qa I have recently undergone a complete gastrointestinal evaluation and the conclusion is that I have lactose intolerance. I substituted lactase-treated milk for regular milk and find it acceptable. But I do miss cheese, especially cottage and swiss, and sugar-free milk puddings. I tried yogurt and found that it caused problems. Is there anything that can be added to dairy products to make them acceptable?

You can take several steps to liberalize your diet. Lactose intolerance is usually not an all-or-nothing phenomenon. Most people who have the condition are able to tolerate some without ill effect. To avoid discomfort, it is a good idea to proceed with caution in establishing your own tolerance level.

Hard cheeses, including swiss, contain so little lactose that most individuals with this condition can eat them without problem. Two exceptions are the whey cheeses, myusostcq and ghetostcq. Ricotta and low-fat and creamed cottage cheese may contain enough to cause symptoms. If you feel uncomfortable after eating yogurt, we question whether the type you ate contained active culture. If not, you may want to try one that does. But begin with just a few bites. If that causes no problems, gradually increase the amount you eat at one time.

The company that produces Lact-aidcq, which converts lactose to simple sugars, also markets cottage cheese and ice cream in some areas in the northeastern part of the country. You can find out if these products are available in local markets by calling toll-free 1-800-257-8650. The company also tells us that many people make their own ice cream and other frozen desserts using Lact-aidcq treated dairy products. If you really miss pudding and find that the mix contains too much milk solids, you can make your own from scratch using lactase-treated milk and artificial sweetener.

Q. Is the use of fluoride substitutes as effective in reducing tooth decay as when a child is exposed to fluoridated water from birth?

A. No, although theoretically it should be. The use of fluoride supplements in amounts equal to what would be ingested if the water supply contained optimal amounts, or was fluoridated, ought to provide equal protection against cavities. But apparently there are two reasons a gap exists. Part of the explanation probably lies in the difference between giving a single dose that provides exposure once a day, and the continuous exposure that results from a child getting fluoride through the water supply.

The second reason has to do with compliance. While it is relatively easy for parents to give infants their fluoride drops, optimal protection is achieved by taking fluoride drops daily from shortly after birth until 16 years of age, when the second molars are fully erupted. It is difficult to maintain a high level of compliance as children get older.

The best age to initiate fluoride is still a matter of debate, with some support for beginning shortly after birth and other evidence suggesting six months as the appropriate starting time. Recognizing the discrepancy, the American Academy of Pediatrics has taken a position favorable to beginning fluoride supplements in breast-fed infants shortly after birth. Fluoride supplementation of formula-fed babies, who get varying amounts in their feedings, is based on the fluoride content of the water supply.