Vitamins A, C, E

In all trials in which the preventive effects of these vitamins have been studied, they were used in different combinations and therefore it is impossible to assess the effect of each of these micronutrients separately.

No significant effects on mortality rates were observed for supplementation with combinations of retinol and zinc [20] or beta-carotene and vitamin A [19]. Supplementation with ascorbic acid (1 g twice per day) was associated with increases in the rates of regression of dysplastic lesions in the stomach [odds ratio (OR) = 5.0; 95% CI 1.7–14.4] [21], whereas in a trial in Linxian (China) supplementation with vitamin C and molybdenum had no effect on overall and cancer mortality [20].

In the study in Linxian, the intervention group receiving supplementation with vitamin E, beta-carotene and selenium experienced a statistically significant (9%) reduction in overall mortality and 13% reduction in cancer mortality, which was mainly due to lower stomach cancer rates (OR = 0.79; 95% CI 0.64–0.99) [20].

In the alpha-tocopherol, betta-Carotene Cancer Prevention Study Group [18] trial alpha-tocopherol had no apparent effect on total and cancer mortality.

It can be concluded that there is no evidence at present that vitamin A, ascorbic acid or alpha-tocopherol supplements have value as cancer chemoprevention agents and they cannot be recommended for use in the general population in this context.