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14+ Potential Health Benefits of Probiotics

Written by Biljana Novkovic, PhD | Reviewed by Genius Labs Science Team | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Reviewed by Genius Labs Science Team | Last updated:

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Note that each number in parentheses [1, 2, 3, etc.] is a clickable link to peer-reviewed scientific studies. A plus sign next to the number “[1+, 2+, etc...]” means that the information is found within the full scientific study rather than the abstract.

Probiotics

According to some researchers, probiotics have enormous potential to improve our GI tract, balance the immune system, fight infections and allergies, and improve our mood and cognitive function. What does the current science say? Read on to learn more.

What are Probiotics?

Gut Microbiota

At birth, the sterile human gut is immediately colonized with several types of microorganisms from both the mother and the environment. By the time they reach one year of age, each individual develops a unique bacterial profile [1].

It is estimated that only 10% of the cells in the human body actually belong to the body itself. The overwhelming majority of the cells consist of the diverse microbiota of nonpathogenic bacteria, 1-2 kg of them living in the gut alone [2].

Gut microbiota consists of at least 1014 bacteria [3], comprised of at least 160 different bacterial species from a pool of 1,000 – 1,150 [1].

Gut microbiota includes ~30 species of Bifidobacterium, 52 species of Lactobacillus, and others, such as Streptococcus and Enterococcus [4].

The genome of the entire gut microbiota named as “microbiome” exceeds the human nuclear genome by at least 100 times [3].

Human gut microorganisms are strongly involved in diverse metabolic, nutritional, physiological, and immunological processes [5]. They play an important role in energy homeostasis and through the microbe-gut-brain axis [3] by impacting our mood and cognitive abilities. They also stimulate the immune response, prevent pathogenic and opportunistic microbes/bacteria, and produce vitamins such as B and K [1].

Diet can exert a profound effect on the gut microbiota profile, and people in different parts of the world have different bacterial profiles [6]. For example, there is an association of Bacteroides and high animal fat or protein diets, while Prevotella is associated with a high carbohydrate diet [6].

Changes in microbiota composition can increases susceptibility to infections, immune disorders, inflammation, oxidative stress and insulin resistance [5].

The gut microbiota are the beneficial bacteria that live in the digestive tract. They are affected by diet, and they exert profound effects on many aspects of human health.

Probiotics

Probiotic bacteria are live microorganisms known as “friendly gut bacteria” which when present and/or administered in adequate amounts can have potential health benefits [1].

The term “probiotic” comes from the Greek term ‘for life’ [5].

Probiotics have been regarded as beneficial since ancient times (particularly lactic acid bacteria – Lactobacilli and Bifidobacteria), but they came into the spotlight in the late 1800s and early 1900s, when it was proposed that consuming yogurt containing Lactobacillus would decrease toxin-producing bacteria in the gut and increase longevity [5].

Naturally occurring probiotic bacteria exist in fermented food products such as yogurt, kefir, sauerkraut, cabbage kimchee, and soybean-based miso and natto [1].

The most common probiotic strains belong to the species Lactobacillus and Bifidobacterium, followed by the genera Streptococcus, Enterococcus, Propionibacterium, Bacillus, and Escherichia. In addition, some yeast species are used as probiotics, for example, S. boulardii and S. cerevisiae [7, 1].

According to some studies, probiotics could potentially enhance the immune system, improve the skin’s function, enhance resistance against allergens, and decrease body pathogens [8].

They may also be anti-inflammatory, help improve blood lipid profile and glucose tolerance, and lower blood pressure and BMI. Note, however, that these benefits remain unproven [9, 10].

Note that in clinical studies, probiotic mixtures are often demonstrated to be better than a single strain for improving indigenous microflora [4].

Probiotics are supplements that contain live colonies of beneficial bacteria. They are available in single strains or mixtures, and they may have wide-ranging health benefits.

Prebiotics

Prebiotics are specific carbohydrates, such as polysaccharides, fructans, and inulins, that can exert beneficial effects on the composition and metabolic activities of gut microorganisms. A diet high in inulin and related fibers, for example, has been shown to increase Bifidobacteria [1].

