Hit the sweet spot

500 mL of milk a day hits right balance for little kids

By imagerymajestic/FreeDigitalPhotos.net

           Can there be too much of a good thing when you are talking about little kids and cow’s milk? A new study suggests there can.
The work, by scientists in Toronto, says that children between the ages of two and five should be drinking half a litre (about  17oz)  or approximately two eight-ounce cups of milk a day.
Less than that and kids may not be getting enough vitamin D, the study suggests. But more than that, and the stores of iron in their blood — which are essential for a developing brain — may start to slip below acceptable levels.
The study was led by Dr. Jonathon Maguire, a pediatrician and researcher at St. Michael’s Hospital in Toronto. It is published in this week’s issue of the journal Pediatrics.
“Cow’s milk is a very important staple in our western diet for children. I don’t want to underestimate the importance of cow’s milk,” Maguire said in an interview about the study.
“Our question was really: Well, how much?”
It’s a query pediatricians face all the time, Maguire said. And they haven’t had a good answer to give because experts are divided on the issue.
Some organizations have argued that young children should consume a litre of milk a day to get the vitamin D they need to build strong bones and avoid rickets, a formerly common bone-softening condition. (Milk is fortified with vitamin D.)
But other groups have warned that children’s consumption of cow’s milk should be curtailed because some studies have shown that kids who drink a lot of milk can have low levels of iron in their blood.
Low iron can lead to anemia, where the body produces too few of the red blood cells that transport oxygen throughout the body.
“It looks like in children who have iron deficiency severe enough to cause them ... to have anemia, those children have difficulties with their cognitive development. Over time they’re not quite as bright as other children,” Maguire said.
Iron deficiency in young children isn’t uncommon in Canada. While it’s just a guesstimate — Maguire said recent studies haven’t been done — it is believed between 10 per cent and 20 per cent of young children in Canada may have low iron stores.
Given the confusing advice and the fact that milk consumption by preschoolers seems to involve a trade-off between vitamin D and iron, Maguire and some colleagues decided to try to find the sweet spot.
They enrolled 1,311 healthy Toronto children ages two to five in a study, evaluating samples of their blood for vitamin D and iron stores and gathering information from parents about the amount of milk the kids drank.
The researchers found that about 500 millilitres of milk a day for most children was the right amount to have adequate levels of vitamin D and iron.
There was an exception: during winter, children with dark skin didn’t hit the vitamin D target with 500 mL daily. The study suggests in winter children with dark skin may need a vitamin D supplement as well as the milk.
The researchers also saw this previously reported inverse relationship, where more milk consumed meant higher vitamin D levels but lower iron stores.
What’s behind the puzzling interplay? The director of the nutrition and metabolism research program at B.C. Children’s and Women’s Hospitals said little kids who drink a lot of milk often aren’t eating enough solid foods to get the needed amount of iron. (There is little iron in milk.)
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