It's a smart eater who heeds the latest advice of the National Institutes of Health and reI duces his daily intake of dietary fat to 30 percent of the calories he consumes and cholesterol to between 250 and 300 milligrams. After all, according to NIH estimates, 100,000 lives each year will be saved from cardiovascular disease by making some basic changes in the foods we eat.

But it's a little more complicated when cooks begin applying that information to the recipes they make at home. Deciphering just where fats lie, and finding ways to eliminate them without diminishing taste, can be overwhelming until cooks learn the secret of substituting with low-fat, low-cholesterol ingredients.

Once the basics are understood, creamy-style soups, high-rising souffle's and apple pies are no longer out of reach. Almost any recipe can be adapted, with experimentation. But experimentation can't begin until cooks know what the culprits are, where they are and how they work in recipes. Fat

Fat is found in both animal and vegetable products. Butter, oil, dairy products, eggs and red meat are high-fat products that need special attention in recipes, said Catherine Angotti, a private Washington nutritionist.

Fat is made up of saturated, polyunsaturated and monounsaturated fatty acids. Saturated fatty acids are the dietary culprits linked to cardiovascular disease and cancer of the colon. Polyunsaturated fatty acids, although also linked to cancer, tend to lower levels of cholesterol.

Recent research indicates that monounsaturated fatty acids may also lower blood cholesterol by keeping high the level of protective HDL (a fatty substance that helps to clear cholesterol from the body). Oils and margarines with a 2 to 1 ratio of polyunsaturated fats to saturated fats are the best choices for cooking. Cholesterol

Cholesterol is a fat-like substance found in body cells of all animals. So all animal products will have some cholesterol. It is measured in milligrams, and the highest concentrations are found in eggs and organ meats.

Cholesterol accumulates as fatty deposits along the arterial walls leading to the heart. It is true that the body does need a small amount of cholesterol for normal bodily function, Angotti said, but it is also true that the body manufactures what it needs. Clogged arteries can lead to arteriosclerosis, heart failure and possibly bypass surgery. "The problem," says Angotti, "is that you can't feel cholesterol overload unless you have angina or a heart attack." Only a blood test will tell you ahead of time. Finding Fat and Cholesterol

Though all foods have some fat, they aren't all poor food choices, said Denise Vilven, a dietitian at the Pritikin Longevity Center in Santa Monica, Calif.

All legumes, fruits (except coconuts) and all vegetables (except olives and avocados, which are high in fat and should be limited) are good nutritional sources so long as they are eaten in their natural state, Vilven said. But certain methods of preparation can quickly turn "perfectly appropriate foods into inappropriate foods," she warned. A potato in its unadulterated form, for example, draws less than one percent of its calories from fat, but when turned into a french fry, that same potato starts drawing 50 percent of its calories from fat. "There's a big difference," she said.

Use the following information as a guide in selecting ingredients for stocking the cupboard to use in recipes. Only by understanding these ingredients can cooks begin adapting their favorite recipe.

Oils, Butter, Lard: Butter and lard, both animal products, are high in cholesterol and saturated fat. Vegetable oils, on the other hand, being vegetable products, contain no cholesterol. However, the ratio of polyunsaturated to saturated fats varies widely among the products. The best vegetable oils to use in cooking are safflower, sunflower, corn and soybean oil.

Avoid margarines that don't list the oils they contain and those made with milk fats (which can contain some cholesterol). Also watch for margarines high in hydrogenated oils, a process converting polyunsaturated fats into monounsaturated fats and saturated fats (the more solid the shortening or margarine, the more hydrogenated fat it will contain). As with vegetable oils, the best products to use in cooking are those made with safflower, sunflower and corn oil.

Butter, lard, margarine and vegetable oils are interchangeable in most recipes. Of course you wouldn't want to use melted butter in making homemade mayonnaise, just as you wouldn't want to make a vegetable oil hollandaise (though it has been done). Butter and margarine burn more quickly than do oil and lard.

Remember that fat gives food both flavor and texture and is especially important in baked products. The quantity of butter, lard or oil you use in baked goods can be reduced, but it will take some experimenting. There is no hard and fast rule for just how much fat is required for a particular quick bread or casserole. Start by reducing the amount called for in a recipe by one-third; if that works then cut it to one-half, and so on until the recipe no longer works.

Red Meat, Fish, Poultry: All meat, fish and poultry products contain some fat and cholesterol, said Pritikin's Vilven. Much of the fat is visible on meat and can be trimmed away. But cholesterol is a different story. It is found in the muscle and cannot be trimmed or cooked away. Cholesterol tends to run around 90 to 100 milligrams in all cuts of red meat.

