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Vitamin C (Ascorbic Acid)

Vitamin C (ascorbic acid) helps tissue and bone grow and repair themselves. While vitamin C supplements are extremely popular, research has yet to establish solid health benefits.

Why do people take vitamin C?

Studies have shown that vitamin C may reduce the odds of getting a cold, but only in specific groups in extreme circumstances, such as soldiers in subarctic environments, skiers, and marathon runners. Studies have not found solid evidence that vitamin C helps prevent or treat colds in average situations.

Vitamin C's antioxidant benefits are also unclear. While some studies of vitamin C supplements have been promising, they have not found solid evidence that vitamin C supplements help with cancer, stroke, asthma, and many other diseases. Evidence does suggest that they do not help with cataracts or high cholesterol.

Data on vitamin C and heart disease are mixed. Some studies show an association between low levels of vitamin C and heart disease risk, yet many studies have linked the use of vitamin C supplements with an increased risk of heart disease. 

Data on taking vitamin C for hypertension are also mixed. Taking vitamin C with antihypertensive medications may slightly decrease systolic blood pressure, but not diastolic pressure. Supplemental vitamin C -- 500 mg per day taken without antihypertensives -- doesn't seem to reduce systolic or diastolic blood pressure. Type 2 diabetics who supplemented with vitamin C and remained on their antihypertensive medications seemed to have a reduction in blood pressure and arterial stiffness. Lower levels of vitamin C in the blood are associated with increased diastolic and systolic blood pressure.

Studies have shown that dietary rather than supplemental sources of vitamin C are more effective in keeping blood pressure in check. 

A substantial number of Americans may have low intake levels of vitamin C due to the inadequate intake of fruits and vegetables. The proven and effective use of vitamin C is for treating vitamin C deficiency and conditions that result from it, like scurvy.

Vitamin C also seems to help the body absorb the mineral iron.

How much vitamin C should you take?

The recommended dietary allowance (RDA) includes the vitamin C you get from both the food you eat and any supplements you take.

Category

Vitamin C: Recommended Dietary Allowance (RDA)

For children under 1, only an adequate intake (AI) is available

CHILDREN

0-6 months

40 mg/day

Adequate Intake (AI)

7-12 months

50 mg/day

Adequate Intake (AI)

1-3 years

15 mg/day

4-8 years

25 mg/day

9-13 years

45 mg/day

FEMALES

14 to 18 years

65 mg/day

19 years and up

75 mg/day

Pregnant

18 years and under: 80 mg/day

19 years and over: 85 mg/day

Breastfeeding

18 years and under: 115 mg/day

19 years and over: 120 mg/day

MALES

14 to 18 years

75 mg/day

19 years and up

90 mg/day

Continued

Although many people take much higher doses of vitamin C, it's not clear that high doses have any benefit. Some studies have found that doses above 200 milligrams are not utilized by the body. Instead, the extra vitamin C is excreted in urine.

The tolerable upper intake levels of a supplement are the highest amount that most people can take safely. Higher doses might be used to treat vitamin C deficiencies. But don't take more unless a doctor says so.

Category

(Children & Adults)

Tolerable Upper Intake Levels (UL) of Vitamin C

1-3 years

400 mg/day

4-8 years

650 mg/day

9-13 years

1,200 mg/day

14-18 years

1,800 mg/day

19 years and up

2,000 mg/day

 

Can you get vitamin C naturally from foods?

Many people get enough vitamin C from their diets. All fruits and vegetables have some vitamin C. Some of the best sources are:

  • Green peppers
  • Citrus fruits and juices
  • Strawberries
  • Tomatoes
  • Broccoli
  • Sweet potatoes

Light and heat can reduce vitamin C levels. Fresh and uncooked fruits and vegetables have the most vitamin C.

What are the risks of taking vitamin C?

  • Side effects. At recommended doses, vitamin C supplements are safe. However, they can cause upset stomach, heartburn, cramps, and headaches in some people. High doses of vitamin C can cause more intense symptoms, such as kidney stones and severe diarrhea.
  • Interactions. If you take any other regular medicines or chemotherapy drugs, ask your doctor if it's safe to take vitamin C. It can interact with drugs like aspirin, acetaminophen, antacids, and blood thinners. Nicotine may reduce the effects of vitamin C.
  • Risks. People who are pregnant or have gout, liver disease, kidney disease, and other chronic diseases should check with a doctor before using high doses of vitamin C supplements.
WebMD Medical Reference Reviewed by David T. Derrer, MD on December 08, 2014

Sources

SOURCES:

National Institutes of Health Office of Dietary Supplements: "Vitamin C - Fact Sheet for Consumers."

Longe, J., ed. The Gale Encyclopedia of Alternative Medicine, second edition, 2004.

Natural Standard Patient Monograph: "Vitamin C."

National Library of Medicine's Medline Encyclopedia: "Vitamin C."

Moser, M. Int J Mol Sci, August 2016.

Buijsse, B. PLoS, 2015. Published online Dec. 18, 2015.

Andre, CM. J Agric Food Chem, Oct. 2015.

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