How monounsaturates may save arteries.

How monounsaturates may save arteries

For years, heart researchers have touted the relative merits of fats high in monounsaturated fatty acids, such as olive and canola oils. Consuming monounsaturates doesn't raise serum cholesterol levels, as saturated fats can, nor tend to lower levels of high-density lipoproteins (HDLs)--believed responsible for clearing cholesterol from the blood -- as can fats high in polyunsaturates, such as corn oil. Now University of California, San Diego (UCSD) researchers report a more direct mechanism by which monounsaturates may slow heart disease.

Artery-clogging atherosclerosis begins when "foam" cells accumulate along artery walls. Low-density lipoproteins (LDLs)--the so-called "bad" lipoproteins--can foster this by providing the lipids (fats) that swell and transform macrophages, cells that scavenge unwanted materials from the body, into these foam cells. Previous work by UCSD's Daniel Steinberg and his co-workers showed, however, that it's not normal LDLs, but oxidized ones, that convert macrophages into foam cells. In the May PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES, (Vol. 87, No. 10), Steinberg's team now reports finding that LDLs rich in oleic acid are "remarkably resistant" to oxidation -- alteration by reactive oxygen molecules.

They incubated LDLs from rabbit blood with oxidants for 14 hours. One third of the LDLs came from animals fed standard rabbit chow, rich in the polyunsaturate linoleic acid. The other rabbits ate chow-based diets containing 10 percent sunflower oil. Half of these rabbits received conventional sunflower oil--containing 20 percent of the monounsaturate oleic acid and 67 percent linoleic acid -- the other animals a version containing 83 percent oleic acid. Compared to LDLs from animals fed regular sunflower oil, those from animals on the monounsaturates-rich diet showed only one-third to one-quarter the oxidation -- and were engulfed by macrophages (a gauge of foam-cell-development risk) at only one-tenth the rate.

As "there is no evidence that monounsaturated fat-rich diets are anything but safe," the La Jolla team writes, these data offer "exciting implications" -- that using oleic acid as a primary dietary fat "may slow the progression of atherosclerosis." To beef up the range of monounsaturated-rich offerings available, Texas A&M University scientists in College Station have experimentally fed livestock high-oleic sunflower oil (HOSO). This boosts the proportion of monounsaturates in pork products by roughly one third, new data by Ki Soon Rhee shows. In the May/June JOURNAL OF FOOD SCIENCE, she also reports developing low-fat HOSO-supplemented hot dogs. Up to 70 percent of their fat is monounsaturated -- well above the usual 40 to 45 percent.