What are probiotics? Here’s everything you need to know.


What are probiotics? Here’s everything you need to know.


Think you should be taking a probiotic supplement but are confused about where to start?

Fair enough – there’s a lot to consider when searching for the right probiotic. What are CFUs? What is the best time to take them? And what is your microbiome?

Uncover all the answers here.


What are probiotics?

Probiotics are live microorganisms that have health benefits when taken at recommended amounts. The microorganisms in probiotic products are the same as or similar to microorganisms that naturally live in your gut.

What is in probiotics?

Probiotics may contain different types of microorganisms. Most are bacteria from the Lactobacillus and Bifidobacterium families (also known as species). Apart from bacteria, probiotics might also include yeasts such as Saccharomyces boulardii.

Why do probiotics have different names?

When scientists refer to specific types of probiotics, they identify them according to their genus (a class of things that have common characteristics), species, and strain. For bacterial probiotics, as an example:

Genus Species Strain
Lactobacillus rhamnosus GG
Bidifobacterium lactis UABla-12


There are many species and strains of probiotics, and each contributes something different to the microbiome. Sometimes they work better in certain combinations, which is why you often find several probiotics in one product.

Can I get the same benefits from eating cultured and fermented foods?

Cultured and fermented foods, such as yogurt, kefir, sauerkraut, and kimchi, contain live bacteria cultures. While cultured and fermented foods can have health benefits, the live microorganism counts in foods aren’t standardised or nearly as high as those in a probiotic supplement. Also, factors such as pasteurisation as well as storage length and conditions affect how many microorganisms are still alive when the food is consumed. Another consideration is that your stomach acid and other digestive enzymes and chemicals can potentially reduce the numbers and effects of microorganisms from foods.⁸

What are CFUs?

CFUs are Colony Forming Units – the amount of viable, live bacteria per serving that can potentially survive, divide, and form colonies in your gut. Typical dosages vary based on the product but range from one to 10 billion CFUs per day for children, and three to 50 billion CFUs per day for adults. They can also be much higher depending on the product and use. Dosing recommendations are based on the particular strains and research. Importantly, a higher CFU count doesn’t necessarily make a probiotic more effective. Also, taking more CFUs isn’t always better for you, especially if you’re new to probiotics. If you’re unsure about the best dosing for your needs, check with your healthcare provider.

What are the maximum CFUs of probiotics that you can take in a day?

The recommended daily CFU amount varies from person to person, and between products. Depending on a person’s health condition, most people can take a maximum daily dose equivalent to 400 billion CFUs.

Should I keep my probiotic supplement in the fridge?

Not necessarily – some probiotics are shelf-stable which means you can store them at room temperature. Other probiotics must be refrigerated to keep the microorganisms alive, but this doesn’t mean they are more effective than shelf-stable products. For maximum effectiveness, always store and use your probiotics according to the directions on the label.

How can probiotics remain alive as they pass through my stomach?

Always buy probiotics that are made with special acid protection technology to package and protect them from gastric acid, digestive enzymes, and bile salts. This enhances the delivery of live probiotics to your lower colon where they’re needed. Probiotics are live microbes that can be inactivated by the acids and chemicals in your digestive tract.

What is the difference between a probiotic supplement and a medical food?

Medical foods might contain probiotics, but a medical food contains specific species and strains of probiotics clinically tested to show benefits for a particular heath condition. They are specially formulated and intended for the dietary management of a disease or condition with distinctive nutritional needs that you can’t meet through diet changes alone.

Probiotics often contain nonspecific strains of microorganisms that support your digestive and immune system in more general ways.

How do you choose a good probiotic or the right medical food?

Certain probiotic species and strains are more effective for particular conditions than others. Other considerations area product’s dose, quality, and how it’s manufactured.

If you want to try a probiotic for general health benefits or a medical food to manage a specific health condition, do your research and talk to your healthcare provider. They can recommend the most effective and high-quality product for your needs.

How do probiotics work?

Different probiotics work in different ways, but generally, probiotics help the body, and especially the gut, maintain a healthy community of microorganisms. They help replenish your microbiota and restore and maintain balance in your gut microbiome which may be disturbed because of certain health conditions or long-term exposure to an unhealthy diet, lifestyle, or toxins.

Who should take probiotics?

