Q. What is the nutritional value of kidney beans?

A. The kidney bean, just one of many derivatives of the ancient common bean aseolus vulgaris, is an excellent food, and its nutritional value can be maximized by careful menu planning.

A cup of cooked beans provides the same amount of protein as two ounces of meat. The protein, like that in all dried beans, is short on the so-called sulfur-containing amino acids. But from a practical point of view, this is not a problem. Proteins from other foods (especially a small amount of animal protein) eaten at the same meal can easily make up for that nutritional shortcoming.

Kidney beans are also rich in iron. A small amount of meat, fish, poultry or some source of Vitamin C included in the meal will improve absorption of the mineral. Beans provide some B vitamins as well.

Considering their high nutritional value and low cost, it is unfortunate that dried beans remain a relatively unimportant food in this country. Consumption has dropped about 20 percent over the last two decades to an estimated six pounds per person each year, with the highest consumption in the South and West. Some, but not all, of this decline is attributed to rising income. And increases both in single-parent families and in women in the work force have meant that many people do not have the time it takes to prepare dried beans.

Q. I have hypertension and am following a low-salt diet. I began using potassium chloride as a salt substitute, but then a friend told me it was just as bad as sodium. Is this true?

A. Some individuals with kidney disease cannot tolerate increased amounts of potassium and therefore should not use these salt substitutes. Beyond that, there are no medical drawbacks.

Potassium salts do not taste like table salt. Individuals must cultivate a taste for them. As an alternative, we prefer to encourage people who want to reduce sodium intake to learn to use herbs and spices to season their food.

There are several ways to get the most out of these seasonings. First, try to buy them in stores that have freshly dried herbs and fresh spices. Second, whenever possible buy whole spices and grind or pulverize small amounts as you need them. If you doubt the difference, compare the aroma and seasoning power of freshly grated nutmeg (easily grated on any home grater) with the powdered variety. We guarantee you will be sold. Finally, buy only what you will use in a reasonable time and keep the spices in tightly covered containers in a cool place.

We also recommend that, if you have not already tried them, you experiment with some of the herbed and fruit-flavored vinegars as well as the several excellent salt-free dijon-style mustards now available. One recipe for homemade vinaigrette calls for oil, tarragon vinegar, thyme, a few grinds of pepper and a healthy spoonful of salt-free prepared dijon mustard. It contains not a grain of salt, but your tastebuds will tell you it loses nothing in the translation.

Q. What is arrowroot?

A. Arrowroot is a starch obtained from the root of a West Indian plant called Maranta arundinacea. From a culinary point of view, it is considered especially useful when a delicate texture is required. Unlike flour and cornstarch, it does not need to be cooked to remove the "rawness," and it thickens at lower temperatures than either of them. That makes it particularly useful in egg or other sauces that should not boil. On the other hand, it does not hold up well on standing, and sauces thickened with arrowroot cannot be reheated.

Nutritionally, arrowroot contains little except calories. But it does provide a sauce-thickening option for individuals with wheat allergies. As wheat-sensitive individuals know, however, so-called "arrowroot cookies" from the supermarket contain arrowroot starch, but the foremost ingredient is wheat flour.