title: Development of colonic fermentation in early life
Creators: name: Parrett, Alison M
Publisher: name: University of Glasgow
Year: 2001
Subjects: subject: Physiology.

description: Carbohydrates that escape digestion and absorption in the small intestine enter the colon where they are anaerobically metabohsed by the colonic bacteria. Colonic fermentation of carbohydrates produces short chain fatty acids (SCFA) (Cummings and Englyst, 1987) which are rapidly absorbed which salvages energy and prevents osmotic water loss (Kien et al., 1990). Bacterial colonic fermentation has been well investigated in adults but our knowledge in infants is limited. Neonatal diet and the weaning period are thought to be critical factors to the establishment of the intestinal microflora. The early events m bacterial colonisation of the gut may be critical in establishing the health of the infant as well as determining the properties of the adult flora. It is well established that the flora of breast-fed and formula-fed infants differs (Balmer and Wharton, 1989) and this is reflected in the profile of faecal SCFA (Edwards et al., 1994). However there is no information on the flora and faecal SCFA of infants that receive a mixture of breast milk and formula milk before weaning. As more mothers begin breast-feeding and then do not continue, this 'mixed fed' group are increasingly important in the UK. Little is known about the factors which change the colonic micro flora at weaning when infants are exposed to a wide range of new substrates. If substrates are undigested and unfermented these substrates will pass through the colon unmetabolised causing increased faecal output and possible diarrhoea. Very few studies have investigated the effect of weaning on the faecal flora. Many weaning foods will contain dietary fibre and other complex carbohydrates and it is important to know how easily these will be fermented and the effect these substrates will have on the development of the colonic microflora. We wished to test the hypothesis that neonatal feeding practice determines the rate and pattern of development of the colonic micro flora during weaning. After consideration of fermentation models an in vitro fermentation model (modified from Adiotomre et al., 1990) was chosen to determine the ability of infants to ferment a range of simple and complex carbohydrates. Breast-fed and formula-fed infants were investigated in a cross-sectional pilot study. Faecal samples were collected from infants at different stages during weaning. The cross-sectional study demonstrated that there were differences in the fermentation capacity of breast-fed and formula-fed infants. In formula-fed infants there was no difference between pre-, early and late weaning for any substrate. In breast-fed infants the ability to ferment raftilose increased at early weaning and the ability to ferment soyabean polysaccharide increased at late weaning. In both groups cultures containing soyabean polysaccharide, produced lower total SCFA than adults, even at late weaning. The pilot study indicated the need for a larger number of infants that would be followed longitudinally in order to draw definitive conclusions. The pilot study allowed us to design the longitudinal study which investigated the relative fermentation capacity for a wider range of carbohydrates. Results of the longitudinal study confirmed those of the cross-sectional study. All infant feeding groups were equally able to ferment the simple sugars and oligosaccharides at all development stages. There were significant increases in total SCFA produced in cultures containing the complex carbohydrates at late and very late weaning breastfed infants. In formula-fed infants no differences were seen between any development stage for any substrate, apart from an increase in total SCFA produced between pre- and late weaning. In mixed fed infants total SCFA produced in cultures containing pectin increased significantly at late weaning. With the other complex carbohydrates total SCFA produced increased at early weaning from pre-weaning. In all infant feeding groups, cultures containing complex carbohydrates produced lower levels of total SCFA than adults.