from indigenous fermented foods and human gut ... - Thapar University

Fig. 2.1 Postulated mechanisms of action of probiotics
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Chapter II Review of Literature
Lactic acid bacteria have been shown to reduce the symptoms of lactose intolerance.
Lactose, a disaccharide composed of glucose and galactose, is the main sugar present in milk
and needs to be cleaved to the monosaccharides in order to be absorbed in the small intestine.
This enzymatic hydrolysis is catalysed by lactase (β-galactosidase), an enzyme present in the
brush border of the enterocytes in childhood. Some adults still express this enzyme and can
benefit from milk as a protein and calcium source, but the expression of this enzyme
generally decreases with age and is, in some cases, completely lost (Szilagyi, 2002). In
individuals with low lactase contents, lactose cannot be absorbed and it can be used as
fermentable substrate by the intestinal microbiota. In addition, water accumulates in the
intestinal lumen due to lactose osmotic properties. As a result, the patient may suffer from
bloating, flatulence, pain, nausea and even diarrhoea (Hove et al., 1999; de Vrese et al.,