Health Benefits of Probiotics

Today, the global probiotics market is a 65 billion-dollar industry, and it is expected to grow to 75 billion by 2026. There are many claims about the health benefits of probiotics, and the list of over-the-counter probiotic supplements seems endless.

So, what are probiotics, exactly? Is there any evidence to support the claims surrounding them? This article will break down the scientific consensus on their effectiveness for five major health conditions being looked at by researchers.

What Are Probiotics?

Probiotics are living microorganisms; mainly bacteria and yeast; that have a physiological effect on human health. They’re naturally produced in certain foods during the fermentation process, but they can also be added to commercial products or taken in the form of a dietary supplement.

In the gastrointestinal tract, probiotics feed on complex carbohydrate chains called oligosacchariades. These sugar molecules serve as their “food.” Some products contain a combination of probiotics and prebiotics. These are called synbiotics.

What They Do in the Body

The totality of microorganism activity colonizing the human colon is called the microbiome. The composition of these microorganisms, and how they interact with each other can affect human physiology.

Ingested probiotics work by influencing the baseline microbiome in a person’s body. Some examples of the effects of probiotics include:

  • Decreasing growth of unfriendly bacteria in the colon.
  • Synthesis of the B complex vitamins and vitamin K.
  • Production of lactic acid to keep the colon at a healthy pH.
  • Neutralization of the toxic byproducts of metabolism.
  • Reinforcing the gut barrier to keep harmful bacteria from entering the bloodstream .

Benefits of Probiotics: A Look at the Evidence

According to the National Institutes of Health Fact Sheet, probiotics have been studied in conjunction with several human health conditions to see if there is a benefit.

Let’s take a look at the relevant research on the impact of probiotics on these five conditions:

  1. Eczema
  2. Obesity
  3. Irritable bowel syndrome
  4. High cholesterol
  5. Pediatric acute infectious diarrhea


Eczema is a common chronic inflammatory skin disorder that affects both children and adults. Several meta-analyses have reviewed the effects of different species and strains of bacteria on the condition.

A 2014 review of 13 studies showed a decrease in symptoms for people 18 years and younger after two months of probiotic supplementation. More recently, a 2018 review showed that treatment with Lactobacilllus, Bifidobacterium, and Propionibacterium decreased the chances of developing eczema in participants between the ages of six months and nine years.

A second 2018 review that looked at eight studies of infants zero to three years demonstrated that supplementation with Lactobacilllus decreased symptom severity, but no significant change was seen in children who took the Bifidobacterium. Worth noting is that supplementation did not significantly decrease symptoms in those with milder forms of the disease.

Conclusion: The available evidence supports the claim that the use of probiotics can reduce the risk of developing eczema in young people, but these products are strain-dependent and might provide only limited relief depending on how severe the patient’s condition is.


The microbiome plays a role in the processing of calories from food. Animal studies using mice have shown that probiotics affect the use of calories from the diet, as well as the number of calories either burned or stored as fat in the body. It remains unclear whether these mechanisms work the same in humans.

So far, the reviews of clinical trials on humans have been mixed. A 2017 review of 14 studies showed that “Lactobacillus given to overweight or obese individuals for three weeks to six months significantly decreased body weight and/or body fat in nine of the trials, had no effect in three trials, and increased body weight in two trials.”

Another systematic review of 15 studies using the same participant criteria found that supplementing with multiple different strains at varying doses resulted in a reduction of weight, body mass index, and total body fat, but the changes were too small to be statistically significant.

The most recent review from 2019, which examined 19 studies, found no change in weight or body mass index after supplementation with either probiotics or synbiotics, though waist circumference was marginally reduced.

Conclusion: The evidence to date suggests probiotics might affect BMI and body weight, but whether these effects are significant enough to warrant recommendations still needs investigating. Also, how well they work may depend on several factors, including specific strains, doses, and duration of treatment. More controlled clinical trials in humans are needed to study the relationship between probiotics and body weight.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that causes abdominal discomfort, pain, bloating, and/or changes in stool regularity. Although scientists aren’t certain of its cause, a growing body of clinical trials suggests that an unbalanced microbiome may play a significant role.

Most meta-analyses have found probiotics to be beneficial for symptom management of IBS. One review of 23 studies found that supplementation with single strains as well as mixtures decreased the duration of symptoms by 21%, and that probiotic mixtures were significantly more effective (12).

A more recent review from 2016, which looked at 35 individual studies, further demonstrated that mixed-strain treatments were more effective at decreasing IBS symptoms than single-strains. This is further evidence that probiotic mixtures are more effective at treating IBS.

Conclusion: The majority of clinical reviews suggest that probiotics can reduce symptoms of IBS. Further research would help to elucidate the most effective strain combinations, as well as appropriate dose-dependence and treatment courses required to be as effective as possible.

