QUESTION -I hear that brewer's yeast is a great source of B vitamins. What are the pros and cons of taking it?

ANSWER - The main drawback of dried brewer's yeast is the taste, which most people don't like, even if they mix it with fruit juice or milk. Its major advantage is, as you say, that it's rich in B complex vitamins, especially thiamin. A single tablespoon, which contains 25 calories, provides the entire day's thiamin requirement as well as one-fifth of the riboflavin quota and 15 percent of the day's needed niacin.Because of this vitamin potency, brewer's yeast is widely used as a supplement in parts of the world where malnutrition is common. In this country, however, our diets usually contain adequate amounts of the vitamins in question. So unless you like the taste, there's probably no reason to put brewer's yeast on your grocery list.

QUESTION - Help! My son has become a pizza addict. I keep frozen pizza on hand for quick meals and serve it with a salad and milk so I feel he's getting a fairly nutritious meal. Lately, though, he's been requesting pizza for breakfast, along with a glass of orange juice. Should I just say no or keep letting him do it?

ANSWER - Don't worry. Pizza for breakfast is unlikely to become a lifelong habit. Your son will probably tire of it before long. Even if he doesn't, there's nothing intrinsically wrong with eating "non-breakfast" foods for breakfast. It's what you eat that matters, not the time of day.

On that point, we do have two reservations about pizza, whether it's eaten day or night: It's high in both fat and salt. We suggest you compare various brands and try to choose one that offers the least salt and fat.

Another step is to drain the pizza on a paper towel to get rid of excess fat. And remember, toppings like salami and sausage add extra salt and fat, too, so you might want to think about buying plain pizza.

QUESTION - If you put warm food in the refrigerator, does it spoil more quickly?

ANSWER - No. The opposite is true, provided you handle the food properly. To promote rapid and even cooling, warm food should always be placed in shallow containers. You run into trouble if you put very large, deep containers of hot food directly into the refrigerator. In that case, the contents around the outside may cool fairly quickly, while the inner portion can remain warm for a long time, setting the stage for harmful bacterial growth.

QUESTION - My friend takes supplements of nucleic acids to fight the aging process. Should I follow suit?

ANSWER - Only if you want to waste your money. The idea that nucleic acids ward off the effects of aging has been kicking around for quite a while. Some years back, nucleic acid-rich sardines were featured in a diet claimed to promote longevity. Nucleic acids have also been touted as a cure for degenerative diseases like atherosclerosis and senility. They've been featured in countless beauty products to prevent hair from graying and skin from wrinkling and to perform other external miracles.

Sorry, folks, there's no scientific evidence to back up any of these claims. As Ponce de Leon found out, the fountain of youth is hard to come by.