Synbiotics

A prebiotic and probiotic combination is referred to as a synbiotic when the net health benefit is synergistic [11].

Purported Health Benefits of Probiotics

Despite the promising evidence we discuss below, remember that the FDA has not yet approved probiotics for any condition or health claim. Take any single study – especially an animal or cell study – with a grain of salt, and remember to talk to your doctor before adding probiotics to your daily health plan.

1) Gut Health

Given the importance of the microbiota in gut health, it’s unsurprising that this is the clearest and best-studied area in which probiotics could have benefits.

Probiotics can decrease the number of potentially pathogenic gastrointestinal microorganisms and pathogens, reduce gastrointestinal discomfort, flatulence and bloating, and improve bowel regularity [8, 12, 13, 14, 15].

Probiotic fermented milk containing B. animalis spp. lactis by healthy women may improve GI well-being and decrease the frequency of GI symptoms [16, 17, 18].

Administration of L. helveticus to healthy human subjects resulted in a significant increase in butyrate, beneficial for gut homeostasis [19].

In various clinical studies, probiotic supplements have also:

  • Improved the composition of the gut flora [20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32]
  • Prevented multiple types of diarrhea [33, 34, 35, 36, 37, 38]
  • Relieved constipation [39, 40, 41, 42, 43, 44]
  • Relieved the symptoms of IBS [45, 46, 8, 47, 48]
  • Relieved the symptoms of IBD [49, 50, 51]
  • Strengthened the gut barrier [4]
  • Prevented drug-induced GI damage [8, 52, 53, 54]
  • Promoted healing of gastric ulcers [4]
  • Prevented and helped resolve necrotizing enterocolitis [55, 56, 57, 58]
  • Relieved the pain associated with various gut disorders [59, 60, 61]

For an in-depth exploration of how probiotics might improve gut health, check out this post.

Probiotic supplementation could have many benefits to gut health, including for the relief of diarrhea, constipation, IBS, and IBD.

2) Immune Function

Certain probiotics may help the human immune system fight off different types of infection, from Candida to H. pylori and even the common cold. The gut microbiota cooperate with the host immune system through an extensive array of signaling pathways [5].

Studies with germ-free animals show that the microbiota are necessary for the development and regulation of immunity in the gut, where it prevents the development of inappropriate inflammation [62].

Probiotics activated both innate and acquired immunity in humans [63, 35, 64, 65, 66, 67, 68, 69, 70, 71, 72].

Perhaps most impressively, probiotic supplementation has helped people fight off a number of infectious diseases, including upper respiratory tract infections like the cold and flu [73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84].

Saccharomyces boulardii has also specifically produced benefits against:

  • E. coli infection [85]
  • B. hominis infection [86]
  • Giardiasis [87]
  • H. pylori [4, 88, 89, 90]
  • Candida [91, 92, 93, 94]

Finally, HIV-positive patients appeared to develop stronger immune responses after supplementation with S. boulardii [95].

The possible benefits of probiotic supplementation on immune function are broad and diverse. For a deep dive, check out this post.

Probiotic supplementation improved immune function in several clinical trials, enabling subjects to better fight off infections like cold and flu, among others.

3) Inflammation

Inflammation may be the widest-ranging area in which probiotics have potential benefits. Broadly speaking, probiotic and synbiotic supplementation reduced biochemical markers of inflammation in multiple clinical trials [11, 96, 97].

More specifically, probiotics have benefited people with:

There is a huge amount of information available for each of these individual potential benefits; check out this post to learn more!

Probiotics downregulated harmful inflammation in multiple clinial studies of a variety of inflammatory conditions, from celiac disease to rheumatoid arthritis.

4) Heart Health

High cholesterol and blood pressure are among the most important risk factors for cardiovascular disease, and certain probiotics have produced beneficial changes to both in clinical trials.

