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To Saturate or Unsaturate:
CHORI Scientist Stirs Debate on Saturated Fat

In a recent publication in the American Journal of Clinical Nutrition (AJCN), CHORI senior scientist Ronald Krauss, MD and his colleagues set out to determine whether observational studies – those in populations studied over time – which assessed saturated fat intake collectively demonstrated any correlation between saturated fat intake and risk of stroke or heart disease – with surprising results.

"When looked at individually, the many studies of saturated fat intake show quite a bit of variability. When analyzed as a whole, however, a significant association of saturated fat intake with increased risk of heart disease or stroke was undetectable."

The idea that the saturated fat - long cast as the great culprit in heart disease - had no significant impact on heart disease and stroke outcomes in 21 different studies analyzed by Dr. Krauss and his colleagues has stirred up the nutritional world. Does this mean we can eat a whole round of Brie in one go? Beef three nights a week? Slather more butter on everything?

The answer, says Dr. Krauss, is a resounding No. As Dr. Krauss explains, the AJCN publication is much more nuanced than simply abandoning or embracing an entire class of calories.

"We were focusing on a specific question: is there evidence to support further reductions in saturated fat to below those levels currently recommended?" says Dr. Krauss, who places the study firmly in the context of a recent movement to change the current United States guidelines for saturated fat intake from 10 or less percent of daily calories, to only 7 percent of daily calories.

"This is the kind of policy recommendation that is used to promote healthful diets in various settings, such as school lunch programs. Such recommendations can be helpful, but we feel very strongly from past history that such recommendations must also be approached with caution."

The past history to which Dr. Krauss refers is the initial public health recommendation to reduce total fat intake, and in particular, saturated fat intake. While on the face of it, such a recommendation seems reasonable, the unintended consequences may be far-reaching.

As Dr. Krauss explains, the industry and public responded to these recommendations by targeting low-fat foods that in fact resulted in a significantly higher intake of refined sugars and carbohydrates. This is no small shift when you consider that all of the metabolic affects related to excess body weight we are currently facing could easily have been aggravated by higher sugar intake.

"If one is going to make recommendations about how to optimize one's diet, one has to consider what kind of calories are going to take the place of those from saturated fat," says Dr. Krauss.
"What our analyses showed and what review of the clinical trials shows, is that there really isn't definitive, strong evidence to show that we should reduce saturated fat more than the current guidelines recommend, especially when the substitutions themselves have their own set of problems which may in fact be even more of a concern to the population we are trying to protect."

The study did have some practical limitations as well, Dr. Krauss points out. In particular, the meta-analysis couldn't rule out the effects of saturated fat intake in population subgroups based on gender, age or ethnicity. It couldn't accurately asses the affects of different caloric substitutions for the saturated fat, such as polyunsaturated fats versus refined carbohydrates, which may have even more impact on overall health than the removal of the saturated fat alone.

So while it isn't time to break out the cheese fondue, the study underscores the need to approach dietary recommendations from a holistic perspective that addresses an individual's diet in its entirety.

"Narrowing in on the evils of saturated fats alone without considering the whole diet may mean that we make the wrong choices, and create new problems by our substitutions," says Dr. Krauss. "What we'd like to do is back away from recommendations that simply eliminate a particular element from the diet, such as saturated fat, and shift to a recommendation for overall dietary balance."
"What we'd like to do is back away from recommendations that simply eliminate a particular element from the diet, such as saturated fat, and shift to a recommendation for overall dietary balance."
In fact , Dr. Krauss points out that there are a variety of lines of evidence that polyunsaturated fats found in fatty fish and in plant foods (such as safflower, sesame, soy, corn and sunflower-seed oils, and nuts and seeds), can have direct benefits on heart disease risk, and he therefore advocates a focus on diets containing plenty of these foods, as well as unprocessed grains.


Tuesday, May 17, 2011 8:19 AM

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