Probiotics are live microorganisms that could confer health benefits on the host, when consumed in significant amounts. The term prebiotic literally means ‘for life’ Probiotics have been proven to promote gastrointestinal health and immune function. The normal human gut (normal gut flora) contains 300-1000 different kinds of bacterial species with about 1014 individual bacteria. The predominant inhabitants of human gut include Lactobacillus and Bifidobacterium.
The World Health Organization (WHO) defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host.”(FAO/WHO, 2001). The term probiotics was coined by the researchers Lilly and Stilwell in their studies in 1965. In 1989, Fuller popularized the term ‘probiotics.’ Dr. Elie Metchnikoff came upon the discovery of the ‘prolongation of life’ through probiotics.
The concept behind probiotics is to enhance good bacteria and discourage bad bacteria in the human gastrointestinal tract. Probiotics help to keep bad bacteria away and out of one’s body. Probiotics help to ‘balance the intestinal bacteria i.e. ensure that there are more ‘good’ bacteria than ‘bad’. The ‘good’ bacteria simply ‘crowd out’ disease causing microorganisms, thereby preventing attachment of pathogenic bacteria by a process known as “competitive exclusion” (Kailasapathy and Chin 2000). Human gastrointestinal tract is supposed to contain 85% “good” bacteria and 15% “bad” bacteria.
Characteristics of probiotics
1. Probiotics neither are enzymes, vitamins or minerals nor foreign substances or chemical compounds. Natural probiotics are microorganisms that reside in the ileum (small intestine) and in the colon (large intestine) which have a symbiotic relationship with humans.
2. The most popular probiotic genuses are Lactobacilli and Bifidobacteria. Lactobacilli love to live in the small intestine and Bifidobacteria love to live in the colon.
3. Probiotics can resist the effects of digestive enzymes, stomach acid and bile. Probiotics support the intestinal microflora against antagonizing microorganisms. Probiotics promote optimal digestion and absorption of nutrients and promote a healthy digestive tract.
4. Probiotics tract assist the gastrointestinal tract to absorb minerals, vitamins and other necessary nutrients and the functions of the immune system. They also exert positive actions at the metabolic level.
5. Probiotics are used in paediatric medicine for babies and young children. Probiotics are acknowledged by the World Health Organization for the benefits of improving gastrointestinal health.
6. Probiotics never lose their beneficial properties during storage.
7. Probiotics are grown, fermented and cultivated from various media such as dairy, vegetables, beans, beets and others.
8. Manufactured probiotics are controlled bacteria (i.e., friendly, healthy, beneficial bacteria) that are manufactured in controlled laboratory environments.
Members referred to as probiotics are bacteria and fungi, most commonly including species of Lactobacillus and Bifidobacterium and species of the yeast genus Saccharomyces. Other bacterial genera which feature prebiotic strains include Streptococcus, Enterococcus and Bacillus.The members of Lactobacillus and Bifidobacterium have long history of use and generally recognized as safe (Generally Regarded As Safe,GRAS status). Lactobacilli which has the ability to produce lactic acid , is classified as Lactic Acid Bacteria (LAB). Probiotic species in the Lactobacilli family found in the human body include L.reuteri, L. casei, and L.rhamnosus. Lactobacilli acidopilus is commonly found in yogurt products. Bifidobacteria are norman inhabitants of the human colon. Bifidobacteria can produce lactic and acetic acids and also grouped as Lactic Acid Bacteria (LAB). Probiotic species in the Bifidobacteria include B.lactis, B. bifidum and B.longum. Streptococci are also found in dairy products. Streptococci thermophilus is commonly used to make yogurt. Enterococcus is a lactic acid – producing bacteria. Two species are commonly found in the intestines of humans: E. faecalis (90-95%) and E.faecium (5-10%). Lactococcus is classified as LAB as the can produce lactic acid.Lactococcus lactis is found in dairy products and is commonly responsible for the souring of milk. The name of the probiotic yeast Saccharomyces is from the Latin meaning ‘sugar fungi.’ Saccharomyces cerevisiae is used in making wine, bread and beer. Saccharomyces cerevisiae is more commonly known as Baker’s yeast.
Probiotic bacteria used in foods for human consumption are generally of human origin and are non-pathogenic. In addition they retain significant viability during processing and transit through the gut.
Yogurt is a probiotic containing food. Yogurt has been used in the past to treat diarrhea, prevent urinary tract infections or treat recurrent yeast infections. Probiotic containing foods include aged cheese. Kefir, kimchi, sauerkraut, miso, tempeh, and some soy beverages. Probiotic commercial products include tomato juice, peanut milk, soymilk, buffalo whey/soy milk and rice. Probiotics are normally added to foods as a part of the fermentation process. The probiotics involved in food fermentation are mainly Lactobacillus and Bifidobacterium. Probiotic bacteria may also be available in capsules or as powder.
Mechanism of action of probiotics
Probiotics deliver active constituents to targets in the host gastrointestinal tract. These active constituents include mainly enzymes, and immunomodulatory and antimicrobial components. Probiotic bacteria promotes human health in any of the following mechanism(s): adherence to intestinal mucosa and mucus, production of antimicrobial substances, antagonism against pathogens, competition for adhesion sites (competitive exclsion), interaction with Gut-Associated Lymphoid Tissue (GALT), immune regulation, in-activation of harmful components within the intestinal contents (binding of toxins), regulation of metabolic activity of intestinal microflora and overall normalization of the intestinal microflora ( Salminen et al 1996, Brassart and Sciffrin 1997).
Health benefits of probiotics
Medical literature supports the use of probiotics for treating a variety of different diseases – ranging from food allergies to ezema; from Crohn’s disease to antibiotic-associated diarrhea. The well documented health benefits of probiotics include the improvement of gastrointestinal health. Probiotics have been documented about the balancing effects on the immune system or enhancing body’s overall resistance to infection. Probiotics are useful in the prevention or treatment of several gastrointestinal disorders such as infectious diarrhea, antibiotic diarrhea and traveller’s diarrhea. Probiotic therapy can be helpful for people with Crohn’s disease and irritable bowel syndrome (IBS) (ref; Nutrition in Clinical Practice). Probiotics may be beneficial for brain function. Probiotic bacteria may have the potential to change brain neurochemistry and treat anxiety and depression – related disorders (ref: PNAS). Consumption of a formulation of Lactobacillus reuteri NC IMB 30242, is able to reduce blood levels of LDL cholesterol (ref: The American Heart Association Scientific Sessions, 2012). Consumption of Bifidobacterium infantis 35624, may have benefits for patients with psoriasis and chronic fatigue syndrome. Probiotics can be used to re-establish healthy vaginal flora and prevent bacterial vaginosis (BV). Probiotics can be used – along with other natural therapies – to treat urinary tract infection(UTI) and yeast infection. Finish researchers reported that large amounts of live Lactobacilli consumed daily may have positive effects on rheumatoid arthritis and ankylosing spondylitis. Benefits have also been shown in skin problems such as eczema and psoriasis. Probiotics may be considered a valid alternative to conventional therapy for alcoholic cirrhosis. Consumption of Lactobacillus rhamnosus and Bifidobacterium lactis reduced the risk of colon cancer.