Does a Low Fat Diet Improve Your Health? - Breast Cancer

Regular readers of this site are probably already aware that many of the "wisdoms" we hear daily may be questionable - for example, it isn't obvious that saturated fat is as bad as the media has advertised, and cholesterol skeptics may have a point in believing that cholesterol is not the source of all heart problems as many would have us believe. A recent series of articles published in JAMA strongly suggests that low fat diets do not effectively prevent cancer or heart disease. These studies are all part of the Women's Health Initiative (WHI) study, that began in 1992, and included a randomized trial whereby some participants consumed a reduced amount of fat (20% of total energy intake), and increased the amount of vegetables and fruit (more that 4 servings a day) and grains (more than 5 servings a day). This is what is referred to as "the low fat dietary pattern". (This is the same study as the one that resulted in halting Hormone Replacement Therapy - click here for more information.)

Of the 49,000 women accepted in to the trial, 20,000 were assigned to receive the low-fat diet. The women were all postmenopausal, aged 50 to 79 years old at the beginning of the trial. 19% of the women self-reported as minority racial/ethnic groups. The duration of the study was approximately 12 years. The participants all started out obtaining about 38% of their calories from fat. Those assigned to the low-fat consumption group, reduced their fat intake to 27% of their total calories. In addition, they increased their consumption of fruit and vegetables.

In general, no significant trend of reduced risk was observed for women on the low fat diet. The Risk Ratio for women on the low fat diet was 0.91, with a Margin of Error between 0.83 and 1.01. Thus any conclusion of risk reduction is just below the threshold of statistical significance, but is plausible. However, the results indicate that women who initially have a higher than average fat intake, do reduce their risk somewhat by switching to a low fat diet. Their Risk Reduction is is approximately 0.78, with a Margin of Error between 0.64 and 0.95 - close to 1.00 (no risk reduction) but slightly below. The authors of the publication state that "... additional research on diet and breast cancer prevention could focus on ... women with diets habitually high in fat", since this venue exhibits more potential.

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Last Modification - February 11, 2006