Almost 90 percent of vitamin C in the typical diet comes from fruits and vegetables, with citrus fruits, tomatoes and tomato juice, and potatoes being major contributors (Sinha et al., 1993). Other sources include brussel sprouts, cauliflower, broccoli, strawberries, cabbage, and spinach. Vitamin C is also added to some processed foods as an antioxidant. Values for the vitamin C content of foods can vary depending on the growing conditions, season of the year, stage of maturity, location, cooking practices, and storage time prior to consumption (Erdman and Klein, 1982).
Data from nationally representative U.S. and Canadian surveys are available to estimate vitamin C intakes (Appendix Table C-1, Table D-1, and Table E-1). In the United States, the median dietary intake of vitamin C by adult men from 1988 to 1994 was about 105 mg (596 µmol)/day and median total intake (including supplements, see Appendix Table C-2) is about 120 mg (682 µmol)/day. For women, the median intake was estimated to be 90 mg (511 µmol)/day and median total intake (including supplements) is about 108 mg (613 µmol)/day. (See Chapter 9 for vitamin C intake of men and women who smoke.) In Canada, the median dietary intake of vitamin C for adult men and woman was lower than in the United States with intake estimated to be about 70 mg (397 µmol)/day (Appendix Table E-1). Although most Americans consume fewer than the minimum of five daily servings of fruits and vegetables recommended by the U.S. Department of Agriculture and the National Cancer Institute, estimated median daily vitamin C consumption is above the Estmated Average Requirement (EAR). Five servings of most fruits and vegetables provide more than 200 mg (1,136 µmol)/day of vitamin C per day.
The Boston Nutritional Status Survey of the Elderly estimated that among this relatively advantaged group of people over aged 60, those who were not taking supplements had a median vitamin C intake of 132 mg/day for males and 128 mg/day for females (Hartz et al., 1992).