Lactobacillus is the name of a genus (a classification) of bacteria that have certain characteristics in common, such as their shape (rod-shaped), the way they absorb stains for viewing under the microscope, their ability to live in low-oxygen environments, as well as other criteria. There are quite a few species in the classification of Lactobacillus. Some lactobacilli are the cause of dental caries (cavities). Lactobacillus bulgaricus is a fermentative bacteria that produces the product "Bulgarian" or "bulgaricus" milk. Lactobacillus acidophilus is a type of lactobacillus producing lactobacillus milk. This bacteria has become widely advertised as the "in vogue" way to a more healthy digestive tract. Are these probiotic bacteria really the answer to more healthy diet? The following is an extract from "And You Thought You Were Safe")
One way some individuals attempt to modulate bacterial gut flora is through consumption of probiotic bacteria. Bacteria responsible for what is considered healthy colonic fermentation or metabolism of foodstuffs, are called probiotic ("pro" for, "biotics" life) bacteria, and these bacteria are considered to be beneficial in some respects. Probiotic bacteria include the bifidobacteria and lactobacilli. Note what we said earlier about the same name used for Bifidobacterium bifidum and Lactobacillus bifidum. These probiotic bacteria are usually not found in significant amounts in the adult human intestine, but can be introduced through consumption of yoghurts and other cultured foods containing live bacteria. Although we can introduce probiotic bacteria into our digestive tracts, they do not reside there long because of the hostile and competitive nature of the normal intestinal bacterial flora. However, we can periodically re-introduce these bacteria into our system through food, and there may be a benefit to this. These probiotic bacteria can compete with pathogenic bacteria for nutrients and inhibit their growth with the biochemicals they produce and thus, may assist in protecting us from the colonisation of these more virulent microbes. Specific components of food called "prebiotics", assist probiotic bacteria in flourishing. Substances in food acting as prebiotics include inulin and various types of polysaccharides.
Although in theory, probiotics and alteration of intestinal bacteria is fine in theory, it is very difficult to achieve. Our resident bacteria are very stubborn and although we can change our diets, the moment we re-introduce certain food, the previously dominant bacteria quickly re-establish high populations. Additionally, resident bacteria can adapt to new food sources and consequently repopulate the gut. Resident bacteria can also adhere to the intestinal walls, which makes elimination virtually impossible, and thankfully so. We can see how limiting or changing bacterial populations can affect the gut when we consider the neonate and its establishing of bacterial gut flora. Until this occurs, the neonate can experience diarrhoea, bloating, and much intestinal discomfort. Travellers' diarrhoea also demonstrates the consequences of disrupting the gut flora via the war that occurs between bacteria when we introduce local strains of E. coli into our gut through consumption of the local food and water we consume while in different areas of the world. Nevertheless, probiotics may have some benefits and with further research we will be more certain. Yoghurts containing live acidophilus may also reduce the episodes of bacterial vaginosis. In regards to the gut, however, It is very difficult to elucidate if an individual is benefiting from a probiotic regimen, simply because it would be very difficult to tell if the bacterial gut flora were altered. To monitor the clinical effectiveness would involve the assistance of sampling and culturing of stool, etc., and is impractical in the home setting. Implementing a probiotic regimen may have benefits, however, from a dietary standpoint. If we consider that Lactobacillus can be divided into the homofermentative group producing only lactic acid, and the heterofermentative group producing other by-products of metabolism, we can say that in general that Lactobacillus metabolise food by fermentation. Lactobacilli are anaerobic, which means they can only live in environments with little or no oxygen. The process of fermentation, which Lactobacilli use to metabolise carbohydrates is an anaerobic process (doesn't use oxygen). Fermentation occurs widely in other bacteria such as bifidobacteria and yeasts as well. During fermentation, sugars are metabolised for energy of the bacteria, and the waste products expelled into the intestine are lactic acid, acetic acid (vinegar) and butyric acid (acidic form of butter) and alcohol. These by-products of fermentation create a more acidic environment in the intestine, inhibiting the growth of other bacteria such as bacteroides.
