Functional foods: probiotics and prebiotics

The main role of diet is to provide nutrients to meet host physiological requirements. As research behind diet and health has evolved, so has the concept of ‘functional foods’ become popular. Foods which are touted as being ‘functional’ are thought to exert certain positive properties over and above their normal nutritional value. While not universally popular and sometimes plagued by inadequate research/claims, the concept is certainly commercially successful, e.g. The Institute of Grocery Distributors (http://www.igd.com) estimates that the functional food market in the UK in 2007 will have annual sales worth around £1800m. This shows an exponential rise from the 1996 figure of £134m. Examples of functional foods include organic and inorganic micronutrients, vitamins, anti-oxidants, dietary fibre, some proteins (e.g. lactoferrin), certain bioactive peptides and polyunsaturated fatty acids. The concept has now moved markedly towards gastrointestinal function, in particular the impact of gut bacteria. Possibly this is driven by the ubiquity of gastrointestinal disorders but also the fact that diet is an important controlling factor with regard to indigenous microbiota activities. The gut microflora contains pathogenic, benign and beneficial microbial species. A predominance of the former can lead towards gut upset which can be both acute (e.g. gastroenteritis) and chronic (e.g. inflammatory bowel disease). Functional foods directed towards the gut microbiota would serve to influence the composition of activities towards a more positive metabolism. Functional Foods and the Gut