Probiotics are safe for most people to take. Depending on your overall health, you may benefit from one with general species and strains of bacteria, or a medical food containing specific species and strains clinically tested and shown to help support a healthy microbiome. Scientific evidence suggests that certain species and strains of probiotics may help support a healthy microbiome in people who are dealing with:

  • antibiotic-associated diarrhea (including diarrhea caused by Clostridium difficile)
  • infant colic
  • periodontal disease
  • maintenance of remission in ulcerative colitis
  • IBS symptoms.


In addition, probiotics have potential effects on weight, digestion, and neurological disorders; and may support heart health, immune function, and symptoms of depression and anxiety.

Who should avoid probiotics?

Evidence suggests that probiotics are safe for most people. Still, it’s always wise to discuss using probiotics (or other supplements) with your healthcare provider.

Probiotics are generally not recommended for anyone with a serious illness or compromised immune system.

Is it normal to have some gas and bloating when first taking probiotics?

When starting to use a probiotic supplement, or increasing consumption of more probiotic-rich foods, some people experience mild upset stomach, diarrhea, flatulence, and bloating. Any side effects might be related to the condition and health of your microbiome, but these symptoms are generally mild and should pass after a few days once your body gets used to the new regimen. If you have known sensitivities, such as to certain ingredients or high-FODMAP prebiotics, make sure you choose a probiotic intended for people with sensitive digestive tracts.

What are prebiotics? Are prebiotics the same as probiotics?

No, prebiotics and probiotics are different. Prebiotics are non-digestible food compounds that act as a source of food for probiotics. Consuming prebiotics enhances the health and effectiveness of probiotics by nourishing them so they can survive, thrive, and work better.  Prebiotics often come from plant foods such as fruits, vegetables, whole grains, legumes, nuts, and seeds. If needed, you can also use a prebiotic supplement.

What are synbiotics?

Synbiotics are products that combine probiotics and prebiotics. Prebiotics are a source of food or fertiliser for probiotics, so combining them with probiotics helps stimulate growth and support the effectiveness of the probiotics.

What time of day should I take probiotics?

Follow the instructions on the label of your probiotic supplement. Probiotics vary depending on manufacturer, and may have different instructions on when they are best to take, so it’s always best to follow the advice on the label.

How long should you take probiotics?

Probiotics can be taken daily anywhere from two weeks to two months to completely recolonise the large intestine’s healthy bacteria. However, it depends on your health condition. For example, probiotics for diarrhea associated with antibiotics may show benefit within two to three days, while you may need several weeks to see improvements in digestive symptoms. If you’re unsure about the best dosing for your needs, check with your healthcare provider.

Should I take probiotics with antibiotics?

Antibiotics will kill both harmful and beneficial bacterial. Taking a probiotic during your course of antibiotics is an effective way to repopulate your beneficial bacterial. When taking antibiotics, you should have a two-hour gap before or after taking the probiotics. Also, continue to take your probiotic for at least two weeks after finishing your antibiotic course. That helps repopulate your microbiome with beneficial bacteria so they can fight off any undesirable microbes.

Your Microbiome

What does “the gut” refer to?

The gut is your digestive tract or gastrointestinal (GI) tract. It most commonly refers to your large intestine, but really, your gut is a long tube that begins in your mouth, includes the esophagus, stomach, small and large intestines, and ends at the anus.

What is the difference between microbes, microbiota, and the microbiome?

Microbes are live microscopic organisms, such as bacteria, yeasts, fungi, protozoa, parasites, and other single-celled organisms found in the human body. There are trillions of microbes throughout your body, but about 70% of them live in your colon or large intestine.

Microbiota refers to the collection of microbes that live in a specific environment, such as your gut. Much of the time, people use the terms microbiota and microbiome interchangeably. Technically, the microbiome includes the microbiota, plus all their genes.

What is intestinal flora?

Intestinal flora (or gut flora) is another term for gut microbiota. It refers to the colony of microbes that naturally live and work together in your intestines.

Why is your microbiota or intestinal flora so important?

 A healthy microbiota or intestinal flora is vital because the microbes living in your gut work together to support your health. They help:

  • produce vitamins and other health-promoting compounds
  • maintain the health and integrity of your intestinal lining
  • prevent harmful microbes from entering your GI tract
  • support your immune system in various ways.
What is dysbiosis?

A healthy gut has diverse and significant amounts of beneficial, health-promoting microbes. Dysbiosis is when there is an imbalance in your microbiota, with less diversity and often more unfriendly microbes. Dysbiosis is associated with many health and digestive conditions, including irritable bowel syndrome. It can happen because of:

  • a health conditions
  • a GI infection
  • an unhealthy diet or lifestyle
  • exposure to various toxins in your environment.