High Cholesterol

Scientists have studied the use of probiotics to improve cholesterol levels, but the evidence is mixed at best. A 2015 review of 30 individual studies demonstrated that “those treated with Lactobacillus acidophilus, a mixture of Lactobacillus acidophilus and Bifidobacterium lactis, and Lactobacillus plantarum were associated with significant reductions in total and LDL cholesterol, but Lactobacillus helveticus and Enterococcus faecium were not.” However, a more recent 2019 review of the effect on cholesterol in healthy people found insufficient evidence to conclude that probiotics lower cholesterol levels.

Conclusion: Research suggests that the use of probiotic mixtures that contain Lactobacillus acidophilus, a mixture of Lactobacillus acidophilus and Bifidobacterium lactis, or Lactobacillus plantarum might reduce cholesterol, but more research is needed before clinicians can make evidenced-based recommendations for treatment.

Pediatric acute infectious diarrhea

Acute infectious diarrhea is a common disease that affects children all over the world. A review of 63 studies involving infants and children found that supplementation with probiotics shortened the length of diarrhea by approximately one day. Treatment also resulted in a decrease in the chances that the condition would last, “four or more days”.

Based on the available evidence, The European Society for Pediatric Gastroenterology, Hepatology, and Nutrition has approved two treatments; Lactobacillus rhamnosus and Saccharomyces boulardii; for children suffering from this condition. However, supplementation may not be cost-effective in developed countries like the U.S., because most episodes require no further intervention beyond fluid resuscitation.

Conclusion: More research is needed to evaluate the usefulness and practicality of probiotics on this disease in the United States.

Ways to Add Probiotics to Your Diet

There are two ways to add probiotics to your diet: naturally (mainly through fermented foods) and through supplementation.


Fermented foods are the main source of naturally-occurring probiotics. Fermentation is the process of breaking down sugars without the use of oxygen, which results in the growth of live and active microorganism cultures.

Foods produced through the fermentation process like cheese, kimchi, kombucha, sauerkraut, miso, and apple cider vinegar, are great sources of these microorganisms, but the health benefits of their particular strains have not yet been thoroughly demonstrated.

On the other hand, foods like yogurt and other fermented dairy products contain microorganisms that have demonstrated benefits, but they might be destroyed by digestive enzymes in the small intestine before they can exert any effect. Anecdotally, as someone who has suffered from IBS since my early 20s, I’ve had good results drinking Kiefer milk, which is a fermented milk product. Kiefer contains 10 live strains of microorganisms, making it a nice product because the available data suggests strain mixtures are more beneficial for alleviating IBS symptoms than single strains. I found that drinking Kiefer daily correlated with less cramping and abdominal bloating after about four weeks or so.

Some unfermented foods like milks, juices, cereals, granola, and infant formulas have probiotics added in, but as mentioned, it’s still unclear whether these cultures remain viable long enough to affect health. Scientists are still studying the best formulations (including the most effective combination of prebiotics and probiotics) to ensure the delivery of live bacteria to the colon.


Probiotics are also available as oral supplements in the form of powders, tablets, capsules and/or liquids. These are the forms most often used in clinical trials. Strains vary depending on the manufacturer. The sheer number of strains and strain mixtures combined with multiple factors that can affect survival in the gut make it difficult to determine the effectiveness of these commercial supplements.

According to the National Institutes of Health Fact Sheet, over-the-counter supplements are measured using colony-forming units (CFU). These units represent the number of viable microorganisms in the product. Though some supplements contain up to 50 billion CFU or more per dose, that doesn’t ensure effectiveness. According to the FDA, manufacturers are only required to list the weight of the microorganisms on a product’s label. They don’t have to verify that the microorganisms contained in the product are alive. Fortunately, manufacturers can voluntarily list the CFUs if they choose.

How to Choose a Quality Product

The most important factor to consider when choosing a supplement is making sure that the product contains live microorganisms. Buyer beware of products that list CFUs “at time of manufacture,” because this does not guarantee the cultures will survive before being purchased.

If you have one of the conditions discussed in this article that has seen a benefit from treatment, you should confer with your physician and registered dietitian. They will know which strains, doses, and treatment courses are most appropriate for you based on the available research.

A Word on Safety

Probiotics are wildly touted for their ability to “boost” the immune system, and while it’s true they interact with gut microflora to influence immune response, their safety in this area has not been demonstrated.

A small 2019 study found that melanoma patients were 70% less likely to respond to cancer immunotherapy if they were also taking probiotic supplements. This is especially concerning since many cancer patients take over-the-counter probiotic supplements to help deal with the gastrointestinal side effects of cancer treatments, like diarrhea.


Beware of recent claims circulating the internet about probiotic supplementation to treat COVID-19. There is currently no data to support taking probiotics in any form to prevent or treat COVID-19. Their safety in this population has not been studied.


We’ve covered extensive research showing that probiotics can have an impact on your gut health and microbiome. While they aren’t a magic cure, they can play an important role in optimizing your overall health.

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