Diets low in saturated fats, trans fats, and cholesterol are associated with improvements in cardiovascular risk factors and lower rates of cardiovascular disease (e.g., heart attack , coronary heart disease , stroke ). But it is not clear whether a diet that focuses on reducing total fat intake—rather than specific types of fat—is beneficial in preventing cardiovascular disease (CVD).

In the February 8, 2006 issue of the Journal of the American Medical Association , researchers report on a study that examined the effects of a low-fat diet in postmenopausal women. They found that, overall, the diet had no affect on CVD risk, but low intakes of saturated and trans fats were associated with a reduced risk of developing CVD.

About the Study

This study was part of the Women’s Health Initiative Dietary Modification Trial, a randomized controlled trial designed to test whether a low-fat diet lowered the risk of certain diseases in 48,835 postmenopausal women. This study sought to determine the diet’s affect on CVD risk.

The women were randomly assigned to a low-fat diet intervention group or a usual-diet comparison group. Participants in the low-fat diet group attended regular group meetings with a nutritionist with goals of reducing total fat intake to 20% of their energy intake, consuming at least five servings of vegetables and fruits per day, and consuming at least six servings of grains per day. The researchers followed the women for an average of eight years, tracking whether they developed CVD.

Overall, the intervention diet had no significant affect on the risk of CVD, including heart attack, coronary heart disease, and stroke. However, the women who reached the lowest levels of saturated fat intake (6% or less of total energy) were 19% less likely to develop CVD, and those who reached the lowest levels of trans fat intake (1% or less of total energy) were 16% less likely to develop CVD. Surprisingly, in the 3.4% of participants who had CVD when the study began, the intervention diet was associated with a 24% increased risk of developing CVD. The researchers note that this finding may be due to chance.

This study is limited because the women only achieved 70% of the desired reduction in fat.

How Does This Affect You?

These findings suggest that a diet focusing on lowering total fat intake may not substantially reduce the risk of developing CVD. However, the saturated and trans fat findings reinforce the notion that it may be the quality —not the quantity —of fats in your diet that has the most influence on your cardiovascular health. While the intervention diet in this study resulted in reduced intakes of potentially harmful fats (i.e., saturated and trans fats), it also resulted in reduced intakes of potentially beneficial fats (i.e., polyunsaturated and monounsaturated fats).

The diet in this study was not designed to reduce the risk of cardiovascular disease, and a diet focusing on other nutrients known to affect CVD risk may have produced more beneficial results. In addition to exercising and maintaining a healthful weight, consuming a diet rich in fruits, vegetables, whole grains, nuts, beans, low-fat dairy products, and fish, and replacing saturated and trans fats with polyunsaturated fats (found in many nuts, seeds, and their oils) is still thought to reduce the risk of developing CVD.