IN WASHINGTON, it's cultured to eat culture.

The average yogurt consumer is a middle-class, college-educated, usually professional woman, 18 to 34 years old, who, no doubt, eats strawberry yogurt from an 8-ounce container.

It's little wonder, then, that residents of the Washington area eat 2 1/2 times more yogurt than the average American, much of it lowfat. We fit the demographics to a T.

Plain yogurt enjoys greater popularity here than nationally, says a representative of a national yogurt producer; it's our third favorite flavor. (Nationally the unflavored variety comes in as fifth; the red yogurts--like strawberry, raspberry, cherry--are the favorites). It takes a sophisticated, cosmopolitan palate to appreciate the plain yogurt, or so the theory goes.

In most of the country, she adds, people eat yogurt for a snack. Washingtonians, however, consume it at lunch.

These statistics help explain the reasons for the continuing rise in yogurt's popularity. The 1960s subculture culture craze is becoming the brown-bagger's special. These busy professionals turn to yogurt because they know it's quick and tastes good, think it will help their diets and have heard that it does wonderful things for their health.

Yogurt's health-giving mystique arises partly from the research of Nobel prize winner Elie Metchnikoff, who attributed the long lives of certain Bulgarians to their high consumption of yogurt. Wives' tales, conjecture and misconception added to Metchnikoff's anecdotal data to convince health-food freaks that yogurt had life- and health-giving qualities above and beyond average food.

Speculation is the mother of scientific investigation, so while Berkeley co-eds consumed boysenberry yogurt and granola, Dr. Khem Shahani, a researcher at the University of Nebraska, started experiments on cultured milk products.

Twenty years later, Shahani cautiously admits yogurt's amazing benefits. There's no doubt, he says, that the bacteria cultures, which change milk into yogurt, increase the B-vitamin content of the product. In addition, those same bacteria produce an enzyme that breaks up milk sugar, meaning that people with milk-digestion problems (lactase deficiency) can digest yogurt.

Shahani takes exception to the assertion that yogurt is no more nutritious than milk. Research shows the bacteria that transform milk into yogurt also split long molecules of fat and protein, making the yogurt easier to digest. This means that you can absorb more nutrients from yogurt than you can from milk.

Researchers have watched it lower blood cholesterol in both humans and test animals consuming yogurt as part of their diets. Furthermore, one type of bacteria in yogurt produces a natural antibiotic. At the federal research laboratories in Beltsville, Md., scientists have observed that rats on diets supplemented with yogurt grow faster and are better able to resist disease than those on diets supplemented with milk.

Even more amazing, Shahani's experiments (supported, in part, by Dannon Milk Products, Inc.) with mice showed that cancer growth slowed when their regular diet was supplemented with yogurt. He says several experiments bear this out, but he's not sure what mechanism inhibits tumor growth. His work in future years will be devoted to finding the answer.

So it just may be true, what they say about yogurt and how good it is for your health. For weight loss, however, there's a different story to be told. Dr. Virginia Holsinger, a U.S. Department of Agriculture research scientist, says, "Yogurt, for some reason, has an image of a diet food. Yet when you look at the calories, it's really quite high."

Sweetened fruit-flavored yogurts can have up to 280 calories per cup. In addition, fruit preserves displace some of the yogurt, decreasing the actual nutrient content. Still, says Holsinger, it is by and large a nutritious food. "Yogurt is an excellent source of calcium, an excellent source of riboflavin a B vitamin , as well as having high quality protein and other vitamins."

Yogurt companies have capitalized on the concern for health by associating themselves with fitness events (such as foot races).

And the food's popularity probably depends no less on convenience and flavor than anything else. Those health-conscious young people of the 1960s and '70s grew up to form two-career families, and they naturally turned to yogurt for a quick breakfast, lunch or dinner on the run. And as babies have arrived, these couples have learned the merits of plain yogurt when they introduce their children to solid foods.

A new generation of yogurt eaters has begun.

SHRIMP AND AVOCADO SALAD (4 servings) For sauce: 1 tablespoon white vinegar 1 1/2 tablespoons olive oil 1/2 teaspoon dijon-style mustard 1/2 cup yogurt 1 large clove garlic, peeled and finely chopped 1 tablespoon picante sauce (substitute taco sauce) Dash hot pepper sauce Salt and freshly ground pepper to taste Juice of 1/2 lemon For salad: 1 large avocado, peeled and cubed Juice of 1/2 lemon 1 pound large fresh shrimp, cooked and peeled 1 small white onion, finely chopped Lettuce leaves

Mix all sauce ingredients together in a small bowl. Put avocado in a large bowl and sprinkle with lemon juice. Add shrimp and onion. Pour enough sauce over top of shrimp mixture to bind and gently toss. Serve on top of lettuce leaves.

