To combat that problem, the Academy recently doubled the amount of vitamin D it recommends for healthy infants, children, and adolescents—from 200 IU (international units) to 400 IU per day.

Many new mothers are vitamin D deficient and can't deliver enough vitamin D to their babies while breastfeeding and may need to consider giving their babies vitamin D supplements starting at birth. Baby formula has enough vitamin D to meet the new recommendations.

"It is important to remember that babies who receive a mixture of breast milk and formula should also get a vitamin D supplement of 400 IU per day," says Anita Moonjely, MD, UI Children's Hospital pediatrician. "These infants are unlikely to drink 32 ounces of formula per day, the amount needed to supply 400 IU of vitamin D."

Check with your physician to see which way is best for you and your family to add vitamin D to your diets.

Here are some suggestions.

• Give older children and teenagers multivitamins
• Listen to Grandma—a teaspoon of cod liver oil contains 400 IU of vitamin D
• Encourage children to drink vitamin D-fortified milk, but be aware that your child will have to drink 32 ounces of milk a day to get the daily recommended 400 IU