The American Academy of Pediatrics recommends a daily 400 IU vitamin D supplement for all breast-fed babies and babies drinking less than 32 ounces of formula a day.

The point is to avoid rickets, a condition that causes brittle and deformed bones and retards growth, says Dr. Ronald Marino, associate chairman of pediatrics at Winthrop University Hospital in Mineola, N.Y.

"Vitamin D is the sunshine vitamin. It's made in the skin when we're exposed to sunlight," he says. "If you're formula feeding, your baby is getting plenty of vitamin D because it's added to the formula."

But if you are breast-feeding, you should give your newborn to 6-month-old the combined liquid vitamin A, C and D formulation because moms don't produce enough vitamin D through breast milk, Marino says. Vitamin D is sold in combination with A and C.

Don't interpret this as a suggestion babies be exposed to sunlight, Marino warns. Babies younger than 6 months shouldn't be in the sun due to the risk of sunburn and future skin cancer.

All children should wear sunscreen, and it blocks the rays needed for vitamin D production.

And don't go crazy with supplementation, Marino warns. Vitamin D can cause vitamin toxicity if you overdo it.

Once babies hit 6 months old, most pediatricians recommend multivitamin supplements for all, Marino says. Check with your pediatrician for further guidance.