LUNCHTIME APPLE YOGURT (4 servings)

Granted, this is a very strange combination of ingredients but the rewards are unusual and memorable. The curry makes it spicy, the yogurt makes it cool, the vegetables make it interesting and filling. All told, it packs easily to make a refreshing lunch, especially in warm weather.

Add less yogurt or more vegetables to make a salad. Add more yogurt and thin with milk to make a soup. 1 hard-cooked egg, chopped 1/2 cup raisins 4 cups plain yogurt 1 cucumber, peeled and chopped 1/4 cup chopped scallions 1 teaspoon salt 1/4 teaspoon pepper 3 tablespoons curry powder (or to taste) 5 green, unpeeled cooking apples, cored and chopped 1 tablespoon fresh parsley, optional

Combine all the ingredients except parsley and chill. Sprinkle with parsley before serving.

ZUCCHINI QUICHE (6 to 8 servings) 1 deep-dish, 9- or 10-inch pie shell, unbaked 1/4 cup grated cheddar cheese 1/2 cup fresh bread crumbs (about 1 slice of bread) 1 1/2 pounds zucchini 2 eggs, separated 1 1/2 cups plain yogurt 2 tablespoons minced chives 3 tablespoons flour Salt and freshly ground black pepper 1 teaspoon lemon juice or vinegar

Combine cheddar cheese and bread crumbs and set aside. Slice zucchini into 1/4-inch slices. Place slices in a saucepan, cover, and steam (without water) over very low heat, 3 to 5 minutes. Beat egg yolks, yogurt, chives, flour, salt and pepper. Beat the egg whites with lemon juice until they are stiff but not dry and fold them into yogurt mixture. Place some zucchini slices in a single layer in the bottom of the pie shell. Cover with a little of the yogurt. Continue making layers until all the ingredients are used and ending with the yogurt mixture. Sprinkle with cheese and bread crumbs and bake for 10 minutes at 450 degrees. Reduce the oven heat to 325 and bake 40 minutes more, or until quiche is puffy and brown.

HORSERADISH SAUCE (About 1 cup) 8 ounces plain yogurt 1 to 2 tablespoons prepared horseradish 2 tablespoons minced green onions Combine ingredients. Serve with baked or pan-fried fish, beef or as a dip for vegetables or as a salad dressing.

LEMON YOGURT CAKE (1 3-layer cake)

Make the lemon curd and buttercream before you start the cake. % Butter for cake pans 1 3/4 cups cake flour 2 teaspoons baking powder 3/4 teaspoon baking soda 1 1/2 sticks butter ( 3/4 cup), softened 1 1/4 cups sugar 3 eggs, separated Grated zest of 1 lemon 3/4 cup plain or lemon yogurt 1 teaspoon lemon extract 1/4 cup plus 2 tablespoons orange juice 2 tablespoons lemon juice Lemon curd (recipe follows) Lemon buttercream (recipe follows)

Butter 3 8-inch cake pans and line the bottoms with rounds of waxed paper. Sift flour, baking powder and baking soda together and set aside. In a large bowl, cream the butter. Gradually add the sugar, beating constantly. Add egg yolks, 1 at a time, beating well after each addition. Combine lemon zest, yogurt, lemon extract and orange juice. Add 1/3 of the dry ingredients to egg mixture and fold in gently. Add 1/3 of yogurt mixture to this and fold in gently. Repeat steps twice more. Beat egg whites with lemon juice until stiff but not dry and fold these into the batter. Pour mixture into cake pans and bake 20 minutes at 350 degrees or until the cake pulls away from the sides of the pan (cake layers may not brown evenly). Remove from pans and turn onto racks. Cool briefly. Spread the tops of 2 of the layers with lemon curd (reserve 2 tablespoons for buttercream). Allow the cakes to cool completely. Stack the layers, placing the layer without lemon curd on top, and cover cake with lemon buttercream.

LEMON CURD (Makes about 1 cup) Grated zest of 1 lemon 1/2 cup sugar 3 egg yolks 1/4 cup lemon juice 1/4 cup butter, melted

Combine zest and sugar. Add egg yolks and lemon juice and beat 1 minute. Pour in melted butter, beating continuously. Pour mixture into a heavy stainless steel or enamel saucepan and cook over medium low heat, stirring constantly, until the curd is thickened. Remove from heat and chill until firm.

LEMON BUTTERCREAM ICING (Makes about 2 cups) 4 tablespoons butter Grated zest of 1 lemon 3 1/2 cups confectioners' sugar 1/4 teaspoon lemon extract 2 tablespoons lemon curd 4 tablespoons plain or lemon yogurt Beat butter until fluffy. Add zest, sugar, lemon extract, lemon curd and yogurt. Stir well to combine, then beat about 3 to 5 minutes. Allow frosting to sit covered in the refrigerator 15 to 20 minutes until it has thickened to spreading consistency.