Definition

Probiotics are a combination of live beneficial bacteria and/or yeasts that naturally live in your body. Bacteria is usually viewed in a negative light as something that makes you sick. However, you have two kinds of bacteria constantly in and on your body — good bacteria and bad bacteria. Probiotics are made up of good bacteria that helps keep your body healthy and working well. These good bacteria help you in many ways, including fighting off bad bacteria when you have too much of it, helping you feel better.

Probiotics are part of a larger picture concerning bacteria and your body — your microbiome. Think of a microbiome as a diverse community of organisms, such as a forest, that work together to keep your body healthy. This community is made up of things called microbes. You have trillions of microbes on and in your body. These microbes are a combination of:

• Bacteria.
• Fungi (including yeasts).
• Viruses.
• Protozoa.

What types of bacteria are in probiotics?

Probiotics may contain a variety of microorganisms. The most common are bacteria that belong to groups called Lactobacillus and Bifidobacterium. Other bacteria may also be used as probiotics, and so may yeasts such as Saccharomyces boulardii. Different types of probiotics may have different effects. For example, if a specific kind of Lactobacillus helps prevent an illness, that doesn’t necessarily mean that another kind of Lactobacillus or any of the Bifidobacterium probiotics would do the same thing.

Lactobacillus: this may be the most common probiotic. It's the one you'll find in yogurt and other fermented foods. Different strains can help with diarrhea and may help people who can't digest lactose, the sugar in milk.

Bifidobacterium: you can find it in some dairy products. It may help ease the symptoms of irritable bowel syndrome (IBS) and some other conditions.

Saccharomyces boulardii: is a yeast found in probiotics. It appears to help fight diarrhea and other digestive problems.

How Do They Work?

Probiotics may have a variety of effects in the body, and different probiotics may act in different ways. Researchers are trying to figure out exactly how probiotics work. Some of the ways they may keep you healthy:

• When you lose "good" bacteria in your body, for example after you take antibiotics, probiotics can help replace them.
• They can help balance your "good" and "bad" bacteria to keep your body working the way it should.

Probiotics might:

• Help your body maintain a healthy community of microorganisms or help your body’s community of microorganisms return to a healthy condition after being disturbed
• Produce substances that have desirable effects
• Influence your body’s immune response.

The benefits of probiotics:

Probiotics have shown promise for a variety of health purposes, including prevention of antibiotic-associated diarrhea (including diarrhea caused by Clostridium difficile), prevention of necrotizing enterocolitis and sepsis in premature infants, treatment of infant colic, treatment of periodontal disease, and induction or maintenance of remission in ulcerative colitis.

Some other benefits of probiotics are following:

• Probiotics can help prevent or treat diarrhea caused by infections or antibiotics.
• Probiotics can improve systems of irritable bowel syndrome.
• Probiotics can boost the immune system.
• Probiotics can reduce inflammation and allergies.

Age

It was demonstrated that the fecal bacterial profile in children was different than in adults, with more Bifidobacteria than Bacteroides and higher counts of facultative anaerobes. With the exception of ammonia concentration and beta-galactosidase activity, the biochemical parameters are comparable to those found in adults. Diseases, like gastroenteritis, are able to change the biochemical and bacterial profile. After antibiotic therapy, the frequency of dysbacteriosis in children is very high. The use of probiotic foods can re-establish the equilibrium of colonic microflora and may help to control the adverse effects of antibiotic therapy. With the improvement in health care, living standards, and socioeconomic status, more adults are living to old age. One of the most remarkable changes with aging is the frequent development of atrophic gastritis and the inability to secret gastric acid. This process affects approximately one-third of older adults in the U.S. and only recently was recognized to be due to infection by Helicobacter pylori in the majority of cases. The lack of gastric acid in atrophic gastritis may lead to small intestinal bacterial overgrowth and influences the absorption of a variety of micronutrients. Lactose maldigestion is a frequent condition in older adults. So, the use of probiotics in this population would yield good results.

Gastrointestinal disorders

Ulcer

The prevalence of peptic ulcer disease has been associated with diet. It was demonstrated that individuals with verified ulcer had a lower intake of fermented milk products and vegetables and a higher intake of milk, meat and bread than normal subjects. A high intake of fermented milk products was associated with decreased risk of ulcer, whereas an increased risk of ulcer was noted with high milk intake. Other studies demonstrated that L. acidophilus and B. bifidum in concentrations of 109 bacteria act as an “ecological” therapy for gastritis and duodenitis.

Diarrhea

A fermented product containing L. acidophilus has been shown to inhibit the growth of pathogenic organisms like S. dysenteriae, S. typhosa and E. coli. The beneficial effect of probiotic feeding in bacterial diarrhea may be due to the antimicrobial substances produced by L. acidophillus, which might neutralize the enterotoxins of E. coli. Silva et al. concluded that the protection against S. enteritidis subsp. typhimorium observed in conventional and gnotobiotic mice treated with bifidus milk was not due to the reduction of intestinal populations of the pathogenic bacteria. However, Gallaher et al. studied the characteristics of the bifidobacteria and their stability in dairy preparations and on the potential effects of bifidobacteria and L. acidophilus in the reduction of colonic flatus production in humans and modulation of C. difficile diarrhea. 

