Live bacteria which offer health benefits, known as probiotics, are commonplace on supermarket shelves but what do they do for us? Iva Pocock reports.
Bacteria which naturally inhabit our guts are now a key focus for scientists and food companies in Ireland and internationally.
Of the 400 different bacteria which have evolved to survive in the human gut, medical and commercial researchers are particularly interested in those species which help maintain digestive health.
In the past 10 years "phenomenal EU funding" has boosted research into live bacteria which confer some health benefit when consumed, says Prof Colette Shortt, director of science at Yakult UK, part of the Japanese multinational company.
Such bacteria are known as probiotics, a word now commonly seen on supermarket shelves.
"The emphasis is on live so they are actually live during transit through the gut," she says. "Viability is maintained not just in the product but as they go through the gut as well."
Beneficial to health is the second key characteristic of probiotics, as agreed by clinicians and scientists at European level, says Prof Shortt. "There are actually many definitions but that's the one where there is most consensus for human nutrition."
There's been renewed interest in the concept of probiotics or manipulation of the bacteria in the gut, although the concept is very old, she says.
From a European perspective, in the early 1900s researchers such as Elie Metchnikoff at the Louis Pasteur Institute had a lot of writings about bacteria being both good and bad and the fact that the good had been little explored.
The research area then went into decline in Europe, but in Japan, a scientist and businessman, Dr Minoru Shirota, succeeded in isolating and growing a lactic acid bacteria found naturally in the human gut. It was named after him - Lactobacillus casei Shirota - as per the scientific convention.
There is nothing new in eating probiotic food. Yoghurt, butter milk, sourdough bread, sauerkraut, fermented meat and miso are examples of probiotic foods traditionally eaten in different parts of the world.
"If you look back maybe 30 years at the Irish diet, people used to drink buttermilk which would invariably have had very high counts of lactobacilli bacteria," says Prof Shortt. "That would be a natural source of probiotic-type bacteria."
In the past five years a number of large scientific trials have pointed to the health benefits of eating probiotics, helping to dispel scepticism about the whole area of bio-therapeutics, she says.
These include research from Finland showing that women at high risk of giving birth to children prone to allergy could reduce the chances of such allergies by 50 per cent if they ate a probiotic.
Another trial highlighted the efficacy of a cocktail of probiotics in keeping inflammatory bowel disease in remission.
These studies have focused on the health benefits of naturally occurring gut bacteria but scientists are also genetically engineering bacteria. In the Netherlands there's a trial under way whereby patients with inflammatory bowel disease are being given a genetically engineered lactococcyl bacteria.
"If the results of these are positive then I think it will really alter what research is done," predicts Prof Shortt.
In Ireland, gut health and the beneficial effects of specific bacteria are key priority research areas following the establishment of the Alimentary Probiotic Centre in University College Cork. "Over €16 million has been placed by Science Foundation Ireland into research in Cork," says Prof Shortt. Funding is also provided by the food industry.
The multi-disciplinary team includes clinicians and scientists encompassing gastroenterology, microbiology, immunology, bio-informatics, molecular biology and food science.
As yet, food companies such as Yakult, which last week formally launched its probiotic drink in Ireland, cannot make specific claims about the health benefits of consuming their products.
Instead, such products are being marketed as useful in maintaining health rather than treating or curing or preventing anything.
Prof Shortt says each container of her company's product contains 65 billion of those bacteria named after Yakult's founder - Lactobacillus casei Shirota. Made in the Netherlands with reconstituted skimmed Irish milk, they also contain water, flavouring, glucose syrup and sugar.
Concerns about the over-consumption of sugar are not of concern to Yakult, says Prof Shortt, because its product has only 50 calories per bottle, equivalent to one apple.