In terms of daily diet, the type of fat one consumes has a greater effect on heart disease risk factors than the amount of fat. And bothtrans fatty acids and saturated fatty acids are associated with elevated risk, according to authors of an ARS-supported study that was published in early 2006. The clinical trial was designed to compare the effect—on plasma lipoprotein profiles—of four different oils as they are commonly consumed.
Trans fatty acids (trans fats) are produced in vegetable oils during a hardening process called “hydrogenation.” Hydrogenation makes vegetable oils chemically more stable and extends the shelf life of food products made with them.
Manufacturers are now required to state on food labels the amount of trans fats in packaged foods. So the researchers addressed the question of whether palm oil, whose functional characteristics are similar topartially hydrogenated fat, would be a good substitute to reduce trans fats in foods.
Lead scientist Alice H. Lichtenstein and colleagues conducted the study. She is the director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Massachusetts.
Fifteen adults, both male and female, volunteered for the study. All were aged 50 or older. Their levels of LDL “bad” cholesterol were moderately high at 130 milligrams per deciliter of blood (mg/dL) or above. Palm oil was studied because it has been touted as a potential substitute for hydrogenated fat.
The volunteers consumed each of four experimental fat diets for 35 days. The fats tested were partially hydrogenated soybean oil (moderately high in trans fat), palm oil (high in saturated fat), canola oil (high in monounsaturated fat), and soybean oil (high in polyunsaturated fat).
At the end of each phase, the volunteers were tested to obtain plasma lipoprotein and fatty acid profiles and other measures related to heart disease.
The findings suggest that consuming either of the diets enriched with equivalent high amounts of palm oil or partially hydrogenated soybean oil resulted in similar, unfavorable levels of LDL cholesterol and apolipoprotein B (a protein that carries bad cholesterol throughout the bloodstream). That’s when compared to consuming either of the diets enriched with canola oil or soybean oil, which are high in monounsaturated and polyunsaturated fats, respectively.
The results suggest that palm oil would not be a healthy substitute for trans fats by the food industry, the study authors wrote. For online information on healthful dietary oils, go to www.mypyramid.gov/pyramid/oils.html.—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.
Alice H. Lichtenstein is with the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, 711 Washington St., Boston, MA 02111; phone (617) 556-3127, fax (617) 556-3103.
"Palm Oil Not a Healthy Stand-In for Trans Fats" was published in the April 2009 issue of Agricultural Research magazine.