Baby needs time in the sun

Infants north of 55 degree latitude up to one year old need 800 international units (IU) of vitamin D between October and April because of the lack of sunlight. They need 400 IU the rest of the year.

"The standard care for years in Canada, and in some other industrialized countries for decades, has always been to supplement infants up to one year of age with 400 IU of vitamin D," says Dr. Raphael Sharon, an Edmonton pediatrician and vice-president-elect of the pediatric section of the Alberta Medical Association.

Fortified milk, cereals and oily fish are the most common food sources for vitamin D, but the best source is sunlight, which prompts the body to make the vitamin when it hits the skin.

Baby formula accounts for 400 IU daily, so formula-fed babies only need an extra 400 IU of vitamin D in the winter.