A low-fat diet decreases good cholesterol along with the bad. But that’s OK, a new study shows. Bad cholesterol is called LDL. It causes heart disease. Good cholesterol is called HDL. It removes bad cholesterol from your bloodstream, thus reducing heart disease risk.

Both kinds of cholesterol go down if you eat a low-fat diet. That’s led some dieticians to recommend a diet with plenty of good kinds of unsaturated fats. The idea is to keep LDL low, while having little or no effect on HDL. Now Sophie Desroches, PhD, and colleagues at Laval University, in Quebec City, Canada, report evidence that a low-fat, high-carb diet may not be bad for your heart.

The researchers signed up 65 male volunteers for the seven-week study. Half ate a low-fat, high-carb diet (58% carbs, 26% fat, 16% protein). The other half ate a high-monounsaturated-fat diet (45% carbs, 40% fat with more than half from monounsaturated fats, and 15% protein).

Foods that are high in monounsaturated fats include nuts, avocados, and olive and canola oils. These fats, which are a main component of the Mediterranean diet, have been linked to lower heart disease risk.

Sure enough, those on the low-fat diet saw their LDL cholesterol drop by more than 20%. Their HDL cholesterol dropped, too - by 10%.

But when the researchers looked at the various types of HDL by high-tech analysis, the picture became clearer. They found that ratios of the different kinds of HDL favored the type of HDL that actually pulls bad cholesterol out of the arteries.

Therefore, the researchers say that despite an overall decrease in good cholesterol, the fact that this particularly beneficial type of HDL remained higher indicates there is no increase in heart disease risk with a low fat diet.

The researchers reported their findings this week’s Arteriosclerosis, Thrombosis, and Vascular Biology Conference in San Francisco.