Q. I'm a new diabetic. I eat cereal for breakfast and would like to follow my usual custom of slicing half a banana into it. But is it true that bananas contain sugar?

A. Yes, like all fruits, they do. When bananas ripen, starch is converted into sugar. But that doesn't mean they and other fruits have to be written out of your life. Fruits provide energy as well as essential vitamins and minerals, and should be an important feature of any diabetic diet.

For diabetics who are not overweight and whose condition is well controlled, it's usually possible to include some sugar in the diet. But most individuals who develop diabetes late in life are carrying around extra weight. In planning their diets, there is no room for the empty calories provided by sugar.

In managing diabetes, diet is key. It sounds as if you would benefit from some expert guidance as you accustom yourself to the condition. A registered dietitian can help you plan a flexible regimen that incorporates your personal preferences -- such as a breakfast banana -- within the boundaries of your situation.

Ask your doctor to recommend a dietitian. Before your appointment, write down any questions you have about specific foods. It's worth taking time out to learn how to adapt as positively as possible to life with diabetes.

Q. Is it true that eggs inhibit iron absorption?

A. Yes. The discovery was made by accident. About 20 years ago, a group of British researchers studying how various iron compounds could be used to enrich flour stumbled on the fact that when eggs were left out of the test breakfast, absorption improved. Further, the inhibiting effect of eggs was found to be far greater when the iron was added to the flour than when it was given as a supplement. And the effect was stronger with some types of iron supplements than with others.

Eggs aren't the only food that interferes with iron absorption. Phytic acid, a compound found in whole grains, can tie up iron and make it unavailable to the body. Large amounts of cellulose also hamper absorption. Tannins in tea and polyphenols in coffee have this effect, too, which is why it's sometimes suggested that these beverages be consumed well apart from meals. However, people who look forward to capping meals off with a cup of tea or coffee find the suggestion impractical.

What may be an easier course is to focus on those foods that enhance absorption of so-called "nonheme" iron, the type found in vegetable foods. The way to do this is by including vitamin C-rich fruits and vegetables in your meals or by eating meat, fish or poultry at meals along with grains and vegetables that provide nonheme iron.

Q. Which is better for reducing tooth decay: using fluoride supplements or exposing a child, from birth on, to fluoridated water?

A. Theoretically, they should provide the same protection. Using supplements in amounts equal to what would be ingested if the water supply contained the optimal level of fluoride should be just as effective in warding off cavities. It should be -- but it isn't.

There are two reasons for the gap. One is that giving a single dose of fluoride once a day may not work as well as continuously exposing the teeth through the water supply. The other explanation has to do with compliance. It's relatively easy for parents to give fluoride drops to babies. But for maximum protection, children should get them from infancy until the second molars are developed, at about 16 years of age. As children get older, it's becomes harder to make sure they take the drops.

Of course, it you live in a community where the water supply isn't fluoridated or if you consistently use bottled instead of tap water, you'll need to rely on fluoride supplements. If you get your children into the habit, so that compliance isn't an issue, you'll have an advantage.

The best age to begin giving the supplements is still under debate. Some experts recommend beginning shortly after birth, while others set the date at six months. The American Academy of Pediatrics, noting the controversy, has suggested this position: For breast-fed infants, fluoride supplements can be given shortly after birth. Supplementation of formula-fed infants, who get varying amounts in their feedings, should be based on the fluoride content of the water supply.

If you have questions about fluoride and your baby, consult your pediatrician.

Q. My husband and I take medications to help rid us of extra fluid. However, I really dislike the idea of being on drugs. Can you tell me if there are certain foods I could eat to accomplish the same thing?

A. We can understand how you might think that some foods could act as natural diuretics. That claim has been floating around for some time. Unfortunately, it's simply not true. We do have a couple of suggestions for you, though. Our hunch is that the reason you and your husband are taking diuretics is that your blood pressures are elevated. If so, chances are that the doctor has indicated two measures that can enhance the effectiveness of the drug: weight reduction and limiting salt. Losing weight, if you need to, can help lower blood pressure, and cutting back on salt may make it possible to use less medication.

Consuming vast quantities of celery, asparagus, watermelon or parsley -- all foods that found their way into popular press as "natural" alternatives to medication -- just won't work.

Q. Recently my daughter brought a friend home from college. The young woman comes from an island in the Caribbean and she prepared some wonderful food for us. One dish we loved was plantains, fried and refried. I'd like to make them again, but I want to avoid frying. Is there any other good way to cook plantain?

A. Yes. While frying is most commonly used, there are other methods. Plantains can be diced and added at the last minute to soups, stews or omelets. They can also be diced, boiled until just tender, and seasoned with lemon juice, pepper, a dash of salt and a bit of margarine.

Plantains are slightly higher in calories than bananas, which they resemble. Three-and-a-half ounces, about half a cup of the diced fruit, contains 120 calories, as opposed to 90 for the same amount of banana. But, as you have observed, it is the absorbed oil, at 125 calories per tablespoon, used for frying that quickly runs up the caloric tally.

In addition to the calories they provide, which come mainly from carbohydrate, plantains are an outstanding source of potassium. Other than that, they contribute only minor amounts of various vitamins and minerals.