If there's any doubt that the nutritional spotlight is firmly trained on calcium these days, one need look no further than the grocery shelf -- lined with calcium-enriched flour, orange juice, cereal and even soft drinks -- or the sales of calcium supplements, for which Americans have spent an estimated $169million thus far this year, according to the Warner-Lambert Co., a producer of two calcium products on the market.

Milk and milk products are generally considered prime sources of calcium, although a host of foods -- including tofu processed with calcium sulfate, fish with edible bones and a number of dark, leafy green vegetables -- also offer considerable amounts of the mineral.

Yet the relative economy of such foods as calcium sources varies greatly, according to Dianne Odland, author of "Calcium: Food Sources and Costs," a report published in a recent edition of Family Economics Review.

In her study, Odland, a home economist with the USDA's Human Nutrition Information Service, ranks a variety of foods from least to most costly by computing food costs per 100 milligrams of calcium, as well as cost per serving.

Odland reports that among dairy products, milks -- nonfat dry, skim, low-fat, whole and buttermilk -- usually offer the most calcium at the least expense. Moreover, these beverages also tend to be lowest in fat of milk and milk products.

Cheese, on the other hand, can cost from two to 12 times as much to provide an equal amount of calcium.

Take cottage cheese, for instance. "I think a lot of people are under the impression that cottage cheese is a good source of calcium," says Odland, yet "it takes 2 1/2 cups of cottage cheese to equal the same amount of calcium as is in a cup of milk." Moreover, on a per serving basis, cottage cheese is higher in sodium than all other dairy products considered in the study.

And cream cheese, in addition to being one of the most expensive sources of calcium in the review, offers the least calcium for its calories. Odland noted that it would take approximately 14 ounces of cream cheese (136 grams fat) to equal the calcium in a cup of 2 percent milk (five grams fat).

Of the nonmilk sources of calcium represented in the report, tofu processed with calcium sulfate was cited as the least expensive, broccoli the most expensive. And noteworthy among economical sources of calcium were calcium-fortified bread and enriched white bread, both of which ranked with milk as best values among the products surveyed.

While the cost of calcium in various foods is the main objective of the report, other nutritional concerns are also addressed: The diet-conscious might be interested to know that for their calories, leafy green vegetables provide more calcium than all other foods analyzed. And while mackerel is the least costly source of calcium among the fish represented in the study (salmon ranked highest), it is also considerably higher in fat and sodium.

Finally, while the survey revealed that the prices of all 18 calcium supplements included in it were lower in cost than nonfat dry milk per 100 mg (elemental) calcium, it concluded that "no supplement assures the variety and amounts of nutrients and energy provided by foods in a varied diet."

Here's an easy-to-prepare meal that provides 15 percent (149 milligrams) of the U.S. RDA for calcium, at a modest 165 calories per serving:

Express Lane list: broccoli, turkey breast, cornstarch, turkey broth, skim milk, cheddar cheese

TURKEY DIVAN (4 servings, about 3/4 cup each)

10-ounce package broccoli spears

1/2 pound turkey breast, cooked and sliced

2 tablespoons cornstarch

1/2 cup unsalted turkey broth

1/2 cup skim milk

1/3 cup cheddar cheese, shredded

1/4 teaspoon salt

Cook broccoli as directed on package until just tender. Drain.

Arrange broccoli in a 1 1/2-quart casserole. Lay turkey slices on top of broccoli.

Mix cornstarch with broth in saucepan until smooth. Add milk. Cook, stirring constantly, until thickened. Remove from heat.

Add cheese and salt. Stir until cheese melts. Pour sauce over turkey and bake in a 375-degree oven until sauce is bubbly, about 25 minutes.