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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 that the American Academy of Pediatrics (AAP) recommends children between two and eight 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.
Dr Maguire and colleagues wrote online that previous studies showed cow's milk increases the amount of vitamin D in a child's blood while also reducing iron levels.
Dr Maguire, a paediatrician at Toronto's St Michael's Hospital, and his colleagues surveyed the parents of 1 311 children ages two to five at paediatricians’ offices in the Toronto area between 2008 and 2010. They also took blood samples from the children.
The researchers found one cup (250 mL) of milk was tied to a 5 nmol/L increase in 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.
What the study found
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.
That's not a blanket suggestion for all children, however. Dr Maguire and his colleagues say darker skinned children may need three to four cups of milk per day during the winter, when their bodies produce less vitamin D naturally from sun exposure.
Dr Maguire said that the findings seem consistent with previous recommendations.
Dr Patsy Brannon, a professor of nutritional sciences at Cornell University in Ithaca, New York, said the finding of two cups of milk is consistent with the US Department of Agriculture's recommendation for two and three year olds, but said older children need two and a half cups.
Also, she points out, the US Institutes of Medicine and the 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 says infants, children and teens should get 400 IU of vitamin D per day. The average cup of milk has about 100 IU of vitamin D.
Dr Brannon recommends 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.
(Reuters Health, December 2012)
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