Why our great-grandparents' diet holds the key to better health today
Modern eating habits have led to a decline in types of healthy bacteria which protect the immune systems of Irish people, a leading gastroenterologist has said.
The systems of microbes that live in our bodies, mainly in the gut, called the microbiome, have become quite different to those that helped protect the health of our great-grandparents, said Professor Fergus Shanahan.
A lack of fibre in highly processed modern foods has resulted in some of the changes to the microbiome of Irish people. As a result, diseases of the immune system have become more widespread in Ireland and in other industrialised countries in recent decades.
The microbiome, consisting of trillions of micro-organisms, plays a vital role in breaking down food to release energy, produce vitamins and protect people from harmful germs.
"We know certain bugs have been disappearing. Even since the 1950s, certain bacteria that we had in the western world are no longer there. We paid a price which is a rise in chronic inflammatory diseases and metabolic diseases, including obesity," he said.
A professor of medicine at University College Cork, Fergus Shanahan has just stepped down from his role as director of APC Microbiome Ireland, an institute based at the university which has become a global leader in microbiome science in the past 15 years, with the help of funding from Science Foundation Ireland.
He referred to the work of APC Microbiome Ireland during a wide-ranging lecture at the Royal College of Physicians in Dublin last Thursday.
"People tend to think of bacteria as parasites, but they are net contributors to our energy intake," he said.
"We have between 10 and 100-fold more bacterial cells in the body than we have human cells. I often make the joke we are only a minority component of ourselves. And there are more viruses in the human body than there are bacterial cells. The viruses are inside the bacteria," he said.
Eating a diversity of unprocessed foods and avoiding overuse of broad spectrum antibiotics can lead to a more beneficial microbiome.
Researchers in Cork look at the microbiome as a bio-marker for health and disease. They also look at ways of manipulating it for health benefits. They are now looking at ways of mining the microbiome in the human body to develop new medicines.
In 1993, Prof Shanahan returned to Ireland from working in the US to become professor of medicine at UCC. He set up a dedicated clinic for patients with inflammatory bowel disease, Crohn's disease and ulcerative colitis. He has seen the frequency of these diseases rise sharply in Ireland and all western countries in the past two decades.
Other diseases of the immune system have also shot up such as multiple sclerosis, asthma, eczema, type one diabetes, and these are all related to the microbiome, he said.
New research led by Prof Shanahan, not yet published, reveals members of the Irish Traveller community have a healthier microbiome than the settled community.
"The Travellers themselves in Cork agreed to help us do this research. And, sure enough, they had a far healthier microbiome than we have in the settled community.
"I believe the reason for this is that Traveller communities have larger families, they live closer together and they live closer to their animals, which benefits their microbiome," he said. "In some ways, as a parallel ethnic group, aspects of their lifestyle are not too dissimilar to what many of us had 100 to 200 years ago."