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Taking the Broad Approach
CHORI Studies Lead to $1.2 Million NIH Grant to Study Impact of Protein Sources on Heart Disease Risks

December, 2011 - In a major new study published in the December issue of the Journal of Nutrition, CHORI senior scientist Ronald Krauss, MD and his colleagues have shown for the first time that decreasing carbohydrate intake and increasing saturated fat intake may only have a negative effect on lipid profiles when the diet is high in beef protein.

“People talk about saturated fat in isolation from the rest of one’s diet as something that raises cholesterol and may increase the risk of heart disease. That is the common wisdom,” says Dr. Krauss. “But what the results of our study suggest is that there is a much greater need to look at saturated fat intake in the context of the rest of the diet, in particular, in combination with the source of dietary protein.”

“The results of our study suggest is that there is a much greater need to look at saturated fat intake in the context of the rest of the diet.”

Heart disease is the number one cause of death in the United States, and saturated fats have long been implicated as contributing to heart disease risk. Research conducted by Dr. Krauss and his colleagues, however, has always indicated a much more complex dietary situation. Utilizing innovative and powerful analytic tools developed by the Krauss group that can assess lipoproteins by their weight and size, they have been able to evaluate the impact of different dietary interventions on a person's atherogenic lipid profile which predisposes to increased risk of cardiovascular disease.

"An atherogenic lipid profile is the combination of triglycerides, high density lipoproteins and a subtype of low density lipoproteins called small dense LDL," says Dr. Krauss.

Previous studies by Dr. Krauss and his colleagues showed that decreasing dietary carbohydrates and increasing saturated fat in a diet with mixed sources of protein increased only large LDL, which doesn't pose the same risks for heart disease as small dense LDL. The Krauss lab expected to find the same was true of a diet with similar levels of carbohydrates and saturated fat but with a high content of beef protein. The results, however, as published in the Journal of Nutrition, were dramatically different.

“The diet which was high in beef and saturated fat significantly increased all LDL particles including small dense LDL, and hence created a lipid profile indicating increased heart disease risk. Moreover, the reduction of carbohydrate intake on the high beef diet did not have the expected beneficial effect on lipids.”

The provocative new results raise more questions than they answer, however, because the study wasn't powered to be a one-to-one comparison of a high beef diet versus one with other sources of dietary protein.

"What this shows is that we need to conduct a careful comparison of saturated fat in the setting of various protein sources, says Dr. Krauss.

Dr. Krauss and his colleagues have just garnered a $6 million five-year National Institutes of Health grant to do just that: compare three diets with three different sources of protein red meat, white meat, and vegetarian sources. Under each of these three dietary conditions, the investigators will then test whether or not the source of saturated fat affects the lipid profiles of the individuals in the study. This will allow the Krauss group to determine whether there is a specific interaction between saturated fat and the protein source that might influence heart disease risk.

"Ultimately, we must move toward a much broader approach to nutritional studies in which the overall food intake and dietary patterns are looked at as influencing heart disease risk, rather than looking at an individual nutrient, such as saturated fat, in isolation," says Dr. Krauss. "We eat foods that bring with them a combination of nutrients, as well as other qualities, such as fiber, that together may have a major influence on how the body responds. These studies are just the first steps in beginning to approach nutrition from a more holistic basis."


Thursday, January 12, 2012 4:05 PM

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