You might have heard the word “probiotics” before. You might have seen it written across yogurt containers, or heard advertisers pitch that their new health drink is full of probiotics. But you might not know exactly why – and how – they are good for you. Here is a breakdown.
What are probiotics?
The Food and Agriculture Organization of the World Health Organization (WHO) defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit to the host.” In short, they are microorganisms – typically bacteria – that are good for us. Probiotics are able to survive the acidic environments of the stomach and intestines. They are capable of adhering to the walls of the gastrointestinal tract and show antimicrobial activity against pathogens.
Which organisms are considered probiotics and where are they found?
There are numerous microorganisms that are considered probiotics, but species under the genus Lactobacillus or the genus Bifidobacterium are the ones that are most commonly referred to.
Probiotics are found in most fermented food. Yogurt is a good, easily available source of probiotics. Other sources include pickles, kimchi, tempeh, sauerkraut, kombucha, and certain types of cheese.
How are probiotics good for you?
The first scientist in the Western world to publish work on the benefits of probiotics was Russian zoologist and 1908 Nobel Prize winner, Ilya Metchnikoff. He wrote that people living in Eastern Europe had greater life expectancy and noted that they lived largely on milk that was fermented by lactic acid bacteria. He proposed that the microorganisms in the colon produced toxic chemicals that led to aging, but consuming the fermented milk helped populated the intestine with lactic acid bacteria that reversed the aging process.
Today, studies have shown that probiotics can improve certain gastrointestinal disorders.
- Antibiotic-associated Diarrhea (AAD)
Antibiotic-associated diarrhea is caused because of an imbalance in the gut microbiome due to the consumption of antibiotics. Antibiotics, in addition to killing pathogenic bacteria, kill some of the good bacteria that are important for digestion. Estimates show that anywhere between 5-39% of patients suffer from AAD. Probiotics can help restore and normalize the gut microbiome when antibiotics are prescribed.
- Clostridium difficile Infection
A mild Clostridium difficile infection typically leads to diarrhea and mild abdominal cramping. Severe infections, however, can even be life threatening and can lead to extreme diarrhea, severe abdominal cramping, weight loss, and dehydration, and can even lead to kidney failure. The infection takes place because C. difficile colonizes the intestine and releases toxins which cause diarrhea. Treatments are not usually fully effective, and patients relapse because some C. difficile spores evade treatment and survive. Studies have shown that probiotics can help prevent and improve symptoms of C. difficile infections.
- Colorectal Cancer
Colorectal cancer refers to any cancer that affects the colon or the rectum. There is evidence that indicates that diet – and probiotics – can reduce the risk of cancers, particularly colorectal cancer. As elaborated in more detail below, probiotics help protect against colon cancer by modifying the composition of the gut microbiome, and lowering the number of bacteria that produce harmful, carcinogenic biproducts. Probiotics produce chemicals that inhibit cell proliferation and act as detoxifying agents. Probiotics can also help in the elimination of carcinogenic compounds from the body.
How do probiotics work?
While there isn’t a single definite answer for how probiotics work, scientists have a few models explaining how they benefit the body.
- They reduce the degree of colonization of the gastrointestinal tract by pathogenic bacteria through competition. Probiotic microorganisms compete for binding sites on the walls of the intestines and compete for nutrients. This is one of the methods that scientists believe could be at play with respect to probiotics being able to reduce the risk for cancer. Studies have shown that patients with colorectal cancer have lower numbers of Lactobacillus (probiotic bacteria) and higher levels of Salmonella and Clostridium, which are involved in the pathogenesis of colorectal cancer. Probiotic bacteria can grow at the expense of bacteria like Salmonella and Clostridium, reducing the risk of cancer.
- There is research that suggests that probiotics could help degrade receptors in the walls of the gastrointestinal tract that bind toxins. boulardii, a yeast, helps protect against C. difficile infection symptoms by degrading the toxin receptor on the intestinal mucosa.
- Probiotic bacteria produce a variety of chemicals including organic acids, hydrogen peroxides, and bacteriocins that inhibit the activity of harmful bacteria. Enzymes produced by bacteria in the intestines – while helping with digestion – can produce carcinogenic biproducts. Organic acids and hydrogen peroxides produced by probiotics acidify the intestinal environment and can inhibit the biochemical activities of these enzymes, reducing the number of carcinogens produced.
- Probiotics help in the elimination of carcinogens. Carcinogenic compounds bind to the cell walls of probiotic bacteria and are eliminated through feces.
- Probiotics produce compounds that have anticarcinogenic activity. Probiotics produce short chain fatty acids which serve as a source of energy for colonocytes and promote the death of cancer cells.
Recent research has shown that the microbes in the gut play a vital role in our overall wellbeing. A lot of questions about how probiotics influence the gut microbiome remain unanswered, in no small part because accessing the gut microbiome to study isn’t easy – it requires invasive surgery. What is clear, however, is that probiotics don’t just give yogurt and kombucha the unique taste that most of us enjoy, but also provide us several surprising health benefits.
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