What are probiotics? Definition, sources and how to choose them

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Probiotics are everywhere: yoghurts, kefir, food supplements… But what exactly are we talking about? Here are the essentials for understanding what probiotics are and choosing the right supplement.

In short

• A probiotic is a live micro-organism that, consumed in sufficient amounts, has a health benefit. Each strain has its own effects.
• A large part of the immune system is in contact with the gut and its microbiota.
• To choose a supplement, look at 6 points: the number of CFU, the full name of the strains, their protection, the format, storage and composition.

What are probiotics?

They are live micro-organisms, mostly bacteria, consumed in sufficient amounts. Experts brought together by the International Scientific Association for Probiotics and Prebiotics (ISAPP) define them as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (Hill et al., 2014).

The most common belong to the Lactobacillus and Bifidobacterium families; a yeast, Saccharomyces boulardii, is also used. Each strain is different: what is observed for one doesn't necessarily apply to another. An analysis of 228 clinical trials confirmed this: results depend on both the strain and the situation studied (McFarland et al., 2018).

How do you read a probiotic's name?

A probiotic's full name has three parts: the genus (Lactobacillus), the species (acidophilus) and often a strain code. The more precise the label, the better you know what you're taking.

What is the gut microbiota?

It's all the micro-organisms living in our gut, mainly in the colon: mostly bacteria, but also yeasts and viruses. Its composition varies with diet, age, lifestyle or antibiotic use.

Researchers estimate that an adult hosts about 38 trillion bacteria, roughly as many as human cells, weighing about 200 grams (Sender et al., 2016). You often read “ten times more bacteria than cells” or “two kilos of bacteria”: these old figures have been revised downwards.

Gut and immunity: what's the link?

The gut wall is the largest contact surface between our body and the outside world. A large share of the immune system's cells are found there, in constant dialogue with the microbiota (Belkaid and Hand, 2014). That's why people often talk about the gut-immunity axis.

This link explains the interest in the microbiota when the seasons change: back to school, autumn, winter. We devote two articles to it: probiotics in autumn and why we fall ill in February.

As for nutrients, vitamin C contributes to the normal function of the immune system and to the reduction of tiredness and fatigue (Regulation (EU) No 432/2012). It isn't stored in the body: a regular intake matters more than an occasional one. To learn more: how to raise your vitamin C levels.

Where can you find probiotics?

• In fermented foods: yoghurt, kefir, raw sauerkraut, kimchi, miso.
• In food supplements: capsules, powders or liquids.

Careful: not all fermented foods contain live bacteria when you eat them. Sourdough bread is baked, canned sauerkraut is pasteurised, beer is often filtered. These foods have other qualities, but they don't provide probiotics (Marco et al., 2021).

Don't confuse them with prebiotics: these are fibres that feed the bacteria in your gut, not bacteria. They're found in garlic, onion, leek, asparagus, slightly unripe bananas and oats (Gibson et al., 2017).

How do you choose a probiotic supplement?

• The quantity: expressed in CFU (colony-forming units) per serving.
• The strains: identified by their full name, for example Lactobacillus acidophilus.
• The protection: the bacteria have to get through stomach acid. Some formulas are microencapsulated for this purpose. In the lab, bifidobacteria protected by a microcapsule survive conditions that mimic the stomach and intestine better than unprotected bacteria (Annan et al., 2008).
• The format: capsule, powder or liquid. Liquid means no capsule to swallow and can be drunk neat or diluted. To compare: Liquid or capsule probiotic: which should you choose?
• Storage: follow the instructions, for example keeping a liquid in the fridge after opening.
• The full composition: look at what comes with the bacteria (vitamins, amino acids, flavourings) and check that it suits your diet (vegan, gluten-free, lactose-free).

When and how to take a course?

• At the same time every day: consistency matters more than timing. Many manufacturers recommend the morning on an empty stomach or before a meal.
• Over several weeks: a course is counted in weeks, not days. A bottle or box usually lasts about a month.
• With a varied diet: the fibre in fruit, vegetables, pulses and whole grains feeds the bacteria in your gut.