In humans, probiotic supplementation has:

  • Decreased LDL cholesterol [5, 115, 5, 116]
  • Decreased total cholesterol [5, 116, 117]
  • Increased HDL cholesterol [3, 11, 118]
  • Decreased triglycerides [5, 116, 119]
  • Decreased blood pressure [120, 121, 122, 123]
  • Reduced arterial stiffness [124]

As these are all considered improvements to risk factors for heart disease, many researchers have suggested that probiotics could therefore help prevent heart disease [125, 126].

For more about probiotics and their potential benefits to heart health, check out this post.

In many clinical studies, probiotic supplementation improved predictors of cardiovascular disease, including cholesterol, triglycerides, and blood pressure.

5) Weight & Metabolism

According to a few studies, consuming probiotics may reduce body weight and BMI. A greater effect was achieved in overweight subjects, when multiple species of probiotics are consumed in combination or when they are taken for more than 8 weeks [127].

In other studies, various Lactobacillus probiotics have:

  • Induced weight loss [128, 129, 129]
  • Decreased visceral and subcutaneous fat [129, 130, 131]
  • Reduced waist and hip circumference [132, 133]

Daily ingestion of milk containing B. animalis ssp. lactis significantly reduced the BMI, total cholesterol, low-density lipoprotein, and inflammatory markers in humans [134].

Several studies suggest that probiotics may have a significant effect on lowering fasting blood glucose and insulin in diabetics [135, 136, 11, 11].

Probiotic and synbiotic supplementation also has the potential to help with multiple types of liver disease [11, 11, 11, 137].

For a complete exploration of probiotics’ effect on weight and metabolic health, check out this post.

Probiotic supplements produced a number of improvements to metabolic markers, especially in overweight and obese people.

6) Reproductive Health

Pregnancy and birth are among the most vulnerable processes in the life of both mother and child, and probiotics supplements may support immune function and prevent reproductive dysfunction during this time.

The use of a specific set of probiotics during the first 1,500 days of life may lower the risk of infections and inflammatory events in infants [138].

Probiotics have improved immune function in both mother and newborn; mothers taking probiotic supplements were less likely to develop breast infections, and preterm babies were better able to develop feeding tolerance [139, 110, 140, 141, 142, 143, 144].

Furthermore, at-risk and premature babies given probiotics grew more quickly [145, 146, 147].

In animal studies, probiotic supplementation has shown promise in endometriosis, age-related decreases in testosterone, and oxytocin production [148, 149, 150, 150].

For more about the amazing potential benefits of probiotics in reproductive health, and especially in pregnancy and preterm birth, check out this post.

Probiotic supplements’ most impressive potential reproductive benefits may be found during pregnancy and in preterm infants, though animal studies suggest benefits to fertility as well.

7) Cognition & Mental Health

There is an intriguing connection between the gut flora and the brain, which scientists have yet to fully unravel. In the meantime, some intriguing evidence suggests that beneficial probiotic species could potentially improve mood, reduce stress, and even make it easier to fall asleep.

Gut probiotics play a major role in the bidirectional communication between the gut and the brain [8], referred to as the “microbiota-gut-brain” axis. It is now generally accepted that microbiota can affect behavior and modulate cognitive function, especially in older adults [6].

The vast number of microorganisms in our intestines may have a major impact on our state of mind [8]. Gut microorganisms are able to produce and deliver such neuroactive substances as serotonin and gamma-aminobutyric acid (GABA) [8].

In human studies, probiotic supplementation has:

  • Reduced negative thoughts in non-depressed individuals [151].
  • Improved mood and reduced depression scores [8, 8, 8]
  • Decreased anxiety, anger, and hostility [152]
  • Decreased cortisol and physical symptoms of stress [153, 154, 155]
  • Improved sleep quality and duration [156, 157]

In animals, probiotic supplementation also protected the nervous system from damage and resolved symptoms in models of OCD, autism, and schizophrenia [158, 159, 160, 6, 161].

To learn more about the potential of probiotics in brain health, check out this post.

Various clinical studies have found a strong link between gut flora and mental state, making it unsurprising that probiotics have improved mood, reduced stress, and decreased depression scores in humans.

8) Skin & Bones

Certain probiotics can improve markers of aging and damage to the skin, teeth, and bones.

