07:52am Tuesday 14 July 2020

High milk intake risks iron deficiency in babies

Iron is essential for healthy brain development, and a lack of the nutrient in babies and toddlers, when the brain is developing rapidly, is associated with subsequent small but important differences in brain function and in child behaviour and learning.

The paper in today’s New Zealand Medical Journal (NZMJ) found that seven percent of New Zealand newborns are iron deficient and established that iron stores are lower in babies whose mothers consumed higher quantities of milk during their pregnancy.

“While milk is an important source of calcium it is a poor source of iron.  Milk is also quite filling and so can reduce the appetite for others foods that are better sources of iron,” says paediatrician, Associate Professor Cameron Grant, from the University of Auckland where the GUINZ study is based. 

“Pregnant women with iron deficiency are more likely to go into premature labour or deliver a baby with low birth weight.  They are also more likely to be iron deficient while they are breastfeeding”, he says.

Using cord blood samples from 131 children from the Growing Up in New Zealand birth cohort, Dr Grant and his team determined the iron status of each newborn. The results were compared to information collected in face-to-face interviews with the mothers to establish whether maternal and infant demographics, pregnancy health and history, and dietary factors were associated with iron status at birth.

“Although the sample of children we tested was quite small, they are broadly generalisable to all children born in New Zealand today, and the results give us a good indication of iron deficiency as an issue,” says Dr Grant.

Iron deficiency is the most common micronutrient deficiency worldwide, with pregnant women and children under five most at risk. The condition is twice as common in young New Zealand children (six months to two years old) than it is in children of the same age living in Australia, Europe or the United States.

Although there is currently no data available for mothers-to-be in New Zealand, the frequency of iron deficiency among women at childbearing age (over 15 years) has increased from three percent in 1997 to seven percent in the most recent survey, conducted in 2008/09.

To prevent negative effects on their child’s early development, Dr Grant recommends that pregnant women who drink large amounts of milk each day take iron supplements.

“An alternative would be to increase the nutrient content of milk consumed by mothers-to-be to keep both the mother and child healthy,” he says.

Growing Up in New Zealand is University of Auckland-led research and funded by multiple government agencies. The government contract for the study is managed by the Families Commission.

Growing Up in New Zealand is a longitudinal study following the lives of approximately 7,000 families that provides a contemporary, population relevant picture of what it is like to be a child growing up in New Zealand in the 21st century. 

The ethnicity and socio-demographic characteristics of the children and families in the cohort are broadly generalisable to those of children being born in New Zealand today. 

Growing Up in New Zealand is unique for its inclusion of significant numbers of Maori, Pacific and Asian children as well as New Zealand European and other ethnicities, and for the representation of families from across the socioeconomic spectrum. This study is unlike any other data source in its ability to contribute evidence of what works in contemporary New Zealand to inform policy evaluation and development.

The full article is available online at this link.


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