Prebiotics and health: Clinical implications

*Professor Department of Biotechnology, Punjabi University, Patiala-147002, Punjab, India. e-mail: aruna_bhatia@rediffmail.com. Ph.No.9878263077. **Research scholar, Department of Biotechnology, Punjabi University, Patiala-147002, Punjab, India. e-mail: umagarg.1055@rediffmail.com. Ph.No. 9463019277.

Abstract

Prebiotic agents have been shown to have significant clinical beneficial effects in the prevention and management of gastrointestinal and non- gastrointestinal conditions. Prebiotics are short chain fatty carbohydrates that alter the composition or metabolism, of the gut microbiota in a beneficial manner. It is therefore expected that prebiotics will improve health in a way similar to probiotics, whilst at the same time being cheaper, and carrying less risk and being easier to incorporate into the diet than probiotics. These observations have led to work demonstrating that an important mechanism of these agents in their close interaction with the gut associated lymphoid tissue [GALT]. The preliminary finding of several recent human clinical trials reviewed in this article indicates that prebiotics may indeed prove to be beneficial dietry supplement, in the context of novel nutritional strategies for the management and systemic conditions.

Humans, Prebiotics, Health effects

Introduction
The term “prebiotic� was coined in 1995 by Prof Glenn Gibson and Prof Marcel Roberfroid. They defined it as a “non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health� (1).

Prebiotics are important because of: [i] the growing belief that there is such a thing as a healthy or balanced gut microbiota, [ii] the demonstration that prebiotics can alter the composition of the microbiota towards this more healthy profile, [iii] as an alternative to probiotics, which can be difficult to handle in some foodstuffs, but whose benefits to health in terms of diarrhea prevention and immunomodulation are becoming increasingly well established and [iv] because prebiotics currently in use, especially inulin and its derivatives, and galacto-oligosaccharides [GOS] are relatively cheap to manufacture or extract from plant sources. In addition to having beneficial effects on the gut microbiota and host, they are also valuable functional ingredients in foods with the potential to give fat-based spreads and dairy products with improved organoleptic properties. Gibson et al (2) reviewed their original prebiotic concept in the light of research published over the past 10 years, particularly the three key aspects of the original definition: [i] resistance to digestion, [ii] fermentation by the large intestinal microbiota and [iii] a selective effect on the microbiota that has associated health-promoting effects. It is now proposed that ‘A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microbiota that confers benefits upon host well-being and health’. The key ideas in both this and the earlier definition are ‘selective’ and ‘benefit/improve host health’ (2).

Sources and Effective dose
Prebiotics are found naturally in many plants including leeks, onions, wheat, garlic, chicory root and artichokes where they function as storage carbohydrates and soluble fibers in pulses, fruit and some cereal products. A number of poorly digested carbohydrates fall into this category of prebiotics including certain fibers and resistant starch (3) but the most widely described prebiotics are nondigestible oligosaccharides [NDO’s]. These are low molecular weight carbohydrates with 2-10 degree of polymerization, which are poorly digested in the small intestine thus reaching the colon largely unaltered and can act as a substrate for the colonic micro flora. Effective doses of oligosaccharides are in the range of 5-10 grams/day for healthy adults. Doses less than 5 grams are generally considered ineffective (2), (4). Here a review of published evidence on the health effects of prebiotics in humans is given.

Characteristics features of Prebiotics
There are many carbohydrates that are non-digestible, hence called dietary fibers. If fermented they promote bacterial growth but only a few are true prebiotics that meet all the criteria. The definition is important because it clearly outlines the three criteria that must be met before an ingredient can be classified as a prebiotic, namely that it should: Besides being non-digestible oligosaccharide, which selectively stimulate the growth and/or metabolic activity of the ‘good’ some more criteria have been recommended;

• It may not be hydrolyzed or absorbed in the upper gastrointestinal tract.
• It should alter the colonic micro flora in favour of a composition more favorable to the individual’s health.
• It must induce luminal or systemic effects which effect a beneficial change in the health of the host organism.
• Be fermented by bacteria in the large intestines.
• It should improve co

Conclusion

The review of literature reveals that prebiotics, the “non-digestible food ingredient beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health� (1). Have positive health effects which include anticancerous effect, anticholestereamic effect, helps in change in the micbiota of the gut and mineral absorption and bones overcome bowel habit and constipation, inflammatory bowel disease, and antibiotic associated diarrhea. These effects have been shown due to effect of prebiotics on microflora and environment of the intestine. Work needs to be carried out to understand the mechanism of health effects of prebiotics especially on the effect immune response.