Recommended Intakes for Vitamin C

A report issued in April, 2000 by the Institute of Medicine (National Academy of Sciences) increased the RDA of vitamin C to:

• 75 mg per day for women;
• 90 mg for men.
• Smokers should add an additional 35 mg per day because their metabolic turnover of vitamin C is more rapid, as is their rate of oxidative stress.

What is the RDA?
RDA (recommended dietary allowance) is the dietary intake level that is sufficient to meet nutrient requirements of 97-98% of healthy individuals in a particular life stage and gender group. Nutritional surveys indicate that about 11% of women and 21% of men in the US currently do not meet the recommended intakes of vitamin C. The revised of RDA's are important because they recognize the different nutritional need of males and females, and also address the needs of children.

The new RDAs for children are:

• 1-3 years: 15 mg
• 4-8 years: 25 mg
• 9-13 years: 45 mg
• 14-18: 75 mg for boys and 65 mg for girls

For pregnant and lactating (breast feeding) women:

• Pregnant: 80-85 mg
• Lactating: 115-120 mg

How much is too much?
The report also includes the newly calculated figures for the "tolerable upper intake level" for vitamin C -- the highest level of daily intake that is likely to pose no risk of adverse health effects to the general adult population aged 18 years an older. For vitamin C this is estimated at 2,000 mg for adults; 400 mg for children ages 1-3 years; 650 mg for children ages 9-13 years, and 1800 mg for young adults aged 14-18 years old. As intake increases above this level, the risk of adverse effects increases.

Vitamin C and dietary antioxidants
Most of us know that vitamin C is effective in fighting off a cold and otherwise enhancing resistance to germs by helping to maintain the immune system. But the role of vitamin C as a dietary antioxidant, and its potential role in disease prevention and treatment, is only beginning to be understood and documented.

Dietary antioxidants are substances found in foods which can help to slow down or prevent the process of oxidation -- the damage done to cells in your body by oxygen. The best evidence for the role of vitamin C in protection against chronic disease is for cardiovascular disease. Oxidation of low density lipoproteins (LDL's) is thought to be a key step in the development of coronary atheroscelrosis. Epidemiological studies indicate that diets rich in fruits and vegetables, C and E and cartotenoids are associated with decreased risk of coronary heart disease.

Other studiessuggest that consumption of diets high intakes of vitamin C is associated with lower risk of cataracts, and that vitamin C therapy may promote improved mental function in people with Alzheimer's Disease, and the reduction of some symptoms of Parkinson's Disease and Amyotrophic lateral sclerosis (ALS). According to the Institute of Medicine report, there is not enough evidence to support the contention that C will help prevent or delay the onset of any of these diseases. Many research programs are underway to address the issue of whether or increased intake of dietary antioxidants such as those found in vitamins C and E can protect against chronic disease.

How can you increase your intake of vitamin C?
Easily! The best way is to eat more fresh fruits and vegetables. A cup of fresh orange juice (120 mg) or grapefruit juice (90 mg) can be a simple jumpstart.

The American Dietetic Association lists these foods as terrific sources of C: broccoli, cantaloupe, grapefruit, green bell peppers, orange juice, oranges, red peppers, strawberries, tomatoes, tomato juice, tropical fruit juices, tropical fruits such as papaya and mango.

Information Provided by the Institute of Medicine of the National Academy of Sciences and the American Dietetic Association.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.