As for the fat content of red meat, even the leanest cuts of red meat -- flank steak or a well-trimmed leg of lamb -- draw 34 percent of their calories from fat, she said. A well-marbled, but trimmed 3 1/2-ounce steak can draw as much as 50 percent of its calories from fat. Veal is somewhat higher in fat, drawing in the leanest cuts 45 percent of its calories from fat, Vilven said.

Cooks who eat red meat should use the leanest cuts in their dishes. According to the American Heart Association, in beef they are flank, round, sirloin tip steak, tenderloin, arm pot roast, heel of round and rump roast; in pork, use tenderloin, loin chops, rib chops, Canadian bacon and boiled or lean center slices; in lamb use well-trimmed leg, leg chop and sirloin chop.

Poultry and fish are the meat choices lowest in fat. Though chicken is relatively high in cholesterol (about 85 milligrams in a 3 1/2-ounce serving), skinless chicken breast is relatively low in the percentage (18 to 20) of its calories drawn from fat; dark chicken meat draws 34 percent of its calories from fat, Vilven said. Most of the fat in chicken lies in and just under the skin. Be sure to remove it before cooking.

Most fish and seafood are relatively low in fat and cholesterol when compared with red meat. But you will want to watch shrimp and crab, mackerel and sardines, all of which have 84 or more milligrams of cholesterol per 3-ounce serving.

No matter what cut of meat you use, it is still important to watch portion sizes, Vilven said. Ideally, serve at most 3 1/2 to 4 ounces per person. When making soups and stocks, be sure to chill throughly and then skim the accumulated fat off the top before reheating.

Organ meats are extremely high in cholesterol and should be avoided by anyone on a restricted diet, Vilven said. Chicken livers are a "graphic example," she said, with 740 milligrams of cholesterol in a 3 1/2-ounce serving. Still, they are low in fat, drawing 23 percent of their calories from fat.

Eggs, Dairy Products, Cheese: One large egg yolk contains 274 milligrams of cholesterol and 5.6 grams of fat. It is hard to do without them in certain recipes as they work to bind, stabilize and moisturize. But it can be done with some experimentation. To get started, remember that when a recipe calls for more than one yolk, simply use one whole egg and then two whites for each additional egg.

A cup of whole milk contains 9 grams of fat and draws 50 percent of its calories from fat, Vilven said. A better choice, though not ideal, is a cup of 2-percent low-fat milk, with five grams of fat and drawing 33 percent of its calories from fat. Nonfat milk is by far the best choice, she said, with less than one gram of fat and drawing less than one percent of its calories from fat.

Milk products are interchangeable in recipes. They are thickened for sauces, poach and adhere equally well as a breading liquid. Low-fat yogurt is a particularly good substitute for heavy cream though its acidic taste may be off-putting to some cooks. That problem is remedied by adding a drop of honey. Evaporated skim milk combined with skim milk thickens soups and gives them a creamy texture. When you want the taste of sour cream, but not the 12 grams of fat found in a quarter-cup serving, make a mock sour cream by blending a cup of one-percent low-fat cottage cheese with 2 tablespoons of skim milk and a tablespoon or two of lemon juice or vinegar.

Cheeses are a real problem for those who love them and are still trying to reduce fats. They tend to be extremely high-fat, high-calorie products. Cream cheese, brie, muenster and american all draw more than 75 percent of their calories from fat and are over 90 calories an ounce. Luckily many cheeses are interchangeable in recipes. Two low-fat, low-calorie selections are farmer and low-fat cottage cheese. While parmesan draws 63 percent of its calories from fat and is 129 calories an ounce, it is a good choice in that it can be finely ground and sprinkled in dishes in small quantities while still adding a good deal of flavor.

While these are the basic switches to make in your recipes, they by no means cover everything you can do. There are more quick hints found on page E14.

Meanwhile, here are some standard recipes to use as guidelines to get you started in making changes in your favorite recipes. They adapt some of our favorites -- fried chicken with pan gravy, creamy soup, a broccoli-and-cheese souffle', chocolate chip cookies and apple pie. They are all low cholesterol and draw 30 percent or less of their calories from fat.

