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How Much Does Vitamin C Help Prevent or Treat Colds?

Vitamin C is a popular natural immunity supplement in the winter and early spring and is often hailed as a remedy for the common cold.  Commonly purchased products are those with high-dose supplements of vitamin C (ascorbic acid) like Airborne and Emergen-C.  These may claim to prevent colds or improve your cold symptoms, but do they really?

Does taking vitamin C help to prevent colds?

Studies have shown that taking vitamin C does not help to prevent colds.

Commonly used over-the-counter vitamin C products like Emergen-C have 1 gram of vitamin C per packet or tablet.  In a systematic review, taking a daily dose of vitamin C (either 1, 2, or 3 grams per day) was not shown to decrease the likelihood of getting sick with an upper respiratory infection (a cold).

Does taking vitamin C help treat a cold once I am sick?

For the most part, taking even high doses of vitamin C after you get symptoms has not been shown to consistently reduce symptom duration severity.

One study from 2018, oof nine randomized controlled trials, suggested that some people who regularly take vitamin C may benefit from adding extra doses when they start to feel the symptoms of a cold coming on.  The analysis found that the extra doses made the difference and that they reduced the duration of a cold by about half a day.

Vitamin C may not reduce cold symptoms, but it helps your immune system.

Vitamin C doesn't appear to prevent colds or do much when it comes to reducing cold symptoms; however, it still plays an important role in your health.  It helps with cell protection, absorption of iron, immune system functioning, and producing collagen, which helps heal wounds.  Most people should get vitamin c from their diets but some groups may be at an increased risk of not getting enough, including smokers, people with limited food variety, and people with certain chronic diseases or absorption issues.

The National Institutes of Health recommends a daily intake of 90 milligrams of vitamin C for adult males and 75 milligrams for adult females.  Smokers require and additional 35 milligrams daily.  That's easily achievable through fruits and vegetables.  For example, a medium orange has 70 milligrams of vitamin C and a medium grapefruit has 78 milligrams.

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Written by Sharon Orrange, MD. MPH.  Article has been edited for brevity.  An unedited article can be found at goodrx.com/blog/does-vitamin-c-prevent-colds/