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Dr Linia Patel (PhD, RD) focuses on probiotics in part one of this series.

Science now tells us there is a whole world inside us. Picture a bustling city on a weekday morning, the roads and pavements packed with people rushing to get to work or to appointments. Now imagine this on a microscopic level. Inside your body exists an ecosystem of trillions of microorganisms (bacteria, viruses and fungi). Known as your microbiota, this collection of microorganisms not only helps you to digest food, but to regulate your metabolism, your hormones, your mood, how strong your immune system is and your risk of diseases. Basically, there isn’t much going on in your body (and mind) that isn’t influenced by the composition of your microbiome. A healthy gut means a healthy body.

One of the ways to ensure you have a healthy gut is to ensure that your diet contains probiotics and prebiotics (aka live gut bugs and food for the gut bugs). In a world where we love convenience, can we shortcut and get what our gut needs from probiotics and probiotic supplements? Let’s explore.

What are probiotics?

Probiotics are defined by the World Health Organization as “live microorganisms that, when administered in adequate amount, confer a health benefit on the host”. In layman’s terms, probiotics contain live microbes that can populate our gut and give us some health benefits. We can find probiotics from foods such as bio-live yogurt, kefir, kimchi, natto, miso, sauerkraut and kombucha. Most of these foods contain lactobacillus or bifidobacterium or possibly bacillus species. Probiotic supplements can also contain beneficial bacteria that are like those normally found in your gut.

The science of probiotic supplements

Probiotic supplements may support the balance of good bacteria in your gut and, in doing so, may provide some relief for specific health symptoms. While more research is needed to fully validate health claims, there is some evidence from human trials that particular strains may help specific symptoms.

Health condition Research summary
Diarrhoea Some studies show lactobacillus rhamnosus GG may help prevent antibiotic-associated diarrhoea.


Saccharomyces boulardii has also been found in some studies to treat diarrhoea symptoms.


Digestive issues such as irritable bowel syndrome (IBS) Some studies show that some lactobacillus and bifidobacterium strains might be able to help prevent or relieve bloating.

For IBS, research suggests that the most effective probiotics are those containing bifidobacterium strains. Other strains like acidophilus and lactobacilli may also help but have been shown to be less effective.


Studies have used different strains and dosages, so it is not yet possible to give precise recommendations when it comes to gut health.


Constipation Bifidobacterium lactis and bifidobacteriumlongum have been linked to relief in some research; however, more rigorous research is needed.


Urinary tract infections Some evidence suggests that lactobacillus fermentum may protect against E-coli and promotes a healthy urinary tract; however, more research is needed.


Vagina health Lactobacilli may promote vaginal health by creating an acidic environment and/or by stimulating the immune system within the vaginal tract; however, more research is needed.

In some research, oral probiotics were found to be more effective than topical probiotics.


When to consider a probiotic supplement

First things first. It’s always better to get nutrients from food. This includes probiotics. If you are generally healthy and have a diverse balanced diet, then you probably need to focus on eating more probiotic foods vs taking probiotic supplements. However, if you eat poorly, then it is not clear if taking probiotic supplements or adding a lot of foods with probiotics to your diet will help you gain a healthier gut. Researchers are still figuring out whether taking probiotics is valuable for your health, in what situations they may help, and which bacteria should be given and how much you need. If you have a specific health need such as diarrhoea, constipation, IBS or experience poor vaginal health then you can work with a dietitian or a registered nutritionist who can then tailor the supplement to your specific symptoms.

How to choose a probiotic supplement

Supplements are not as regulated as medicines. This means that the quality and ingredients can vary greatly from product to product. However, if you choose to take a probiotic, keep in mind the following:

  1. Are you getting enough bacteria? A general recommendation is to choose probiotic products with between one million and one billion colony-forming units. However, more isn’t necessarily better as it depends instead on the dose that has been shown to be effective in human studies. Some probiotics have been shown to provide benefits at much lower amounts and others need much higher doses. Work with a dietitian to find the right supplement for you.
  2. Which strains of bacteria are you getting? Different strains of bacteria perform different functions in the body. Like a sports team, probiotic strains work in together to enhance each other’s functions. Sometimes these teams can even perform functions together that each strain cannot accomplish alone. So, instead of taking one probiotic that contains a high CFU of one probiotic stain, it is more beneficial to supply your gut flora with a variety of strains and species to help restore and maintain optimal balance. In general, current recommendations are to look for the genus names that contain lactobacillus, bifidobacterium, bacillus or saccharomyces boulardii.
  3. How do your probiotics need to be stored? Heat can kill off microorganisms in your probiotics if they are not stored correctly.
  4. Is the brand backed by science? It is important to purchase brands that can prove their supplements can survive the journey through the gastrointestinal tract.

