The human digestive system contains millions of bacteria that constitute the gut microbiota and a healthy digestive system has a delicate balance of both beneficial and harmful bacteria. The beneficial or good bacteria are essential for good health as they aid digestion, stimulate the immune system and inhibit the growth of disease causing bacteria. If this balance between the beneficial and harmful bacteria is upset due to lifestyle and dietary factors such as taking antibiotics, eating a diet that is low in fibre and high in refined carbohydrates, harmful bacteria can flourish increasing the risk of diarrhoea, vaginal yeast infections and many other health problems. That is where prebiotics and probiotics come in to play as they work together synergistically to maintain the health of the digestive system.
Probiotics are defined as live micro-organisms that confer health benefits on the host by improving the intestinal microbial flora when administered in adequate amounts. The major sources of probiotics for humans are fermented dairy-based products that contain either Lactobacillus or Bifidobacterium. Lactobacillus acidophilus is the most commonly used bacterial strain in the manufacture of fermented dairy products and is a species of Gram-positive, rod-shaped bacteria that is found naturally in the gut of humans and animals. It is an anaerobic organism that produces lactic acid which reduces the pH which in turn has an inhibitory effect on other organisms especially candida. Yeast like Saccharomyces boulardii are also used extensively as probiotics.
Besides curd and yoghurt, other fermented dairy products such as kefir, koumiss, some soft cheeses and foods such as sauerkraut, miso, tempeh, kombucha, kimchi, sour mustard-based pickles, indigenous foods such as fermented rice gruel, pazhan kanji, pakhala bhaat or panta bhaat; fermented ragi porridge and traditional beverages such gajar ki kanji are rich in probiotics.
Probiotics have been shown to benefit digestive health by improving the balance of the intestinal microbiota and help to reduce the symptoms of diarrhoea especially acute diarrhoea and antibiotic induced diarrhoea. Although more research is needed, there is encouraging evidence that probiotics also help:
Improve symptoms of constipation
Prevent and treat vaginal yeast infections and urinary tract infections
Control irritable bowel syndrome (IBS), inflammatory bowel disease such as Crohn’s disease
Boost immunity and reduce respiratory infections. During the process of transient colonisation some probiotic strains have been shown to boost both the innate and acquired immune response
Reduce the symptoms and duration of respiratory infections both in children and adults
Prebiotics on the other hand are non-digestible components of food which beneficially affect the host by selectively stimulating the growth or activity of specific colonic bacteria thereby preventing the growth of harmful bacteria and improving the health of the host. In other words, prebiotics are nutrients that are used by the colonic bacteria as a fuel to create a balance in the gut microbiota.
Prebiotics include non-digestible carbohydrates mainly oligosaccharides like inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides; resistant starch and non-starch polysaccharides that are found in foods such as whole grain cereals, pulses, onion, leek, garlic, tomato, asparagus, banana, apple, chicory.
In order for a component to be classified as a prebiotic it must:
Not be hydrolysed nor absorbed in the upper gastrointestinal tract
Be a substrate for growth or activity of one or a limited number of beneficial colonic bacteria
Be able to alter the colonic microflora towards a healthier composition
Induce luminal or systemic effects which are beneficial to the health of the host
To date only fructo-oligosaccharides (FOS) have met all of the criteria mentioned to qualify as a prebiotic. Commercially FOS is now being added to supplement several products, such as dairy products, infant formulas, protein supplements, etc.
While probiotic supplements and drinks are most beneficial when one is suffering from diarrhoea and other digestive disorders, for normal healthy people consuming a balanced diet that includes fruits, vegetables, curd and other traditional fermented foods is the best way to obtain both prebiotics and probiotics.
(Writer is a consultant nutritionist with 19 years of experience, practicing at Panaji and can be contacted on firstname.lastname@example.org)