Health & nutrition
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 organisation 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 anaemia.
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 paediatrician 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 paediatricians' 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 millilitres) of milk was tied to a 5 nanomoles per litre (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.
SUPPLEMENTS AND OTHER SOURCES
That's not a blanket suggestion for all children, however.
Maguire and his colleagues say darker skinned children may need 3 to 4 cups of milk per day during the winter, when their bodies produce less vitamin D naturally from sun exposure.
Maguire told Reuters Health that the findings seem consistent with previous recommendations.
"I don't think there is too much cause for concern. I think this is probably old news for some parents," he said.
Patsy Brannon, a professor of nutritional sciences at Cornell University in Ithaca, New York, said the finding of 2 cups of milk is consistent with the U.S. Department of Agriculture's recommendation for two and three year olds, but said older children need 2.5 cups.
Also, she points out, the U.S. Institutes of Medicine and AAP recommend a vitamin D level in children of at least 50 nmol/L, which is lower than the Canadian society's suggestion.
Currently, the AAP recommends infants, children and teens get 400 international units (IU) of vitamin D per day. The average cup of milk has about 100 IU of vitamin D.
Brannon recommends taking a daily vitamin D supplement to reach that recommendation, but adds that people can also get the vitamin from fortified cereals, grains and other foods.
"There are other sources of vitamin D in the diet besides what comes from milk. We have to be concerned about excessive milk consumption in this age group," she said.