How to keep your gut happy

Most of us have had “gut reactions” to things in our lives, or “gut feelings” about people or events. But new research shows that these may be more accurate than we could ever have imagined. While most people are aware of the crucial role gut bacteria plays in digestion, with studies linking the microbes in our large intestines to everything from allergies to immunity to weight, a growing number of researchers are exploring how our gut flora can influence our mood and stress levels, too.

Last week, a team of researchers at University College Cork found that men who took a probiotic containing a strain of healthy gut bacteria for four weeks performed better in stress tests than those who took a placebo. The men taking the daily probiotic — called bifidobacterium longum 1714 — also reported less anxiety and lower levels of the stress hormone cortisol in their saliva than those on the placebo.

These new findings, presented at the Society of Neuroscience’s annual meeting in Chicago, add to a body of recent research linking the performance of our brains to the bacteria in our guts. In one fascinating study, it was discovered that stress could even be transferred from one animal to another through the transplanting of gut bacteria alone.

The research, from McMaster University in Canada, found that when bacteria was transferred from the guts of stressed mice into the guts of calm ones, the tranquil ones quickly became stressed. “By transplanting the bacteria from the gut of a stressed mouse, the researchers transplanted its stress,” says Tim Spector, professor of genetic epidemiology at King’s College London, whose British Gut Project is at the forefront of research into the ways our guts influence our bodies and minds. How can this be?

The gut is home to your enteric nervous system, sometimes referred to as the “second brain”, says Prof Spector. Neurotransmitters essential to brain health are produced in the gut and scientists now believe some 95 per cent of our serotonin — a neurotransmitter essential to mood stability that antidepressant medication helps regulate — is made in our guts.

But we’re still only at the very beginning of research into how this “gut-brain” axis actually works and are not yet still certain how neurotransmitters, such as serotonin found in the gut, can influence or reach the brain, Spector explains. One theory is that the vagus nerve — a long, critical nerve extending from the abdomen to the brain — acts as a neural highway for chemicals made in the gut to get to the brain. Prof Spector adds: “The chemicals that the microbes in the gut secrete could switch genes on and off in the gut lining, affecting the brain.”

Mood stabiliser

Gut bacteria certainly play a role in mood problems, says Dr David Perlmutter, a New York-based neuroscientist. In his book “Brain Maker: the Power of Gut Microbes to Heal and Protect Your Brain — For Life”, Dr Perlmutter cites scientific papers linking the bacteria in our guts to mental and neurological problems, including depression, anxiety and even autism, though he agrees more study is needed to cement the link. He points to research from December last year in which scientists from Oxford University gave women prebiotics — foods that probiotics feed off, such as fibrous vegetables.

The women in the study experienced positive psychological effects and reacted less negatively to emotionally charged images or words than those who had been given a placebo. “It’s the same effect that has been observed among individuals on antidepressants or anti-anxiety medication,” says Dr Perlmutter. “The researchers also discovered that people who took the prebiotics had lower levels of cortisol in their saliva.” This adds to the volume of human studies “showing a relationship with gut bacteria and mental health, especially with regard to anxiety”.

Indeed, a study of 700 students at the College of William and Mary in Virginia found that those who ate more fermented foods such as yoghurt, pickles and sauerkraut, which are high in natural probiotic cultures, had fewer symptoms of social anxiety and neuroticism than those who ate less or none at all. “Though such studies are not conclusive, they do show a consistent theme coming through of a potential role in stress, anxiety and possibly depression played by the influence of gut bacteria on the brain,” says Dr James Kustow, a consultant psychiatrist at the Nightingale Hospital and Barnet Hospital, London.

“When I see a patient with mental health difficulties like these, in addition to exploring their diet and bowel function, I am on the look-out for a history of excessive antibiotic use, which can influence the state of an individual’s gut bacteria,” he says.

“Studies have looked at the effect of probiotics on physical health problems such as food allergies, but we’re only just exploring whether this extends into the field of mental health,” he adds.

Healthy gut foods

A diet high in fibrous vegetables will feed the healthy probiotic bacteria in your gut. “The best prebiotics are chicory roots, Jerusalem and globe artichokes, leeks, onions, garlic, celery, bananas, apples and pears,” says Prof Spector. The microbes in your gut also feed off foods containing antioxidants called polyphenols found in seeds, nuts, extra virgin olive oil, coffee and dark chocolate.

An unhealthy gut is usually the result of a diet high in processed foods, exposure to environmental toxins and antibiotic use. As part of his research, Prof Spector put his son on a diet of fast food for 10 days and then tested his gut flora before and after. “He lost 40 per cent of his gut bacteria,” says Prof Spector, who argues in his book “The Diet Myth” that weight problems are partly down to unhealthy bacteria. Too much antibiotic use can also have a harmful impact.

“The average 20-year-old has had 18 courses of antibiotics; some people’s gut bacteria will take two weeks to recover from one course, others may take six months, while others will never recover,” says Prof Spector.

Generally, it takes two months for the average gut to recover from one course of antibiotics, but you can improve this recovery time with a diet of probiotics and prebiotics. “Supplements can help regrow bacteria if you’re on antibiotics,” Prof Spector says, but eating fermented foods including yoghurt, sauerkraut, kimchi (a Korean pickle) and kefir (a milk drink popular in Eastern Europe) is better because these contain fibre along with cultures, and they’re also more likely to get to the lower gut than taking a pill.

–The Telegraph Group Limited, London 2015

The happy gut guide

Keep processed food to a minimum — it’s murderous to healthy gut bacteria.

Eat fermented foods — try live yoghurt, sauerkraut, miso (soya bean paste native to Japan) kimchi (a Korean fermented vegetable) and Kefir (fermented milk drink).

Prebiotics feed healthy bacteria such as chicory roots, Jerusalem and globe artichokes, leeks, onions, garlic, celery, bananas, apples and pears.

Seeds, nuts, extra virgin olive oil, coffee, dark chocolate and wine are rich in anti-oxidants.

Take probiotic supplements if you’re on antibiotics (or have a history of taking them) or you eat a diet high in processed food and low in vegetables.