Food allergy

Some studies demonstrated that probiotic bacteria (L. GG) may promote endogenous barrier mechanisms in patients with atrophic dermatitis and food allergy, and by alleviating intestinal inflammation, may act as an useful tool in the management of food allergy. For the treatment of gastrointestinal disorders, the antigenicity of the diet should be taken into consideration, when introducing novel probiotic functional foods. It has been demonstrated that probiotics (L. GG) not only restore aberrant macromolecular transport, but they also have a specific effect on mucosal degradation depending on the dietary antigen.

Helicobacter pylori infection

In cases of H. pylori associated pathology, the deficiency of Lactobacillus sp. in the stomach was found. Studies also revealed a decrease in the population level of Bifidobacteria sp. with the simultaneous increase of opportunistic enterobacteria and changes in local immunity. So, it can be concluded that the correction of microecological and immune disturbances with probiotic preparations containing bifidobacteria and lactobacilli, may be yielded good results. On the other hand, it has been demonstrated that a certain amount of time is necessary for H. pylori to come in contact with the gastric epithelium and that the composition of the gut flora is important for the establishment of H. pylori infection. On the basis of clinical criteria, the use of probiotics containing lactobacillus and bifidobacteria, simultaneously with “triple” antibacterial therapy, has been found to be curative in the treatment of H. pylori associated gastroduodenal pathology in children. The prescription of bifidobacteria containing probiotics is recommended in the early stages of etiotropic therapy. Studies performed in vitro have demonstrated that L. salivarius but not L. casei nor L. acidophilus proved to be capable of producing high amounts of lactic acid and thus completely inhibiting the growth of H. pylori in a mixed culture. Based on these findings, L. salivarius was found to be a potentially effective probiotic against H. pylori.

Lactose intolerance

It is postulated that lactobacillus supplementation could enhance lactose fermentation and thus improve symptoms of lactose intolerance. Studies have shown that the consumption of lactobacilli-containing products reduces the activity of fecal bacterial enzymes, including beta-glucuronidase, nitroreductase and azoreductase. Colonic flora may adapt quickly to and metabolize most of the lactose malabsorbed in the small intestine. L. acidophilus result in an improvement of in vitro lactose fermentation when a stable bacterial population and/or an adaptation of colonic flora to lactose load is not established. L. acidophilus strain LA-1 improves lactose digestion during the initial phase, and may suggest that metabolic alteration by lactobacilli supplementation is most likely to occur when colonization resistance is reduced, that is, when a stable microflora has not been established.

Cancer

A high percentage of human tumors is reported to be related to dietary habits. Specific strains of lactic acid bacteria used to ferment milk are promising candidates that may be antimutagenic and anticarcinogenic. Different fermented fresh yogurts containing viable bacteria (L. delbrueckii sp. bulgaricus and S. thermophilus or L. acidophilus and Bifidobacteria) showed protective effects as well. Other fresh fermented milk products (buttermilk, kefir and Dickmilch) were demonstrated not to be antimutagenic. These results imply that some bacteria used in milk processing have an antimutagenic potential and that this property is specific for the bacterial strain. The antimutagenic effects of milk and milk cultured with Bifidobacterium or Lactobacillus strains towards the mutagenicity induced by direct mutagens and dietary indirect mutagens were investigated. The results showed that each cultured milk sample and control milk had a significant antimutagenic effect but uninoculated milk had a greater inhibitory effect than cultured milks towards dietary indirect mutagens. In another study the incidence of aberrant crypts in animals fed different skim milks (skim milk fermented with Bifidobacteria sp. Bio (Danone strain 173010) and skim milk fermented with lactic acid bacteria) were compared to uninoculated skim milk. The tested diets reduced the incidence of aberrant crypts by 49%, 61% and 51% respectively. The mix of Bifidobacteria sp. Bio (Danone strain 173010), casein and calcium probably contribute to the total protective effect of dairy products against induced mutagenicity. However, Gallaher et al. did not find any effect of the bifidobacteria and lactobacilli on protection from development of aberrant crypts in rats. Other bacterial strains (L. helveticus, Bifidobacteria sp. and a mix of S. thermophilus and L. bulgaricus) induced a significant, although variable, reduction in the growth rate of HT-29 cells, which resulted in a 10–50% decrease in the cell number at steady-state.

Immune system

Fukushima et al. found that the intake of bifidobacteria can enhance local production of IgA in milk and the intestine, which may help to protect both pups and dams from exposure to food antigens. A study conducted to determine the effect of the consumption of milk fermented with L. casei strain Shirota on the composition and metabolic activities of the intestinal microflora and immune parameters in humans, demonstrated that the consumption of L. casei Shirota fermented milk was able to modulate the composition and metabolic activity of the intestinal flora and indicated that this milk did not influence the immune system of healthy immunocompetent males. These results are in accordance to the ones obtained by Schiffrin et al. who demonstrated that L. acidophilus La 1 and B. bifidus Bb 12 do not modify lymphocyte subsets in humans, but phagocytosis of E. coli sp. was enhaced in both groups. On the contrary, another study suggested the involvement of lactic acid bacteria in cytokine production under healthy conditions. They found that yogurt intake containing 1011 bacteria led to increase in 29–59 synthetase activity in human blood mononuclear cells. This result may suggest an interferon action in a peripheral way.

Probiotics-containing foods

You can find probiotics in supplements and some foods, like yogurt, Kefir, Sauerkraut, Tempeh, Kimchi, Miso, Kombucha, Pickles, Traditional Buttermilk, Natto and some types of Cheese.