Effect of ascorbic acid on incidence of spontaneous mammary tumors and UV-light-induced skin tumors in mice.

Two large-scale studies of the effect of different amounts of L-ascorbic acid in the food on tumor-free survival have been conducted. One involved the incidence of spontaneous mammary tumors in RIII mice, with seven ascorbic acid and three control groups, 50 mice per group. With increasing ascorbic acid in the diet, there was a highly significant delay before appearance of the first tumor. Median age at first tumor was 82.5 wk in ad libitum controls, 124.9 wk in the highest-dose ascorbate group. The proportion of mice with tumors was also reduced. The other study involved dermal neoplasms in mice irradiated with ultraviolet light. A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of malignant lesions was observed with high statistical significance. By 20 wk approximately five times as many mice had developed serious lesions in the zero-ascorbate as in the high-ascorbate group.