Jews and their digestive problems are the subject of countless bad standup comedy routines, but a recent study may have identified exactly why so many Jews are afflicted.

For years, scientists have known that people of Ashkenazi Jewish descent were two to four times more likely to develop inflammatory bowel disease than other people. IBD, which includes Crohn’s and colitis, is marked by inflammation in the intestines caused by an abnormal immune response to bacteria and microorganisms that are vital to digestion and bowel function. Symptoms can range from diarrhea to pain and cramping to bloody stool. In rare cases, the condition can even lead to fatal complications. 

While researchers have previously identified some genetic variations that are associated with IBD, they now have a greater understanding of how it’s passed down in Ashkenazi Jews.

While previous studies had largely focused on general European populations, the new study is the first to look at variants specific to Ashkenazi Jews. The study was published by a team of researchers from the U.S., Canada and the United Kingdom in the April edition of Nature Communications.

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The founder effect

Co-author Yuval Itan, an associate professor of genetics and genomic sciences at New York’s Icahn School of Medicine at Mount Sinai, explained that these variants are unique to Ashkenazi Jews because of the “founder effect,” which turns up in groups “descended from a small founding population and that was not mixed to a large extent with the surrounding populations.” Previous research had found that a variety of genetic variations can lead to IBD, so Itan theorized that there would be variations unique to Ashkenazi Jews with the disease that wouldn’t be found in others with the same illness. 

The team analyzed the genetics of 1,734 Ashkenazi Jews with IBD and compared them to a control group of 2,719 who did not have the disease. They found 10 genes with variations linked to the disease. While two were previously known in the general population, eight of them were new and unique to Ashkenazis. 

“From what we see now, there is a distinct genetic architecture in Ashkenazi Jews causing IBD,” said Itan. 

The interplay between genes can be complex and it’s rare for an individual variation to be 100% responsible for the development of a sickness. Itan stressed that these eight variations were merely linked to increased risk of developing IBD and, on its own, none would be completely responsible for someone becoming ill. 

“Depending on the variance, it’s basically anything between a few percent increase to a 20-fold increase,” said Itan. 

Future genetic treatments

While genetic treatments for a whole host of ailments are being developed, the technology is still in its early stages and few have proven to be more effective than conventional therapies. But Itan said the new knowledge can lead to more effective strategies for taking on IBD, including better screening and helping doctors make more specific choices for treatment options. 

“There are many different ways to treat such a complex disease and if you know the very specific mechanism and the very specific pathway that is underlying IBD in this specific patient, then better drug treatments can be made by the clinician,” said Itan. 

This article was originally published on the Forward.