Which Probiotics?

The importance of variety

Different strains of probiotic bacteria have slightly different functions. They also colonise different places along the digestive tract. So probiotic supplements that contain multiple strains are more effective than products which contain very high concentrations of just one or two strains.

Moreover most strains work synergistically with each other to influence your health. So, beyond a certain number, more diversity of strains is probably more important than sheer numbers of probiotic bacteria.

In the West, we have considerably less microbial diversity than in other parts of the world and the likely cause is over use of antibiotics, antibacterial sprays and the prevalence of processed food which is largely produced in a sterile environment.

Significantly, most less-developed countries may have higher rates of infectious diseases, but they generally have much lower levels of allergies and asthma.

A wide ranging review of the subject in Nature Reviews Genetics, entitled ‘The Human Microbiome: at the interface of health and disease’, confirmed the importance of bacterial diversity. It found that:

“In H. pylori-negative individuals, gastric microbiota diversity is high.”

H. pylori (Helicobacter pylori) is a very common but potentially dangerous bacterium that causes ulcers and gastric inflammation. Cancer Research UK also confirms that H. pylori is the cause of one in three stomach cancers. Other research suggests it may be a risk factor for heart disease.

The same Nature Reviews Genetics paper confirms that reduced microbial diversity and imbalances in the microbiome are strongly linked to Crohn’s Disease, liver disease, rheumatoid arthritis and obesity.

The most important probiotic strains

The Lactobacillus species are the predominant bacteria that reside in the small intestine. These species are responsible for producing lactase, the enzyme required to break down lactose (the sugar in milk). So a probiotic containing lactobacillus is often recommended in cases of lactose intolerance.

They also collectively ferment carbohydrates in the gut, producing lactic acid as a result of this process. Lactic acid helps create an acidic environment in the digestive tract, which discourages many unwanted microorganisms that thrive in an alkaline environment. Lactic acid also increases absorption of minerals such as calcium, zinc, copper, magnesium and iron.

The important point to remember is that probiotic bacteria work synergistically with each other and several strains have duplicate functions. So you don’t have to include all of the following. But you should have at least 5 - 7 shelf stable resistant strains in an effective probiotic supplement.


  • L. acidophilus
  • L. casei
  • L. plantarum
  • L. rhamnosus
  • L. paracasei
  • L. fermentum
  • L. bulgaricus


  • B. lactis
  • B. bifidum
  • B. longum
  • B. infantis


  • B. coagulans


  • S. thermophilus
  • S. salivarius

Variety achieves two things. It increases the number of strains in your intestines, which we know is correlated to health. We also know that some strains significantly benefit one person but not another. So having a wide variety gives you the best chance of the probiotic benefiting you.

By combining strains, a supplement has the best chance of improving immune function, enhancing digestion, controlling candida, inhibiting the growth of pathogens like Helicobacter pylori and even viruses, creating natural internal antibiotics, relieving IBD symptoms, improving mood and assisting in weight control – because different strains have different effects.

♦ See the list of the most important strains of probiotic bacteria and what they do.

Will probiotics reach the gut?

Until recently, the medical view was that probiotic yoghurts and supplements were questionably effective, because the hostile environment of the stomach meant that most never reached the gut. And those that did mostly passed through to be excreted. That’s why most supplements contain billions of bacteria on the assumption that some will get through.

Yet this mass casualty theory didn’t square with the fact that many people taking probiotic supplements do report very real benefits and so many recent research papers concur.

A possible explanation of this apparent dichotomy was put forward in a 2016 at UCLA called ’Microbes: From Your Food to Your Brain’. The suggestion was made panel discussion in May that the newly consumed probiotic bacteria could be exchanging genetic information with existing probiotic bacteria on their way through the GI (gastro-intestinal) tract and thus improving the balance.

This is quite plausible as we do know that such exchanges occur. Indeed genetic exchanges – via DNA strands called plasmids – are how pathogenic bacteria can develop antibiotic resistance.

Even so, it is hardly a ringing endorsement of probiotic supplementation.

The breakthrough – and the reason why occasional probiotic supplementation can and should be part of your health regime – lies in two developments: the effective delivery of endospore probiotics and of particularly hardy strains of Lactobacillus and Bifidobac.


When scientists discovered a 25-million-year-old bacterium in suspended animation within a fossilised bee, the obvious question was how could it have survived so long? The answer was that it was an endospore bacterium, which has a protective shell structure.

Scientists have now developed current probiotic bacteria with the same shell mechanism that preserved the bacillus endospore bacterium within that bee. These strains are able to survive the harsh acids of the bile duct and stomach and the anaerobic environment of your intestines. Once endospores reach the small intestines, the shell disintegrates, so the bacteria remain in the gut and can reproduce to form a colony.

The Department of Microbiology at Cornell University states:

“Endospores can survive environmental assaults that would normally kill the bacterium. These stresses include high temperature, high UV irradiation, desiccation, chemical damage and enzymatic destruction.

“The extraordinary resistance properties of endospores make them of particular importance because they are not readily killed by many antimicrobial treatments.”

Endospore ‘good’ bacteria


The University of Nebraska started research on probiotic bacteria as early as 1925, so they have perhaps the most extensive database in the world.

The work at Nebraska has culminated in the development by Dr Shahani of a unique version of the probiotic strain Bacillus coagulans trademarked “ProDURA”. Bacillus coagulans ProDURA is an endospore bacterium that is stable at room temperature for up to three years’ storage. It is activated only with the specific conditions of heat, pH, and moisture found in the large intestine. Upon arrival, Bacillus coagulans cells begin multiplying and colonising the intestinal tract, which is the key to effectiveness.

In recent research, Bacillus coagulans showed promise for relieving symptoms of patients with IBS, for increasing immune response against adenovirus and influenza A, and even in reducing inflammation in arthritis sufferers.

Other resistant ‘good’ bacteria


The University of Nebraska started research on probiotic bacteria as early as 1925, so they have perhaps the most extensive database in the world.

The same team at Nebraska University have also developed a strain of L. acidophilus called DDS-1 which is shown to be activated by the mucosa of the intestines. Unlike other strains, it remains stable even at room temperature for as long as 24 months. In clinical studies it has been shown to enhance immune function and help suppress pathogenic bacteria such as E. coli and salmonella.

L. acidophilus DDS-1 and other strains developed at Nebraska are originally isolated from a human source. This is important, as strains isolated from animal sources – as in some yoghurts – do not implant or multiply in the intestinal tract well.