Children should take vitamins, mostly because so many kids don’t eat enough fruits and vegetables, and because their diets are often full of processed and refined foods. However, vitamin supplements shouldn’t be substitutes for whole foods, especially fruits and vegetables.
Teach children of any age to enjoy healthy food by involving them in its preparation, even if they’re only in the kitchen to observe. In "The Healthy Kitchen," Rosie Daley and I give a number of ideas for recipes and snacks that kids will like. Also, try to discourage your children from eating too much fast food, processed food, sugar and caffeine (in cola and other soft drinks). There’s no harm in the occasional ice cream, pizza or candy bar in the context of a well-balanced diet, but try to encourage snacking on healthier foods – fresh or dried fruit; a small handful of raw, unsalted nuts such as cashews and walnuts; a piece of flavorful, natural cheese; or a piece of dark chocolate.
As far as supplements are concerned, give children a complete antioxidant formula as well as multiminerals. Be sure to keep the vitamins out of the reach of young children – some supplements for kids taste and look like candy and there is a danger of overdosing, especially when supplements contain iron.