Your lean guide to good fat Yes, we said good fat. Here's how to find it.

SCIENCE 101

Food contains three basic types of fat, in varying proportions: saturated, polyunsaturated and monounsaturated. Each affects the body differently, depending on chemical characteristics. (What to expect from each type is outlined at right.)

Not all fat is bad. Eating enough of the right fats is essential to health. Here is a guide to help you choose.

GOOD FATS

Olive oil: A top favorite of most health experts, it is highly monounsaturated. (Monounsaturated fat is the safest fat of all, declares researcher Gene Spiller of the Health Research and Studies Center in Los Altos, Calif.) That means it is apt to lower bad LDL cholesterol while preserving good HDL cholesterol. Studies indicate that people whose main source of fat is olive oil live longer and have less heart disease and cancer, especially breast cancer. New Italian research finds olive oil contains antioxidants, similar to those in tea and red wine, that combat disease processes, including LDL cholesterol's ability to clog arteries. For the greatest benefit, choose extra virgin olive oil. Heating olive oil may destroy some antioxidant activity.

Fish oil (omega-3 fat): A must. New research shows omega-3 fatty acids, in fish and some plants, may help save you from cardiovascular disease, cancer, respiratory problems, inflammatory ailments (such as arthritis) and neurological disorders (including depression). Fish oil also revs up antioxidant activity, perhaps explaining why fish eaters live longer. Best choices: fatty fish such as salmon, herring, sardines, mackerel, tuna. If you can't eat fish two or three times a week, fish oil capsules are an alternative, says John Weisburger of the American Health Foundation. Three capsules, each with 300 milligrams of omega-3 fatty acids, equal a serving of fatty fish. A non-fish food high in omega-3's: walnuts.

Canola oil: Excellent, because it's low in saturated fat, high in monounsaturated fat and particularly rich in beneficial omega-3 fatty acids. Use it in salad dressings, for sauting or frying, or in any recipe that calls for cooking oil.

Macadamia nut oil: Excellent. Highest of all salad oils in monounsaturated fats.

Grapeseed oil: Good. In studies, it has raised good HDL cholesterol. High in antioxidants.

Avocado oil: OK. Like avocados, it's rich in beneficial monounsaturated fat.

Walnut oil: OK. High in omega-3's.

Flaxseed oil: Used as a supplement by some experts. It is exceptionally rich in omega-3 fatty acids and appears to have anti-cancer benefits. It's usually sold in health food stores.

SO-SO FATS

Soybean oil: OK sometimes. Best when eaten in tofu (soybean curd) and whole soybeans, which also contain antioxidants that help neutralize the potentially detrimental effects of the oil itself. Soybean oil is safer than corn oil, but not nearly as healthful as olive oil and canola oil, research suggests. Unfortunately, much soybean oil is hydrogenated - or hardened - making it particularly harmful. (See section on margarine, opposite page.)

Peanut oil: OK sometimes. High in bad omega-6 fatty acids, which can overrun cells, promoting cancer, inflammatory reactions and immune malfunction - but also contains relatively high amounts of beneficial monounsaturates. Tip: Make your own peanut butter by grinding peanuts, or look for peanut butter without hydrogenated fats.

BAD FATS

Animal fats (butter, cheese, meat fat): Experts agree that saturated fat in animal products is a prime enemy in raising cholesterol and clogging arteries, leading to cardiovascular disease. It may harm immune functioning and increase cancer risk.

Corn oil: A risky choice, high in omega-6 fatty acids. In a six-month study by Harvard researcher George L. Blackburn, daily doses of corn oil doubled the odds of recurrence and spread of colon cancer. Corn oil is also rapidly oxidized (saturated with oxygen), releasing floods of disease-causing free radicals inside the body. Experts say nearly everyone should cut back on corn oil, regular safflower and sunflower seed oils (all laden with omega-6 fatty acids).

Margarine and other foods high in trans-fatty acids: Trans-fatty acids are created when vegetable oils are hydrogenated, or hardened. Some experts, such as Harvard researcher Walter Willett, blame trans-fatty acids, especially margarine, for high rates of heart disease. Some evidence finds trans fats as bad as saturated fats in raising cholesterol. To be safe: Restrict margarine, solid shortening and processed foods rich in hydrogenated or partially hydrogenated vegetable oils. If you use margarine, choose tub or liquid over stick. Packaged foods apt to be high in trans fats: doughnuts, frozen french fries, pound cake, crackers, chocolate chip cookies, microwave popcorn.

Tropical fats (palm and coconut oils): Other vegetable fats have little saturated fat, but these tropical fats are 50-85 percent saturated fat.

HOW MUCH FAT?

Federal guidelines say no more than 30 percent of daily calories in fat, with no more than 10 percent in saturated fat. Many experts say the total should be 10 to 20 percent to reverse heart disease and prevent cancer.

Many experts say the type of fat is as important as how much. Unlikely to hurt you in larger amounts (over 30 percent of fat calories): olive oil, canola oil, monounsaturated fats.

Bottom line: Severely restrict saturated, polyunsaturated vegetable and hydrogenated fats. Eat only enough fat to maintain a normal weight.

Jean Carper's current best-selling book is Stop Aging Now! Comments? Write: Eat Smart, 1000 Wilson Blvd., Arlington, Va. 22229-0012 CLICK HERE TO E-MAIL EAT SMART Please include your age and daytime phone number. Because of the volume of mail, not all will be answered.

2 GOOD-FAT RECIPES

Quick Good-Fat Salmon Patties

1 large (14- or 15-ounce) can salmon (pink salmon has as much beneficial omega-3 as more expensive red salmon)

8 low- or non-fat saltine crackers, crushed

1/2 cup egg substitute

Black pepper, to taste (use cracked pepper for more bite)

Drain salmon; remove and discard skin. Mash salmon. Combine with crackers and egg substitute. Form into four patties; sprinkle with pepper. In a non-stick pan coated with canola oil, saute over medium heat until patties are browned, 2-3 minutes per side. Serves 4.

Serve with lime or lemon wedges. Or try this quick sauce: Combine 1/2 cup non-fat yogurt, 1 Tbs. horseradish and a dash of lemon juice.

SALMON: Per patty: 190 calories, 24g protein, 4.5g carbohydrates, 0.2g fiber, 7.7g fat (1.9g saturated, 2.5g monounsaturated, 2.6g polyunsaturated), 208mg sodium.

SAUCE: Per tablespoon: 9 calories, 0.9g protein, 1.4g carbohydrates, 0g fiber, 0.02g fat, 13mg sodium.

Classic Olive Oil Dressing

3 Tbs. extra virgin olive oil

1 Tbs. vinegar, preferably balsamic

1 crushed clove garlic

Salt, to taste

Whisk together all. Toss with mixed greens or raw or steamed vegetables.

Per tablespoon: 91 calories, 0g protein, 0.5g carbohydrates, 0g fiber, 10g fat (1.4g saturated, 7.5g monounsaturated, 0.9 polyunsaturated), 1mg sodium.