Irritable Bowel Syndrome (IBS) and probiotics

What is IBS?

Irritable Bowel Syndrome (IBS), is a functional bowel disorder which causes chronic or recurrent abdominal pain and symptoms such as gas, bloating, diarrhea, and constipation at least one day a week. With IBS:

  • The pain often improves after a bowel movement
  • Your symptoms are associated with changes in your stool form or appearance (watery, loose, or hard to pellet-like)
  • You have a change in stool frequency (you have to go more or less often)


IBS affects millions of people worldwide, primarily women under 50 . It’s not clear exactly what triggers IBS, but potential causes include:

  • Inflammation in your gut caused by an infection
  • Genetics
  • Increased intestinal permeability (leaky gut)
  • Problems digesting certain foods
  • An imbalance in the microbiome (dysbiosis) might cause changes in how your intestines move waste along, increased sensitivity in your GI tract, or changes in your gut-brain axis.
Are there different types of IBS?

 There are three main types of IBS, characterised based on your bowel patterns:

  • IBS with diarrhea (IBS-D)
  • IBS with constipation (IBS-C)
  • IBS with mixed bowel habits (IBS-M).
What is constipation?

Constipation is a change in your bowel habits or stool consistency. You have fewer than three bowel movements a week along with stool that is hard, dry, and difficult or painful to pass. You may also feel like not all stool has passed.¹

What is the gut-brain axis, and how does it affect IBS?

The gut-brain axis is a communication link between your central nervous system (your brain and spinal cord) and your enteric nervous system, which controls your digestive tract. Your gut and brain are connected through a complex system of nerves and chemical messengers. There is also evidence that your gut microbiota can affect your gut-brain axis.²

This system helps manage the muscle contractions in your digestive tract that control the movement of food and waste. It also manages the nerves that sense pain in your intestines. Because the gut-brain axis is a two-way communication system, feelings of stress or anxiety can affect how your gut works and the degree of abdominal pain you feel.

What are the best probiotic species and strains for IBS?

There is clinical evidence that certain species and strains of probiotics can support the improvement of IBS symptoms. For example:

  • L. plantarum reduced abdominal pain and bloating in a four-week study.⁴ A 12-week study showed it reduced the severity of abdominal pain by 67%, diarrhea by 70%, and constipation by 79%. It’s also worth noting that L. plantarum may help improve the quality of life in those with IBS. People who took this probiotic reported a 110% improvement in mental well-being after 12 weeks.⁵ Adults diagnosed with functional constipation reported more regular bowel movements after supplementing with the probiotic B. lactis for 28 days, compared to those who took a placebo.⁶
  • After 12 weeks, adults with moderate to severe IBS-related pain who took the probiotic L. acidophilus reported significantly less abdominal pain compared to those who took a placebo.⁷


1. Canavan C, West J, Card T. The epidemiology of irritable bowel syndrome. Clin Epidemiol. 2014;6:71-80. Published 2014 Feb 4. doi:10.2147/CLEP.S40245

2. Quigley EMM. The Gut-Brain Axis and the Microbiome: Clues to Pathophysiology and Opportunities for Novel Management Strategies in Irritable Bowel Syndrome (IBS). J Clin Med. 2018;7(1):6. Published 2018 Jan 3. doi:10.3390/jcm7010006

3. Sniffen JC, McFarland LV, Evans CT, Goldstein EJC. Choosing an appropriate probiotic product for your patient: An evidence-based practical guide. PLoS One. 2018;13(12):e0209205. Published 2018 Dec 26. doi:10.1371/journal.pone.0209205

4. Ducrotté P, Sawant P, Jayanthi V. World J Gastroenterol. 2012;18(30):4012-4018.

5. Krammer H, Storr M, Madisch A, Riffel J. Z Gastroenterol. 2021 Feb 8;59(2):125–34.

6. Ibarra A, Latreille-Barbier M, Donazzolo Y, Pelletier X, Ouwehand AC. Gut Microbes. 2018 May 4;9(3):236-51.

7. Lyra A, Hillilä M, Huttunen T, Männikkö S, Taalikka M, Tennilä J, Tarpila A, Lahtinen S, Ouwehand AC, Veijola L. World journal of gastroenterology. 2016 Dec 28;22(48):10631

8. Rezac S, Kok CR, Heermann M, Hutkins R. Fermented Foods as a Dietary Source of Live Organisms. Front Microbiol. 2018;9:1785. Published 2018 Aug 24. doi:10.3389/fmicb.2018.01785


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