If you’re like many people, you probably don’t think too much about vitamin C — other than, perhaps, if you’re feeling unwell with a cold or the flu. But vitamin C is worth paying attention to, since it plays so many roles in the body.
What is vitamin C?
Vitamin C, which is also called ascorbic acid, is a water-soluble nutrient found in certain foods, especially some fruits and vegetables. “Water-soluble” means that the vitamin dissolves in water. Vitamin C and B vitamins (the other family of water-soluble vitamins) are carried to the body’s tissues, but they’re not stored in the body, unlike fat-soluble vitamins.
Because the body doesn’t store vitamin C, we need to consume foods or supplements that contain this vitamin every day.
What does vitamin C do?
Long before vitamin C was “discovered” in 1933, it was well known that feeding oranges and lemons to sailors could prevent scurvy, a disease that leads to bleeding gums, skin problems, anemia, and weakness.
Vitamin C has some pretty important and impressive responsibilities in the body.
- It’s an antioxidant that protects cells from damage from free radicals.
- It makes collagen, a protein found in skin, ligaments, tendons, connective tissue, bones, and teeth.
- It prevents scurvy.
- It helps the body absorb iron.
- It supports a healthy immune system.
How much vitamin C do you need?
The Food and Nutrition Board of the National Academies have established the following Recommended Dietary Allowances (RDAs) for vitamin C for adults:
|14-18 years||75 mg||65 mg||90 mg||115 mg|
|19+ years||90 mg||75 mg||85 mg||120 mg|
People who smoke are advised to consume 35 additional milligrams (mg) of vitamin C each day, since smoking can deplete vitamin C levels in the body.
To get cutting-edge diabetes news, strategies for blood glucose management, nutrition tips, healthy recipes, and more delivered straight to your inbox, sign up for our free newsletter!
What foods contain vitamin C?
Fruits and vegetables are the main sources of vitamin C, and by eating a variety of foods every day, you can get the amount that you need. Sources include:
- Citrus fruits (oranges, grapefruit, lemons, limes) and their juices
What about taking vitamin C supplements, and how much should you take?
As long as you are eating a varied diet that includes vegetables and fruits, you likely don’t need to take a vitamin C supplement. But some people could benefit from a supplement, including those who:
- Smoke or who are exposed to secondhand smoke
- Don’t eat many fruits or vegetables
- Have certain types of digestive disorders
- Have certain types of cancer (check with your provider first)
- Get dialysis for kidney disease
If you decide to take a vitamin C supplement, go easy on the dosing (remember, more isn’t necessarily better). The Food and Nutrition Board has set 2,000 mg daily as an upper level for vitamin C. At vitamin C doses above 1,000 mg daily, absorption falls to less than 50%; any vitamin C not absorbed is excreted in the urine.
For most people, large doses of vitamin C are not dangerous. But some people should be careful about taking megadoses of this vitamin, including:
- People with hemochromatosis
- People with a history of kidney stones
- People who are getting chemotherapy
Vitamin C can interact with some medicines, such as:
- Protease inhibitors
What happens if you take too much vitamin C?
The most common side effects of taking large doses of vitamin C are:
What about taking vitamin C to prevent a cold?
Despite all the hype around loading up on vitamin C to ward off the common cold, the research doesn’t support it. However, a handful of studies suggest that taking at least 200 mg of vitamin C daily might lessen the duration and severity of a cold, especially when taken at the start of symptoms. Taking vitamin C once the cold has taken hold doesn’t seem to provide any benefits in terms of duration or severity.
How does vitamin C help people with diabetes?
Some studies suggest that vitamin C could be helpful to people with diabetes in terms of blood sugar and even blood pressure control. A meta-analysis published in the February 2021 journal Diabetes Care concluded that vitamin C supplementation “significantly lowers HbA1c, fasting and postprandial glucose, triglycerides, total cholesterol, SBP (systolic blood pressure), DBP (diastolic blood pressure) and MDA (a marker of lipid oxidation) in people with type 2 diabetes.” However, the authors added that more studies with a larger sample size and longer supplementation periods are needed.
Another, smaller study, published in the journal Diabetes, Obesity and Metabolism in 2019 of just 31 people with diabetes showed that the group given two 500 mg doses of vitamin C daily had a “significant 36% drop in blood sugar spike after meals.” They also had lower blood pressure.
Higher intakes of vitamin C may protect against heart disease, which is common in people with diabetes, although there is no recommended dose to aim for. But there is evidence that supports eating vegetables and fruit can lower the risk of heart disease, as well as some types of cancers.
If you have a wound that is healing, such as a foot ulcer or other type of cut or sore, talk with your provider or registered dietitian about increasing your vitamin C intake, including taking a supplement. Vitamin C is necessary for collagen formation (necessary for wound healing), as well as overall skin health.
- Make a point to include vitamin C-rich foods in your eating plan every day.
- If you think you’re not getting enough vitamin C, talk with your provider or dietitian about taking a supplement.
- Go easy on the amount of vitamin C that you take as a supplement, especially if you are receiving treatment for cancer.
- Focus on getting enough vitamin C in your diet and possibly with a supplement if you have a foot ulcer or any other type of wound.