Multivitamins, Folate Prevent Colon Cancer
A high intake of folate may reduce risk for colon cancer, but the dosage and duration relations and the impact of dietary compared with supplementary sources are not well understood. Giovannucci E, et.al, in a paer published in Ann Intern Med. 1998;129-517-524. attempted too evaluate the relation between folate intake and incidence of colon cancer.
They evaluated 88,756 women from the Nurses' Health Study who were free of cancer in 1980 and who provided updated assessments of diet, including multivitamin supplement use, from 1980 to 1994.There were 442 women with new cases of colon cancer.
Measurements: Multivariate relative risk (RR) and 95% CIs for colon cancer in relation to energy-adjusted folate intake.
Results: Higher energy-adjusted folate intake in 1980 was related to a lower risk for colon cancer (RR, 0.69 [95% CI, 0.52-0.93] for intake >400 mg/d compared with intake _ 200 mg/d) after controlling for age, family history of colorectal cancer, aspirin use, smoking, body mass, physical activity, and intakes of red meat, alcohol, methionine, and fiber.
When intake of vitamins A, C, D, and E, as well as calcium were also controlled for, results were similar.
Women who used multivitamins containing folic acid had no benefit with respect to colon cancer after 4 years of use (RR, 1.02) and had only nonsignificant risk reductions after 5 to 9 (RR, 0.83) or 10 to 14 years of use (RR, 0.80). After 15 years of use, however, risk was markedly lower (RR, 0.25 [CI, 0.13-0.51]), representing 15 instead of 68 new cases of colon cancer per 10 000 women aged 55 to 69 years.
Folate from dietary sources alone was related to a modest reduction in risk for colon cancer, and the benefit of long-term multivitamin use was present across all levels of dietary intake.
Conclusion: Long-term use of multivitamins may substantially reduce risk for colon cancer. This effect may be related to the folic acid contained in multivitamins.