As a digestive health dietitian I get a lot of questions about probiotics and if they should be supplemented. Recently probiotics gained popularity and have been added to different foods and personal care items, such as drinks, cookies, protein bars, infant formulas, dog food, soap, shampoos, toothpaste and etc.

In this article I would like to tell you about probiotics and if you really need them in supplement form.


Our gut is populated with various critters, such as bacteria, viruses, fungi, archaea, and protozoans. They live in symbiosis as a microbiome and help our bodies to function properly promoting overall health and well-being.  Having a diet that is diverse in plant foods can help to promote the growth of healthy bacteria in the gut.

What are the benefits of good bacteria in the gut?

Healthy bacteria aid in digestion, nutrient metabolism, synthesis of some vitamins and have other healthful functions in the body. They assist in further breakdown of carbohydrates, proteins and polyphenols when they enter the large intestine. When undigested carbohydrates reach the colon, bacteria uses them as a fuel source to produce various metabolites, such as short chain fatty acids (SCFAs) and gases. The majority of SCFA are acetate, propionate, and butyrate which have been shown to have the number of beneficial effects on the human body.  One of them is to keep the lining of the gut barrier intact fighting off the microorganisms that cause illness. (3)

In clinical studies some bacteria strains have shown improvements in symptoms in people with lactose intolerance.  Other strains were responsible for healthy immune system and helped to eliminate various pathogens from the body.  (1)

Also, colonic bacteria can produce certain important vitamins, such as vitamin K and B-vitamins that are essential for humans. We need these vitamins to sustain normal functions in the body. (4)

Dysbiosis occurs when bad bacteria outnumbers the good bacteria in the gut. This may lead to various health problems associated with digestive and autoimmune disorders, obesity, mental health and many more. (4) People may experience bloating, increased flatulence, diarrhea, constipation and other symptoms.  Adding a probiotic to your diet may help to alleviate these symptoms.

What are the probiotics?

The word “probiotics” derived from the Greek language and means “for life”.  Probiotics are live microorganisms that are found in some foods or supplements and usually are referred to as “good bacteria”. According to Food and Agriculture Organization of the United Nations and World Health Organization probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. (5) The research on probiotics is conflicting but many studies show that probiotics promote the growth of good bacteria in the gut and are associated with the number of great benefits. (1) Some scientists believe that it may enhance the immune system and improve the digestive health. (2) In addition, studies show that probiotics may help with antibiotics-associated diarrhea and relieve the symptoms. When probiotics were not sold as supplements, people used to get them from foods and still can nowadays.

Probiotics are usually found in fermented and cultured foods

  • Kefir , yogurt and acidophilus milk
  • Aged cheese
  • Fermented vegetables (cucumbers, beets, carrots, cabbage and others)
  • Sauerkraut
  • Sourdough
  • Injera, a flatbread which is a national dish in Ethiopia and Eritrea
  • Kimchi, popular in Korea
  • Kombucha
  • Miso, nato and tempeh
  • Idli and dosa, fermented from rice and lentils, popular in Indian cuisine
  • Dhokla, fermented batter from rice and split chickpeas.
  • Kvass, fermented beverage made from rye bread, which is famous in Russia
  • Fermented bean curd made from fermented tofu, popular Chinese condiment

In order to get an effect on your microbiome you needs to consume a food that contains live microorganisms, which have to reach the colon live.  These live microorganisms have to survive the shelf life of the product, as well as the acidic environment of the stomach to reach the microbiome in the colon to proliferate.  Not all of the microorganisms will get there.

How much of the probiotic you actually need

In order to get a benefit of probiotics you need to get adequate amounts. How much is adequate?  If you look at probiotics packaging, you probably notice the gigantic amount of millions or billions of live bacteria listed. If you thought the more bacteria you get, the better – you are wrong.  It all depends on the strain of the bacteria studied and how much of the benefit this strain can provide. If 100 million of live bacteria were identified to confer a health benefit or treat a specific condition, you do not need to take billions of this strain to have a better effect. In addition, the health benefit of specific bacteria strain is determined by clinical studies. Different strains of probiotics can have different health benefits.

Do you need to take a Probiotics Supplement?

Even though supplementation with probiotics shows great results in some people, it may not work for others.  The investigation of probiotics and how they affect human health is still under research but shows promising outcomes.  If you include fermented and cultured foods, as well as follow a healthful diet with plenty of fruits, vegetables and whole grains, you do not need to take a probiotic. If you were prescribed a course of antibiotics or experience some digestive issues, you may add a probiotic supplement to your diet. Since probiotics are not clearly regulated by FDA, there is no set dose or directions of administration. In most cases probiotics are safe and don’t cause any symptoms, however check with your healthcare provider for any interactions.

How to choose a food that contains a probiotic

Probiotics contain live bacteria and it can be killed by stomach acid, time and heat. In food production, some foods undergo pasteurization, filtration or preparation that may kill all bacteria, both harmful and beneficial, such as in kefir and yogurt. Thus, choose the foods that have live bacteria added back after pasteurization. It should be listed on the packaging. Otherwise, you are paying for dead bacteria in your food.  Make sure you consume the food before it expires to get the most benefits.  Time decreases the amount of bacteria in the food.



  1. Kechagia M, Basoulis D, Konstantopoulou S, et al. Health benefits of probiotics: a review. ISRN Nutr. 2013;2013:481651. Published 2013 Jan 2. doi:10.5402/2013/481651
  2. Shi LH, Balakrishnan K, Thiagarajah K, Mohd Ismail NI, Yin OS. Beneficial Properties of Probiotics. Trop Life Sci Res. 2016;27(2):73–90. doi:10.21315/tlsr2016.27.2.6
  3. Rowland I, Gibson G, Heinken A, et al. Gut microbiota functions: metabolism of nutrients and other food components. Eur J Nutr. 2018;57(1):1–24. doi:10.1007/s00394-017-1445-8
  4. Clemente JC, Ursell LK, Parfrey LW, Knight R. The impact of the gut microbiota on human health: an integrative view. Cell. 2012;148(6):1258–1270. doi:10.1016/j.cell.2012.01.035
  5. Hill, C., Guarner, F., Reid, G. et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol 11, 506–514 (2014).
  6. Davani-Davari D, Negahdaripour M, Karimzadeh I, et al. Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods. 2019;8(3):92. Published 2019 Mar 9. doi:10.3390/foods8030092

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