What Are Probiotics?

Probiotic Food and Supplement

Getty Images / Science Photo Library

Table of Contents
View All
Table of Contents

Probiotics are a combination of live bacteria and yeasts, which are generally good for your well-being but are especially great at promoting digestive health.

When you think of bacteria, it's easy to immediately associate it with conditions like acne or more serious diseases. 

However, there are good and bad forms of bacteria. Probiotics are one of the good guys—so much so that they live naturally in your body and can help to fight off bad bacteria that can negatively affect your health.

As an organism within your body, probiotics make up what is known as the microbiome—a community of microorganisms like fungi, viruses, protozoa, and, as we’ve seen, bacteria. The microbiome is important for maintaining immunity, improving digestive health, and preventing heart disease. Probiotics may be found in the gut, mouth, vagina, urinary tract, skin, and lungs.

As a result of the many potential health benefits, probiotic supplements are widely used. In fact, a 2012 National Health Interview Survey found that about four million American adults had used probiotics within a recorded month.

It's important to note that while probiotics are commonly consumed as dietary supplements, they are also found in foods such as yogurt and kimchi and may also be ingredients in pharmaceuticals. If you consume a variety of probiotics through your diet, you probably don't need to supplement. And if you do decide to supplement, it's a good idea to do so under the supervision of a registered dietitian or medical practitioner.

While easy to mix up, probiotics are not to be mistaken for prebiotics—a dietary fiber that feeds probiotics and other good bacteria in your body.

Strains of Probiotics

Probiotics are named by identifying the genus, species, and strain.

For example, let's look at Bifidobacterium lactis HN019.

  • HN019 signifies the strain, or the simplest level of identification, which can be thought of like an individual family member.
  • Lactis is the species or the larger immediate family of the bacteria.
  • Bifidobacterium is the genus or the strain's extended family.

Each strain has specialized benefits for the health. There are many types of strains, but seven main genera (plural of genus, or the strain's larger family) of probiotics typically found in probiotic supplements. These include:

  • Lactobacillus
  • Bifidobacterium
  • Saccharomyces
  • Streptococcus
  • Enterococcus
  • Escherichia
  • Bacillus

As we noted, probiotics are also found in yeasts. Common probiotic yeast strains include Saccharomyces cerevisiae var. Boulardii, Metschnikowia ziziphicola, and Saccharomyces cerevisiae.

Sources of Probiotics

You can get your probiotics fix from two of the most popular fermented foods — yogurt and cheese.

Other sources of this good bacteria include:

  • Japanese miso
  • Sauerkraut
  • Kefir
  • Kombucha
  • Sourdough
  • Kimchi
  • Olives
  • Pickles
  • Fermented soy foods like tempeh

Probiotic strains have also been found in non-fermented foods like:

  • Cereals
  • Legumes
  • Cabbage
  • Maize
  • Sorghum

These foods also contain prebiotics. Prebiotics are the "food" for probiotics. They help probiotics thrive and populate and in addition to helping to improve gastrointestinal health, they may also potentially enhance calcium absorption.

Probiotics may also be found in interesting places like the foremilk (colostrum) of breastmilk and your gastrointestinal tract. It is also present in animal gut—pigs, rats, some marine/freshwater fish, as well as certain poultry have probiotics lurking in their insides.

Characteristics of Probiotics

For microbiomes to be counted as probiotics, they have to possess the following characteristics:

  • Durability in harsh conditions: Probiotics must be able to power through low pH levels in the stomach or gastric juices.
  • Survival in the intestine after digestion: This will require resistance to bile acid, as well as stomach acid.
  • Antimicrobial activities: Probiotics should be able to fight against microbes like fungi and even bacteria.
  • Isolation from different sources: Probiotics used by humans are popularly isolated from dairy or non-dairy sources such as fermented foods. However, they may also be isolated from the human body for our use.
  • Safe for consumption: Probiotics must be deemed safe in order for humans to enjoy their health benefits.

How Do Probiotics Work?

Probiotics supply their health benefits primarily from the gastrointestinal tract, which includes the mouth, esophagus, stomach, small and large intestine, as well as the anus. However, probiotics have a laser focus on microorganisms in the intestine, which they work on to improve and maintain health.

Unfortunately, it isn’t exactly certain how probiotics perform their role in the body. What has been determined is that they can boost the body’s immunity against dangerous outsiders. They also work to make sure the body gets better at fending off these invaders.

In addition to immunity, probiotics perform anti-inflammatory roles within the body. Claims have also been made that probiotics may help with managing the body’s response to pain.

