Certain foods and substances, including caffeine, sugar alcohols, and some types of dietary fiber, can worsen IBS-D symptoms by increasing gut motility or retaining fluid in the intestines. These factors explain, in part, why a low-FODMAP diet is recommended for people with IBS-D.
In a 12-week randomized controlled trial, researchers compared a low-FODMAP diet to one that replaced cereal grains (like wheat) with Tritordeum (a hybrid of durum wheat and wild barley), and found that both diets were equally effective at reducing IBS-D symptoms.[1]
Traditional dietary advice — such as avoiding trigger foods, limiting alcohol, and eating smaller, more frequent meals — is also effective (though the low-FODMAP diet is slightly more effective.)[2][3]