According to the research centre at the University of Kentucky, for a product to be called a probiotic, the micro-organisms must:

• be live
• be present in sufficient
• bestow a health benefit

Note that the number of bacteria is measured in “colony-forming units” – abbreviated to CFUs.

So should you take probiotics in food or supplement form?


The website Medical News makes the point that the term ‘contains live and active cultures’ often used on yoghurt labels refers to the organisms used in the fermentation process. But it’s possible that yoghurts labelled this way may not contain sufficient amounts of live microorganisms to bestow a health benefit on the consumer. For example, pasteurised yoghurts have been flash heated at high temperatures so many microorganisms are destroyed.

Many other yoghurt labels will claim: "made with live bacteria” or "made with probiotics”, rather than saying "contains" them.
That’s because by the time the pot is transported to the store and stands in the chiller cabinet for a week or so, the bacteria may be dead or very few in number.

yaourt à l'ancienne

Assuming yoghurt-delivered probiotics do survive until you consume them, then they must now survive the harsh acidic environment of the stomach. The problem is that the milk culture gives little protection. Moreover, many yoghurts contain sugar which helps encourage the ‘bad’ bacteria.

So if a yoghurt doesn’t state how many probiotic bacteria it contains – in billions – it may only have token amounts and therefore be of little benefit.

Even if the label states the number of probiotic units, it may say, for example, “5 billion per pot”. If the pot contains 500 grams of yoghurt, that’s only 10 million per gram. It still sounds a lot but, for example, the ProDURA variant of endospore bacteria Bacillus coagulans contains as much as 20 billion per gram, ie. 200 times more!

Numbers matter, because however hardy the strain, many will not survive to colonise the gut – which is the intended end result. A University College London study in 2014 tested some top brand yoghurts and found that very few of their friendly bacteria survived in the stomach.

Indeed a December 2016 article written by an eminent gastroenterologist on Medscape states:

“... expected clinical end points may not be achieved by generically recommending yoghurt to patients in whom a purported probiotic benefit is desired ... (although) yoghurt consumption has other benefits including improved lactose tolerance and the provision of protein, vitamin D, and calcium.”

But if yoghurts are not the best way to help achieve probiotic balance, why do they have such a good image?

Yoghurts – the difference is in the modern processing

In the early 1900s, a researcher called Dr Metchnikoff was intrigued that so many Bulgarian villagers were living to 100 or more. He attributed their longevity to the consumption of large quantities of raw yoghurt fermented by lactic acid producing bacteria which inhibited pathogens.

We’ve seen there is indeed a direct correlation between health and probiotic balance and range, so Dr Metchnikoff was right. But the conclusion he reached with raw cultures is not applicable to modern mass-produced, largely high-temperature-pasteurised, yoghurts. Not only does pasteurisation kill bacterial strains but many other nutrients are heat sensitive and reduced in level by pasteurisation – including vitamin C, B vitamins and vitamin E.

Mainstream yoghurt tastes good and is a pleasant, safe addition to your diet, but not the best choice for a true probiotic boost. And do try to choose ‘live’ ones with no added sugar, ideally made from organic cow’s milk, sheep’s or goat’s milk (because the animals will have been grass- fed) or plant-based (eg. soy).

All this suggests that the delivery mechanism of probiotics in supplement form should be superior to a yoghurt for real health benefits.


You should choose a supplement brand that provides evidence of a proper scientific approach.

The University of Nebraska has tested over 200 probiotic products over the years. They found that 70% had CFU (colony-forming unit) counts lower than on the label and a significant proportion had as little as 10% of the claimed count!

Powder, tablet or capsule form?


The disadvantage of powders is that they are exposed during transit and storage to variations in heat and humidity which can reduce the viability of the bacteria. And when consumed, they are immediately exposed to stomach acid.


Tablets are a poor choice as they are subjected to very high heat in the process of manufacture, which will kill most of the bacteria.


By far the best delivery system is vegetable hard-shell capsules. They resist breakdown in the stomach for a time – enough for a majority of the probiotic bacteria to reach the gut, as long as they are resistant strains.

The combination of endospore and other resistant strains of probiotics coupled with hard shell capsules containing billions of live bacteria per capsule is the gold standard in probiotic supplementation.

Will the probiotic bacteria colonise?

A review article in the American Journal of Clinical Nutrition posed this very question. It started by acknowledging that some researchers were sceptical about the effectiveness of probiotics. Having examined hundreds of studies, however, it concluded that some ingested probiotics can indeed affect the composition and behaviour of intestinal microflora and:

“Probiotics, perhaps in combination with prebiotics, may become an important means of preventing and treating disease. For example, several types of diarrhea have been successfully treated with probiotics.
“This practice, however, may represent only the “tip of the iceberg” because the potential benefits of probiotic therapy promise to be almost limitless.”

Probiotic bacteria are living things. So they need food if they are to thrive and if new colonies are to take hold. This nourishment is the role of prebiotics.


Prebiotics are non-digestible plant fibres which promote the growth of probiotics in the intestines. Prebiotic fibre is found in many fruits and vegetables, such as apples, bananas, onions, leeks and garlic, Jerusalem artichoke, asparagus, chicory root and legumes like lentils, chickpeas, and beans. It is also found in wholegrains.
♦ See the top prebiotic foods

Well-designed microbiome booster supplements ideally also include prebiotics such as inulin and fructo-oligosaccharides (FOS) as a ‘kick starter’ to the process of colonisation when the probiotic bacteria ‘wake up’ in the gut.
A supplement – as the name implies – is additional to the basis of a good diet; in this case a diet rich in probiotics and prebiotics.
So although there is good evidence to take periodic probiotic supplements to boost the level and variety of good bacteria in your gut, you do need to incorporate prebiotic and probiotic foods into your daily and weekly diet.

♦ See the list of the top probiotic foods.