Long term dietary folate decreased risk of colon cancer in women
Question Is folate intake from diet or dietary supplements associated with a decreased risk of colon cancer in women?
Population based cohort study of women in the Nurses' Health Study with 14 years follow up.
88 756 female registered nurses who were 30–55 years of age in 1976 (baseline). Exclusion criteria were cancer other than non-melanoma skin cancer before 1980, ulcerative colitis, familial polyposis syndrome, implausible high or low scores for total energy intake, missing data on food frequency questionnaires between 1980 and 1992, or incomplete information on aspirin or multivitamin use in 1980.
Assessment of risk factors
Nurses completed postal questionnaires at baseline and every 2 years thereafter. Food frequency questionnaires included information on 61 foods and beverages, vitamin and mineral supplements, and brands and types of breakfast cereals and multivitamin products. For analysis, nurses were divided into quartiles based on folate intake in 1980 (≤200, 201–300, 301–400, …