Babies who continue to receive any breastmilk beyond the first six months of life have a healthier pattern of growth than those breastfed for less time or not at all, according to a new Deakin University study.
The study – published today in the journal Obesity – shows prolonged breastfeeding correlates with a healthier body mass index (BMI) for children across the first five years of life.
Lead author Dr 'Jazzmin' Miaobing Zheng, a research fellow in Deakin's Institute for Physical Activity and Nutrition (IPAN), said her study was the first to examine the relative impact of breastfeeding duration and the timing of solid food introduction on children's growth patterns over time, from birth to age five.
"We found children who were breastfed for more than six months had a healthier body weight from ages three months to five years, compared to those breastfed for less than six months.
"That includes any breastfeeding, even if occasional or supplemented with formula. The beneficial effects of longer breastfeeding duration also remained evident after accounting for a child's birth weight, maternal factors like education level and pre-pregnancy body weight status.
"In contrast, we found no effect of the timing of solid food introduction – if before or after six months of age – on children's body weight at age five."
Dr Zheng said the study's findings identified a possible avenue to address Australia's unprecedented levels of childhood overweight and obesity.
"Right now, one in five Australian kids under five are above a healthy weight, and these children have a higher likelihood of overweight and obesity later in life," she said.
Dr Zheng's research will continue to explore how breastfeeding protects against obesity.
"At the moment this is not exactly clear, but the most likely reason is the slower growth of breastfed babies," she said.
"Systematic reviews have suggested that rapid infant growth – defined as crossing one percentile line in the growth chart, and known to parents in their child record health books – is associated with a three times higher risk of subsequent overweight or obesity," she said.
"Breast milk also has a lower protein content than infant formula, which is likely to be protective as higher protein intake during infancy has been associated with an increased risk of subsequent overweight and obesity."
Data for the Deakin study was collected from 542 children as part of the Melbourne Infant Feeding, Activity and Nutrition Trial (InFANT) Program led by IPAN Professors Karen Campbell and Kylie Hesketh.
The proportion of children in the sample who were breastfed for more than six months was 59 per cent, which is close to the national estimate.
Dr Zheng said it was important to consider the potential barriers to breastfeeding past six months, including a mother's earlier return to work, cultural expectations and practices, and community support.
"It's also important to acknowledge that for some women breastfeeding or prolonged breastfeeding may not be possible," she said.
"But overall our findings strongly endorse current policies, public health campaigns, and interventions that seek to promote and support breastfeeding."