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How to buy the best probiotic: A guide

How to buy the best probiotic: A guide by Nutritionist Kay Ali

There are a ton of probiotics on the market to choose from. It’s a minefield. Adding to that, in the UK (and Europe) approved regulatory health claims on probiotics supplements haven’t yet caught up with the research. As a result, there’s very little brands can actually share about the benefits of their probiotics, even if the bacteria used has a wealth of evidence behind it. Unless you’re an expert, this makes working out which formulations are great versus the not so great, difficult. Nevermind knowing which bacteria is the right kind for you. To help, I thought I’d pull together a quick guide on how to assess and shop for the best quality probiotic.

What is a probiotic?

The World Health Organisation defines what a probiotic is best. They are:

Live microorganisms which when administered in adequate amounts confer a health benefit on the host.

The host being you. So, there are three clear criteria for a bacteria to actually be classified as a probiotic.

  1. It’s live.

  2. You’re taking it in meaningful amounts.

  3. It has proven benefits on humans.

Seems pretty straightforward right? If only.

Is the bacteria alive?

There are of course issues that can undermine whether the bacteria in a probiotic supplement (and even food) is in fact live. Chiefly, bypassing the gastric juices in the stomach. Depending on the bacteria, it can result in premature die-off. As a result, it’s best to opt for bacteria with proven resistance to low pH environment that is similar to stomach acid. Bonus points if it’s delivered in a mechanism that provides delayed release. This might help increase the likelihood of the bacteria reaching your intestine.

How to buy the best probiotic: A guide by Nutritionist Kay Ali

Is the bacteria researched?

Then there’s the not so tiny matter of ‘does the bacteria actually work?’. This requires high quality evidence; the best are randomised double blind placebo control trials on humans. If there’s one fact you take away from this post it would be this – most evidence on a bacterial specie is strain specific. Let me explain.

Focus on the strain, not the specie.

Like all organisms, bacteria belong to a kingdom of classifications. Think taxonomy 101. Bacteria ultimately belong to a genus. For example, Lactobacillus. This class is further stratified into species. To use the same example, you have Lactobacillus Acidophilus or Lactobacillus Casei. Most brands share their probiotic formulations at this level. Yet, within each specie you have many different strains with their own unique characteristics and behaviours. So, if we’re concerned about how a bacteria functions as per WHO’s definition of a probiotic, you’ve got to review it at the strain level. Still with me? Let me break this down further.

Dogs are a really good example of how being strain specific determines function and behaviour. All dogs belong to the same specie, right? Canis. Yet, not all dogs look and act the same. It’s their breed that determines their characteristics. Just like bulldogs act and look differently to Labradors, a strain of bacteria can function differently to another even if they come from the same Acidophilus family.

Expert Nutritionist Kay Ali with Beauty Pie's Supergut probiotic

To complicate things further, many experts use the term specie and strain interchangeably. But they’re not the same thing, clearly. For example, most of the research we have that proves Lactobacillus Acidophilus specie works is in fact carried out on the DDS1 strain. There’s no guarantee a different strain elicits the same effect. This is why the strain matters!

Is the dose meaningful?

Finally, check that the bacteria delivered is at the dose proven to work. This will depend entirely on the researched benefit, so you might need to work with a practitioner or do a little bit of research yourself. For example just 2 billion Colony Forming Units (CFU) of Lactobacillus Acidophilus DDS1 was shown to prevent traveler's diarrhea in one study. Whereas, in another 10 billion was proven most effective for reducing symptoms associated with Irritable Bowel Syndrome.



1. Hill C, Guarner F, Reid G, Gibson GR, Merenstein DJ, Pot B, 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 2014;11:506-14.

2. Sanders M. E. (2008). Clinical use of probiotics: what physicians need to know. American family physician, 78(9), 1026.

3. Senhert KW. Effect of DDS-acidophilus, A case study. 1989.

4. Martoni, CJ, Srivastava, S, Leyer, GJ, “Lactobacillus acidophilus DDS®-1 and Bifidobacterium lactis UABla-12™ Improve Abdominal Pain Severity and Symptomology in Irritable Bowel Syndrome: Randomized Controlled Trial” Nutrients 2020 12, 363

Disclaimer: The statements made in this blog post are for educational and entertainment purposes only. They are not intended to diagnose or treat any individual or condition. If you are concerned about your health please consult your licensed medical doctor before changing your diet or taking supplements. This website uses affiliate links, which means the author may earn from products and services recommended although it should be noted that this is not at an additional cost to the consumer.


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