A good gut feeling

Diversity of 'good' bacteria in our gut is essential in maintaining good health, writes MICHELLE McDONAGH

ADVANCES IN molecular technologies have seen the humble gut microbiota become a crucial target for improving human health and reducing disease risk over the past decade. It is now accepted that the human intestinal microbiota plays an important and complex role in the maintenance of our health – this knowledge has the potential to offer targeted dietary intervention to promote and maintain health in vulnerable populations throughout life, particularly during periods such as infancy and old age.

“The human intestine is full of bacteria which is why we are always urged to wash our hands after going to the toilet. We think it’s all bad, but it turns out there is a community of organisms down there that is essential for normal health,” explains Dr Paul O’Toole of the department of microbiology and alimentary pharmabiotic centre in University College Cork.

The human body relies on vast numbers of microbes to function efficiently and healthily. (Microbiota refer to the complete set of micro-organisms present in an environment including viruses, bacteria, protozoa, fungi and yeast.) There are up to 100 trillion microbes in the human gastrointestinal tract alone. There are in fact, 10 times more bacterial cells in the GI tract than human cells in the body and 100 times more bacterial genes than human genes inside the human body.

“If Martians came to earth and looked at the human body, they would say ‘Wow, isn’t that a clever thing the microbiota have developed to carry themselves around in’,” Dr O’Toole quips.

The landmark Eldermet project at UCC ( eldermet.ucc.ie) is one of several worldwide projects that is working to catalogue the microbiota of the human gut. Researchers on the project are exploring interactions between the microbiota, diet, health and lifestyle in older Irish adults.

Eldermet, which is co-funded by the Department of Agriculture, Food and Marine, and the Health Research Board’s food for health research initiative, will provide fundamental evidence upon which future functional health foods, specific to older populations, will be based. The project is a collaborative effort between scientists and clinicians at UCC, Teagasc Moorepark’s Food Research Centre and the HSE hospitals in the Cork area.

Dr O’Toole, who is the project co-ordinator of Eldermet explains: “It’s only since we have had the ability to examine the composition of the microbiota of the gut relatively recently with cutting-edge, culture-independent techniques that we have begun to realise how much more important it is than was previously thought. Alterations in the gut bacteria have been increasingly linked to variations in health, including obesity, heart disease and inflammatory conditions and there is emerging evidence that gut microbiota can even affect how the brain works and could be related to the rate of loss of mental function. It’s still not clear which body defence functions and mechanisms are most dependent on gut bacteria and this is what we aim to find out.”

The most recent findings from Eldermet published last Friday in British journal Nature show that the individual microbiota of people in long-stay care is significantly less diverse than that of community dwellers – due mainly to differences in diet – and loss of community-associated microbiota correlates with increased frailty.

The researchers studied the faecal microbiota composition from 178 elderly subjects living in the community, day-hospital, rehabilitation or in long-term residential care. While other factors undoubtedly contribute to health decline, this new data suggests that diet shapes the microbiota which then affects health in older people.

The authors explain: “Diet-determined differences in microbiota composition may have subtle impacts in young adults in developed countries. These would be difficult to correlate with health parameters, but become far more evident in the elderly who are immunophysiologically compromised. This is supported by the stronger microbiota-health associations evident in the long-stay cohort, and there is now a reasonable case for microbiota-related acceleration of ageing-related health deterioration.”

The association of the intestinal microbiota of older people with inflammation and the clear association between diet and microbiota outlined in this and previous studies argue in favour of an approach of modulating the microbiota with dietary interventions designed to promote healthier ageing.

“Dietary supplements with defined food ingredients that promote particular components of the microbiota may prove useful for maintaining health in older people.

On a community basis, microbiota profiling . . . offers the potential for biomarker-based identification of individuals at risk for, or undergoing, less-healthy ageing,” the authors state.

Findings published from the Eldermet project earlier this year confirmed that the gut microbiota of older people was strikingly different from that of younger people.

However, more unexpectedly, the research also showed that there was a huge variation of gut microbiota among the cohort of older people, mainly from the Munster area.

“There was also a striking variation in the proportion or number of bacteria associated with disease found among the older group. Some people had very high levels of potentially harmful bacteria and very little good bacteria. This is the generation beyond probiotics and we believe our findings will probably have good application in some new products,” Dr O’Toole says.