A saturated fat to enjoy without guilt.

A saturated fat to enjoy without guilt

Since saturated fatty acids tend to raise blood-cholesterol levels, people with high cholesterol are often warned to limit their dietary fat -- especially saturated fat. But this generic warning against saturated fats is too simplistic, according to a study reported in the May 12 NEW ENGLAND JOURNAL OF MEDICINE. Though stearic acid -- one of the primary constituents of beef aand other animal fats -- is saturated, it does not raise blood-cholesterol levels. In fact, its cholesterol-lowering effects match or surpass that of oleic acid -- the monounsaturated fatty acid on olive oil and rapeseed often recommended for cholesterol watchers.

Eleven hospitalized male volunteers, aged 59 and older, were randomly and successivly assigned to each of three, three-week-long high-fat (40 percent of calories) liquid diets. The diets were basically identical except for their fat. One contained 45.1 percent palmitic acid, a primary saturated fatty acid in palm oil, and 38.8 percent oleic acid. A second contained 42.9 percent stearic acid and 39.4 percent oleic acid. The third contained 79.7 percent oleic acid, with traces of stearic and palmitic.

The subjects' blood cholesterol was 14 percent lower on the high stearic-acid diet than on the high palmitic-acid diet -- and 4 percent lower than it was in the high oleic-acid diet. Similarly, low-density-lipoprotein cholesterol levels on the high-stearic diet were 22 percent lower than on the high-palmitic diet--and 6 percent lower than on the high-oleic diet. Andrea Bonanome and Scott M. Grundy of the Universuty of Texas Southwestern Medical Center at Dallas, the study's authors, speculate that one partial explanation for the stearic effect is that the body quickly converts it into oleic acid. What this doesn't explain is why stearic appeared to outperform oleic acid in cholesterol lowering.

Experts caution that other saturated fats found in meats and oils still pose a health risk.

In an editorial in the same issue of the journal, Irwin Rosenberg and Ernst Schaefer of the Agriculture Department's Human Nutrition Research Center on Aging in Boston, note one advantage of oleic and stearic over polyunsaturated fatty acids -- like the linoleic found in corn oil -- is that they don't reduce blood levels of high-density lipoproteins, the so-called "good lipoproteins." They also say these findings could lead to new cholesterol-lowering margarines that "taste more like butter than the margarines currently available."

Gary Smith, head of animals science at Texas A&M University in College Station, points to another potential application of these findings. "We love the satiety associated with eating things that have fat," he notes. In fact, researchers and physicians find people tend to abandon diets that don't contain enough fat to satisfy that taste craving. So while very lean animals can be developed, he says, you run the risk of creating a meat that people won't want to eat. "But if stearic turns out to be the good guy that it appears it is, we may be able to produce animals with more of this in them," Smith says--and in so doing create a meat with a satisfying amount of fat, yet with the nutritional benefits of formerly unpalatable ultra-lean cuts.