Recently, the Journal of the American Medical Association reported three research studies conducted on approximately 48,000 postmenopausal women to examine the effects of eating a low-fat diet (approximately 20% of calories from fat) on developing cancer or having a heart attack.  Half of the women were randomly assigned to eat a low-fat diet, while the other half made no change in their diet.  After eight years, the results did not show a health advantage for women eating a low-fat diet.

These results may surprise some people because it has been widely believed that a low-fat diet is the best way to prevent heart disease and cancer; however, research has failed to show that low-fat diets are beneficial in preventing these diseases.  Harvard’s Nurses’ Health Study also found that total fat intake was not associated with the risk for cancer or heart disease.   Furthermore, five years ago the National Institutes of Health and the Institute of Medicine both recommended increasing the upper limit of total daily fat intake from 30% to 35% of calories.

What research has consistently shown is that the amount of fat is not as important in preventing heart disease or stroke; the type of fat eaten is what is most important.  Risk is lowered by consuming vegetable oils or unsaturated fats and is increased by eating animal and saturated fats.

What it Means:

Diet is important in preventing cancer and heart disease.  For preventing heart disease, it is not important to eat a low-fat diet but a diet low in saturated and trans-fats with adequate amounts of unsaturated fats.  Research also supports eating high amounts of fruits and vegetables (8-9+ servings per day) to reduce the risk of high blood pressure, heart disease, and stroke.  Eating lower calorie diets that result in losing excess body fat reduces the risk for both cancer and heart disease.

Source: Prentice R.L. et al (Feb. 2006). “Low-fat dietary pattern and risk of breast cancer, colorectal cancer, and cardiovascular disease.” JAMA.