Here are some tips on keeping the body going while being very active. This is excellent advise not only for adults but children too. Especially, children who are in competitive sports.
Keep a well-balanced diet. Keep to the basic food groups not overdoing any particular group.
Drink lots of pure water. By the time you are thirsty your body is dehydrated. Keep the body hydrated throughout the active periods and throughout the day.
Electrolytes (sodium and potassium) are key to staying hydrated. Just make sure you watch the sugar intake.
Carbohydrates are important, especially for children. There are excellent sources of carbohydates that are not refined or sugary.
More vitamins for active adults and children are not necessary. The key is to take the correct amount of vitamins.
A healthy meal before an activity or sport competition is very wise. We need our energy throughout.