I read an article about vegetarian diets. It said that vegetable proteins "complement," or improve, each other. It didn't give details. Can you explain?

As you may know, proteins are composed of amino acids. Some amino acids can be manufactured in the body; others cannot. The latter group, termed "essential," must be obtained from foods we eat.

In plant proteins one or more of these essential amino acids is in short supply. These are generally referred to as "limiting" amino acids. The net effect is that if plant proteins are eaten by themselves the body cannot use them efficiently.

Lysine, methionine and tryptophan are the three most limiting amino acids in plant proteins. Fortunately, all plant proteins do not suffer the same shortcomings. While grains tend to be low in lysine, they are high in methionine. Legumes, with the exception of peanuts, are low in methionine and tryptophan, but high in lysine. In nuts and seeds, it is again lysine which is in short supply.

Complementarity comes into play in the natural course of eating numerous different combinations of plant proteins; in rice and beans, a staple of many diets; in a peanut butter sandwich; or in a bowl of pasta and bean soup, to name just a few.

Of course, in addition to mixtures of vegetable proteins, small amounts of animal proteins readily contribute the amino acids in short supply in a particular plant food.

When I make chicken soup or stew, I first remove all the skin and trim off most of the fat I can see. But how can I estimate how much fat is still left? Does chicken fat, cooled or chilled, rise to the top of the pot the way other meat fat does?

Yes, it does. Fat is lighter than water and floats to the surface. Because that is true, by using the right techniques you can keep fat in your chicken soup or stew to a minimum.

Step one: prepare the chicken soup or stock. Then remove the chicken meat, trim it of all visible fat, and chill it. Strain the broth and chill that thoroughly. The layer of chicken fat will rise and can be lifted off the top of the cold broth, leaving the soup virtually fat-free. It is then possible to cook the vegetables in the broth, and add the chicken back at the end of the process. A cup of light meat chicken, about 4 1/3 ounces, prepared in this way will contain almost 6 grams -- just over a teaspoon -- of fat, while the same amount of dark meat will still have only twice that amount.

1987, Washington Post Writers Group