(RxWiki News) Milk is that classic childhood drink that we always hear is good for kids' bones. That's partly true, but there's also a tradeoff in drinking milk. The drink is finding a happy medium.
Milk is a source of vitamin D, which does help children's bones. But milk can also have an effect on a child's iron levels.
If Goldilocks were looking for "just the right amount" of milk to drink, the magic number would be two cups. Two cups of milk keeps vitamin D and iron levels at the best place.
For dark-skinned children not taking vitamin D supplements in winter time, though, three to four cups appears best.
"Two cups of milk a day is best for kids."
The study, led by Jonathon L. Maguire, MD, MSc, from the Applied Health Research Centre of the Li Ka Shing Knowledge Institute at the University of Toronto's St. Michael’s Hospital in Canada, looked at the impact of drinking cow's milk in children.
Cow's milk increases vitamin D in the human body, but it decreases iron levels. Finding the balance between these two nutrients is important in determining how much milk is appropriate for children.
The researchers studied 1,311 children, aged 2 to 5, whose milk intake was recorded by their parents. The researchers then measured the levels of vitamin D and iron in the children, taking into account whether the child was taking any vitamins that included vitamin D.
They also took into account the season of the year and the children's skin pigmentation since both of these play a part in how much vitamin D can be absorbed from sunlight.
As expected, the researchers found that the more milk the children drank, the lower their iron levels were, and the higher their vitamin D levels were.
Overall, drinking two cups of cow's milk each day was best in maintaining good vitamin D levels without causing children to lose too much iron.
For children with darker skin who were not taking vitamin D supplements during the winter time, three to four cups of cow's milk was best for keeping their vitamin D levels high enough.
"Vitamin D deficiency in children has been linked to bone health issues and iron deficiency has been linked to anemia and delays in cognitive development," said Dr. Maguire, in a release about the study. "Being able to answer parent's questions about healthy cow's milk intake is important to avoiding these potentially serious complications of low vitamin D and iron stores."
The study was published December 17 in the journal Pediatrics. The research was funded by the Canadian Institutes of Health Research Institute of Human Development, Child and Youth Health and the Institute Nutrition Metabolism and Diabetes, as well as the St. Michael's Hospital Foundation and a grant from The Hospital for Sick Children Foundation. The authors declared no conflicts of interest.