The following is a review of the study, Dietary fats, carbohydrate, and progression of coronary atherosclerosis in postmenopausal women, published in The American Journal of Clinical Nutrition. It’s one of those studies that can make your blood boil because it would indicate that we’ve been given some really bad information over the years about what to eat to prevent heart disease. This summary of it got me interested in checking out the details:
“A 2004 study from Brigham and Women’s Hospital and Harvard School of Public Health showed that in postmenopausal women, the more PUFA [polyunsaturated fatty acids such as from vegetable oil] they ate, and to a much lesser extent the more carbohydrate they ate, the worse their atherosclerosis became over time. The more saturated fat they ate, the less their atherosclerosis progressed; in the highest intake of saturated fat, the atherosclerosis reversed over time.”
They chose for their study postmenopausal women who’d already had a heart attack and who had measurable atherosclerosis in their arteries. This study is important because it shows that the advice we have been given by the USDA and major medical organizations for preventing cardiovascular disease is the opposite of what actually works. The fact that some of these women were able to reverse the progression of their atherosclerosis is significant as well. We don’t often hear of that happening. The participants eating the most saturated fat were also eating more total fat. In general, the ones eating the most saturated fat had the best lipid profiles. Those eating the most saturated fat were eating more protein and less carbohydrate than other groups. Those eating the most carbohydrate had the greatest decline in coronary artery size. To a lesser extent, those eating the least total fat had the greater decline in coronary artery size. Among types of fat, polyunsaturated fat was associated with the greater progression of atherosclerosis. Particularly noteworthy were actual improvements seen when monounsaturated fat displaced saturated fat and when protein displaced polyunsaturated fat. Stearic acid, most often found in animal fats, was associated with lesser progression (better outcome) than other saturated fats. Oddly, smoking was inversely associated with progression of atherosclerosis. I would say that the summary I read the other day held up under closer review.
This was an observational study. There were no interventions done. In the discussion section of the study, they presented a chart of intervention studies. Many of them studied an intervention to increase the ratio of polyunsaturated fat to saturated fat. Most of these showed improved outcomes for the intervention group. I have to wonder, though, if intervention groups were eating better in other ways as well. Perhaps they were eating less processed foods, too, which could have a tremendous impact on the results of the study. After all, in this study that I just read, carbohydrate intake was highly correlated to progression of atherosclerosis. Considering that grain desserts and pizza are the largest identified sources of saturated fat in the American diet according to the USDA, this could well be the case. Intervention studies in the chart where they increased consumption of certain whole foods generally showed a strong trend in improved outcomes. Only an examination of the other individual studies could determine if change in consumption of processed foods was properly accounted for and analyzed for confounding. Did these studies have only two groups, a single intervention group and a control group? It would be more interesting to see a single study with multiple intervention types and compare those outcomes since an intervention group is more likely to be conscientious, and conscientiousness is likely a confounding factor when comparisons are made to controls. An observational study such as the one I just read would be less impacted by conscientiousness. As for a multiple intervention study, I wonder if scientists would be brave enough to create an intervention group where saturated fats from grain desserts and pizza were replaced by higher quality sources of saturated fat that did not come with a boatload of refined carbohydrates, thus retaining the level of consumption of saturated fat but eliminating the junk. Comparing that intervention group to an intervention group increasing the ratio of polyunsaturated fat might yield different results entirely. It remains to be seen. Interestingly, studies where the ratio of monounsaturated fats was increased were not listed. Have they not been done?