Changes in diet during adult life and risk of colorectal adenomas.

To evaluate the associations of changes in diet during adult life with adenoma risk, data from a case-control study of 146 colorectal adenomas and 226 controls were analyzed. Dietary habits during the year before sigmoidoscopy and when subjects were 30 yr old were collected using a food-frequency questionnaire. Change in frequency of consumption during adulthood was calculated by subtracting frequency of consumption of specific foods or food groups at age 30 yr from frequency of consumption during the previous year (recent consumption). Associations with changes in frequency of consumption were estimated by odds ratios (ORs) and 95% confidence intervals (CIs). There was no association for foods or food groups consumed at age 30 yr. For recent consumption, more frequent consumption of red meat, breakfast sausage, and pork chops/ham steaks and less frequent consumption of fish, chicken/turkey, and vegetables were related to a higher risk. Compared with individuals with the highest reduction in consumption since age 30 yr, risks were higher for those with smallest reduction in red meat intake (OR = 2.8; CI = 1.1-7.3), particularly for hamburgers/cheeseburgers (OR = 2.8; CI = 1.2-6.8) and pork chops/ham steaks (OR = 3.7; CI = 1.6-8.7). In contrast, individuals in the highest quartile of increased consumption of fish (OR = 0.6; CI = 0.3-1.1) and vegetables (OR = 0.5; CI = 0.3-1.1) had a lower risk compared with those with minimal increase in consumption. In conclusion, irrespective of frequency of consumption at age 30 yr, a greater reduction in consumption of red meat and a larger increase in consumption of vegetables since age 30 yr were associated with a decreased risk of colorectal adenomas later in life.