Analytical versus food table values for vitamin C in foods: the effect on calculated vitamin C intake of elderly subjects.
During a longitudinal study of vitamin C nutrition in 23 healthy elderly people, samples of cooked vegetables and liver, canned meats, canned vegetables and fruit drinks were analysed for vitamin C content. The analytical data are presented here and the effect on calculated daily intake of vitamin C of using the analytical values in place of food table values is assessed. For cooked foods the analysed values were close to food table values; exceptions were spring cabbage, cauliflower and canned potatoes. Fortified fruit drinks contained 20-60 mg vitamin C per 100 ml and made an important contribution to intake. Canned meats contained 0.3-61.4 mg per 100 g (mean 14.9 mg), but their contribution to intake was considered small. The difference between daily intakes calculated using analytical and food table values was greater than 5 mg in 37 per cent of 1-day periods and in 17 per cent of 7-day periods. These differences were not sufficient to significantly alter the correlations between intake and biochemical indices found in the original study. Nevertheless, given the discrepancies between calculated and analysed vitamin C intakes reported in the literature, analytical work is probably essential in studies of vitamin C nutrition.