WASHINGTON (AP) - The National Institutes of Health unveiled new guidelines Tuesday that called for more aggressive treatment of high cholesterol in people at risk for heart disease.

The new guidelines recommend use of different tests to screen for high cholesterol and revise the optimal standards for good and bad cholesterol.

Diabetes would be added to the conditions indicating an increased risk for heart disease.

Under the guidelines, the number of Americans using prescribed cholesterol drugs could jump from about 13 million to 36 million, the NIH estimated. The number of people prescribed a restricted diet to lower cholesterol would also grow sharply.

"Studies show conclusively that lowering the level of low-density lipoprotein, or LDL, the bad cholesterol, can reduce short-term risk for heart disease by as much as 40 percent," said Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute.

The guidelines, being published in this week's issue of the Journal of the American Medical Association, also take more note of "good" high-density lipoprotein. Current guidelines list 200 milligrams per deciliter of total cholesterol as the desirable level, over 240 mg as high, and less than 35 mg of HDL as too low.

The new guidelines remain the same for total cholesterol, but add that 100 mg of LDL is optimal for that form. They also add a listing of 130-159 mg of LDL as borderline high, 160 mg as high, 190 mg as very high. The too low reading for the good HDL is raised from 35 mg to 40 mg.

Lenfant said many people don't receive aggressive treatment because they have not been identified as at high risk.

Some 53 million Americans have high cholesterol. Only a small fraction of those with the worst cholesterol levels use prescription medication. Many don't know they have high cholesterol, while others don't have insurance coverage for prescription drugs. Plus, many doctors don't follow current federal prescribing guidelines.

The new recommendations should reduce the burden of heart disease in America, said Dr. Ronald M. Krauss of the University of California Berkeley.

Changes include listing people with diabetes and those with metabolic syndrome as at high risk for heart disease. Metabolic syndrome is a combination of risk factors including obesity - particularly abdominal fat - high blood pressure and other conditions.

"The metabolic syndrome has emerged as being as strong a contributor to early heart disease as cigarette smoking," said Dr. Scott Grundy of the University of Texas Southwestern Medical Center in Dallas. Grundy was chairman of the panel that put together the recommendations.

The guidelines call on physicians to make an added effort to identify patients at risk of high cholesterol, including using a test called a lipoprotein profile as a first test for high cholesterol.

Currently the recommended first test is merely a screening for total cholesterol and HDL. The profile breaks that down into total, HDL, LDL and other components.

"The new guidelines will help doctors determine heart attack risk more precisely than was possible before. That allows treatment to be more individualized," said Grundy.

The panel also recommended a new set of "therapeutic lifestyle changes" to help lower cholesterol. These include limiting saturated fats to 7 percent of total calories, increasing intake of soluble fiber and plant stanols, weight reduction and increased physical activity.

Plant stanols are included in certain margarines and salad dressings. Foods high in soluble fiber include legumes, cereal grains, peas, beans and many fruits and vegetables.

Cholesterol has received increasing attention in recent years as it has become more obvious that high levels of this fat are a major risk factor for heart disease.

It can't be eliminated completely, however. Cholesterol is a vital part of the body, a soft, waxy substance found among the fats in every cell. It's used to form cell membranes, some hormones and other needed tissues.

But if there is too much LDL, it can slowly build up in the walls of the arteries feeding the heart and brain, forming a thick, hard deposit that can clog those arteries.

A clot in the region of this plaque can block the flow of blood to part of the heart muscle, causing a heart attack. A clot in the brain causes a stroke.

On the other hand, HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body.

The American Heart Association reports that some experts believe HDL removes excess cholesterol from arteries.

Some cholesterol is produced normally in the liver, with additional amounts coming from foods, especially egg yolks, meat, poultry, fish, seafood and whole-milk dairy products.

Copyright 2001 The Associated Press. All rights reserved.