According to one study, probiotics may be able to restore acidic skin pH, alleviate oxidative stress, attenuate photoaging, improve skin barrier function, and enhance hair quality [162].

Some researchers believe that the topical application of probiotic bacteria may enhance the skin’s natural defense barriers. Additionally, probiotics, as well as resident bacteria, can produce antimicrobial peptides that benefit skin immune responses and eliminate pathogens. Finally, probiotic creams increased skin hydration and clearness [163, 164, 165, 166, 167].

Meanwhile, some researchers believe that probiotics may be beneficial for managing gingivitis, caries, and periodontitis [168, 110, 169, 170].

Long-term consumption of L. rhamnosus containing milk reduced caries development in children [110].

Finally, Lactobacillus probiotics increased serum calcium levels in elderly adults, and animal studies suggest that they could also increase bone density and prevent bone loss [171, 172, 173, 174].

For more about the potential benefits of probiotics to the skin and bones, check out this post.

Probiotic supplements have delayed or reversed age-related damage to skin, teeth, and bones. They also reduced caries development in children and may help manage other oral diseases.

9) Physical Stress & Wounds

The human body is very, very good at recovering from physical stress: from exercise to wounds to surgery, it heals and does its best to come out stronger on the other side. However, when the body struggles, could gut flora and probiotics pick up the slack? Some research suggests a role for probiotic supplements in exercise , wound healing, and even postoperative recovery.

Human and animal studies suggest that probiotics could improve the healing rate of diabetic ulcers and other types of surface wounds [175, 176, 177].

Probiotic blends improved postoperative outcomes, shortened the duration of antibiotic therapy and hospital stay, and reduced mortality in multiple human studies [178, 179, 180].

In young adult athletes, Lactobacillus probiotics reduced fatigue, improved immune function, and improved mood in multiple studies [181, 182, 182].

Probiotics have had other benefits to athletes as well. In various clinical studies, they:

  • Enhanced protein absorption [183]
  • Reduced muscle damage [183]
  • Accelerated physical recovery [183]
  • Increased vertical jump power [183]
  • Increased time to fatigue [184]

For more about how probiotics can improve the response to various types of physical stress, check out this post.

Probiotics helped people recover from a variety of physical stresses, from exercise to surgery.

10) Detox

Certain probiotic bacteria have demonstrated an ability to bind to some toxins (like heavy metals) and even degrade others (like certain organophosphate pesticides). Could probiotic supplements help prevent damage to the human body caused by such toxins? Some research suggests that this could be the case.

Some species of probiotic bacteria may bind and prevent the absorption of:

And others may degrade:

In the gut, Lactobacillus species may bind and inactivate toxins purported to cause “leaky gut,” inflammation, and even cancer [196, 197, 198, 199, 200, 201].

FInally, probiotics reversed some of the damage to the immune system of smokers [202, 203, 204, 205].

For more about how probiotic supplementation could benefit the human detox system and prevent uptake of toxins, check out this post.

Some probiotic bacteria bind and degrade heavy metals and toxins that can cause health problems in humans.

11) Healthy Aging

When we age, the composition of our gut flora shifts, and our immune response declines. Are these connected? Some researchers think they might be. For one thing, levels of Bifidobacteria decrease as we age [206].

B. animalis spp. lactis beneficially modified gut microbiota in the elderly, increasing Bifidobacteria, Lactobacilli, and Enterococci and reducing Enterobacteria [207].

In multiple studies of elderly subjects, Bifidobacterium and Lactobacillus probiotics enhanced immunity, increased white blood cell activity, and prevented harmful inflammation [208, 209, 210, 211, 212].

Some researchers attribute these benefits, at least in part, to the antioxidant activity of probiotic bacteria like L. casei, L. helveticus, L. fermentum, B. bifidum and B. subtilis [213, 214, 215, 216, 217, 218].

For a more detailed look at the interactions between probiotics and aging, check out this post.

Because human gut flora changes significantly as we age, some researchers are looking into whether probiotic supplementation with species missing from elderly adults could have beneficial effects on the aging process.

12) Nutrient Absorption

Some species of probiotic bacteria directly produce nutrients like folate, while others may create an environment in which more nutrients are available to be absorbed from the gut [195].

