Intakes of vitamins A, C, and E and use of multiple vitamin supplements and risk of colon cancer: a pooled analysis of prospective cohort studies

Abstract

Objective: To evaluate the associations between intakes of vitamins A, C, and E and risk of colon cancer.

Methods: Using the primary data from 13 cohort studies, we estimated study- and sex-specific relative risks (RR) with Cox proportional hazards models and subsequently pooled RRs using a random effects model.

Results: Among 676,141 men and women, 5,454 colon cancer cases were identified (7-20 years of follow-up across studies). Vitamin A, C, and E intakes from food only were not associated with colon cancer risk. For intakes from food and supplements (total), the pooled multivariate RRs (95% CI) were 0.88 (0.76-1.02, >4,000 vs. ≤ 1,000 μg/day) for vitamin A, 0.81 (0.71-0.92, >600 vs. ≤ 100 mg/day) for vitamin C, and 0.78 (0.66-0.92, > 200 vs. ≤ 6 mg/day) for vitamin E. Adjustment for total folate intake attenuated these associations, but the inverse associations with vitamins C and E remained significant. Multivitamin use was significantly inversely associated with colon cancer risk (RR = 0.88, 95% CI: 0.81-0.96).

Conclusions: Modest inverse associations with vitamin C and E intakes may be due to high correlations with folate intake, which had a similar inverse association with colon cancer. An inverse association with multivitamin use, a major source of folate and other vitamins, deserves further study.

Fig. 1

Study-specific and pooled multivariate RRs (adjusted for covariates listed in Table 2 legend c) of colon cancer in multivitamin users versus nonusers. The squares and horizontal lines correspond to the study-specific multivariate RR and 95% CIs, respectively. The size of a square reflects the study-specific weight (inverse of the variance), and the diamond represents the pooled multivariate RR and 95% CI. The vertical dotted line represents the pooled RR. The abbreviations of the studies are the same as in Table 1