NEW YORK (Reuters Health) - A type of unsaturated fatty acid found in corn and safflower oil appears to activate genes that promote inflammation inside blood vessels, a risk factor for heart disease, new research suggests.

This fatty acid, known as linoleic or omega-6 fatty acid, also appeared to reduce cells' ability to protect themselves from oxidative damage. Oxidative damage is caused by free radicals, byproducts of the body's normal processes that can damage body tissues.

While unsaturated fatty acids in general are thought to be healthier than saturated fat, the findings support previous research showing that omega-6 fatty acid can injure cells lining the insides of blood vessels, leading to inflammation.

``If people consume high amounts of antioxidants, unsaturated fats could be healthier than saturated fats,'' Dr. Michal Toborek of the University of Kentucky in Lexington, a study author, told Reuters Health. He stressed that other types of unsaturated fatty acids have been shown to protect against heart disease.

``The real problem is that people eat high-fat diets, which are rich in omega-6 fatty acids, without balancing such diets with antioxidants,'' compounds that neutralize free radicals, Toborek added.

To investigate how certain fatty acids lead to inflammation, the researchers exposed human cells that line the insides of blood vessels, making up the endothelium, to several different unsaturated fatty acids in a test tube. Omega-6 fatty acid substantially increased the activity of two proteins that triggered an inflammatory gene, while linolenic (omega-3) acid, found in fish oil, had only a moderate effect on these proteins.

Both omega-3 and omega-6 stimulated the formation of a protein blocking an enzyme that normally protects against free radicals and allows cells to defend themselves against oxidative stress.

Oleic acid, the predominant fatty acid in olive oil, either had no effect or helped block processes leading to inflammation, the researchers report in the January issue of the American Journal of Clinical Nutrition.

``Specific unsaturated dietary fatty acids can induce highly individual effects on endothelial cell activation and contribute differently to induction of the inflammatory genes in vascular endothelial cells,'' the study concludes.

In an interview, Toborek said that more research into the health effects of different types of fat is sorely needed.

``This is an important issue because more and more Americans consume fast and convenient foods, which contain high amounts of omega-6 fatty acids,'' he said.

SOURCE: American Journal of Clinical Nutrition 2002;75:119-125.

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