90 mg of vitamin C daily (about 3/4 cup of orange juice) and women get 75 mg daily.

People who get less than 10 mg daily for one month or longer could develop scurvy, a disease caused by weakened connective tissues, fatigue, or anemia. This type of deficiency is rare in developed countries, according to Harvard Health. 

Many popular vitamin C supplements contain significantly more than the recommended daily amount. For example, one packet of Emergen-C “Super Orange” drink mix contains 1,000 mg. That’s about the maximum amount of vitamin C the body can fully absorb in one day before the excess starts to exit the body through urine, according to Harvard Health.

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Doses at that level generally aren’t harmful – though taking 3,000 mg or higher could trigger some side effects like diarrhea and kidney stones – but are they helpful?

VERIFY looked at the results of a Cochrane Library study published in 2013. Researchers compared the frequency and severity of colds between people taking less than 200 mg of vitamin C per day with people taking more than 200 mg, with most participants receiving between 1,000 and 4,000 mg.

This data included seven therapeutic trials in which participants took vitamin C supplements after feeling sick. The results showed the groups taking vitamin C didn’t fight off colds any better than the control groups. 

“Trials of high doses of vitamin C administered therapeutically, starting after the onset of symptoms, showed no consistent effect on the duration or severity of common cold symptoms,” the authors wrote.

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Guidance from Yale Scientific echoes these findings.

"Despite the myth deeply-entrenched in our culture, vitamin C is not a go-to solution for the common cold. The human body and its relationship to nutrition are far too complex for a single vitamin to cure sickness," writer Christine Xu said in an article.

The Cochran Library researchers also found that taking the supplements regularly, as opposed to when symptoms first start, didn’t prevent colds. 

“Regular ingestion of vitamin C had no effect on common cold incidence in the ordinary population, based on 29 trial comparisons involving 11,306 participants,” the authors wrote. 

But the study did find that taking supplements over time could cut down on cold duration, though the length of the trials examined in the study differed and the authors didn’t determine a recommended timeline.

Among participants who took vitamin C supplements regularly, the duration of colds for adults was reduced by 8% and in children by 14% and the severity of sickness was reduced.

“In our opinion, this level of benefit does not justify long-term supplementation in its own right,” the authors said. 

The high dose-supplements like the ones used in the studies aren’t necessary for people with a balanced diet, registered dietitian Mary-Eve Brown told VERIFY.

“Yes, we need vitamin C in our diet. But more may not be really what [your] body needs. And you can get it in your food supply really, really easily. Just eat your fruits and vegetables and you're going to get enough vitamin C in your diet. So taking supplements for most people, it's not really needed,” she said.

Many researchers point to flawed recommendations made by scientist Linus Pauling in the 1970s as the basis for long-held misunderstandings about the benefits of vitamin C.

The Linus Pauling Institute at Oregon State University says Pauling’s original recommendation of 2,000 mg a day was based on “theoretical arguments.” Today, the institute recommends lower doses from food sources high in vitamin C like kiwis, strawberries and red peppers.