The paragraphs preceding ingredient listings explain what has been changed in the recipes. Note that light-faced ingredients listed in parentheses are not to be used and are only listed to show what has been eliminated or modified. The fat and cholesterol counts following each recipe are per serving. CREAMY SPLIT PEA SOUP (4 to 6 servings)

Eliminates sweating vegetables in butter, substitutes evaporated skim milk and skim milk for 2 cups heavy cream, and eliminates parmesan cheese for flavoring the croutons.

16-ounce package split peas

(2 tablespoons butter eliminated)

1 whole spanish onion, stuck with 2 cloves, diced

1 whole leek, rinsed and finely chopped

1 large carrot, rinsed and chopped

1 rib celery, leaves removed and chopped

1 bay leaf

2 ham hocks

3 to 4 sprigs fresh parsley

Freshly ground pepper

1 cup evaporated skim milk (added)

1 cup skim milk (added)

(2 cups heavy cream or whole milk or half of each eliminated)

FOR THE CROUTON GARNISH:

3 slices white bread

( 1/2 cup freshly grated parmesan cheese eliminated)

Rinse split peas, cover with 2 inches of cold water and soak 8 hours. Rinse twice during soaking. Drain a final time and in a heavy soup pan cover with 1 inch cold water. Add vegetables to split peas along with ham hocks, parsley and freshly ground pepper and simmer 2 hours with the lid askew, or until peas are soft to the bite.

Ladle soup mixture into blender to fill 3/4 full. Pure'e and place in another sauce pot. Continue until you have pure'ed all the mixture. Mixture will be very thick and gloppy. Thin to desired consistency with equal amounts of evaporated skimmed milk and skimmed milk. Slowly reheat, just to serving temperature. Meanwhile, remove crusts from bread. Cut into 1/2-inch cubes and dry in a 350 degree oven for about 15 minutes.

Grind some fresh black pepper in the bottom of serving bowls. Ladle in soup and decorate with croutons.

Before: 54.7 grams fat, 190 milligrams cholesterol, 64 percent calories from fat

Revised: 1.25 grams fat, 3.75 milligrams cholesterol, 4 percent calories from fat BROCCOLI CHEESE SOUFFLE (4 servings)

Grease pan with vegetable oil, instead of butter. Also eliminates butter in bechamel sauce, switches from whole milk to low-fat or skim milk, eliminates egg yolks and reduces amount of cheese and switches from gruye re to parmesan.

Vegetable oil and bread crumbs for mold

(2 1/2 tablespoons butter eliminated)

6 tablespoons plus 1 cup low-fat or skim milk, heated (added)

(1 cup milk eliminated)

2 1/2 to 3 tablespoons flour

1 cup broccoli florets, cooked crisp-tender

1 teaspoon nutmeg

Salt and pepper to taste

Cayenne pepper to taste

(4 egg yolks eliminated)

6 (from 5) egg whites

1 teaspoon cream of tartar

5 tablespoons parmesan cheese (added)

( 3/4 cup gruye re cheese eliminated)

Coat 1 3/4-quart souffle' dish with vegetable oil and coat with bread crumbs. Warm 6 tablespoons milk and whisk in flour. Boil 2 minutes, without browning, to cook the flour. Remove from heat, add remaining milk and beat until well mixed. Return to heat and return to a boil, stirring constantly. Cook 1 minute more. Remove from heat, add broccoli, and season with nutmeg, salt, pepper and cayenne pepper.

Beat egg whites with cream of tartar until stiff. Gently fold egg whites into broccoli mixture along with 4 tablespoons parmesan cheese. Gently fold into souffle' dish, sprinkle remaining parmesan on top. Bake at 350 degrees for 35 minutes. Serve immediately.

Before: 19.8 grams fat, 312 milligrams cholesterol, 61 percent calories from fat

Revised: 2.91 grams fat, 6.87 milligrams cholesterol, 25 percent calories from fat CRISPY OVEN-FRIED CHICKEN WITH PAN GRAVY (4 servings)

Removes skin from chicken. Eliminates deep-fat frying. Switches from whole milk to skim milk and eliminates egg for breading. Eliminates butter in gravy.

3 1/2-pound chicken, cut up, skin and fat removed (skin and fat left on)

Salt, black pepper and cayenne pepper to taste

1 cup skim milk (added)

(1 cup whole milk eliminated)

1 cup homemade bread crumbs

(1 egg eliminated)

(2 cups vegetable oil eliminated)

FOR THE PAN GRAVY:

2 tablespoons flour

(2 tablespoons butter eliminated)

1 cup defatted chicken broth

Rinse chicken, remove skin and fat. Season one side with salt, pepper and cayenne to taste. Let sit for 10 minutes. Turn and season other side and let sit 10 minutes. Coat each piece with milk and roll in bread crumbs. Chill chicken for 20 minutes.

