It’s a lesson in life cycle nutrition. We have different nutrition needs at various stages of life and applying adult dietary approaches to children is potentially hazardous – this is just one example.
One senior researchers in this area is Professor Berthold Koletzko from Munich University in Germany. His research is central to our understanding that infants need lower protein intakes than previously thought. The story starts with observational studies that noted that babies and toddlers to 2 years of age with rapid weight gain had an increased risk of obesity later in life. Further, those babies who were breastfed – and the longer the better – were far less likely to have such rapid weight gain and consequently have a lower risk of being overweight or obese years later. We’re not talking small number here. The magnitude is in the range of a 15-25% lower rate of obesity in breastfed kids.
The question therefore is what is it that is protective about breastfeeding? Or conversely, what is it about formula feeding that promotes the increased weight gain?
One of the differences between the two forms of milk is the protein content. Human milk is an amazingly complex mix of proteins involved not just in growth, but those that have roles in immunity, digestion and in promoting a healthy gut. In short, the quality and quantity of proteins is very different to those found in formula. To try to replicate the quality of protein, particularly with respect to the amino acid profile, infant formulas have a far higher quantity of protein present.
This is even more marked for babies 6-12 months of age. The protein content of human breast milk declines over the first year (human milk is far higher in carbohydrate and lower in protein, reflecting the human infant’s nutrition needs).
“The protein content of human breast milk declines over the first year”-
Conversely, follow-on formulas designed for 6-12 month old infants tends towards a higher protein content that the starter formulas. The result is that formula-fed infants consume about twice the protein of breast-fed infants.
This observation lead researchers to hypothesise that it is this considerably higher protein intake that is driving the rapid weight gain in formula fed infants. So Professor Koletzko and his team, along with several other European countries in the European Childhood Obesity Project, set out to test the hypothesis. They compared three groups of infants. The reference group was infants breastfed for at least 3 months. Those who were being formula fed were then randomized to receive either the conventional higher protein formula, or an intervention formula with a lower protein content closer to that found in breast milk (although still slightly higher)
So here’s what they found. There were no differences in the length of babies by 12 months, but from 6 months of age the higher protein formula group had significantly higher weight, weight-for-length and BMI compared to the lower protein formula group (Figure 1).
Figure 1: Median and 90th and 95th percentiles of BMI by study group from 3 months to 6 years of age and the number of children (Weber et al., 2014).
By 6 years of age the differences between the groups were marked with the higher protein group showing far higher BMI values and rates of overweight compared to the breast fed group. The lower protein formula fed children were far closer to the breastfed group, such that by 6 years of age there was no significant difference between the groups.
Interestingly, these differences were more marked in those children at the high end of the BMI percentile range – in other words the bigger children had an amplified risk of overweight if fed a higher protein formula. A lower protein formula normalised this risk in line with breastfeeding.
“A lower protein formula normalised this risk in line with breastfeeding.”-
So what can we do? This research adds to the knowledge we already have that “breast is best”. We have a fantastic uptake of breastfeeding in this country with around 96% of mums choosing to do so at birth. However, there is a rapid drop-off in rates such that by 3 months, only 39% of babies are exclusively breastfed and by 5 months only 15%. Greater support from lactation consultants and other health professionals (as well as societal shifts in attitudes to breastfeeding) could significantly boost these rates. But perhaps also knowing the clear benefits of breastfeeding might also help mums to keep going for longer.
“This research adds to the knowledge we already have that “breast is best'”-
However, breast-feeding is not always possible or for a myriad of reasons is not the choice a mother wants to make. Modern formulas are improving all of the time and offer a safe alternative. But this research clearly shows they can be better. A change in legislation will allow formula companies to reduce the protein content to one closer to that in breastmilk, while maintaining the protein quality. This has the potential to make a significant impact on our childhood obesity rates. For now, parents can compare the protein content of currently available formulas and choose those at the lower end of the range.
Finally, we need more research to understand the implications of a higher protein intake beyond infancy and into the first few years of life. Until we understand more, it seems prudent to avoid excessively high protein intakes and instead focus on a broad range of whole foods and cutting back on the amounts of discretionary foods with a high energy-density and low nutrient-density.
Dr Joanna McMillian
Accredited Practising Dietitian