Our Liquid Probiotic

The Liquid Probiotic provides 10 billion CFU per 15 ml serving, from 4 microencapsulated vegan strains: Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus plantarum and Lactobacillus salivarius. It also contains 50 mg of L-glutamine and 80 mg of vitamin C, which contributes to the normal function of the immune system. One serving a day, in the morning on an empty stomach or 30 minutes before a meal, as a shot or diluted in a glass of water. A 500 ml bottle contains 33 servings; once opened, keep it in the fridge. It's part of our range of liquid food supplements.

What our customers say

“I really love the liquid format and the taste of this supplement. Easy to take and not sickly at all!”
Mélanie D., Liquid Probiotic, review published on our Amazon store

“If you don't like or can't swallow pills, this product is ideal for taking probiotics. You just pour 15 ml into water or juice. […] As with any product, you have to try it to see if it works for you.”
Lespetitsdétailsdejess, Liquid Probiotic, review published on our Amazon store

“I love it, really tasty and very easy to take.”
Nathalie K., Liquid Probiotic, review published on vitamoon.fr

Further reading

• Tiredness and bloating: the role of the gut and habits that help
• Probiotics in autumn
• Why you (still) fall ill in February
• The secret to a light stomach when travelling
• Liquid or tablet vitamins: which should you choose?

Frequently asked questions

Probiotic or prebiotic: what's the difference?

A probiotic is a live micro-organism. A prebiotic is a fibre that feeds the bacteria already in your gut. The two are complementary.

Liquid or capsule probiotic?

The format matters less than the strain, the amount of live bacteria and their protection. Liquid is easy to swallow, its dose is precise and its strains can be microencapsulated; capsules are often cheaper. We compare the two in this article.

Is eating yoghurt enough?

Yoghurt and kefir provide live bacteria and have their place in a varied diet. Their strains and quantities aren't always stated: a supplement specifies the number of CFU and the name of each strain.

Can I take probiotics with antibiotics?

If you are taking antibiotics, wait until the end of the treatment before starting a course.

Can I take them if I'm pregnant, breastfeeding or have a chronic illness?

If you have a chronic illness, are on treatment that weakens the immune system, or are pregnant or breastfeeding, ask your doctor for advice.

How long does a course last?

A course is counted in weeks. A bottle of Liquid Probiotic lasts 33 days at 15 ml a day.

Should a liquid probiotic be kept in the fridge?

Yes, in the fridge once opened.

Can a supplement replace a good diet?

No. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

In summary

• Probiotics are live micro-organisms. Their effects depend on each strain.
• A large part of the immune system is in contact with the gut.
• They're found in fermented foods and in supplements.
• To choose a supplement, look at the number of CFU, the names of the strains, their protection and the format that suits you.

Sources

• Hill C. et al. (2014). Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology, 11, 506-514.
• McFarland L.V., Evans C.T., Goldstein E.J.C. (2018). Strain-specificity and disease-specificity of probiotic efficacy: a systematic review and meta-analysis. Frontiers in Medicine, 5, 124.
• Sender R., Fuchs S., Milo R. (2016). Revised estimates for the number of human and bacteria cells in the body. PLoS Biology, 14(8), e1002533.
• Belkaid Y., Hand T.W. (2014). Role of the microbiota in immunity and inflammation. Cell, 157(1), 121-141.
• Marco M.L. et al. (2021). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nature Reviews Gastroenterology & Hepatology, 18, 196-208.
• Gibson G.R. et al. (2017). Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics. Nature Reviews Gastroenterology & Hepatology, 14, 491-502.
• Annan N.T., Borza A.D., Hansen L.T. (2008). Encapsulation in alginate-coated gelatin microspheres improves survival of the probiotic Bifidobacterium adolescentis 15703T during exposure to simulated gastro-intestinal conditions. Food Research International, 41(2), 184-193.
• Commission Regulation (EU) No 432/2012 of 16 May 2012 establishing a list of permitted health claims made on foods.