The skinny on fat?
By Tom Valeo
Published February 27, 2007
Last February during American Heart Month, the long-standing belief that a low-fat diet protects against heart disease was seemingly demolished by a huge, well-designed study that found no such correlation.
Yet, one year later, doctors still advise patients to cut back on dietary fat to reduce their risk of heart disease.
The study, reported in the Feb. 8, 2006, issue of the Journal of the American Medical Association, seemed air tight. It had been conducted by the Women's Health Initiative.
Titled the "Dietary Modification Trial," the study involved nearly 50,000 women between the ages of 50 and 79, who were followed for more than eight years.
Nearly 20,000 were told to follow a diet that reduced their fat intake from the average 38 percent of the calories they consumed to 20 percent. They received coaching on how to achieve this goal.
The rest of the women in the study were told to continue eating as usual.
The expectation: The group on a low-fat diet would suffer fewer heart attacks and strokes.
Sorry! Wrong numbers
But that didn't happen. In fact, the women in the low-fat group who had heart disease at the beginning of the study seemed to experience an increased risk of heart disease.
So should we forget about the dietary guidelines on fat and indulge in French fries, ice cream and well-marbled steaks?
Not so fast.
Critics of the study point out that few of the women in the low-fat group actually managed to reduce their fat intake to just 20 percent of calories consumed. The average was closer to 29 percent.
And even that figure may not have been reached because members reported on their own eating habits - which invites misrepresentation.
"I don't put a lot of stock in this study," said Peter Knight, M.D., an associate professor of cardiology at the University of South Florida College of Medicine. "They just lowered all fat, and we know from a lot of studies that the type of fat makes a lot of difference."
According to Knight, trans-fat in the diet raises "bad" cholesterol and lowers "good" cholesterol, while omega 3 and omega 6 fatty acids have been shown to reduce heart disease significantly.
So rather than steering his patients away from fat in their diet, Knight encourages them to consume monounsaturated fats - in olive oil, canola oil and nuts - and polyunsaturated fats - in salmon and haddock.
He also urges them to avoid trans-fat completely.
Fats not created equal
Dr. Dean Bramlet, medical director and founder of the Heart and Lipid Institute of Florida in St. Petersburg, agrees with this approach.
"Fats come in many different types," he said, "and they influence blood lipid levels in different ways."
Bramlet advises patients to keep fat to about 30 percent of calories consumed. But he urges them to hold saturated fat from animal sources to less than 7 percent of calories, and to eliminate completely the hydrogenated trans-fat found in crackers, pastries and a host of other foods.
Also, raising HDL - the "good" cholesterol - may be a very important strategy, according to Bramlet, because it ferries the LDL "bad" cholesterol out of the bloodstream, thereby preventing it from adhering to the lining of arteries.
One other factor affecting the way dietary fat affects your risk of heart disease is much harder to control: your genetic profile. Genes can have an enormous effect on how your body processes fat.
Thus, for some people, dietary fat seems to go straight to the bloodstream, boosting cholesterol levels and causing a fatty liver, which is associated with insulin resistance and diabetes. Other people seem to burn fat with no apparent ill effects.
The conclusion to these contradictory views: When it comes to dietary guidelines for preventing heart disease, one size definitely does not fit all.
Freelancer Tom Valeo writes about medical and health issues. Write to him in care of Pulse, St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731, or e-mail email@example.com.
[Last modified February 27, 2007, 07:34:41]
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