Among the nutrients either produced or made more available by probiotic bacteria are:

For more about how probiotics might benefit nutrient status, check out this post.

Some probiotic bacteria produce important nutrients, while others may produce an intestinal environment that promotes nutrient absorption.

13) Food Sensitivities

Certain probiotics may help the human body to distinguish between safe and dangerous compounds and avoid allergic reactions to otherwise harmless foods. Probiotic bacteria can degrade:

Some researchers have therefore suggested that probiotic supplementation could reduce symptoms of intolerance to these compounds.

For a deeper discussion of probiotics in food sensitivities, check out this post.

Some probiotic species can also degrade other compounds that produce symptoms in sensitive individuals, including lactose, histamine, oxalate, and MSG.

14) Cancer

Probiotic bacteria have shown antitumor activities, and some studies suggest they could potentially reduce the incidence of cancer. They may delay cancer onset and progression as well as regulate cell growth mechanisms [234].

Consumption of soy isoflavones in combination with L. casei decreased the risk of breast cancer among Japanese women [235]

L. casei administration significantly reduced the recurrence rate of bladder cancer and colorectal cancer in cancer patients [236].

Beyond this, research into probiotics and cancer has been restricted to animals and cells. For a deep dive into the future of this research, check out this post.

L. casei supplementation has been linked to lower rates of some cancers, while animal research has uncovered a number of other potential avenues for research into probiotics and cancer.

Safety

Remember to talk to your doctor before adding a probiotic to your daily regimen.

Most probiotics are considered safe. However, we do not recommend taking probiotics if you are severely ill or immunocompromised. There have been rare incidents of sepsis, endocarditis, and liver abscess during the use of Lactobacilli; additionally, fungemia has been reported with the use of S. boulardii, primarily in patients with severe comorbidities [33].

The most common reported side effects of probiotics are constipation, flatulence, hiccups, nausea, infection, and rash [33].

Some probiotic bacteria can produce biogenic amines: L. brevis and L. lactis can produce tyramine and putrescine [237, 238, 239]. S. thermophilus can produce low amounts of histamine and tyramine [240]. L. reuteri is able to produce histamine [241, 242].

There is at least one case of S. cerevisiae inducing an allergic response [243]

B. bifidum cell-surface biopolymers (BPs) can interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti-TPO and anti-Tg, respectively). There is a possibility that Bifidobacteria play a role in the pathogenesis of autoimmune thyroid diseases (ATD) in those with a genetic predisposition to ATD [244].

Formulation

Probiotic products can be formulated as capsules, tablets, powders (which are regulated as a dietary supplement), and food ingredients (e.g., yogurts, kefirs) [7].

L. acidophilus and B. longum can survive and adhere better to the gastric mucosa than S. thermophilus and B. infantis/adolescentis/bifidum [4].

L. acidophilus can survive a pH of 3 for 3 hours, and L. rhamnosus can survive 4 hours of incubation at pH 2.5. The viability of several strains of Bifidobacterium was maintained for about 3h in the pH range of 1.5 – 3.0. On the other hand, L. delbrueckii and S. thermophilus do not readily survive stomach acidity [4].

To overcome the inability of some probiotics to survive transit through the stomach, microencapsulated or coated probiotic strains have been developed [4].

Furthermore, even though some viable probiotic strains do not survive gastric transit, their dead forms remain beneficial. These nonviable probiotics are now known as ‘para probiotics’ or ‘ghost probiotics’. Non-viable probiotics ameliorated the anti-inflammatory response in rats with colitis, protected against Candida, and prevented the growth of cancer cells [4].

Each probiotic species comes in many different strains. Some of the properties of each species may be strain-specific or vary between strains. You can find information about each strain in the references linked above.

Further Reading

By Benefit

We’ve compiled much deeper dives into each potential benefit of probiotics. Check them out here:

By Strain

For more technical information, check out these individual probiotic chapters:

Buy Probiotic Supplements

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About the Author

Biljana Novkovic

Biljana Novkovic

PhD
Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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