Two cups of cow's milk per day may be enough for most kids to have the recommended amount of vitamin D in their blood while maintaining a healthy iron level, suggests a new study.
"One of the common questions I get from parents when their kids become toddlers is, ‘how much milk should they be drinking?' But we didn't have a good answer," said Dr. Jonathon Maguire, the study's lead author from Toronto's TARGet Kids! Collaboration.
One reason for the confusion, according to the researchers, is the American Academy of Pediatrics (AAP) recommends children between 2 and 8 years old drink two cups of milk per day, but in another guideline, the organization also says children need supplemental vitamin D if they drink less than four cups per day.
The researchers write in the journal Pediatrics that previous studies showed cow's milk increases the amount of vitamin D in a child's blood while also reducing iron levels. Iron, which the body can get from meats and beans, is important for developing brains and protecting against anemia.
Vitamin D, which is naturally produced in the body during sun exposure, helps the body absorb calcium and prevents the bone-softening disease rickets. People also get the vitamin by eating fortified foods, such as milk and fatty fish.
Maguire, a pediatrician at Toronto's St. Michael's Hospital, and his colleagues surveyed the parents of 1,311 children, who were between 2 and 5 years old and at pediatricians' offices in the Toronto area between December 2008 and December 2010. They also took blood samples from the children.
The researchers found one cup (250 milliliters) of milk was tied to a 5 nanomoles per liter (nmol/L) increase of vitamin D in the children's blood, and a small decrease in iron levels.
The Canadian Pediatric Society suggests children maintain a vitamin D level in their blood of at least 75 nmol/L. On average, the children were drinking just under two cups of milk per day, and were exceeding their recommended vitamin D level.
The researchers concluded that two glasses of cow's milk per day is enough to keep most kids at the suggested vitamin D levels while also maintaining a healthy amount of iron.