Why ARE probiotic yogurts so good for us? Scientists have finally worked out exactly how live bacteria interact with the gut to boost the body's defenses

  • Scientists have offered the first comprehensive explanation of how yogurt feeds the gut in a way that boosts its defenses
  • They did this by analyzing bacteria in one of the most popular probiotic supplements 

Scientists have finally dissected why probiotic yogurts are good for our bodies.

We are all hounded by adverts and health alerts telling us probiotic yogurts or supplements are packed with friendly bacteria that boost the body's defenses.

But to date, the science behind that connection has been murky.

Now, researchers have managed to shed light inside the black box of probiotics to uncover the mechanism by which these live bacteria confer health benefits to the gut. 

We are all hounded by adverts and health alerts telling us probiotic yogurts or supplements are packed with friendly bacteria that boost the body's defenses. Now we know why

We are all hounded by adverts and health alerts telling us probiotic yogurts or supplements are packed with friendly bacteria that boost the body's defenses. Now we know why

The benefits are down to the communication between the probiotic bacteria and the human host.

This involves the bacterial secretion of a novel polysaccharide that tells the immune system to release certain immunity-stimulating chemicals.

The study looked at the bacteria strain Lactobacillus paracasei DG found in the one of Italy's most popular supplements Enterolactis on sale for the past two decades.

In the experiments, researchers isolated the polysaccharide, which are large polymers of sugar molecules.

They form coverings over the surfaces of many bacterial cells, and the bacteria sometimes secrete them, as well.

Using nuclear magnetic resonance imaging and chemical methods they then determined the polysaccharide's structure and composition.

Professor of Chemical Biology Andrew Laws at the University of Huddersfield said: 'We showed that a significant proportion of the polysaccharide is made from the sugar, rhamnose.

COULD PROBIOTICS CURE ALZHEIMER'S? 

Eating yogurts or health drinks which contain live bacteria may help improve the memories of people with Alzheimer's disease, research suggests.

Drinking milk carrying the 'good bacteria' found in pro-biotic drinks similar to those found in Yakult and Activia yogurt led to improvements in people suffering from the incurable disease.

There were 'moderate but significant' improvements among the Alzheimer patients – who were aged 60-95, the study found. 

Professor Mahmoud Salami, senior author on the study from Kashan University in Tehran, Iran, said: 'In a previous study, we showed that probiotic treatment improves the impaired spatial learning and memory in diabetic rats, but this is the first time that probiotic supplementation has been shown to benefit cognition in cognitively impaired humans.' 

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'This sugar predominates in a number of polysaccharides that are secreted by probiotic bacteria.'

Co-author Dr Simone Guglielmetti, professor of microbiology at the University of Milan, then exposed certain human immune cells to different doses of the polysaccharide.

The scientists found cells released immune-stimulating chemicals, particularly pro-inflammatory cytokines and chemokines.

Their releases suggested L. paracasei would aggravate conditions such as ulcerative colitis, or ulcers caused by Helicobacter pylori, instead of mitigating them, as it has been found to do in clinical trials.

Prof Laws added: 'We have evidence that our polysaccharides bind to and mildly activate the receptors which release pro-inflammatory messengers.

'We believe that this generates a lesser inflammatory response than what would occur if the same receptors were activated by pathogenic bacteria.'

The study was carried out because of the dearth of information as to how the polysaccharides on the bacterial cells interact with the cells of the gastrointestinal tract.

The findings were published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.  

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