Most of us have been constipated at some point. Constipation refers to difficulty with or infrequent bowel movement. There has been a lot of research focused on exploring the role of probiotics in preventing and treating chronic constipation.
The human gut is home to trillions of microorganisms of more than a thousand different species of bacteria. While one-third of microbiota that resides in the gut is common to many, two-thirds of these are specific to every individual. Both the number and type of microorganisms are believed to play a key role in gut health.
Prevalence of constipation
As the most common digestive health-related complaint, constipation is the reason behind 2.5 million outpatient clinic visits in the U.S. every year. Apart from the severity of symptoms ranging from bloating to dry, hard or lumpy stools, pain during defecation, and loss of appetite, the cost of treating constipation with laxatives can often run into billions of dollars.
As per an analysis of four surveys including the National Health Interview Survey, the National Ambulatory Medical Care Survey, the National Hospital Discharge Survey, and the Vital Statistics of the United States, more than four million people suffer from frequent constipation in the U.S. A 2018 review revealed a worldwide prevalence of 16 percent, while in Europe, prevalence rates are as much as 81 percent according to a meta-analysis.
While constipation is in itself not a disease, it can be a sign of another medical problem. In recent times, there is an increasing interest in the concept of ‘functional foods’ that offer health benefits beyond nutrition. These foods promote health, aid in disease prevention as well as in managing symptoms. ‘Functional food’ is a term that was used first in Japan for substances in foods other than the traditional nutrients that could delay the onset of some diseases or lower disease risk.
Across the globe, functional foods are known as nutraceuticals, therapeutic foods, biotherapeutics, or superfoods. Probiotics are one such functional food that have been extensively researched for their role in preventing and relieving constipation, among other conditions.
What causes constipation?
The causes of chronic constipation include the lack of physical activity, insufficient fluid intake, stress, ignoring the urge to pass stools, among others. As per the National Institutes of Health (NIH), constipation is likely to occur in the following categories of people:
- Women who are pregnant or following childbirth.
- Older adults.
- People who consume very little or no dietary fiber or a diet low in fiber-rich fruits and vegetables.
- Certain dietary supplements or medicines (pain medications such as morphine and codeine, antidepressants such as fluoxetine and Imipramine, antiepileptic drugs including phenytoin and carbamazepine, iron, and calcium supplements).
- Certain health problems such as irritable bowel syndrome, diverticulosis, intestinal obstruction, cancer of the digestive system, and other chronic conditions such as Parkinson’s disease, diabetes, or stroke.
What are probiotics?
“Pro” means ‘for’ and “biotics” mean ‘living organisms.’ Probiotics are living organisms such as yeast or bacteria that confer additional health benefits. The World Health Organization (WHO) defines probiotics as “live microorganisms that confer a health benefit on the host when administered in adequate amounts.”
Probiotics were discovered by Elie Metchnikoff, a Russian zoologist, in 1907, who proposed that the longer life span of Bulgarian peasants was due to the yogurt they consumed that contained live bacteria. Metchnikoff postulated that bowel health and lifespan could be enhanced by replacing harmful bacteria in the intestine with beneficial lactic acid bacteria.
The human intestine has between 300 and 1000 species of bacteria, and most of them are found in the colon. Commonly found species are Bacteroides, Bifidobacterium, Peptostreptococcus, Clostridium, and Peptococcus, while Lactobacillus is present to a lesser extent. While many beneficial microorganisms have been identified, Lactobacilli and Bifidobacteria are commonly associated with probiotics. While Bifidobacteria gets passed on to the intestine through breast milk, lactobacillus is found in certain foods. These organisms begin to colonize the intestine after birth. The concentration of these microorganisms can be increased by consuming a high-quality and multi-strain probiotic like Jetson.. Insoluble fiber present in whole grains, fruits, and vegetables promotes the growth of probiotics, and acts as a “food” for the good bacteria.
Probiotic foods as generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA). To be classified as a probiotic, the food, pill or drink must contain live cultures of microorganisms.
Constipation and gut microbiota
Studies show that probiotics significantly reduce transit time, increase stool frequency while improving stool consistency. Probiotics also improve other symptoms associated with constipation, including the feeling of incomplete evacuation, bloating, hard stools, and ease of expulsion.
Ohkusa et al. carried out PubMed searches of studies till 1st August 2018, and found that stool samples of IBS with constipation sufferers had lower levels of a probiotic bacteria called Actinobacteria, including Bifidobacteria, while there was a higher concentration of Bacteroidetes. Researchers found that probiotics were effective in most randomized controlled trials in relieving chronic constipation with few side effects. Evidence points to the fact that gut microbiota dysbiosis could be a contributing factor for functional constipation and irritable bowel syndrome with constipation as the chief complaint.
Khalif et al. showed that patients who had functional constipation had lower levels of beneficial bacteria, including Lactobacillus, Bifidobacterium, and increased levels of harmful microbes such as fungi, Escherichia coli, and Staphylococcus aureus.
While stool samples were taken to analyze fecal microbiota in many studies, Parthasarathy et al. conducted gene sequencing with an analysis of 16S rRNA metagenomics. This study found that while there was no difference in the number of bacteria in healthy control groups and those with constipation, increased levels of harmful Bacteroidetes were present in the mucosa of people who had IBS.
