Probiotics are microorganisms, usually bacteria found in the human gut, which are beneficial to health. They’re also called “friendly” or “good” bacteria. They are ubiquitous and symbiotic throughout the gastrointestinal system, where they have an important and protective role. Probiotics are not just normal and helpful, but essential to prevent illness and improve function.
Lactic acid bacteria and bifidobacteria constitute the major types of colon flora. Lactobacillus acidophilus has a long history of safe use in the dairy industry and exists naturally in the human gastrointestinal tract. Bifidobacteria are added to foods for probiotic purposes, providing protection against gastrointestinal infections and inflammatory bowel disease, antagonizing pathogens, and conferring antiallergenic properties on the immune system. (2,4) As you can see, probiotics have a number of health benefits, and not just for gut-related conditions like Candida.
The Early Days Of Probiotics
The characteristics, actions, effects, and importance of probiotics have merited a renewed popularity in contemporary culture, but probiotics are ancient history. Thousands of years ago, a Roman naturalist named Pliney the Elder recommended drinking fermented milk to treat intestinal problems. Fermented foods are also mentioned in the Bible and the sacred books of Hinduism. Climates in the middle East and Asia favored the souring of milk products, which were recommended for intestinal illness. This represented the therapeutic use of probiotics, even before the bacteria contained within them were recognized. Many of the same soured milk products are still being consumed today.
In 1899, Henry Tissler, a research scientist at the Pasteur Institute in Paris, France, reported detecting a Y-shaped bacteria in the intestines of breast-fed infants. He called the organisms “bifidobacteria” (singular – bifidobacterium.) “Bifid” literally means “forked into two parts or branches.” Tissler reported that infants with bifidobacteria in their digestive tracts had fewer gastrointestinal problems, evidenced by fewer diarrheal illnesses.
The quest to find a fountain of youth was a popular occupation for scientists and physicians of that era. Eli Metchnikoff (pictured above), a Russian scientist also at the Pasteur Institute in Paris, was studying lactic acid bacteria. It was known that the breakdown of dietary proteins by clostridia (bacteria normally found in the digestive tract) produced some substances toxic to the human body, including ammonia, phenols, and other compounds, a type of “intestinal auto-intoxication”. He theorized that the lactic acid bacteria conferred a type of protection from, or reversal of, the intestinal auto-intoxication. Mitchnikoff had observed that rural dwellers in Bulgaria lived to very old ages, despite extreme poverty and harsh climate. They had an average lifespan much greater than wealthier Europeans, and he noted that they drank fermented milk products. Metchnikoff surmised that the lactic acid bacteria associated with fermented milk products had anti-aging health benefits. He named the organism “Lactobacillus bulgarius”. Metchnikoff went on to publish “The Prolongation of Life: Optimistic Studies”, stating that “Ingesting microorganisms could have substantial health benefits in humans.” (7)
Metchnikoff and his colleagues began drinking sour milk to populate their digestive tracts with the lactobacillus, marking the introduction of probiotics as dietary supplements. In 1908 Metchnikoff received the Nobel Prize in medicine for his work demonstrating that harmful microbes can be replaced by beneficial microbes to treat intestinal illnesses. After Metchnikoff’s death in 1916, much of the interest and research about probiotics started shifting to the United States.
A German physician and scientist, Alfred Nissle, was intrigued by the potential uses and benefits of probiotics. Methods were needed for treatment of infectious diseases; there were no antibiotics at the time. During an outbreak of shigellosis (shigella is a bacteria that causes severe diarrhea), Nissle isolated a new strain of Eschericia coli from the feces of a World War I soldier who was afflicted with shigella but did not develop the diarrheal illness. The new bacterial strain was named “Eschericia coli Nissle 1917.” Nissle used the strain to treat intestinal diseases, like shigella and salmonella, with great success. Nissle’s namesake probiotic actively interacts with the body’s immune system, and is still in use today. (1)
The year of 1920 saw a setback in the development of probiotics. Experiments by Professor Leo F. Rettger seemed to show that Metchnikoff’s Lactobacillus bulgarius could not live in the intestine, and was in fact destroyed by stomach acid. We now know that probiotics can indeed survive stomach acid, but at the time it seemed to disprove Metchnikoff’s theory that his bacteria conferred longevity on those who consumed it. Soon, the therapeutic use of fermented food fell out of favor. However, Rettger also demonstrated that other bacteria which naturally exist in the gut could be effective as probiotics, helping to restore normal bacterial colonization when introduced into the human digestive tract. One of these bacteria, Lactobacillus acidophilus, has been shown to be an effective treatment for constipation. (3)
The word probiotics comes from the Latin pro (“for”) and the Greek bios (“life”). Metchnikoff is generally considered to be the “father of probiotics,” but there are numerous other scientists who have individually been credited with coining the word itself – for example Kollath (1953), Lilly and Stillwell (1965), Parker (1974), Fuller (1989), and others. They each had their own definition of the term. The World Health Organization and the Food and Agriculture Organization of the United Nations developed in 2001 a widely used definition. According to this definition, probiotics are “live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host.” These microorganisms can be bacterial, viral, or yeast, and can generally only be seen under a microscope.
