My daughter came home from school and said she liked salads containing alfalfa sprouts. I realize they are sometimes regarded as "health foods," but what is their nutritional value?

The value of alfalfa sprouts, if you like them, really lies in the texture they add to a salad or sandwich. You would have to eat a huge amount to gain any nutritional benefit. Four cups contain 56 calories, about half of them from protein, as well as small amounts of iron, B vitamins and ascorbic acid.

If you consume alfalfa in any quantity, you will find it far more economical to grow your own. The seeds are readily available in most health-food stores. Local libraries have books providing simple directions showing how to do it with equipment you already have in your home. It is a project especially suited to young children because the time between planting and harvesting is brief.

What is the difference between mayonnaise and mayonnaise-type salad dressing?

Nutritionally, the former contains 11 grams of fat and 100 calories per tablespoon while the latter has just over half that amount, 6 grams and about 65 calories. The difference is accounted for by the fact that the Federal Standard of Identity (the official recipe for mayonnaise) specifies that it contains at least 65 percent oil by weight compared to 30 percent of the weight of mayonnaise-type salad dressing.

Both products have many ingredients in common. These include oil and egg, acidifying agents such as vinegar, lemon or lime juice and citric acid, and seasonings such as salt, sugar and spices like mustard or paprika. However, mayonnaise depends entirely on the emulsifying properties of egg yolk for its thick texture, while salad dressing is thickened in part by a paste made either from food starch or from wheat, rye or tapioca flour.

In an article about milk, I read that homogenized milk contains xanthine oxidase, an enzyme linked to hardening of the arteries, and that goat's milk, which contains less of the enzyme, is a better choice. Is that true?

No. The only reason to choose goat's milk, if you can get it, is if you prefer the taste. (Actually, many people find it objectionably tangy.) No relationship between xanthine oxidase and heart disease has ever been demonstrated. In fact, we are surprised to hear that a hypothesis ruled out several years ago is still finding its way into print.

The xanthine oxidase-heart disease link was proposed 15 years ago by Dr. Kurt Oster, who claimed that homogenization was "a procedure which foists unnaturally small particles on our digestive tract." Oster claimed that xanthine oxidase, absorbed from tiny fat droplets in milk, caused tissue damage and set in motion an atherosclerotic process that led to heart disease. Xanthine oxidase supposedly destroyed plasmalogen, a phospholipid found in heart cells.

A review of the evidence gathered for more than a decade after the theory was first put forth found insufficient evidence to support the idea that plasmalogen depletion is a cause of heart disease. Available studies failed to demonstrate that xanthine oxidase is even absorbed from the intestine or that there is a link between consumption of dairy products containing homogenized fat and blood levels of xanthine oxidase.

Prolonged intravenous feeding of xanthine oxidase to laboratory animals does not destroy arterial or coronary tissue plasmalogens and does not induce plaque formation. This indicates that even if minute amounts were absorbed, they would have no effect.

In short, these and still other pieces of evidence suggest the time to bury the xanthine oxidase/heart disease connection is long overdue.

A friend recently served a casserole of rice and chicken giblets, including necks, gizzards and hearts. Since the whole family enjoyed it and it is economical to prepare, I took the recipe. But I would like to know about its nutritional value. In particular, since the hearts and gizzards are organ meats, I am concerned about their cholesterol content. Can you give me the facts?

The concentration of cholesterol in giblets, including heart and gizzard, is higher than in chicken meat. Three ounces of cooked chicken provides about 75 milligrams (mg.) of cholesterol, while the same amount of gizzard or heart would contain more than double that, or 170 mg. (Remember that a single large egg, the traditional standard when it comes to comparing cholesterol levels, has about 275 mg.)

Since giblets are usually served by the piece, it makes sense to consider them in that manner. At the low end of the scale in terms of cholesterol are the necks, which are not organ meats. An average chicken neck from a broiler or fryer weighs about 2 ounces without the skin and provides only about 2/3 of an ounce of meat. It contains 30 calories, 4 grams of protein, only 1 gram of fat and just 14 mg. of cholesterol.

A single gizzard, weighing about 3/4 of an ounce, contains 35 calories, 6 grams of protein, and just 1 gram of fat. It contains 42 mg. of cholesterol. Eight or nine chicken hearts weigh about an ounce and provide almost 60 calories, 6 grams of protein, 2 grams of fat, and 57 mg. of cholesterol.

Finally, the liver, which many people include in giblet casseroles, is the most concentrated source of cholesterol. A single liver from a broiler or fryer weighs about 2/3 of an ounce and contains just 30 calories. It also provides 5 grams of protein and only about a gram of fat, but it contributes about 125 mg. of cholesterol.

So if you want to control the cholesterol content of your casserole, it would be best to rely most heavily on chicken necks and use smaller amounts of the organ meats.

1987, Washington Post Writers Group