Kids' Diet: Two Cup Limit for Milk
Each cup consumed was linked to 6.5% higher vitamin D and 3.6% lower iron on average, the group reported online in Pediatrics.
Two cups a day seemed sufficient to keep vitamin D levels up with minimal effect on iron for most 2- to 5-year-olds, they found in the primary practice-based study, although children with darker skin pigmentation may require more milk during winter months.
The study findings fit with guidelines from the American Academy of Pediatrics that suggest no more than two cups (500 mL) of cow's milk a day from ages 2 to 6 to avoid iron deficiency.
Both nutrients are critical for kids. Vitamin D is necessary for bone health and likely disease prevention too; iron plays a key role in brain and psychomotor development.
The study included 1,311 healthy children, ages 2 to 5, seen at seven large Toronto primary care group practices in the TARGet Kids! research network.
Parents reported that the average daily intake of cow's milk was a little under 2 cups (460 mL).
About a third of the children had 25-hydroxyvitamin D levels under the 75 nmol/L threshold recommended as optimal in Canadian guidelines; 6% were deficient with levels under 50 nmol/L.
Serum ferritin averaged 31 μg/L, with 4% falling under 12 μg/L.
How appropriate those iron levels might be wasn't clear, as there aren't any consensus recommendations on optimal iron stores for children, the investigators noted.
Children who drank three 250-mL cups of milk a day versus two had:
- 5.5-nmol/L higher 25-hydroxyvitamin D (95% CI 3.9 to 7.1)
- 1-μg/L lower serum ferritin (95% CI 0.3 to 1.7)
That group apparently required 3 to 4 cups of cow's milk per day to maintain 25-hydroxyvitamin D at the same threshold, although as the researchers noted, the observational results couldn't determine causality.
Higher milk intake didn't appear to be as good for children still using a bottle. In these children, higher milk intake didn't correlate with higher vitamin D levels, but were associated with sharper decreases in iron levels across gender, skin pigmentation, season, and vitamin D supplementation scenarios.
Possible explanation for this findings could be that parents under-reported milk intake from bottles, or other things like juice put in them, or that bottle use by this age group replaces vitamin D- and iron-containing solid foods, Maguire's group suggested.
"Regardless, reported cow's milk consumption among children using a bottle appears to have little benefit on micronutrient stores, suggesting that bottles should not be filled with cow's milk or used at all in this age group," they wrote.
Parent reporting was a limitation of the study, as was inclusion of children in a single urban setting at a northern latitude, which may limit how generalizable the results are.
The
TARGet Kids! program was supported overall 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.
The analysis was supported in part by the Canadian Institutes of Health Research. The Pediatric Outcomes Research Team was supported by a grant from The Hospital for Sick Children Foundation.
The researchers reported no conflicts of interest.
The analysis was supported in part by the Canadian Institutes of Health Research. The Pediatric Outcomes Research Team was supported by a grant from The Hospital for Sick Children Foundation.
The researchers reported no conflicts of interest.
Primary source: Pediatrics
Source reference:
Maguire JL, et al "The relationship between cow's milk and stores of vitamin D and iron in early childhood" Pediatr 2013;131:e144–e151.
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