Milk, it does a body good. But how much milk does the most good?
According to new research from the University of Toronto, while milk builds bones, too much may not be so great for children’s iron levels.
Milk is fortified with vitamin D, which can be hard to manufacture naturally without sufficient exposure to sunlight. But for some reason that’s not entirely clear, drinking milk can decrease iron stores; kids who slurp up lots of milk tend to have severe iron deficiency.
The solution? More specific guidelines for how much milk children should drink, advice that doesn’t currently exist in any helpful form for parents. The American Academy of Pediatrics (AAP) advises vitamin D supplements for kids who aren’t drinking four cups of milk a day. But the AAP’s iron recommendations state children should be drinking just two to three cups.
“One of the most common questions pediatricians get from parents is how much milk should my child be drinking?” says lead author Dr. Jonathon Maguire, a researcher at St. Michael’s Hospital in Toronto. “The amazing thing is, children’s doctors don’t know.”
Maguire tried to address that oversight by linking children’s milk intake to their vitamin D and iron levels. He and his colleagues looked at more than 1,300 children ages 2 to 5, taking into account how much time they spent outside, their skin pigmentation (dark-skinned children have a harder time getting enough vitamin D from the sun), their body-mass index and whether they drank from bottles, which can increase milk-drinking because bottles tend to be refilled. Blood samples showed that those children whose parents reported they drank more milk had increased vitamin D levels and lower iron stores. “It’s a bit of a trade-off,” says Maguire.
After crunching the numbers, the researchers settled on the threshold amount for where milk’s vitamin D benefit was offset by the drop in iron — two cups. Kids who drank two cups of milk daily had healthy levels of Vitamin D and iron, according to the results of the study, published in the journal Pediatrics. “Beyond that, any more milk isn’t giving much more benefit in terms of vitamin D but children are still paying a price because their iron stores are going down,” says Maguire.
There are some caveats, particularly for children with darker skin, who don’t make as much vitamin D from the sun. In the winter, doctors suggest they take vitamin D supplements. But the average child doesn’t appear to need extra fortification beyond sunshine and vitamin D-laden foods such as fatty fish such as salmon, mushrooms and fortified cereals).
The somewhat surprising recommendations may require some new thinking on the part of parents, who have been taught to see milk as a staple of kids’ diets. “Maybe,” says Maguire, “too much of a good thing is not such a good thing.”