The lower levels of protein found in breast milk compared to formula milk could explain why breastfed babies grow more slowly than their formula-fed counterparts, new EU-funded research suggests. According to the scientists, the findings highlight both the importance of promoting breastfeeding and the ongoing need to improve the composition of formula milk. EU support came from the EARNEST ('Early nutrition programming: long-term efficacy and safety trials and integrated epidemiological, genetic, animal, consumer and economic research') project, which is financed under the 'Food quality and safety' Thematic area of the Sixth Framework Programme (FP6), as well as from two earlier projects funded through the Fifth Framework Programme (FP5). A number of studies have revealed a link between rapid weight gain in infancy and a tendency towards obesity later in life. Furthermore, formula-fed children are known to grow faster during the first year of life than babies that are breastfed. In this study, the researchers investigated whether the higher levels of protein found in formula milk could be behind this phenomenon. The scientists recruited parents who had already opted to bottle feed. They then divided more than 1,000 formula-fed babies from 5 countries into 2 groups, one of which received formula with high protein content while the other was given formula with lower protein content. The children were weighed and measured at 3, 6, 12 and 24 months of age. Their development was compared to that of a third 'control' group, made up of babies who were exclusively breastfed. The results are published in the American Journal of Clinical Nutrition. After two years, the formula-fed children were the same height, but those fed the high-protein formula were heavier than those fed the low-protein formula. Because there was no difference in height, which is associated with lean body mass, the researchers conclude that the difference in weight and in body mass index is probably due to a difference in body fat. Interestingly, the children fed the low-protein formula were in the same weight range as the breastfed group. 'These results from the EU Childhood Obesity Programme underline the importance of promoting and supporting breastfeeding because of the long-term benefits it brings. They also highlight the importance of the continual development and improvement in the composition of infant formula,' said the lead author of the paper, Professor Berthold Koletzko of the University of Munich in Germany. 'Limiting the protein content of infant and follow-on formula can normalise early growth and might contribute greatly to reducing the long-term risk of childhood overweight and obesity,' he added. The protein content of the formulae used in the study fell within the limits allowed by the EU Directive on Infant and Follow-on Formulae and what was commercially available in Europe at the time of the study. The protein content of formula milk was at its highest (4 grams per 100 kilocalories) in the 1970s, when those designing the formulae were motivated by the desire to ensure that children fed formula would not suffer from a lack of protein. In contrast, there were few concerns about the possible effects of giving children too much protein. Protein levels have fallen since the 1970s (the low- and high-protein formulae used in this study contained 1.77 g/100kcal and 2.9 g/100kcal of protein, respectively), but studies show that formula-fed children continue to take in more protein than those that are breastfed. The scientists now plan to continue observing the children to see if those fed low-protein formula will turn out to have a lower risk of obesity later in life.