Vitamin C is a Good Antioxidant

"An apple a day keeps the doctor away," This is an old quote referring to the health benefit of an adequate intake of vitamin C in our body, that is, increased resistance to the common colds and other various diseases. Thus, we have been taught at home and in school to eat fruits and vegetables because they are rich sources of this vitamin.

An important function of vitamin C not known to many is its being an antioxidant. In fact, it has been recognized and accepted by the US Food and Drug Administration (FDA) as one of the four dietary antioxidants, the others being vitamin E, beta-carotene and selenium.

A dietary oxidant is a substance in food that significantly decreases the adverse effects of harmful chemicals like reactive oxygen and nitrogen species, and other free radicals on normal physiological functions in human. It acts as a scavenger, sweeping these chemicals away from the body thereby protecting other substances from oxidative damage. For example, the presence of vitamin C in the stomach or duodenum prevents the formation of harmful oxidants in the gastric juice, thereby protecting against gastric cancers. In the process of getting rid of foreign invaders and monitoring the systems for any sign of tumor cells, vitamin C stimulates the production of antibodies and interferon, the protein that also protects the body form viral invaders and cancer cells. Antioxidant vitamins prevents the oxidation of LDL cholesterol thus may reduce platelet adhesion to the arterial wall. Platelet adhesion favors development of atherosclerotic plaques, blocking the flow of blood.
The Recommended Dietary Allowance (RDA), 1989 for Filipinos for vitamin C, published by the Food and Nutrition Research Institute, Department of Science and Technology (FNRI-DOST), is 30 mg/day for infants; 35 mg/day for 1-3 children; 75 and 70 mg/day for male and female adults, respectively. This recommendation is the minimum amount of intake required to prevent nutritional deficiencies. In order to obtain the protective effect of Vitamin C against different types of cancers, atherosclerosis, antioxidant mechanisms, expert suggest increasing our intake of Vitamin C about 90-100 mg/day. This can be easily achieved by including 2-3 servings per day of Vitamin C-rich fruits and vegetables in the diet.

The current RDA for the different nutrients including vitamin C are under review by the Food and Nutrition Research Institute, Department of Science and Technology (FNRI-DOST) together with the RDA Task Force whose members are expert from the academe and from the government and private institutions.

The initial signs of Vitamin C deficiency are irritability, general weakness, lack of appetite and lowered resistance to infection. Severe vitamin deficiency results in scurvy, characterized by bleeding, swollen gums, and loose teeth. Occasional adverse effects like diarrhea and gastrointestinal disturbances have been noted in intakes higher than 2000 milligrams (mg).

Below is a list of Vitamin C values of some common fruits and vegetables in serving portion (Source: The Philippine Composition Tables 1997, Food and Nutrition Research Institute, Department of Science and Technology).