Three decades ago, it was proposed that disease risk in human adults may be programmed by environmental influences acting on hormones, metabolites and neurotransmitters, during sensitive periods of early development. Since then, much supporting evidence for this hypothesis has accumulated from epidemiologic and experimental studies and clinical trials. For example, numerous studies have reported programming effects of infant feeding choices on later obesity. Three meta-analyses of observational studies found that obesity risk at school age was reduced by 15 to 25 per cent with early breastfeeding compared with formula feeding.
A new paper in the American Journal of Clinical Nutrition reports on investigations into whether breastfeeding protects against later obesity by reducing the occurrence of high weight gain in infancy. One reason for this may be the lower protein content of human milk compared with most infant formula (the early protein hypothesis).
Researchers are testing this hypothesis in the European Childhood Obesity Project, a double-blind, randomized clinical trial that includes >1000 infants in 5 countries (Belgium, Germany, Italy, Poland, and Spain).
Healthy infants who were born at term were randomly assigned to receive for the first year infant formula and follow-on formula with higher or lower protein contents, respectively. The follow-up data obtained at age 2 y indicate that feeding formula with reduced protein content normalizes early growth relative to a breastfed reference group and the new World Health Organization growth standard, which may furnish a significant long-term protection against later obesity.
Researchers conclude that infant feeding practice has a high potential for long-term health effects, and the results obtained should stimulate the review of recommendations and policies for infant formula composition.
It is interesting that the authors do not also suggest public health action to encourage higher rates of breastfeeding.
All current guidelines, including those from the Department of Health (DH), recommend exclusive breastfeeding for newborns and for the first six months of infancy.
Breast milk provides all the nutrients required at this age in a form that is hygienic and easy to digest. The protein, carbohydrate and fat profiles are unique to breast milk and differ in many ways from other animal milks. Breast milk also contains a range of bioactive components, including anti-microbial and anti-inflammatory factors, digestive enzymes, hormones and growth factors. Growth factors are thought to be important for gut maturation. Lactoferrin is one of several specific binders in human milk that greatly increase the bioavailability of micronutrients.
The role of leptin in breast milk may be of particular importance in the early development of both adipose (fatty) tissue and appetite regulatory systems in the infant, and ultimately on propensity to obesity in later life.
Despite the many benefits of breastfeeding, less than 1 per cent of women in the UK are still breastfeeding at 6 months. Studies have shown that women in the UK experience substantial barriers to breastfeeding.