Many foods that contain probiotics also contain prebiotics. Prebiotics are the "food" for probiotics. They help probiotics thrive and populate and in addition to helping to improve gastrointestinal health, they may also potentially enhance calcium absorption. Prebiotics are found in food such as such as bananas, onions, garlic, leeks, asparagus, artichokes, beans and whole-grain foods.

Benefits of Probiotics

Probiotics offer a variety of health benefits. They may have the following beneficial effects on the body:

Regulate the Body’s Immune Response

Probiotics regulate the body's immune response in different ways.

Probiotics can encourage the activities of antibodies like T cells and stop bad bacteria in their tracks by preventing them from accessing the intestine's protective covering or barrier. They also enhance the protection offered by the intestine's covering and stimulate an anti-inflammatory response when the body is confronted by dangerous outsiders.

Improve Symptoms of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a disorder of the intestine that can cause diarrhea, cramps, gas, and constipation. While it's a little hard to pinpoint what causes this condition, links have been drawn to food sensitivity, brain-gut interactions, as well as bacterial overgrowth.

Probiotics can protect against harmful, IBS-causing bacteria through their bacteria-fighting properties. They also support the intestinal barrier to prevent attacks by dangerous outsiders. Studies show that probiotics may help to normalize bowel movements in people living with IBS.

Reduce Atopic Dermatitis in Children

Probiotics may help manage the appearance of atopic dermatitis (an itchy skin inflammation that usually affects children) depending on the severity of the condition, and can also provide prenatal support to prevent the baby from contracting this condition.

Probiotics may induce skin repair after facing the inflammation that led to dermatitis. They have also been shown to increase the rate of skin tissue turnover. This encourages the appearance of newer, better-looking skin.

This bacteria can also tap into its immunity-boosting abilities to reduce the severity of atopic dermatitis.

Help Manage Antibiotic-Induced Diarrhea

Taking antibiotics to manage or prevent bacterial infections can sometimes lead to diarrhea. This occurs because antibiotics tend to disturb the microbiomes in the intestine, which can cause excessive fluid to build up. The intestinal fluid build-up encourages diarrhea, and the disruption of the microbiome may also increase the risk of infections from other disease-causing organisms.

Certain probiotic strains are able to reduce the chances of antibiotic-associated diarrhea. This applies to patients of all ages, especially those above 65 who are at a higher risk of developing this condition.

May Control Obesity

There's a chance that probiotics may help with managing weight.

In animals, some strains of probiotics have been shown to prevent weight gain when consumed with a high-fat diet.

For humans, while it isn't always certain, there is a chance that probiotics can cause a significant decrease in body weight and body fatafter continuous use over a period of weeks or months. This is made possible by the manipulation of gut bacteria by probiotics.

This particular benefit requires more research because some studies suggest that probiotics have very little impact on weight loss. It should also be noted that taking probiotics alone will not result in weight loss.

Side Effects of Probiotics

Despite the many potential benefits of probiotics, the jury is still out on just how safe probiotic supplements are. There have been rare reports of fungemia (a condition that leads to the presence of yeast or fungi in the blood) and bacteremia (the presence of bacteria in the blood). Probiotic use may also be linked with an inflammation of the tissue lining the heart.

You also want to be careful with using probiotics if you're suffering from a serious illness, have recently had surgery, or are currently experiencing a compromised immune system.

Note that probiotics can be marketed as a dietary supplement, a drug, or a food ingredient. Most probiotics are sold as dietary supplements, which are not regulated by the Food and Drug Administration (FDA), so you may want to take a closer look at the product before taking it.

Always consult with your health care practitioner before adding a supplement, such as probiotics, to your routine. Different strains of probiotics have different functions in the body so the type you need may depend on what you are using it for.

A Word From Verywell

Probiotics are beneficial bacteria that can be an excellent addition to a healthy lifestyle. They help to maintain gut health, are useful for maintaining immunity, and may even offer protection against certain skin diseases.

Even better, this bacteria is readily available in fermented foods and is naturally present in specific parts of the body. To support your probiotics consumption, dietary supplements are also readily available. Before supplementing, discuss your needs with your physician or registered dietitian.

Was this page helpful?
26 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Zheng D, Liwinski T, Elinav E. Interaction between microbiota and immunity in health and disease. Cell Res. 2020;30(6):492-506. doi:10.1038/s41422-020-0332-7

  2. hreiner AB, Kao JY, Young VB. The gut microbiome in health and in disease. Curr Opin Gastroenterol. 2015;31(1):69-75. doi:10.1097/MOG.0000000000000139

  3. Tang WHW, Li DY, Hazen SL. Dietary metabolism, the gut microbiome, and heart failure. Nat Rev Cardiol. 2019;16(3):137-154. doi:10.1038/s41569-018-0108-7

  4. Myclevelandclinic.org (n.d) Probiotics: what it is, benefits, side-effects, food and types

  5. Nccih.nih.gov (n.d) Statistics from the National Health Interview Survey

  6. Klemm, Sarah RDN, CD, LDN. Prebiotics and Probiotics: Creating a Healthier You. Academy of Nutrition and Dietetics. Updated February 2020

  7. National Institutes of Health Office of Dietary Supplements. Probiotics Fact Sheet for Consumers. Updated March 24, 2021.

