prebiotics
Prebiotics
Stephanie Allen
Liz Wells
Advanced Research Dietitians HONEI, Hull York Medical School, University of Hull
Stephanie Allen is an Advanced Research Dietitian working for the Hull York Medical School at the University of Hull. She originates from Australia where she trained and worked as an Accredited Practising Dietitian. Liz Wells is an Advanced Research Dietitian working at the Hull York Medical School. Prior to entering the world of academia she worked as a critical care specialist and a Macmillan Oncology Dietitian.
24
In the past, research and interest has been predominantly focused on probiotics but in the context of human health the future looks bright for prebiotics, with a wealth of information being gathered in the last two decades (1). They are considered attractive to researchers and industries, not only due to their nutritional benefits, but also their economic benefits and are used in food, particularly in the production of functional foods (2). Prebiotics are defined as ingredients that selectively stimulate the growth and/or activity of one or a limited number of species/genera of bacteria in the microbiota, thereby providing benefits to the health and well-being of the host (2). According to Gibson et al (3), a food component must meet the following requirements to be considered prebiotic: • be resistant to salivary, pancreatic and intestinal enzymes; • be fermentable by the intestinal microbiota; • selectively stimulate the growth and/ or activity of intestinal bacteria to contribute to health and well-being. Currently, only non-digested carbohydrate molecules, a range of di-, oligo- and polysaccharides, resistant starches and sugar polyols have been claimed to have prebiotic properties (4). Once prebiotics have reached the colon, they are hydrolysed to small oligomers and monomers which are then further metabolised by anaerobic bacteria (5). This process, known as fermentation, serves the bacteria, as it provides energy for proliferation and results in the production of short chain fatty acids (e.g. acetate, propionate, butyrate and L-lactate). The process also yields production of gases (H2, CO2, CH4) which are metabolically useless to the host, but now assist us in determining the degree to which these prebiotics are broken down, using the method of breath testing (6).
NHDmag.com December 2014 / January 2015 - Issue 100
Benefits of prebiotics
The list of prebiotic effects on the human body is growing as more is discovered about their mechanism and a deeper understanding is gained. It is postulated that prebiotics can influence the immune system, aid blood lipid control, aid mineral absorption and prevent the development of colon cancer. Lipid profiles
Prebiotics may have a role in the prevention of chronic diseases as they play a role in lipid level controls. Deranged lipid profiles, along with smoking and hypertension, is one of the key risk factors for cardiovascular disease. It is estimated that half of British adults have raised serum cholesterol levels, which rises with age. One of the by-products of fermentation of prebiotics is acetate, a gluconeogenic substrate, which might contribute to inhibition of cholesterol synthesis and regulation of adipose. It has been demonstrated mainly by a reduction in triglyceridaemia and only a relatively slight decrease in cholesterolaemia mostly in (slightly) hypertriglyceridaemic conditions (7). Gastrointestinal
Prebiotics are also thought to have a positive effect on bowel health as they specifically stimulate the growth of Bifidobacteria and Lactobacilli in the microbiota. Lactobacilli aids lactose digestion, resistance to infections such as Salmonellae, prevents travellers’ diarrhoea, helps relieve symptoms of irritable bowel syn-
