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Dr Asheesh Mehta, Internal Medicine Specialist September 14, 2017
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Probiotics are defined by Food & Agriculture Organization, a United Nations agency and by World Health Organization as live microorganisms which when administered in adequate amounts, confer a health benefit on the host. The word probiotic is derived from Greek “pro” meaning promoting and “biotic” meaning life. The Nobel laureate Elie Metchnikoff is widely accepted as being the first to recognize the relevance and importance of probiotics to our health and is sometimes referred to as the father of probiotics. He observed that Bulgarian peasants had unusually long life spans in spite of living hard lives in dire poverty and facing very harsh climatic conditions. He suggested that their good physical and mental health could be attributed to beneficial effects from colonization of the gastrointestinal tract by favourable bacteria present in yogurt at the expense of potentially harmful bacteria. Since then probiotics have been the subject of much research.

We are vulnerable to a variety of infections caused by many different types of microorganisms such as bacteria, protozoa, fungi, etc. Most of these microorganisms are able to cause infections only through breaches in external barriers such as the skin or the lining of the gastrointestinal tract; a few more aggressive microorganisms are able to pass through these intact external surfaces also. A number of different protective mechanisms prevent microorganisms from invading or attacking us. Integrity of the skin and mucus membranes serves as a mechanical barrier to most microorganisms with immune responses to these tiny life forms serving as another type of barrier. With normal defence mechanisms of this sort most microorganisms do not cause any infections. Surfaces accessible to microorganisms such as the skin and the lining of the gastrointestinal tract are inhabited by many millions of microorganisms which colonize these areas usually with a symbiotic effect of being beneficial for both the host human and the microorganism. However, sometimes clinically significant infections result when mechanical integrity of protective barriers is breached or immune system is compromised as happens in diseases like AIDS. The microorganism that normally colonize areas such as the gastrointestinal tract serve a number of useful purposes including enhancing resistance against infections, helping the immune system to mature and synthesis of some nutrients such as vitamins and short-chain fatty acids. Alteration of this normal population of microorganisms may cause symptoms such as diarrhoea and dyspepsia and such illnesses can sometimes even be serious enough to be life-threatening.  One of the commonest causes of change in normal bacterial flora of the gut is use of antibiotics. Whether changes in bacterial flora in the gut are also responsible for more subtle health abnormalities is less clear. Probiotics are live microorganisms administered with the aim of favourably altering the bacterial flora in parts of our body such as the gut or the skin.

Probiotics may be sourced from food as well as from medicinal preparations such as tablets, capsules, syrups or creams specially prepared to contain live microorganisms. Yogurt is the
most popular food source of probiotics.
Quite a few microorganisms are considered to have a probiotic effect. These include specific strains of various genera like Lactobacillus, Saccharomyces, Bifidobacterium, Enterococcus, Streptococcus, Pediococcus, Leuconostoc, Bacillus and Escherichia coli. It is worth stressing that only specific strains of these genera are probiotics and other strains, especially of streptococci and E.coli have the potential to cause serious infections. Lactobacillus acidophilus, Saccharomyces boulardii and Bifidobacterium bifidum are among the more popular strains in commercial preparations. Most of the microorganisms considered to be probiotics are bacteria but a few are yeasts. The effects of a probiotic are generally accepted to be specific to the strain of microorganism consumed. However, there is still a lot of confusion about the quantum of health benefits with the specific strain of microorganism consumed, the desirable dose of a particular probiotic, effect of using different probiotics together, etc. It is desirable that the probiotic/s used should be able to withstand any destructive effect of acid which is normally present in the stomach. Since consumption of probiotics means that one is taking in live microorganisms, it is evident that their incapability to cause any type of infection is assured.

Probiotics may be sourced from food as well as from medicinal preparations such as tablets, capsules, syrups or creams specially prepared to contain live microorganisms. Yogurt is the most popular food source of probiotics. The probiotic content may differ quite a bit depending on whether the yogurt is heat treated after it is made and whether beneficial microorganisms are added after this process. Some commercial brands are marketed as probiotic sources and special efforts are made to enhance their content of desirable microorganisms. A few other milk products such as buttermilk, kefir and fermented varieties of cheese also have a fairly high content of probiotics. Sauerkraut is finely shredded cabbage that has been fermented by different types of lactic acid bacilli. It is an integral part of traditional cuisine in many parts of Europe including Germany and the Netherlands. It has an excellent probiotic content. Kimchi is a spicy Korean dish made from fermented cabbage or other vegetables and this too is a good source of probiotics. Food items such as tempeh, miso and natto originating from different parts of the world are all based on fermentation of soyabean and are also rich in probiotics. A vast number of commercial preparations of probiotics are also available. They are marketed in various forms as tablets, capsules, syrups, powders, lozenges, gums and even skin creams. A major problem with the commercial preparations is poor standardization, unclear regulation and quality control in most countries. These preparations are supposed to deliver live microorganisms. It is often not clear which microorganisms are present in the preparation, the individual quantity of different microorganisms, what percentage or quantity of live or viable microorganisms will still be available for delivery at the end of the expiry period of the preparation, whether and to what extent the microorganisms will be destroyed by acid in the stomach and whether any specific mode of delivery (such as acid resistant capsules) has been adopted to prevent such destruction. Selection of probiotics is further confounded by the fact that even doctors and researchers themselves are not really clear which microorganisms among the probiotics are best for which problems and what the dose should be.

Many health benefits have been claimed for probiotics. Evidence for some of the purported health benefits is much more convincing than for some of the other claims. Their most widely accepted application is to prevent or treat some types of diarrhoea. One of these is antibiotic antibiotic associated diarrhoea. This is a problem with many antibiotics, especially when taken orally and is usually due to the antibiotic killing off many of the bacteria normally inhabiting the colon with replacement of the normal flora by more aggressive microorganisms. Most cases are of mild diarrhoea which settles without specific therapy in a few days after withdrawal of the antibiotic. Sometimes more serious diarrhoea occurs which can be life-threatening. This is generally known as pseudomembranous colitis because of the appearance of a membrane like deposit lining the colon in some of the affected individuals. It is caused by bacteria called Clostridium difficile and is particularly common in people admitted to hospital, although it is also seen quite regularly in community practice. The infection often does not resolve in spite of withdrawal of the offending antibiotic. Other antibiotics that are effective against C.difficile have to be administered but antibiotic resistance is a significant problem. Probiotics have been found to be useful in prevention and treatment. Another common problem is rotavirus induced diarrhoea, commonest in small children. The infection can be prevented by vaccination and should be routine for all children. Probiotics as supplementation of infant formula may be helpful in both prevention and treatment of htis very common illness. Traveler’s diarrhoea refers to the diarrhoeal illness many people suffer when traveling abroad. This is an umbrella term for a variety of gastrointestinal infections with different types being commoner in different countries or areas. Probiotics may help in preventing and treating this problem too.

Certain strains of probiotics may be helpful in food allergy and atopic eczema. Exposure to bacterial antigens in early life is believed to reduce allergic diseases. In other words, children brought up in excessively aseptic environments have a higher risk for development of allergic problems. The presence of microorganisms of probiotic types in the intestines of small children may reduce or prevent food allergy and atopic eczzema. The incidence of asthma, the third common type of allergic problem, is however not affected by probiotic use. It has also been reported that milk allergy may be favourably affected by probiotic use. Among other possible but less convincingly documented health benefits attributed to probiotics are improvement of general immunity, lower blood pressure, lower cholesterol, improvement in ulcerative colitis and a beneficial effect in irritable bowel syndrome and lactose intolerance.

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