In an exceedingly strange turn of events, data from a clinical trial dating from the 1960s, long thought to be lost, has now been resurrected and may contribute important new information to the very contemporary controversy over recommendations about dietary fat composition.
The American Heart Association has long urged people to increase their consumption of polyunsaturated fatty acids (PUFAs), including omega 6 PUFAs, and reduce their consumption of saturated fatty acids. The recommendations are based on the simple observation that PUFAs lower total and LDL cholesterol while SFAs have the opposite effect. However, the cardiovascular effects of substituting PUFAs for SFAs have never been tested in randomized, well-controlled clinical trials, and a growing proportion of experts now suspect that simple changes in total cholesterol and LDL cholesterol may not tell the whole story.
One trial that actually tested the hypothesis was the Sydney Diet Heart Study, which ran from 1966 through 1973. In the trial, 458 men with coronary disease were randomized to a diet rich in linoleic acid (the predominant omega 6 PUFA in most diets) or their usual diet. Although total cholesterol was reduced by 13% in the treatment group during the study, all-cause mortality was higher in the linoleic acid group than in the control group. However, in the original publications, and consistent with the practice at the time, deaths from cardiovascular (CVD) and coronary heart disease (CHD) deaths were not published.
Now, in a new paper published in BMJ, Christopher Ramsden and colleagues report that they were able to recover and analyze data from the original magnetic tape of the Sydney Diet Heart Study. The new mortality findings are consistent:
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I suppose the Dietfascists might move their attention to the banning, or imposing, of other foods. There are plenty to choose from.
The American Heart Association has long recommended limiting saturated fats and using healthier fats, such as mono- and poly-unsaturated fats, instead. The association bases its recommendations on a robust body of scientific studies that demonstrate a strong association between eating a diet high in saturated fat and the development of atherosclerosis, which clogs arteries and causes heart disease.
“The British Medical Journal study is interesting, but not conclusive. The researchers admitted their analysis was limited by the fact that they did not have access to the original study protocol, so they could not fully appraise its accuracy. Their findings are offset by a large body of scientific evidence that continues to show cardiovascular benefits associated with eating mono- and poly-unsaturated fat, rich in Omega-6 linoleic acids, in place of saturated fats,” said Penny Kris-Etherton, Ph.D., R.D., American Heart Association spokesperson and distinguished professor of nutrition at Pennsylvania State University.
“The American Heart Association continues to recommend limiting saturated fats to less than seven percent of total calories consumed and supports eating between five to ten percent of total calories from Omega-6 PUFAs, within the context of an overall healthy dietary pattern that emphasizes fruit, vegetables, high-fiber whole grains, low-fat dairy products, lean meat, poultry and fish,” Kris-Etherton said.
American Heart Association and American Stroke Association volunteers write medical scientific statements and recommendations on cardiovascular disease and stroke topics. The statements are systematic reviews of scientific studies published in recognized journals and have a rigorous peer review and approval process.