How to take a probiotic supplement 

There is no simple answer to how often you should take probiotics. Probiotics have been shown to be safe for healthy adults if taken daily; however, there is some new research indicating that this may not be optimal. If you take a probiotic routinely for a very long period, then you will be adding more of one type of bacteria and however ‘good’ these bacteria might be, it can risk upsetting your own delicate balance within your microbiome. For this reason, in my clinical practice, I recommend cycling on and off probiotic supplements vs taking them for a long period of time. Depending on the type and brand of supplement, a general recommendation is to take your probiotic supplement regularly for at least four weeks to see if it is effective or not, then cycle on and off as you need them. If you are taking probiotics for a specific reason and the probiotics are working, then you should be able to notice the change. For example, you may feel less bloated or you may notice that your bowel habits are more regular.

I recommend that probiotics are taken on an empty stomach and in a liquid formulation instead of solid where possible, as the bacteria in liquid probiotics don’t have to rehydrate in the gut so may be more effective.

Do keep in mind that you are an individual, so a probiotic supplement that helps one person might not help someone else. Some people experience an increase in gas, bloating or thirst when they start taking probiotics. These side effects should go away within the first week; however, if they don’t, maybe that probiotic supplement isn’t for you. Similarly, some probiotics can produce histamine within the digestive tract. If you suffer with a histamine intolerance, you may need to play around with a number of supplements before finding the ‘right’ one.

Take-home messages

  1. Eat something fermented daily. Kefir, bio-live yogurt, kimchi, miso or sauerkraut.
  2. If you are thinking of adding a probiotic supplement into your diet, speak to and work with a dietitian or an expert who keeps up to date in this growing field so that you can ensure you take the right one in the right way.
  3. Opt for a multi-strain blend or choose a product containing specific strains that have been clinically tested to help with your health condition.
  4. If you have a severely weakened immune system due to an illness, be sure to speak to your doctor before staring a probiotic supplement.
  5. Remember that everyone’s microbiome is different and exists in a delicate balance.

Ready to read part 2? Check it out here: Prebiotic and probiotic supplements: All you need to know, part 2


  1. Rad et al (2016), The comparison of food and supplement as probiotic delivery vehicles, Crit Rev Food Sci Nutr.,56(6): 896-909.
  2. Hungin et al (2018), Systematic review: Probiotics in the management of lower gastrointestinal symptoms – an updated evidence-based international consensus, Gastroenterology, 14,539.
  3. Khalesi S et al (2018), A review of probiotic supplementation in healthy adults: helpful or hype, European Journal of Clinical Nutrition, 73: 24-37.
  4. Zhang Y et al (2016), Effects of probiotic type, dose and treatment duration on irritable bowel syndrome diagnosed by Rome III criteria: a meta-analysis, BMC Gastroenterology, 16:
  5. Kothari D et al (2010), Probiotic supplements might not be universally effective and safe: A review, Biomed Pharmcother., 111: 537-47.
  6. Reid G et al (2010), Responders and non-responders to probiotic interventions, Gut Microbes, 1(3): 200-204.

About the Author

Dr Linia Patel

Dietitian and sports nutritionist

As a self-confessed “total foodie”, being an award-winning dietitian and sports nutritionist comes naturally to our resident dietitian and long-time Fitpro magazine contributor, Dr Linia Patel. She likes to take a block of science and slice it up into easy-to-digest and practical advice. With a PhD in Public Health and over 100 published articles on diet and health, she is a British Dietetic Association Spokesperson and is regularly seen appearing on national TV and being quoted in the press. She’s the science expert for Tess Daly’s best-selling book 4 Steps to a Happier & Healthier You, is a qualified fitness instructor and has worked extensively in high performance sport. She is particularly passionate about women’s health, helping women to be the best version of themselves.

Key expertise:

  • Translating science into easy-to-digest, practical advice
  • Dietitian and sports nutritionist
  • Media spokesperson
  • Women’s health (athletes, non-athletes and everything in between)
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