Preserving the nutrients in your food with care

The various vitamins and minerals are susceptible to destruction by air, light, water, acid, alkali, heat, time and the action of enzymes in the foods themselves. However, you can cut losses and significantly increase your nutrient intake by the care you take in choosing, storing and cooking foods. What to Choose

Lean meats, skinless poultry and low-fat dairy products have more nutrients per calorie than their fattier versions. Whole grains (for example, whole wheat pasta, oatmeal, brown rice) have more nutrients than foods made from refined grains, even if they are enriched. Whole grain foods leavened with yeast have less phytate, which can inhibit the absorption of calcium, iron and zinc. Parboiled, or converted, white rice is more nutritious than regular white rice. Dark green leafy vegetables and deep-yellow vegetables have more vitamin A than lighter-colored ones.

Fresh or frozen fruits and vegetables have more nutrients than canned ones (canning may reduce the amount of some vitamins by half). But fresh is not necessarily better than frozen, since frozen foods are usually processed soon after picking whereas fresh foods may spend days in transport and storage (both in the store and at home) before being consumed. If you cannot shop often, frozen produce may be more nutritious than fresh. Cooked vegetables that are reheated after being kept in the refrigerator for two or three days lose more than half their vitamin C.

Look for produce that has been kept cold in the store, since cold inhibits nutrient-destructive enzymes and the loss of vitamin C. Except for pineapples, fruits ripened on the plant and in the sun have more vitamin C than those picked green. Tomatoes grown outdoors have twice the vitamin C of greenhouse tomatoes. Purchase produce that is free of bruises. Buy milk and margarine that are fortified with vitamin A and milk that has added vitamin D.

In buying processed foods, don't avoid additives that preserve nutrients: Sulfites increase the stability of vitamin C and A; ascorbic acid protects vitamins A and E, thiamin and folacin; the antioxidants BHA and BHT protect vitamins A and D. How to Handle and Store

In general, the longer food is stored in the refrigerator, freezer or cupboard, the greater the nutrient losses. Ripe fruits and vegetables are best kept cold until they are to be eaten. Ripe bananas can be stored in the refrigerator too. Orange juice can be kept refrigerated in a covered container for several days before any vitamin C is lost.

Store potatoes, canned foods and grain foods in a cool, dark, dry place, but don't refrigerate potatoes. Milk and bread should be kept in an opaque container to prevent destruction of riboflavin and vitamins A and D.

Frozen foods should be stored at or below 0 degrees. Wash produce quickly. Soaking washes away water-soluble vitamins and minerals. Refrigerate immediately all cooked foods that are not going to be eaten right away. Keep all fresh, cut and cooked foods well-wrapped to reduce exposure to air. Do not cap strawberries until they are ready to be eaten. How to Prepare

The three R's for nutrient preservation are to reduce the amount of water used in cooking, reduce the cooking time and reduce the surface area of the food that is exposed.

Waterless cooking, pressure cooking, steaming, stir-frying and microwaving are least destructive of nutrients. Frozen vegetables can be steamed. If food is cooked in water, add it to a small amount of boiling water, cover the pot and cook it rapidly. If possible, save the cooking water for making soup, sauces or gravy. Destructive enzymes are inactivated by heat so it is best to cook foods in a preheated pan or oven or in water that is already boiling. Don't wash rice before cooking it.

The smaller the pieces food is cut into, the greater the chances of losing nutrients. On the other hand, small pieces mean faster cooking. If possible, delay cutting up fruits and vegetables and preparing salads until shortly before they are to be cooked or served. Use acids in salad dressing (lemon or vinegar) to inhibit enzyme action, but do not cook green vegetables with baking soda since it destroys thiamin and vitamin C.

Cook potatoes in the skin and uncut. Frying leads to some loss of vitamin C but its main disadvantage is the increase in fat calories, which detract from the nutritive value of potatoes. Deep-fat frying also destroys vitamin E in vegetable oils.

Cooking in iron pots can destroy some vitamin C, but it can also add nutritious iron to the food, especially if the food is acidic. Unlined copper detroys vitamins C and E and folacin. Cooking utensils made of glass, stainless steel, aluminum or enamel or lined with a nonstick coating have no effect on nutrient content.

The longer meat is roasted, the more thiamin is lost. Use defatted pan drippings from meat and poultry to make gravy or soup.