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Some studies suggest that high-fat diets or high intakes of different types of fat in the diet may be linked to several cancers, including colon, lung, and postmenopausal breast cancer, as well as heart disease and other chronic diseases.
More research is needed to better understand which types of fat should be avoided and how much of each type alters cancer risk. Although monounsaturated and polyunsaturated fatty acids have been studied for a number of years, their effects are still unclear. More recent research on the effects of trans fatty acids also has yet to reach definitive conclusions.
The 2005 Dietary Guidelines for Americans recommend getting less than 10 percent of calories from saturated fatty acids and keeping trans fatty acid consumption as low as possible for general health and the prevention of chronic disease, including cancer and heart disease. The Guidelines also recommend keeping total fat intake between 20 and 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.
Intakes of total fat, and of the major fatty acids—saturated, monounsaturated, and polyunsaturated—all as a percentage of total calories.
Total fat: Falling slightly, then stable
Data collected in 2003-2004 show that total fat made up one-third (33 percent) of the calories people consumed, a level within the recommendations of the Dietary Guidelines. In the same period, saturated fatty acids accounted for 11 percent of calories; monounsaturated, 13 percent; and polyunsaturated, 7 percent.
No more than 30 percent of daily calories from fat.
(The Healthy People 2010 target calls for 75 percent of the population to reach this level. However, this recommended level pre-dates the 2005 Dietary Guidelines for Americans.)
Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican Americans all have average total fat intakes between 20 and 35 percent of calories, though their saturated fat intakes are slightly above current dietary recommendations. Polyunsaturated fat intakes tend to increase as education levels increase.
Researchers are studying how fat and fatty acids alter cancer risk. Precise and reliable measures of the amount and type of fat are needed—such as improved self-reported measures and biological indicators of fat intake that might be determined from a blood test.Trans fatty acids account for only about 2 to 3 percent of energy intake, but most of these come from sources that are not clearly labeled. Major food sources of trans fatty acids are cakes, cookies, crackers, etc; animal products; margarine; fried potatoes; chips; and shortenings. Some manufacturers have recently discontinued the use of trans fatty acids.