Place on an ungreased baking dish in a 300-degree oven for 45 minutes, raise temperature to 400 degrees and bake 20 minutes more.

Meanwhile make the gravy by browning the flour in a saucepan over low heat until lightly colored. Let cool. Shake the flour with half the broth until smooth. Return to saucepan, add remaining broth and simmer until thickened. Season with salt, pepper and cayenne to taste.

Before: 479 grams fat, 369 milligrams cholesterol, 89 percent calories from fat

Revised: 6.12 grams fat, 5 milligrams cholesterol, 10 percent calories from fat VINAIGRETTE (6 servings)

Substitutes yogurt for sour cream and low-fat milk for heavy cream.

1/2 cup yogurt (added)

(1 cup sour cream eliminated)

2 tablespoons white wine vinegar

1 to 2 tablespoons dijon mustard

2 tablespoons low-fat milk (added)

( 1/4 cup heavy cream eliminated)

Salt and pepper to taste

1 tablespoon chopped parsley or other fresh herb

Whisk all ingredients together and chill.

Before: 35.5 grams fat, 91.1 milligrams cholesterol, 89 percent calories from fat

Revised: .62 grams fat, 4.37 milligrams cholesterol, 7 percent calories from fat CHOCOLATE CHIP COOKIES (Makes about 30 cookies)

In this recipe, adapted from "Better Eating for Better Health," by the American Red Cross, the fat and sugar are decreased and fiber is increased with the use of whole wheat flour. The final product is a thicker, airier cookie.

1 1/2 (from 2 1/4) cups white flour

1 cup whole-wheat flour (added)

1 teaspoon baking soda

1 teaspoon salt

1/2 cup (from 1 cup) butter or margarine, softened

1/2 cup (from 3/4 cup) firmly packed brown sugar

1/2 cup (from 3/4 cup) white sugar

1 teaspoon vanilla extract

1 (from 2) whole egg

3/4 cup (from 1 cup) semisweet chocolate morsels

(1 cup chopped nuts eliminated)

In a small bowl, combine flours, baking soda and salt; set aside. In a large bowl, cream butter, sugars and vanilla extract. Beat in egg. Gradually add flour mixture, mix well. Stir in morsels. Drop by rounded tablespoonfuls onto ungreased cookie sheets. Bake at 375 degrees for 8 to 10 minutes.

Before: 11.1 grams fat, 34.7 milligrams cholesterol, 46 percent calories from fat

Revised: 2.6l grams fat, 16.4 milligrams cholesterol, 28 percent calories from fat APPLE PIE (8 servings)

Substitutes vegetable oil for butter and skim milk for ice water to add additional flavor to the crust, and totally eliminates butter from the filling.

2 cups all purpose flour

1 1/4 teaspoons salt

1/3 cup vegetable oil (added)

(10 tablespoons butter eliminated)

3 to 6 tablespoons cold skim milk (added)

(3 tablespoons ice water eliminated)

FOR THE FILLING:

4 cups apples, sliced and peeled

1 cup sugar

1/2 teaspoon cinnamon

1/2 teaspoon vanilla extract

Grated rind of half a lemon

1 tablespoon lemon juice

(1 tablespoon butter eliminated)

Mix flour and salt together into a mixing bowl. Mix the oil with the cold milk, and pour all at once into the flour. Stir lightly with a fork until blended, adding more liquid if necessary to make dough to hold together. Refrigerate for 20 minutes to make dough easier to work. Divide into 2 portions. Flatten one ball of dough slightly and place on waxed paper or plastic wrap. Put another sheet over top, and roll out quickly to fit a 9-inch pie plate with 2 inches extra for the edges. Remove top sheet of paper and turn dough over onto pie plate. Remove second sheet, and lift crust around the edges so it settles into the plate. trim the edge so you have a 1-to-2-inch border. Chill the crust. In a bowl, mix the sliced apples with all but 1 tablespoon of the sugar, cinnamon, vanilla, lemon rind and juice. Place in chilled, unbaked crust, roll out top crust and lay on top of apples. Fold edges together by rolling and fluting. Cut steam holes. Bake 10 minutes at 450 degrees, then reduce oven heat to 350 degrees and bake 30 to 35 more minutes. Sprinkle with left-over tablespoon granulated sugar. Crust adapted from "The American Heart Association Cookbook."