Colorectal Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Description of the Evidence
Cardiovascular Risks Associated With Celecoxib and Rofecoxib Dose/Drugs continued...
Other studies suggest that the polyps with the greatest potential to progress to CRC are larger polyps (i.e., >1.0 cm), which include most of those with villous or high-grade histologic features. Retrospective cohort studies also show the harms associated with polypectomy, including bleeding.[83,84]
Dietary fat and meat intake
Colon cancer rates are high in populations with high total fat intakes and are lower in those consuming less fat. On average, fat comprises 40% to 45% of total caloric intake in high-incidence Western countries; in low-risk populations, fat accounts for only 10% of dietary calories. In laboratory studies, a high-fat intake increases the incidence of induced colon tumors in experimental animals.[87,88] Several case-control studies have explored the association of colon cancer risk with meat or fat consumption as well as protein and energy intake.[10,89] Although positive associations with meat consumption or with fat intake have been found frequently, the results have not always achieved statistical significance. A number of prospective cohort studies have been conducted in the United States and abroad. In Japan, an increased risk of colon cancer with increased frequency of meat consumption was observed in the group with infrequent vegetable consumption among a group of 265,000 men and women. In Norway, an increased risk for processed meat only was found, a finding that was confirmed in the Netherlands. A clearly defined gradient in the risk for frequency of meat and poultry consumption was not observed in a population of Seventh Day Adventists that included a large proportion of vegetarians. A prospective study among female nurses showed an increased risk of colon cancer associated with red meat consumption (beef, pork, lamb, and processed meat) and also with the intake of saturated and monounsaturated fat, predominantly derived from animals. In two other large prospective studies, the CPS II and the Iowa Women's Health Study (IWHS), no increase in the risk of colon cancer was seen with meat or fat consumption.[96,97] In a prospective cohort study of a low-risk population of non-Hispanic white members of the Adventist Health Study, a positive association between meat (both red and white) intake and colon cancer was observed (RR for ≥1 time per week vs. no meat intake = 1.85, 95% CI, 1.19–2.87, P for trend = .01). It has been hypothesized that the heterocyclic amines (HCAs) formed when meat and fish are cooked at high temperatures may contribute to the increased risk of CRCs associated with meat consumption that has been observed in epidemiologic studies. A population-based case-control study in Sweden, however, found no evidence of increased risk associated with total HCA intake; for colon cancer the RR was 0.6 (95% CI, 0.4–1.0), and for rectal cancer it was 0.7 (95% CI, 0.4–1.1).[99,100]