Hot topic: Prebiotics and probiotics

Probiotics are bacteria that live in the gastrointestinal tract and confer health benefits. In recent years there has been growing interest in the role of probiotics in disease prevention, how different diet patterns or antiobiotic treatments affect the probiotic populations, and whether “functional foods” can be developed to enhance probiotic effects. Prebiotics are poorly-digested carbohydrates (fibres and other carbohydrates) that can be digested (fermented) by the probiotics. Prebiotics thereby provide food for the probiotics. The “waste products” of the bacterial fermentation process can be used as energy by the host. In fact, this is the process by which cattle obtain between 60- 80 % of their energy requirements using the microbes in the rumen to produce nutrients that the cow can use. In humans, the process may contribute around 10% of total energy requirements. In addition, the nutrients produced by probiotics may have special health benefits. However, intensive research in this area is still ongoing.

Examples of prebiotics include soluble fibres such as inulin, which is found in several types of vegetables, bananas, tomatoes, grains such as barley and rye. Dairy products also have prebiotics that are most abundant in fermented products such as yogurt, kefir and buttermilk. Probiotics (usually from the Lactobacillus and Bifidobacterium types of bacteria) may also be added to dairy or other products. The ingredient list of a product often specifies whether prebiotics or probiotics has been added, although Canada currently has no regulations for addition of probiotics. Prebiotics like inulin may be purchased as supplements, in which case they fall under the same regulations as vitamins or other nutritional supplements.

Of course, what everyone wants to know is, “If I take prebiotics or probiotics, will it improve my health?” The answer to that question is still emerging from the research and in many cases there is not enough evidence to say definitively one way or the other. The results of some recent research are listed in the table below.

Health Condition Evidence for benefits of probiotics or prebiotics For more information
Irritable bowel syndrome Probiotics relieved symptoms but there was not enough data on prebiotics Ford et al. American Journal of Gastroenterology 109:1547, 2014
Prostate cancer No specific evidence Mandair et al. Nutrition & Metabolism 11:30, 2014
Atopic dermatitis in children Probiotics prevented or decreased severity Foolad et al. JAMA Dermatology 149:350, 2013
Enhanced growth in preterm or low birth weight babies fed formula Not enough evidence Mugambi et al. Nutr J 11:58, 2012

There is considerable interest in whether prebiotics or probiotics might be useful therapeutics for prevention or treatment of several common metabolic diseases such as obesity, type 2 diabetes, non-alcoholic fatty liver disease as well as colon cancer and other cancers. However, trials to evaluate the effectiveness of probiotics or prebiotics have not been published in any number; most of the evidence suggesting benefits comes from observational or small experimental studies. There are currently more than 600 clinical trials registered to study effects of probiotics on everything from weight loss to depression to constipation to arthritis. The outcomes of these studies should help to establish the health benefits of probiotics and their food, the prebiotics.

Some information for this blog article came from EatRight Ontario ( and Healthy U (