"Trans fat," says Lichtenstein, "is a double whammy, because like saturated fat, it raises levels of LDL or 'bad cholesterol,' but it also lowers levels of HDL or 'good' cholesterol." Most of the trans fats we eat are formed during the partial hydrogenation of oils used in fried foods and commercial baked goods. Partially hydrogenated oils provide processed foods with longer shelf lives and therefore greater economic profitability.
"But, trans fat is just one part of the diet. In general, people are still eating far more saturated fat than trans fat, and both need to be reduced in order to maintain optimal cholesterol levels and promote heart health," says Lichtenstein. "And the big giant total calories is always looming in the background."
In one study to assess the effects of consuming different types of oils on cholesterol levels, led by Lichtenstein and published earlier this year, fifteen adult volunteers with moderately high LDL cholesterol were fed each of four diets with a different source of primary fat, including partially hydrogenated soybean oil (trans fat), palm oil (50 percent saturated fat), non-hydrogenated soybean oil (only 16 percent saturated fat), and canola oil (only 7 percent saturated fat).
The results, published in the American Journal of Clinical Nutrition (AJCN), reported that after a trial of 35 days on each diet, participants consuming the partially hydrogenated soybean oil and palm oil diets had levels of LDL cholesterol that were 12 and 14 percent higher, respectively, than when consuming the non-hydrogenated soybean oil diet. An even greater difference was observed when the partially hydrogenated soybean oil and palm oil diets were compared to the canola oil diet. While participants were on the partially hydrogenated soybean oil and palm oil diets their LDL levels were 16 and 18 percent higher, respectively, than when on the canola oil diet.
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Contact: Siobhan Gallagher
617-636-6586
Tufts University
22-Dec-2006