DEAR DR. DONOHUE: I have five grandchildren ranging in age from 7 to 16. All of them are involved in sports, including baseball, softball, basketball and soccer. In discussing physical fitness with my grandchildren, I was told that prior to participating in their sports, they often do not eat a properly balanced meal. They tend to skip breakfast, lunch or dinner, depending on the time of the activity. Would you comment on the proper diet for youngsters participating in physical activities? — S.L.

ANSWER: All your grandchildren are at ages when they’re growing rapidly. That in itself is a major consideration for pushing good nutrition. Add to it an active sports life, and attention to nutrition becomes a must.

Most athletic energy comes from stored carbohydrate — glycogen. Glycogen is found in muscles and in the liver. It’s the major fuel for activity. We have quite a large glycogen fuel tank, but supplies of it can be depleted if no attention is given to what’s eaten. Breakfast is especially important. Your grandchildren have gone about 12 hours without any food: eight hours of sleeping and four hours from dinner to bedtime. If they have four hours from breakfast until they are engaged in physical activity, they can eat a large meal. It takes about four hours for the stomach to empty of food.

A large breakfast is one with lots of carbohydrates — pancakes, whole-grain cereals, whole-grain bread or toast, low-fat milk, fruit and fruit juices. If they have only an interval of about an hour before they’re practicing, then they should eat less food. A bowl of cereal, some fruit or fruit juice and toast with peanut butter and jelly. That meal should pass through the stomach moderately fast, so they won’t have a full stomach when they’re running around. Two tablespoons of peanut butter has up to 190 calories, and it’s also a good source of protein.

In addition to carbohydrates, protein intake has to be kept in mind. Lean meat, fish, poultry, beans and eggs are good protein foods. Your grandchildren shouldn’t skip any meal, but breakfast is especially important.

TO READERS: People interested in learning the ins and outs of fitness will find useful information in the booklet on that topic. To order a copy, write: Dr. Donohue — No. 1301, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I am a part-time assistant coach at a high school, just because I love sports. One of our players had a tooth knocked out this past football season. How should that be treated? I’m not sure we did the right thing. — H.L.

ANSWER: The tooth should never be held by its roots, only by the biting surface. The roots have delicate ligaments that anchor it back in its socket. If the tooth is covered with dirt and grime, put it in a bowl of warm water for a short time, a minute at most. Don’t scrub it, and don’t put it under running water. Try to position the tooth back into its socket. Have the athlete gently bite down on gauze to keep the tooth in place.

If you can’t reposition it, then put it in a container and cover the tooth with milk or salt water (1/4 teaspoon of salt in a cup of water). You might want to look into investing a little money in a commercially available container that comes with fluid for transporting a tooth. The brand name of one of these containers is Save-A-Tooth, and you can reach the manufacturer at www.save-a-tooth.com. The most important treatment is getting the player to a dentist ASAP.

DEAR DR. DONOHUE: Do you think a mouth guard is necessary for basketball? My son’s school insists on them. I think it’s overkill. — B.P.

ANSWER: I think mouth guards should be worn in any sport where there’s a danger of losing a tooth or damaging one. Basketball is said to be a noncontact sport, but it isn’t. Tell your son to clean his mouth guard after every use. Bacteria and molds can take up residence in them if they aren’t kept clean.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.