It should be noted that the European Food Safety Authority (EFSA) rejects the WHO’s definition because it contains a health claim which is not measurable. The EFSA states that, “the scientific evidence remains insufficient to prove a cause and effect relationship between consumption of probiotic products and any health benefit”. (5)
There are multiple reasons for the renewing of interest in probiotics. Antibiotics, although they have been lifesaving, have created some new problems as their usage has exponentially risen. It is widely recognized that antibiotics can cause imbalances in the protective flora of the gastrointestinal and vaginal tracts, leading to weakened immune systems and digestive problems. And there are now an increasing number of pathogens like Candida albicans developing resistance to our drugs, as a result of the widespread overprescribing and misuse of antibiotics. In fact, many in the pharmaceutical industry fear that we will not be able to develop new, effective antibiotics at a rate sufficient to compete with microbial resistance to standard antibiotics. (1,7)
The health-affirming effects of probiotics include aiding the digestion of food, manufacturing vitamins B-12 and K, and supporting our immune systems. They inhibit the action of disease-causing alkaline bacteria by maintaining an acidic environment in the gut. Probiotics can also increase the nutritional value of some foods by augmenting the breakdown and absorption of nutrients. Some produce antibiotics and are anti-carcinogenic. Some probiotics boost the immune system and help prevent urinary tract infections, vaginal infections, and inflammatory bowel disease. There are numerous other claims that have yet to be proved scientifically, but existing research leaves no doubt that some probiotics do exert positive effects, especially on the intestinal tract. (3,4,7)
It should be noted that the positive effects of bacteria can be negated by our lifestyle choices. For example, some of the biggest threats to probiotics are chlorine in our water supplies, and antibiotics in pesticide or herbicide residues on fruits and vegetables. These can kill pathogenic bacteria, but they will inhibit our friendly bacteria too. (1,2)
Future Uses For Probiotics
Probiotics are already widely used to prevent the side effects of antibiotics and improve digestion. In the future, one of the most promising uses of probiotics may be for the treatment and prevention of depression. For example, it is known that stress changes the composition of animal gut flora. Rats showing depressive behavior due to maternal separation were fed the probiotic B. infantus. The rat’s behavior normalized and their immune systems became healthier. (9)
There is also a human study in which some subjects received active probiotic organisms and some received placebos. The placebos were identical in appearance to the live probiotics, but with no active ingredients. The study was double-blind – neither the subjects nor the scientists knew who received the probiotics nor who received the placebos. Before treatment the subjects completed a questionnaire in which they assessed their perceived stress. Following weeks of treatment the subjects completed the same assessment tool about their perceived level of stress and associated symptoms. The subjects who received probiotics reported significantly lower levels of stress than were present before treatment. (9)
A similar human study, double-blinded and comparing probiotics versus placebos, was performed among individuals diagnosed with severe fatigue. The results were similarly promising. The individuals who took probiotics reported significant improvements in their symptoms. (9)
The term “psychobiotics” has been coined for probiotics which show promise for the prevention and/or treatment of psychiatric illnesses. Dr. John Krystal, Editor of the Biological Psychiatry journal, states that, “This intriguing new area of research may open new possibilities for the treatment of depression.” (10) For more information on this and more, check out my article on the possible future uses of probiotics.
1. Goldin, BR, Gorbach, SL, Clinical indications for probiotics: an overview. Clinical Infectious Disase 2008;5096-5100
2. Snydman, DR, The safety of probiotics. Clinical Infectious Disease 2008; 46:5104-5111
3. Hoffman, FA, Hiembach, JT, Executive summary: scientific and regulatory challenges of development of probiotics as foods and drugs. Clinical Infectious Diseases 2008; 46:553-557
4. Mach, T, Clinical usefulness of probiotics against chronic inflammatory bowel diseases. Journal of physiology and pharmacology, 57 suppl 9:23-33: http://www.nbci.nlm.nih.gov/pubmed/17242485
5. European Food Safety Authority (EFSA) – committed since 2002 to ensuring that Europe’s food is safe: http://www.efsa.europa.eu/en/search.htm?text=probiotics8p=10
6. Fuller, R, Probiotics in man and animals. Journal of applied bacteriology, 66(5): 365-378 DOI:10.111/j.1365-2672. 1989.tb05105.x
7. Probiotics for clostidium difficile, [Ann Pharmacother.2007] -Pub-NCBI: http://www.ncbi.nlm.nih.gov/pubmed/17595306 2013-03, 2013-04-22
8. Raoult, D, Probiotics and obesity: a link? Nature reviews microbiology 7Sept2009(9)616: http://www.nature.com/nrmicro/journal/v7/n9/full/nrmicro2209.html
9. Cryan JF, Dinan, TG, “Mind altering microorganisms: the impact of the gut microbiota on brain and behavior.” Nat Rev Neurosci 2012;13:701-712
10. Krystal, J, Psychobiotics: a novel class of psychotropics. Biologic psychiatry, 15 November 2013, Vol 74, Issue 10, p720-736