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GENETICS DETERMINE HOW OFTEN YOU GO TO THE BATHROOM

A study confirms that there is a relationship between the genetics of each person and intestinal transit

Do you have trouble going to the bathroom regularly? What is regularity? A new study indicates that genes may influence how often you defecate. In addition, these genes give clues to the causes of gastrointestinal disorders, such as irritable bowel syndrome (IBS).

Previous articles also showed that IBS may have a genetic component. Other factors, such as a person’s diet and stress levels, are likely to have a greater effect on symptoms of the disorder, according to Emeran Mayer , a gastroenterologist and neuroscientist.

HOW OFTEN DO YOU SIT ON THE PORCELAIN THRONE?

The new study included genetic sequences and health data from 167,875 people registered with the UK Biobank, a huge biomedical database and four smaller databases selected by the Netherlands, the US, Belgium and Sweden. Some of these patients had IBS whose symptoms are intestinal, such as recurrent abdominal pain, bloating, gas, and changes in bowel function, such as constipation, diarrhea or both, reports UCSF Health, University of California Medical Center. In addition to providing their DNA for analysis, these people answered a question: “How often do you go to the bathroom to defecate ?”

Some of the people studied defecated up to 20 times a day

Based on the participants’ responses and genetic sequences, the team found that the frequency with which a person defecates shows “modest but detectable heritability,” meaning it is partly influenced by genetics.

To determine this, they identified 14 stretches of the genome that appeared to be linked to stool frequency.

Those who defecated less frequently showed similar patterns of genetic variation within those 14 areas, and those who did so more often also shared a similar genetic makeup in those genetic regions.

In general, most of the participants said that they had defecated once, twice or three times a day; fewer people reported four, five or six times, and a smaller group, up to 20 times a day, explained Mauro D’Amato , one of the study authors.

THE HIGHEST FREQUENCY, WITH DIARRHEA

To see if they could predict which participants were experiencing IBS symptoms based on these different genetic profiles, the researchers calculated a polygenic risk score for each individual. This risk score indicated the probability that each participant had a high stool frequency based on the presence of certain genes in their DNA.

They found that those with higher scores had a five times greater risk of IBS than the rest of the participants, specifically the IBS subtype that causes increased diarrhea (IBS-D).

The team examined which specific genes appeared in the 14 stretches of DNA and how they might be related to defecation and IBS.

Each of these DNA regions contains several genes, and when looking at genes with known functions, some of them made perfect sense, D’Amato said. One gene encodes brain-derived neurotrophic factor (BDNF), a protein that helps neurons divide and regenerate. Evidence suggests that increasing the level of BDNF in the intestine can increase motility, or the speed with which material moves through the gastrointestinal tract.

THE GUT-BRAIN CONNECTION

Some other genes also appear in this analysis, including those that code for neurotransmitters, hormones, and other molecules that help control nerve cells involved in intestinal peristalsis – the wave-shaped movements that push poop through the intestine. In addition, many of these molecules have functions in the brain.

This finding is consistent with a previous study that suggested that genetic risk factors for IBS overlap with those for anxiety and depression. These genetic data are also consistent with the clinical observations of IBS patients, who often experience elevated levels of anxiety prior to their IBS symptoms. The research suggested that IBS involves both the brain and the gut, rather than the gut in isolation, Mayer clarified.

For now, Mayer continued, patients should be aware that while genetics may play a very small role, there are many more important behavioral and lifestyle factors that can be modified. That is, diet changes, therapies to help with stress reduction, and medications that relieve intestinal symptoms can be very helpful for IBS patients.

REFERENCES

GWAS of stool frequency provides insights into gastrointestinal motility and irritable bowel syndrome

Genome-wide analysis of 53,400 people with irritable bowel syndrome highlights shared genetic pathways with mood and anxiety disorders

Photo: Marco Verch Professional Photographer

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