DALLAS, April 10 -- A new study gives one more reason why you may be better off beginning the morning with a breakfast of low-fat yogurt, cereal or juice instead of toast slathered with margarine or a croissant.
A study of 91 elderly women reported in this month's Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association finds that a fatty breakfast can cause elevations in a blood-clotting factor, called factor VIIa, that has been associated with heart attack.
Louise Mennen, M.D., and researchers at the division of human nutrition and epidemiology, Agricultural University, Wageningen, The Netherlands, conducted the study to identify dietary fats that might raise the risk of heart disease. "Factor VIIa increases after intake of dietary fat," says Mennen, the study's lead author.
The study found that saturated as well as unsaturated fats increased levels of factor VIIa.
"The rise in factor VIIa after a meal should be kept as low as possible, and this is best achieved by reducing the total amount of fat rather than by changing fat composition," says Mennen, who is now a researcher at INSERN, in France.
Factor VIIa circulates in the bloodstream, and elevated levels can "lead to an explosive" formation of the enzyme thrombin. Thrombin is a catalyst in the formation of fibrin, one of the essential components of a blood clot. Too much clotting can lead to blockages in the blood vessels, setting the stage for a heart attack or stroke.
In the study, four different fat-rich breakfast diets, each of which contained 50 percent of calories from fat, were tested. The diets differed in fatty acid composition. One had palmitic acid (a highly saturated fat found in animals); one had stearic acid (found in beef and cocoa butter) and the other two contained different ratios of linoleic and linolenic acid (found in corn, canola and other vegetable oils).
The high-fat breakfasts consisted of a bun, margarine, jam, cake and orange juice. A control or "low-fat breakfast" that included a low-fat bun and yogurt was also tested. Four different margarines were used and buns and the cakes were baked with these margarines.
Factor VIIa levels were calculated by subtracting the levels of factor VIIa taken before the meal and levels taken at 1 and 3 p.m.
The Factor VIIa responses rose significantly -- about 11 to 16 milli unit (mU/mL) -- in those who ate the high-fat diets. In contrast, levels were lowered by about 6 mU/ml in the control diet.
"But most importantly, there were no differences among the fat-rich breakfasts," according to Mennen. "The results of our trial support the view that the factor VIIa response to a high dietary fat intake is independent of the type of fat," says Mennen, who adds that this response would probably occur after any fat-rich meal, not just breakfast.
He stresses that there is not enough information to know if a fat-rich meal increases a person's risk of heart disease directly, since the study only looked at the association between fat and factor VIIa.
"It is not clear if factor VIIa is a causal risk factor for heart disease, but if it were, this would mean that individuals would be at risk for heart attack after a fat-rich meal," he says.
Co-authors are Dr. Moniek de Maat; Dr. Gert Meijer; Dr. Peter Zock; Dr. Diederick Grobbee, Dr. Frans Kok; Dr. Cornelis Kluft; and Dr. Evert Schouten.
Materials provided by American Heart Association. Note: Content may be edited for style and length.
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