Part of the annual Nutrition and Health Live event – November 2013

Christine Edwards, Professor of Nutritional Physiology at the University of Glasgow, gave a talk entitled Priming the Gut: the Role of the Colonic Microflora in Food Allergy and Intolerance, in which she explained the revolution that has taken place in how we look at gut bacteria.

We know:
* there are 10 times more bacterial cells in the body than human cells;
* there is 100-150 times more genetic information in those bacteria, than in your body;
* there are at very least 1,000 species of bacteria in the gut.

We also know these bacteria provide us with metabolic functions which we did not evolve ourselves, and which ‘educate’ our immune system.

But the ecosystem is complex. The complexity and variety means there is enormous amounts of data to analyse, requiring the use of difficult-to-access supercomputers, to ‘ask’ even the most basic question. The biggest problem microbiologists face is that these bacteria cannot usually be grown: around 60% are non-culturable, because they either need to grow alongside other bacteria, are anaerobic, or they need something from their human hosts to grow which we have not identified. We cannot study them, or find out what they do.

What we do know is that they are very important for digestion – and we should not be flushing them out with colonic irrigation. Some functions include:

* producing short-chain fatty acids (which may have an impact on satiety and metabolism regulation)
* promoting colonic absorption of water (which is why, when good bacteria levels dip, we get diarrhoea)
* providing energy
* reducing colonic pH
* increasing mineral absorption
* inhibiting pathogens
* producing a wide range of vitamins
* metabolising complex molecules like polyphenols, releasing antioxidants.

Factors influencing gut microbiome and infant colonisation of the gut include:

* genetics
* perinatal antibiotics
* vaginal versus Caesarean birth
* weaning practises
* where you were born / live
* ethnicity
* any digestive disease
* diet
* probiotic intake

Studies show, said Edwards, that allergic infants are less likely to have lactobacilii and bacteroides bacteria, and are less often colonised by entercoccoi bacteria.

Delivery by c-section increased the risk of allergic disease, and a vaginal home birth is more protective than a vaginal hospital birth. There is a decreased risk of food allergy in vaginally delivered babies when parents are atopic.

In conclusion, Edwards said bacterial composition is important for digestion and health, that early diet and environment is very influential on the development on the gut microbiota and allergy, and that there is some evidence linking disturbed microbiota to allergy – but not to intolerance.

November 2013

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