Consumer advocates do not eat nails, or even sawdust, as some of their antagonists might think. Many of them don't limit their diets to brown rice and alfalfa sprouts, either.Some actually love a tremendous variety of foods and like to cook.

But they are very concerned about what is put into their food and like Dr. Sidney Wolfe, director of Ralph Nader's Health Research Group (HRG), choose it very carefully.

Dr. Wolfe is best known as a gadfly of the Food and Drug Administration's regulatory practices. The public interest group he heads has petitioned the FDA to ban the use of many artificial colors in foods, particularly Red No. 2, sodium nitrite in processed meats, polyvinyl chloride in food packaging. The reason: HRG says they are serious health hazards.

Dr. Wolfe lives in a household that consists of two other adults and his 13-year-old daughter, Hannah. All take turns doing the cooking, but no one ever prepares hot dogs, bacon, boil-in-the-bag peas in butter sauce or cream sauce from a mix.

Wolfe said he hasn't bought things with additives "for three or four years now.

"Needles to say, medical school doesn' teach about nutrition or other aspects of food," Wolfe explained, "so it takes a while to learn these things."

Wolfe said the kind of cooking done in his house has economic advantages, too. "We are really eating very inexpensively because we are not eating processed foods. Processed food mean someone other than the person who cooks them in making them."

As a consequence food for four people costs $44 to $48 a week, including breakfasts, dinners and brown bag luches for two.

The kitchen cupboard has no sauce or cake mixes, just items such as peanut butter, raisins, nonfat dry milk and chick peas. The refrigerator-freezer has no bacon, ham or bologna; instead it contains ground beef, chicken and fish.Bananas, oranges and apples sit out in a bowl in the kitchen.

In addition to avoiding processed foods, Wolfe tries to keep the fat content down by draining off any excess when ground beef or sausage is cooked. He also makes salad dressing without oil. He said it isn't just that the fat is extra calories, and bad for the heart, but when it is drained off "you are getting rid of the bulk of the additives and the pesticides that concentrate in the fat."

After trying other schemes for dividing up the cooking chores, the people in Wolfe's house have decide to take a week each. They shop for seven days of meals but cook only the five week nights. They all agree it's much easier than trying to cook with the ingredients someone else bought.

Hannah Wolfe cooks one night each week. On week ends everyone is left to his or her own devices, using part of the weekly food purchase.

Wofe said they don't complain about each other's cooking though there is an occasional, "You put too much pepper in this" kind of comment and Hannah doesn't like some fo the meatless dishes one of the residents likes to prepare. Otherwise the group is quite happy with what is served.

When it's Hannah's turn to cook, she sticks to the more traditional, making things like spaghetti sauce "out of her head." She decides what will go in the sauce by "smelling everything to see if it tastes good together." She tried her hand at homemade pasta with a plastic pasta machine, a Christmas gift, but isn't conviced it's worth the trouble. "It takes about 15 minutes to make a foot of noodles," she said.

Hannah also adds dessert to the menu when she is cooking; otherwise it isn't served. Her favorite is "carrot cake - because it doesn't taste like carrots. Otherwise I wouldn't like it."

She also bakes yeast breads, which she learned by reading a book and looking at the illustrations.

While most of the meals are fairly simple, all the cooks have more unsual favorites. Among them: cioppino, a fish stew from San Francisco; Chinese food and curries. But nothing takes more than the amount of time there is between arrival home from the office and 7 o' clock.

Two weeks ago, when Wolfe last cooked, fettuccini was served Monday; beef, sausage and butternut squash casserole Tuesday; curried chicken and rice casserole with raisins Wednesday; broiled round steak tips seasoned with garlic and oregano Thursday; bulgar wheat salad with egg, green peppers, spinach, chick peas, onion, "lots of garlic" and vinaigrette dressing Friday.

Breakfasts are orange juice and milk or coffee with toast or cereal. Hannah takes lunch to school. It may be a tuna fish sandwich with green pepper or a can of sardines, but always a piece of fruit.

Shopping is easy and varied: The house is within walking distance of two supermarkets, several Spanish stores and an Italian market in the Columbia Road and 18th Street area. In good weather there is an open-air fruit and vegetable market.

Resources like that make it easy to burnish the image of a consumer activist who eats well but judiciously. BEEF, SAUSAGE AND SQUASH CASSEROLE (6 servings) 3/4 pound ground beef 1 pound sausage 2 pounds butternut squash Salt and freshly ground black pepper to taste 1/2 cup lemon juice 1 stick cinnamon 1 teaspoon dried tarragon 1/2 ounce grated fresh ginger Few dashes cloves 1/2 cup tomato puree

Cook the ground beef and sausage in skillet until brown, stirring to break it up. Meanwhile peel squash, cut in chunks and cook in enough water to cover until almost tender; drain. Pour off all fat from meats. Combine with remaining ingredients and spoons into casserole. Bake covered at 350 degrees for 30 to 40 minutes. IOPPINO

(8 servings) 1/3 cup olive oil 1 cup chopped onion 1 cup chopped green onion 1 cup chopped green pepper 3 cloves garlic, crushed 3 or 4 small hot chile peppers, seeded and finely chopped 4 medium zucchini, chopped 1 can (1 pound 12 ounces) tomatoes 1 can (8 ounces) tomato sauce 1 cup dry red wine 1/4 cup chopped parsley Salt and pepper to taste 1/2 teaspoon oregano 1/4 teaspoon basil 1 cup water 2 pounds cod or mixture of cod, red snapper or rock fish, cut in large pieces

Heat oil in a large pan. Saute the onion, green onion, green pepper, garlic and chile peppers. Stir occasionally until onion begins to become tender. Add the zucchini and cook until onion is tender (another 2 or 3 minutes). Add tomatoes, tomato sauce, wine, parsley, salt and pepper, oregano, basil and water. Mix well. Bring to boil; reduce heat and simmer, covered, 30 minutes. Add fish; return almost to boil, reduce heat and simmer 10 minutes.

TOMATO CHICKEN CURRY

(4 servings) 2 medium onions, thinly sliced 4 tablespoons oil 3 cloves garlic, crushed 4 cloves 1 tablespoon ground coriander 1 teaspoon ground cumin 1 teaspoon grated fresh ginger 1/2 teaspoon turmeric 1/4 teaspoon cayenne pepper 2 1/2 pound cut-up chicken 3 large tomatoes, chopped 1 cup yogurt Salt to taste 1/2 cup water

Brown onions in oil. Add garlic, cloves, coriander, cumin, ginger, turmeric and cayenne. Fry 2 to 3 minutes - do not let it burn. Put in cut-up chicken and fry til brown on both sides, coating with spices. Add tomatoes; simmer 5 minutes. Add yogurt, salt and water. Cover and simmer until chicken is tender, stirring occasionally.

- From "A Taste of India" by Mary S. Atwood