Digestive problems are nothing new for Jews. In fact, they were apparently so prevalent in ancient times that the Mishna (Shekalim 5:1) notes that ben Ahiya, one of 15 officials who served in the Temple in Jerusalem, was responsible for treating priests with “intestinal disorders.” The Talmud Yerushalmi (ibid. 13b) states that the priests suffered from such ailments in part because of the large quantities of meat from the sacrifices that they would eat, and that ben Ahiya “knew which particular wine was good for healing the intestines, and which type of wine would be bad for the bowels.” 

Source: JPost

While there is no such thing as a "Jewish gene,"Jewish communities across the globe share a common "genetic thread", according to a 2010 study led by geneticist Harry Ostrer of Albert Einstein College of Medicine in New York. Genetic analysis of seven Jewish groups (Iranian, Iraqi, Syrian, Italian, Turkish, Greek and Ashkenazi) identified two distinct clusters that split about 2,500 years ago: European/Syrian Jews and  Middle Eastern Iraqi and Iranian Jews.

Because Ashkenazi communities tended to marry among themselves, any mutations that may have arisen at random would have increased in prevalence among their numerous descendants. This led Ashkenazi gene sequences to be some of the most distinct among humans today.

Source: Haaretz

Ashkenazi Jews' shared genetics have led to a prevalence of several stomach-related issues, often centralized under the term Inflammatory Bowel Disease. 

IBD is an umbrella term that describes inflammatory disorders of the digestive tract such as Crohn’s disease and ulcerative colitis, often goes undetected. 

IBD is characteristically a lifelong (chronic) condition in which there is inflammation of the lining of the gastrointestinal tract for no apparent reason. The inflammation might be located just in one part of the digestive tract, for example, in the large intestine (colon), but it can appear anywhere along the digestive tract, from the mouth to the anus. IBD occurs as two major types and two rare types. Crohn’s Disease and Ulcerative Colitis are the two diseases that most people recognize because they are the most common.

Alan Kligerman (born 1930) was the son of Jewish immigrants from Ukraine and Belarus, Cornell dropout and third-generation milkman. In 1974, Kligerman developed the first of two game-changing remedies: Lactaid, a form of milk fortified with the enzyme lactase, which enabled the digestion of milk products. Then, in the 1980s, Kligerman began investigating the facets of vegetables, specifically their polysaccharides and oligosaccharides, that can cause flatulence. In 1990, this product Beano went on the market.

Source: Nosher

• https://www.ccfi.co.il/the-israel-crohns-disease-and-ulcerative-colitis-foundation-ccfi/ 

• https://www.cedars-sinai.org/blog/ashkenazi-jews-and-crohns-whats-the-connection.html 

• https://www.haaretz.com/science-and-health/2015-07-08/ty-article/.premium/12-facts-about-jewish-genetics/0000017f-f808-d044-adff-fbf9706f0000 

• http://www.ibdsf.org/index.php/about-ibd 

• https://www.myjewishlearning.com/2007/09/20/my-stomach-my-ruler-my-king/ 

• https://www.myjewishlearning.com/the-nosher/the-jewish-history-of-beano-and-lactaid/