Researchers have also found that gut microbiota of Crohn’s disease (CD) patients had lower diversity with increased amounts of harmful bacteria such as Enterobacteriaceae, Fusobacteriaceae, Pasteurellaceae, Neisseriaceae, and reduced levels of beneficial ones including Bifidobacteriaceae, Clostridiales, and Erysipelotrichaceae.
What’s the evidence?
Researchers from King’s College of London undertook a meta-analysis titled “The effect of probiotics on functional constipation in adults: a systematic review and meta-analysis of randomized controlled trials” published in AJCN (American Journal of Clinical Nutrition).
Fourteen well-conducted studies where people with constipation were assigned randomly to consume either a placebo or probiotics were reviewed. Researchers found that probiotics, on an average, slowed down the transit time of food in the gut by 12.4 hours, while weekly bowel movements increased by 1.3 times. Probiotics also helped soften stools, which made them easier to pass. Bifidobacterium was the probiotic that seemed to be the most effective.
In 2010, Del Piano et al. conducted a large scale randomized controlled trial (RCT) and found that Lactobacillus plantarum, Bifidobacterium lactis, or Bifidobacterium breve were able to relieve constipation-related symptoms such as abdominal pain, difficulty in the evacuation, and hard stools.
An earlier study found that Lactobacillus casei Shirota increased the frequency of bowel movement and softened stools significantly in patients suffering from irritable bowel syndrome (IBS). In a 2013 study by Wu et al., Lactobacillus reuteri was found to improve the frequency of bowel movement in adults as well as children.
Huang and Hu reviewed six RCTs that studied the effect of probiotics in relieving constipation in children and found a significant increase in stool frequency.
In a 2018 double-blind, randomized study in Korea, researchers found that probiotics (L. Plantarum) significantly improved stool consistency in people who had chronic constipation. Additionally, it was found that the beneficial effect continued even after the probiotic supplementation was stopped.
The possible mechanisms of action
Several studies have examined the possible mechanisms of action of probiotics in treating constipation. Grehan et al. propose that probiotics work by altering gastrointestinal microbiota in a positive manner. Another mechanism proposed is that probiotics exert an antinociceptive role (blocking painful sensation), which helps open colonic tight junctions while promoting the action of nitric oxide in the gut. Nitric oxide is linked to a range of functions in the gastrointestinal tract, including motility, blood flow regulation, mucosal function, and reduction of inflammation.
Waller et al. proposed that probiotics increase short-chain fatty acids and lactate production in the gut while decreasing luminal pH, which increases gut peristalsis (contraction), which, in turn, promotes gut motility.
Sources of probiotics
Yogurt: One of the most widely consumed probiotic foods is yogurt. In the U.S., probiotic yogurt should contain 100 million live cultures of probiotics per gram of yogurt to get the National Yogurt Association (NYA) seal of “Live & Active Cultures.” Frozen yogurt should contain, at the time of manufacturing, a minimum of 10 million live cultures per gram. The main bacterial species in yogurt include Streptococcus thermophilus and Lactobacillus bulgaricus. Lactobacillus rhamnosus is also used in yogurt and other fermented dairy products. Some commercial probiotic products contain Lactobacillus casei Shirota as the main culture. Though yogurts contain live cultures, they also contain A LOT of sugar, which is why it’s best to opt for a different source for your probiotics.
Kefir: The fermented beverage is said to have originated in Russia and Turkey. The sources of Kefir is milk from different animals, including cow, sheep, goat, or plant-based sources such as rice, soy, and coconut. To the milk, cultures of Lactobacillus kefiri or Lactobacillus rhamnosus gg are added, and the milk is allowed to ferment. After the fermentation, the grains of probiotics are strained out. While Kefir is a source of probiotics, it isn’t a good option for anyone who’s avoiding dairy or who has a dairy intolerance.
Kimchi: Kimchi is a fermented, well-known traditional food in Korea. There are many types of Kimchi, based on processing methods and raw materials. The most widely used among these are cabbage and radish, with the taste described as sour, sweet, or carbonated. Microorganisms present in Kimchi include lactic acid bacteria with Weissella, Leuconostoc, and Lactobacillus believed to play a central role in the fermentation of Kimchi.
Sauerkraut: Like Kimchi, Sauerkraut that translates to “sour cabbage,” is raw cabbage fermented by different types of lactic acid bacteria. With a distinct sourness, sauerkraut is popular in many European countries.
Aged cheese: Lebne is a fermented product made from yogurt and is popular in the Middle East as a spreadable form of cheese. Aged cheeses such as Swiss, Cheddar, Gouda, Parmesan have the starter culture as lactic acid bacteria. Propionibacterium freudenreichii plays a key role in the fermentation of some types of cheese, such as Emmental cheese and Jarlsberg cheese.
Miso: Miso is a Japanese fermented food and is made by fermenting soybeans. The starter culture for fermentation is typically Aspergillus oryzae fungus. Miso paste is used to make different foods, including spreads, sauces, soups, and pickled vegetables.
Kombucha: The fermented drink is made using a specific culture called scoby and sweetened tea. Scoby is short for ‘symbiotic culture of bacteria and yeasts.’ These microorganisms convert the sugar in tea to ethanol and acetic acid, giving the tea a sour taste.