People with irritable bowel syndrome (IBS) become exquisitely attuned to the rumblings and sensations in their bowels. They know that digestive mishaps—unexpected flatulence, can’t-stop-it diarrhea, painful cramps, etc.—can occur at any moment. Frequent bathroom trips become a way of life and prevent some people from even going out.

Even more frustrating, their doctors can’t always help. It’s difficult to predict what will make symptoms better or worse. Food sensitivities are often involved, but the tests to identify them have never been proven to work.

What’s new: Scientists at Yale University School of Medicine have conducted the first double-blind, randomized clinical trial to “test the test.” They found that a commonly used blood test accurately identified problem foods for individual patients—and that those who altered their diets based on the findings achieved impressive improvements.


Between 8% and 20% of Americans meet the diagnostic criteria for IBS—recurrent abdominal pain, frequent constipation and/or diarrhea, “urgency” after meals, etc. Yet only a small percentage of those with IBS are ever diagnosed. Some never see a doctor, and those who do seek help are sometimes told that the disease is mainly due to stress…or that the only solution is to take drugs or resort to a highly restrictive diet.

IBS is a difficult disease to manage, or even to recognize, because many of the symptoms can be caused by such factors as stress, diet, poor sleep or disrupted routines, as well as medication side effects, abnormal intestinal bacteria and/or dysfunctional bowel contractions. There are many IBS triggers—and they are different for everyone. The challenge for doctors and patients is to identify the particular triggers or trigger combinations that can worsen the condition.


According to reports from IBS patients, more than 60% react to one or more foods. Their symptoms get worse when they eat particular foods or food groups, and they feel better when they avoid them. But which foods should they avoid?

Until recently, the only way to know for sure was to conduct food challenges, a difficult process in which patients give up, and then eat, suspected foods—one at a time—to see what happens. This might mean giving up carrots for, say, a month…then giving up peppers…then giving up something else. It’s considered the gold standard for diagnosing food intolerances, but it’s time-consuming and frustrating—and almost impossible for busy physicians to supervise.

One catchall approach has been to avoid fermentable oligosaccharides, disaccharides, monosaccharides and polyols, or FODMAPs, a class of hard-to-digest carbohydrates that are found in many foods and food ingredients—garlic, onions, high–fructose corn syrup, stone fruits (such as cherries and nectarines), beans, cereals, dairy, etc. Most restaurants serve gut-churning amounts of FODMAPs.

Patients often improve on a low-FODMAP diet, but it’s highly restrictive, and most people hate it. It’s rare for people to stick with this kind of diet for more than a month.

The missing link: A test to identify specific foods that cause problems. For one person, it might be garlic or onions. For another, it might be cinnamon or yellow squash. This information would allow patients to know exactly what to avoid.


A number of blood tests have been developed for detecting food sensitivities. However, none of the tests had been proven to be effective. The main evidence that they worked (or didn’t) was anecdotal—until now. Among the most commonly used tests is the antigen leukocyte activation test known as Alcat. It involves extracting leukocytes (a type of immune cell) from blood, then mixing the cells with individual food extracts to see if the cells change—a sign of intolerance.*

Important new study: At Yale, researchers conducted a clinical trial of 58 patients. Some had severe symptoms of IBS, while others had milder cases. All were given the Alcat blood test in which their immune cells were exposed to 200 food extracts. Based on the findings, half the patients were told to avoid certain foods for four weeks. The most frequently restricted foods included strawberries, cinnamon, almonds, apples and pears—all of which are common IBS triggers. Patients in a control group were told to follow a sham diet that had nothing to do with their test results.

Results: Patients who avoided foods that were identified as problematic did much better—in terms of bowel urgency, firmer stools, fewer stools per day, etc.—than those in the control group. According to one measure (the Symptom Severity Scale), patients in the active-treatment group showed an improvement of 121 points, compared with 60 points for those on the sham diet. The study, funded by the manufacturer but designed and conducted by Yale researchers, was published in BMJ Open Gastroenterology. 


It’s reasonable for patients with IBS to start with a blood test such as the Alcat (see above) to identify foods that will probably make their symptoms worse. Note: Check with your insurance to make sure the test is covered. For long-term control—and long-term adherence to a diet—it’s much easier to avoid a few foods than to try to follow a highly restrictive diet.

While some patients may find that dietary changes alone will relieve—if not completely eliminate—their symptoms, others may do better when they combine dietary changes with medication. Medications prescribed for IBS include alosetron (Lotronex)…lubiprostone (Amitiza)…eluxadoline (Viberzi)…and rifaximin (Xifaxan).

For more on IBS, check the website of the International Foundation for Functional Gastrointestinal Disorders,

*For information on ordering the test, go to

Related Articles