The Healthy Diet »

Milk and other dairy products — including butter milk, cheese and yogurt are the most important dietary sources of calcium, supplying about three fourths of our intake of this mineral. One cup of milk contains about 300 milli­grams of calcium, which constitutes a substantial portion of the 800 milligrams recommended for most adults, and the 1,200 to 1,500 milli­grams suggested for pregnant, lactating and post-menopausal women. Although dairy products are the richest source of calcium, other foods can supply significant calcium if eaten in sufficient quantity.

Calcium is essential primarily for the growth and maintenance of bones and teeth. Yet studies have shown that more than two thirds of American women and up to half of all American men do not consume as much calcium as they should.

Calcium deficiency is an important factor in osteoporosis, a pro­gressive loss of bone density afflicting at least 15 million Americans, mostly older women. Research has shown that consuming adequate calcium — not just in childhood but throughout one's life — may prevent, or at least delay, osteoporosis. Inadequate calcium consump­tion can also lead to weakening and loss of teeth, and studies have linked low calcium intake to high blood pressure, which affects an estimated 60 million Americans.

Besides supplying calcium, milk and milk products provide most of the other essential nutrients. One cup of milk (whole, lowfat or skim) contains about 15 to 20 percent of the protein an adult needs daily, and it comes in a form that is almost completely absorbed and used by the body. And, because its protein is complete, milk complements legumes, cereals and breads, supplying the two amino acids (lysine and methionine) that these protein sources lack.

The vitamins in whole milk include A and D and the B vitamins. Because skim and lowfat milk lose the fat-soluble vitamins A and D when they are defatted, they are almost always fortified with these substances. Milk contains only a minimal amount of vitamin C, which is further decreased by the high temperatures used in pasteurization. Milk's roster of minerals includes phosphorus, potassium and a very small amount of easily absorbed iron, as well as some magnesium, copper, chlorine and sulfur. Unfortunately, milk also contains a fair amount of sodium, and most cheeses contain a great deal of sodium, which is added during processing.

The most serious drawback to milk is that, in its whole form, it contains a considerable a of saturated fat. But lowfat milk has about half the fat of whole milk, and skim milk has almost no fat and approximately half the calories of whole milk. Three glasses of skim milk a day provide an adult's daily requirement of 800 milligrams of calcium with just 240 calories, compared to 450 calories for the same amount of whole milk. Skim milk and lowfat milk products such as buttermilk, lowfat yogurt and lowfat cheese (including farmer cheese and skim-milk ricotta) are also preferable to whole-milk products because they have far less fat yet the same nutrients. Most hard cheese is high in fat, so it should be consumed in moderation.

Some people can digest only a small amount of milk because of its lactose (milk sugar) content. This problem occurs because the diges­tive enzyme lactase, which helps break lactose into its component sugars, is produced in insufficient an Lactose-intolerant individuals suffer from bloating, gas, cramps and diarrhea, the result of the undigested sugar passing through the intestines.

People with lactose intolerance can try consuming more cultured milk products, such as cheese, live-cultured yogurt, buttermilk and acidophilus milk (cultured milk to which special bacteria have been added). In all of these foods, lactose has already been partially broken down by beneficial microorganisms. Even if you consume only cultured milk products, you can still meet your daily calcium re­quirement. If you have lactose intolerance, avoid eating dairy" on an empty stomach and limit the amount you consume at one sitting. You can also add packaged lactase to dairy products at home or buy milk products that have been treated with lactase. Cultured milk prod­ucts are not only easier to digest, but they may increase the body's use of calcium. Preliminary evidence also suggests that such products may reduce the risks of bowel cancer. Many of the recipes in this volume use lowfat culture milk products.

Because dairy products are so nutritious, you should incorporate them into as many dishes as possible — at breakfast, lunch and dinner. Take care in cooking them, though: Milk's flavor, odor and texture can be adversely affected by prolonged high-heat cooking. Stir milk often as it cooks, or heat it in a double boiler. And be sure to cover the pan. If you do not, a skin will develop on the surface of the milk, blocking steam release and possibly causing the milk to boil over. If you skim the skin, you will lose valuable nutrients. Milk also tends to scorch and curdle, so cook dishes with milk in them over moderate heat.

You can substitute nonfat dry milk powder for fresh milk in most recipes by sifting it with other dry ingredients and compensating for the loss of liquid with water. Using nonfat milk powder is an easy way to increase the nutritional value of a dish while adding only a few calories to it.

Cheese should be heated over low temperatures to prevent toughening or coagulation. Cheese sauces may separate if overheated. When baking, use moderate oven temperatures and try to add, the cheese near the end of the cooking time. Cheese dishes bake better if the baking dish is placed in a pan of hot water, or if the cheese is covered with bread crumbs or another insulating topping.

Buying and Storing Guide

1. Milk is available innumerous forms. The most common are whole milk (in which fat comprises 48 percent of the calories, lowfat milk (about 30 percent fat calories), skim milk (four percent fat filled milk (milk fat removed and replaced by another type of fat), buttermilk (fermented calories), skim or lowfat milk), yogurt (a fermented product made from either whole or lowfat milk), sour cream (86 percent fat calories), heavy cream (97 percent fat calories), evaporated milk (60 percent of water evaporated, then sealed and sterilized), dry milk (in powder form, water removed), acidophilus milk (milk whose lactose has been predigested by special bacteria), low-sodium milk (95 percent of sodium removed) and lactase-treated milk (for people with lactose intolerance). Unpasteurized raw milk is sold in some states, but it may contain dangerous bacteria.

2. Store milk in the container comes in; keep it in the coldest part of your refrigerator. Exposing milk to light not o changes its flavor, but also destroys its riboflavin. Pasteurized fresh milk keep up to five days after. Purchase.

3. While hard cheese will keep in the refrigerator for several weeks, soft cheese must be used within several days. Wrap hard cheese tightly to protect it from drying out. Hard cheese can be frozen if it is cut into pieces and then tightly wrapped in plastic wrap. Do not freeze soft cheese such as cottage cheese; freezing adversely affects its texture.