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How Much Vitamin C Do You Need?

Experts disagree about exactly how much vitamin C each individual needs. People who don't eat fruits and vegetables should take a supplement.

Vitamin C, isolated and named more than 100 years ago, is crucial for good health. Even before it was discovered, vitamin C entered history. A lack of fresh fruits and vegetables on long sea voyages meant sailors were susceptible to scurvy. This sapped their energy and caused pain and shortness of breath. Bleeding gums made it difficult for them to eat the hardtack biscuits that were frequent fare. By the mid-18th century, James Lind of the Royal British Navy had figured out that a ration of citrus juice would prevent scurvy. Although it took decades before the navy implemented his findings, ultimately British sailors were issued lemon or lime juice, earning them the nickname “limeys.” But how much vitamin C do humans need?

How Do We Know? A Seminal Study from World War II:

For years, public health authorities have advised us how much vitamin C we need based on research conducted during World War II. The British navy had already ascertained that the vitamin was essential to prevent scurvy, but ascorbate-rich foods like lemons and oranges were in short supply during the war.

In one experiment, conscientious objectors were deprived of vitamin C for a lengthy period of time. Out of the 20 subjects, 2 developed life-threatening cardiac complications. Eventually they recovered, however, and the British government set the minimum vitamin C requirement at 10 mg per day. That was the amount needed to prevent frank signs of scurvy and wounds that would not heal.

A new analysis of the data from this study seven decades ago comes to a different conclusion (American Journal of Clinical Nutrition, Aug. 16, 2021). The original study had included experimental wounds and reports on scar strength. Modern statistical analysis reveals that the study subjects needed more than 10 mg daily to get their wounds to heal properly. According to the researchers, most people would need 95 mg of vitamin C daily to foster healing. Moreover, recovery from vitamin C deprivation takes longer and calls for more vitamin C than the original study concluded.

Too Little Vitamin C Can Lead to Bleeding Gums:

People who have trouble with bleeding gums may not be getting enough vitamin C (ascorbic acid). A meta-analysis of 15 clinical trials shows that bleeding gums and retinal bleeds can be a red flag for low ascorbic acid blood levels (Nutrition Reviews, Feb. 1, 2021). Even when people have blood levels adequate to prevent scurvy (11 to 28 micromol/L), they may still experience bleeding gums that can be rectified with additional ascorbic acid. A supplement of 100 to 200 mg a day or extra servings of foods like peppers, kiwi or citrus fruits rich in ascorbic acid might help.

How Much Vitamin C Should You Get?

Q. My dad can’t drink any citrus juice because it does not agree with him. He eats green vegetables, but not every day. Could he be low in vitamin C? If so, how much vitamin C should he take in a supplement?

A. The recommended dietary allowance (RDA) for ascorbic acid is 90 mg for adult men and 75 mg for adult women. Smokers need more. So do women who are pregnant or breast feeding. (Here is the detailed breakdown.)

Where Was Your Ascorbic Acid Made?

Q. Where in the United States can I buy pure ascorbic acid powder that does not come from China? I like to use vitamin C powder, but I worry that what I buy, even if “organic,” may not be as pure as possible.

A. One of the loopholes in product labeling involves the sourcing of ingredients. In other words, a vitamin tablet or powder may be manufactured in the US, but the raw materials are often imported. Unless a company specifically confirms that it makes its ascorbic acid products from US sources, you can’t assume that it originates here.

How Much Vitamin C Is in Your Diet?

According to the CDC, nearly 16 million Americans get too little ascorbic acid, less than 30 mg a day. Some experts suggest supplementing with 200 to 300 mg a day to be safe. Citrus foods are a wonderful source, but not everyone can tolerate them. Other foods high in ascorbic acid include bell peppers, kiwifruit, broccoli, strawberries and Brussels sprouts. Cantaloupe, cabbage and cauliflower are also rich in this vitamin.

Why You Need Vitamin C:

This vitamin is critical for the immune system, skin and connective tissue and has anti-cancer activity. This vitamin also promotes the absorption of nonheme iron from plant foods, and thus helps prevent iron deficiency anemia. The RDA may protect people from deficiency (scurvy) but it might not dictate optimal levels for good health.

Many people believe that taking extra ascorbic acid can prevent colds. Scientists have not confirmed that, but they have found that people who take the vitamin when they catch a cold recover more quickly and suffer less. Researchers are also studying possible benefits of vitamin C against infections, including COVID-19.

You can read more about unusual uses for vitamin C, such as to calm a cough due to asthma or to protect the stomach from damage caused by aspirin or other NSAIDs. Tell us about your experience using ascorbic acid supplements.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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  • Hujoel PP & Hujoel MLA, "Vitamin C and scar strength: analysis of a historical trial and implications for collagen-related pathologies." American Journal of Clinical Nutrition, Aug. 16, 2021. DOI: 10.1093/ajcn/nqab262
  • Hujoel PP et al, "Bleeding tendency and ascorbic acid requirements: systematic review and meta-analysis of clinical trials." Nutrition Reviews, Feb. 1, 2021. https://doi.org/10.1093/nutrit/nuaa115
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