Watching your cholesterol? If so, a plate of spaghetti with olive oil and clam sauce may sound as forbidden as an eight-ounce rib-eye steak.

Not so, according to a recent study by Dr. Scott Grundy, director of the Center for Human Nutrition. Worldwide statistical studies suggest that the eating habits of a nation are reflected in its incidence of coronary heart disease. Both Japan and Italy, for example, have much lower death rates from coronary heart disease than the United States.

A typical American diet includes a high proportion of saturated fats from meat and dairy products. Steaks, ice cream, burgers and fries, fried chicken--all add saturated fats that encourage cholesterol to build up in the bloodstream.

The Japanese diet, typical of many Oriental countries, is lower in fat and higher in carbohydrates than the American, but it is equal in protein. By steaming vegetables and by favoring fish and chicken for protein, Orientals consume only about half as much fat as Americans.

In fact, a low-fat diet based on an Oriental eating style is frequently recommended for people with elevated cholesterol levels. Many Americans, however, prefer Mediterranean cuisine to Oriental, says Grundy. Italian, Greek and Spanish cooks depend heavily on pasta, fresh vegetables, chicken, seafood and olive oil. Although the fat content is as high as an American diet, the monounsaturated fat found in olive oil does not raise cholesterol levels and contribute to heart disease.

Grundy's study, carried out on the metabolic ward at the Veterans Administration Medical Center in Dallas, compared the different eating styles on a scientific basis. He formulated liquid diets with proportions of calories typical of each eating style. Eleven patients stayed on each of the three diets for four weeks at a time. Their blood lipid levels were tested during the final two weeks of each diet.

The typical American formula had a 40:43:17 ratio of fat, carbohydrate and protein; the Oriental, 20:63:17; the Mediterranean, 40:43:17. The predominant fat in the American diet was saturated. In the Mediterranean diet it was monounsaturated.

As expected, the typical American formula resulted in higher-than-normal blood cholesterol and low density lipoproteins (LDL). Both of these contribute to atherosclerosis. The Oriental diet formula successfully lowered total cholesterol an average of 8 percent below the American diet. It dropped LDL cholesterol 15 percent.

However, the low-fat/high-carbohydrate diet had two undesirable effects. It caused the "good" high density lipoproteins (HDL) to fall and triglycerides to rise significantly. The Mediterranean diet formula dropped total cholesterol 13 percent from the American diet, with a 21 percent drop in LDL. There was no decrease in HDL or rise in triglycerides. Unlike the low-fat diet, all results were desirable.

The Mediterranean-style diet, including a higher proportion of monounsaturated fat and a lower proportion of carbohydrates, may even be preferable for people with high triglyceride levels. "The good news coming out of this study," says Grundy, "is that Americans concerned about their cholesterol can enjoy an occasional alternative to a low-fat regimen. It should be a welcome change."

One note of warning, however: Each gram of fat contains over twice as many calories as a gram of carbohydrate or protein, so a low-fat diet makes it easier to control calories.

"A Mediterranean diet is just as effective as an Oriental diet at lowering cholesterol, but it could easily be more fattening if you were weighing food instead of counting total calories," concludes Grundy.