Writing in Nature Reviews Immunology, Dr Martin Blaser puts forward a theory that implicates infant formula milk and caesarean births in the disappearance of certain bacterial species that have evolved over time.
Dr Blaser, a professor of Microbiology at New York University School of Medicine, thinks that the vertical transmission of bacteria, in which the infant microbiota is inherited from the mother, is being hampered by caesarean births.
In his comment piece, Dr Blaser also describes the horizontal transmission of bacteria as another contributing factor, pointing to increased sanitation standards, particularly clean water supplies, as detrimental to gut microbiota.
“Such a pattern of transmission suggests that if there are extinctions of microbial taxa in one generation, this loss would be passed down to the next generation,” he said, “unless there are opportunities for the missing taxa to be regained by horizontal transmission.”
While clean water has been crucial for avoiding infections with high-grade and lethal pathogens, an unexpected consequence has been the decreased horizontal transmission of commensal microbiota.
Dr Blaser said that clean water is so important to overall health that the idea that it might have some biological costs by reducing horizontal transmission of the microbiota has received scant attention.
An infant’s first 1000 days are also within Dr Blaser’s focus as he also asks questions on the over reliance of infant formula milk as a replacement for breast milk.
His concern centres on formula milk composition, in which macronutrients form the main ingredient necessary for healthy infant growth.
Dr Blaser highlights the lack of micronutrients in formula, such as particular oligosaccharides, that foster the survival of inherited and beneficial microbiota.
“The composition of breast milk seems to have evolved to favour (select for) those microorganisms that have a well-established commensal relationship, having been passed down over the millennia,” he explains.
“Loss of commensals in one generation (for example, owing to formula milk feeding) and the diminution of both vertical and horizontal transmission, suggests that microbial extinctions become fixed and cumulative across generations.
“There is already evidence to support the worrying notions of microbial extinctions and of cumulative effects over generations.”
Much controversy continues to rage over infant formula feeding versus breastfeeding.
The advantage is primarily convenience, with formula feeding suitable for adaptation to comfort level, lifestyle, and specific medical situations.
The Lancet raised a few eyebrows in 2016 as it claimed formula-fed infants got sick more often than breastfed children did.
Breastmilk has always been held up as the gold standard of infant feeding due to its blend of essential nutrients.
However, in recent years, formula milk manufacturers have sailed close to the wind in their promotional approach, which include nutritional and health claims as well as images that idealize infant formula.
Breast is best
In May, last year the World Health Organisation (WHO) stepped in with a report that recommended the use of clear instructions on how to use the product and carry messages about the superiority of breastfeeding over formula and the risks of not breastfeeding.
Nestlé informed DairyReporter that they backed the report’s findings that breast is best up to two years of age, where possible.
“We support the WHO recommendation of six months exclusive breastfeeding, followed by the introduction of adequate nutritious complementary foods along with sustained breastfeeding up to two years of age and beyond," a company spokesperson said.
“For infants who cannot be breastfed as recommended, infant formula is the only suitable breast milk substitute (BMS) recognized as appropriate by the WHO.”
Source: Nature Reviews Immunology
Published online ahead of print: doi:10.1038/nri.2017.77
“The theory of disappearing microbiota and the epidemics of chronic diseases.”
Authors: Martin Blaser