  8. Agarbati A, Canonico L, Marini E, Zannini E, Ciani M, Comitini F. Potential Probiotic Yeasts Sourced from Natural Environmental and Spontaneous Processed Foods. Foods. 2020;9(3):287. Published 2020 Mar 4. doi:10.3390/foods9030287

  9. National Institutes of Health Office of Dietary Supplements. Probiotics Fact Sheet for Health Professionals. Updated June 3, 2020.

  10. Sornplang P, Piyadeatsoontorn S. Probiotic isolates from unconventional sources: a reviewJ Anim Sci Technol. 2016;58:26. Published 2016 Jul 19. doi:10.1186/s40781-016-0108-2

  11. Syngai GG, Gopi R, Bharali R, Dey S, Lakshmanan GM, Ahmed G. Probiotics - the versatile functional food ingredientsJ Food Sci Technol. 2016;53(2):921-933. doi:10.1007/s13197-015-2011-0

  12. Myclevelandclinic.org (n.d) Probiotics: what it is, benefits, side-effects, food and types.

  13.  Fijan S. Microorganisms with claimed probiotic properties: an overview of recent literature. Int J Environ Res Public Health. 2014;11(5):4745-4767. Published 2014 May 5. doi:10.3390/ijerph110504745

  14. Sornplang P, Piyadeatsoontorn S. Probiotic isolates from unconventional sources: a review. J Anim Sci Technol. 2016;58:26. Published 2016 Jul 19. doi:10.1186/s40781-016-0108-2

  15. Shahrokhi M, Nagalli S. Probiotics. In: StatPearls. StatPearls Publishing; 2021.

  16. Yan F, Polk DB. Probiotics and immune health. Curr Opin Gastroenterol. 2011;27(6):496-501. doi:10.1097/MOG.0b013e32834baa4d

  17. Saha L. Irritable bowel syndrome: pathogenesis, diagnosis, treatment, and evidence-based medicine. World J Gastroenterol. 2014;20(22):6759-6773. doi:10.3748/wjg.v20.i22.6759

  18. Didari T, Mozaffari S, Nikfar S, Abdollahi M. Effectiveness of probiotics in irritable bowel syndrome: Updated systematic review with meta-analysis. World J Gastroenterol. 2015;21(10):3072-3084. doi:10.3748/wjg.v21.i10.3072

  19. Crovesy L, Ostrowski M, Ferreira DMTP, Rosado EL, Soares-Mota M. Effect of Lactobacillus on body weight and body fat in overweight subjects: a systematic review of randomized controlled clinical trials. Int J Obes (Lond). 2017;41(11):1607-1614. doi:10.1038/ijo.2017.161

  20. Nih.gov (n.d) Probiotic skin therapy improves eczema in children, NIH study suggests.

  21.  Rusu E, Enache G, Cursaru R, et al. Prebiotics and probiotics in atopic dermatitis. Exp Ther Med. 2019;18(2):926-931. doi:10.3892/etm.2019.7678

  22. Barbut F, Meynard JL. Managing antibiotic-associated diarrheaBMJ. 2002;324(7350):1345-1346. doi:10.1136/bmj.324.7350.1345

  23.  Rouxinol-Dias AL, Pinto AR, Janeiro C, et al. Probiotics for the control of obesity - Its effect on weight change. Porto Biomed J. 2016;1(1):12-24. doi:10.1016/j.pbj.2016.03.005

  24. Brusaferro A, Cozzali R, Orabona C, et al. Is It Time to Use Probiotics to Prevent or Treat Obesity?. Nutrients. 2018;10(11):1613. Published 2018 Nov 1. doi:10.3390/nu10111613

  25.  Borgeraas H, Johnson LK, Skattebu J, Hertel JK, Hjelmesaeth J. Effects of probiotics on body weight, body mass index, fat mass and fat percentage in subjects with overweight or obesity: a systematic review and meta-analysis of randomized controlled trials. Obes Rev. 2018;19(2):219-232. doi:10.1111/obr.12626

  26.  Shahrokhi M, Nagalli S. Probiotics. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan.