I've been advised by my physician to take a calcium supplement. I've read that all calcium supplements aren't created equal - that some dissolve better than others and are absorbed more efficiently. How can I be sure that the one I'm using is O.K.?ANSWER - You can do your own, simple test for solubility. Put the tablet in a glass of vinegar at room temperature and stir it vigorously over a 30-minute period. At the end of that time, the tablet should have disintegrated into fine particles.

The problem of solubility of calcium salts surfaced years ago, when it was discovered that about half the products tested failed to meet United States Pharmacopeia standards for disintegration or solubility. It should be emphasized that nationally advertised products were fine, but many house brand and/or private-label products were not. At the time the report appeared, some manufacturers indicated that they would redesign their products to increase solubility.

After you've made sure that your supplement passes the solubility test, there are two other steps you can take to promote absorption. One is to take the supplement along with meals, especially if it contains carbonate or phosphate. Another is to be sure to take them with plenty of water, at least six to eight ounces.

QUESTION - I have lactose intolerance and regularly use liquid Lact-aid in milk. Occasionally I have Lact-aid tablets at a meal if it contains dairy products. Is there any reason I should be concerned about how much of a commercial product I'm taking?

ANSWER - No. The product you're using is an enzyme that your body apparently doesn't manufacture in amounts sufficient to break down the lactose in the dairy products you consume. Enzymes are proteins and, therefore, will be broken down and digested as are other proteins.

Low-fat milk and other lactose-containing dairy products are valuable foods that contribute important amounts of many essential nutrients. We would encourage you to continue to use them with the amount of enzyme preparation it takes to avoid the discomfort of lactose intolerance.

QUESTION - My cousin works in a restaurant where only the highest-quality ingredients are used. However, she tells me that often the fish has worms in it when it comes in. They simply discard the worms and cook the fish. This both disgusts and worries me. I've been sufficiently alarmed that I haven't eaten fish for a long time. Do all fish have worms?

ANSWER - No, and even when they do, most worms in fish cannot survive inside the human body. While it may seem unpleasant, the fact is that if they went undetected, they would just be digested when the fish were eaten. What's more, those few worms that can pose a hazard are killed by cooking up to 140 degrees Fahrenheit or by freezing to minus 4 degrees for 24 hours. So only if you eat raw, lightly cured or insufficiently cooked fish can even those cause problems.

From a practical point of view, stores that sell fish are well aware of the fact that consumers get upset if they find worms in their fish. Many fish processors "candle" their fillets by placing them on a plate of glass lit from below to find any that have escaped the processing. Unfortunately, those deeply embedded in the filletsmay go undetected.

It seems a shame to miss out on the joys of fish. Now that you know the score, perhaps you'll reconsider.

QUESTION - Does coffee provide any nutrients?

ANSWER - Let's put it this way: Coffee is no nutritional powerhouse. A six-ounce cup has a negligible three calories contributed by the very small amount of carbohydrate it contains. It also provides about 7 percent of the U.S. Recommended Daily Allowance for niacin, one of the B vitamins, as well as some potassium and minute amounts of other vitamins and minerals.

Coffee consumption in this country has been on the decline for some time now, down over 28 percent from 20 years ago. In actual amounts, that represents a drop from 36 to 26 gallons a year per person.