Bacteroides are anaerobic (live in low or no oxygen environments) bacteria that inhabit the oral, respiratory, intestinal and urogenital cavities of humans and usually constitute one of the main bacteria of the colon. Bacteroides in comparison to bifidobacteria, digest nutrients such as proteins by putrefaction. Putrefaction is the enzymatic decomposition, especially of proteins, with the producing of ammonia, hydrogen sulfide, mercaptans (sulfur containing compounds), and other foul-smelling compounds. In theory, the by-products of putrefaction during the metabolism of proteins by bacteroides, can be absorbed by the intestines and transported to other tissues in the body, affecting the well-being of an individual.
Therefore, in theory, a diet high in protein and saturated fats can cause overgrowth of bacteroides with production of harmful by-products of metabolism. In comparison, a diet with adequate complex carbohydrates and non-starch polysaccharides (fibre) stimulates bifidobacteria. And since the by-products of bifidobacteria are supposed to be less harmful and even beneficial to a degree, this is the logic for dietary revision. However, careful consideration is required since it is unhealthy to consume a low protein diet. Vegetarian diets for example, provide lower amounts of protein than those diets including meats. However, adding soy bean the vegetarian diet can compensate for this loss, since the soy bean contains little starch and is rich in protein. As we discussed in our chapter on susceptibility to disease, adequate amounts of protein are required for virtually every aspect of normal metabolism. Additionally, in the average individual bifidobacterium in the large intestine are usually more numerous than Bacteroides. Nevertheless, it is worth noting that a healthy well-rounded diet will help to ensure overall maintenance of health, but may also adequately help balance the intestinal flora. Different types of diets are in theory, supposed to promote the decrease in nitrogen waste production by intestinal bacteria. Nitrogen waste products such as ammonia, phenols, urea, indols, nitrates and nitrosamines are unhealthy by-products of bacterial metabolism. Under normal conditions, the liver can detoxify any of these absorbed substances. The idea behind probiotics is that if we can decrease these substances 1) the liver will have less of these substances to detoxify and 2) that less of these substances will be available to put the individual at risk. In this respect, a vegetarian diet produces the least amount of nitrogenous wastes in the urine. However, this is not always indicative of bacterial production of nitrogenous waste products, since general protein metabolism will generate these types of by-products, which can also be measured in the urine. Furthermore, including meat in the diet will cause nitrogen waste products considering the higher amount of available protein in meat in comparison to vegetables and nitrogenous wastes are not always indicative of ill-health, but rather metabolism of essential protein. Additionally, measurements of these by products in the urine will change considerably irrespective of diet, with activities such as intensive physical training.
For those wishing to experiment with probiotic diet there are a few considerations to be aware of. Firstly, any probiotic supplement should not entirely replace your diet, but rather supplement it, unless there is a specific reason given by your doctor. Probiotic supplements should also be gradually introduced into the diet considering the body is not accustomed to them. Considering probiotic bacteria transitory, the risk of immune modulation is low. However, we must take in consideration that bacteria do escape through the intestinal barrier. When microbes escape, the liver has a population of macrophages (Kupffer's cells), which intercept bacteria in order to prevent bacterial spread in the blood. The more probiotic bacteria we introduce, the higher the risk that these bacteria may bypass the intestinal barrier, only to be phagocytised (engulfed) by liver macrophages as well as macrophages in other areas of the body. The point to keep in mind is that macrophages also process and present bacteria that they have trapped to other immune cells such as lymphocytes. This can cause antibody production, and subsequent allergies or other problems. We shall discuss the immune system in some detail during our reading. Thus, when radically changing diet, or any other modulation of our normal eating habits, it may be wise to implement these practices slowly and in moderation. And of course before embarking on any alteration of diet, careful consideration, education, planning, and consultation from a medical professional is always beneficial.