Taking Stock of Saturated Fats

Consumers have been wary about saturated fats since 1961, when the American Heart Association (AHA), Dallas, first warned Americans to reduce their saturated-fat intake due to overwhelming evidence linking it to heart disease. Saturated fats raise blood levels of LDL cholesterol and total cholesterol. High LDL cholesterol and total cholesterol levels in the blood are major risk factors for coronary heart disease (CHD), which leads to heart attacks and an increased risk of stroke.  

Most health organizations agree that Americans need to reduce their saturated-fat intake. According to "Healthy People 2000", a report released by the National Center of Health Statistics, Hyattsville, MD, less than 10% of dietary energy should come from saturated fats. The Chicago-based American Dietetic Association (ADA) recommends that 7% to 10% of total calories consumed come from saturated fats. The AHA suggests a saturated-fat plus trans-fat intake of less than 10% per day (less than 7% for those with CHD, diabetes or high LDL cholesterol). And the National Cholesterol Education Program (NCEP), Bethesda, MD, recommends dietary intervention as a primary prevention method against elevated blood LDL-cholesterol levels. NCEP also suggests "therapeutic lifestyle changes," including less than 7% of total calories coming from saturated fats.

Saturated fats, usually solid at room temperature, are found primarily in animal sources such as meat, poultry and fat-containing dairy products, and some vegetable oils like coconut, palm and palm-kernel. A saturated fatty acid has the maximum number of hydrogen atoms attached to every carbon atom, making them both "saturated" with hydrogen atoms.

The most common saturated fatty acids in foods are palmitic, stearic and myristic acids. Their chemical structure makes saturated fatty acids more stable than unsaturated fatty acids, which aids in preventing rancidity, off-flavors or odors in foods.

Research leads scientists to believe that not all saturated fatty acids are created equal when it comes to their effects on plasma lipids. Myristic acid is the most hypercholesterolemic saturated fatty acid. Stearic acid, common in beef, cocoa powder and fully hydrogenated vegetable oils, appears to have a neutral or possible lowering effect on serum-cholesterol levels. This has prompted some scientists to call for a different grouping for stearic acid when it comes to saturated-fat guidelines. However, FDA continues to include stearic acid under its definition of saturated fat for labeling purposes.

The AHA encourages more research on saturated fatty acid's function on blood cholesterol, and scientists are currently pursuing the ideal fatty-acid profile for new oils.

Let's not forget hydrogenated fats. Many food manufacturers turned to hydrogenated vegetable oils as replacements for saturated animal fats, and they lend a hand in the stability and texture of food products from margarine to baked goods. The hydrogenation process adds hydrogen molecules directly to a monounsaturated or polyunsaturated fatty acid, thus making it more saturated. Trans-fatty acids, under fire for raising LDL cholesterol levels, are also formed during partial hydrogenation of vegetable oils.

Skhinder Kuar, Ph.D., Memorial University, St.John's, Newfoundland, studies the regulation of genes involved in cholesterol metabolism by saturated fats. Her work indicates that fats act as ligands to bind transcription factors and regulate the cholesterol ester transfer protein gene (CETP), resulting in the production of LDL or HDL cholesterol. The saturated fats bind the transcription factors to the gene that produces CETP, thus sending more LDL into the bloodstream.  

Another study, conducted at the USDA Human Nutrition Research Center on Aging at Tufts University, Boston, fed identical twin sets two diets with equivalent palatability, fiber content and calories per ounce, one containing 40% fat and the other 20% fat. Four sets of twins ate more calories from the high-fat menu, while the other three sets preferred the low-fat menus, suggesting that genetic influence may result in the choice of certain diets.  

The popularity of low-carbohydrate, high-protein/high-fat diets has further complicated the battle against saturated fats. The AHA's Nutrition Committee reviewed high-protein diets and found that the Atkins diet provides 53% of its calories from fat, mostly saturated.

"The guidelines from the Institute of Medicine say that we should try to keep our saturated-fat intake as low as possible. Diets that promote high fat and protein are usually high in saturated fat, and this is a concern for heart health," says Dawn Jackson, R.D., L.D., and ADA spokesperson.

The food industry has responded to America's interest in low-saturated-fat foods by offering lower- saturated-fat food products. In meat and dairy foods, which contribute the majority of fat and saturated fat to the American diet, a lower-saturated-fat trend has emerged. Reduced fat trimming by butchers spurred a 27% reduction of separable fat on retail cuts of beef, and ground-beef fat content is 10% lower than it was 40 years ago. Low-fat and fat-free milk now outsell whole milk, not to mention the variety of lower-fat dairy products available these days. And non-fat and reduced-fat milks generated the most significant impact in the health-claims area.  

It seems Americans get the message, as they are consuming less saturated fat, from 14% in the early 1970s to 11% in the 1990s, according to The Journal of the American Dietetic Association. But even though saturated-fat percentage intakes may be declining, total daily caloric intakes are climbing, indicating that Americans may be consuming more grams of saturated fat per day. Perhaps if we can just stop super-sizing our diets, maybe that 7% to 10% saturated-fat goal for America can be a reality.

Sharon Palmer is a registered dietitian with a 16-year career in health-care food and nutrition management. She now focuses her interest on the world of journalism as a freelance writer and editor, cookbook contributor and culinary instructor.

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