Many patients with IBS (Irritable Bowel Syndrome) have discovered that certain foods simply don’t agree with them and avoiding those makes the symptoms better. In fact, over 60% of patients with IBS report symptoms related to food and improvement when avoiding these foods. Trying an elimination date on your own is hard and often frustrating, even with the help of a nutritionist or allergist the process is a lengthy one. This may change soon if the studies of this exciting study out of Yale University can be reproduced by others.
Existing blood tests not rigorously studied – until now
While many commercially available blood tests that claim to diagnose food intolerance have been available, most are not scientifically validated. Among the more highly used ones are leukcocyte activation tests. They are used to guide elimination diet recommendations. The first randomized controlled study that rigorously examines the efficacy of individualized diets in patients with irritable bowel syndrome was just published (1). The diet advice was based on the results of the leukocyte activation test.
What is the ALCAT leukocyte activation test?
The ALCAT (Antigen Leukocyte Cellular Antibody Test) is performed using a regular blood sample. The leukocytes (white blood or immune cells) are separated from the blood sample and then exposed to 200 (or more) test food extracts. After 15 minutes the white cells are counted and classified into size classes. The statistical distribution curves vary and are classified as no, a mild, moderate or severe leukocyte activation. Foods that led to moderate or severe activation are then avoided in an individualized diet plan.
How was the study set up?
58 participants in this Yale University study were randomized to a 4-week diet. Group 1 got a diet where all foods which caused leukocyte activation were eliminated and those which did not were allowed (“good foods”). Group 2 received the exact opposite, foods that led to leukocyte activation were allowed, and those which did not, eliminated (“bad foods”). The participants did not know on what basis the foods were chosen and they were randomly assigned to group 1 and 2.
What were the findings?
Statistically significant benefits were seen in global improvement and in symptom severity in a 4-week diet guided by leucocyte activation testing (“good foods”) compared to a matched comparison diet (“bad foods”). This study provides novel data suggesting that a leucocyte activation test can be used to develop an individualized diet that can alleviate symptom burden in IBS, distinct from other types of dietary interventions.
What should we think about this?
Strengths of this study include may features researchers associate with a high quality study: an adequately powered, randomized design, with a matched comparison diet utilizing a rigorous blinding strategy, validated outcome measures, an intention-to-treat analysis, high levels of dietary adherence, and minimal dropout. Drawbacks were the relative short study duration and a limited not very diverse study population.
Furthermore, this is the first study of its kind and more work is clearly needed. However, food avoidance is one of the safest (and probably also most effective) treatment approaches for IBS. The testing is commercially available, although not yet covered by insurance. It may be right for certain patients, make an appointment with Dr. Klaus Gottlieb to discuss.
- Ali A, Weiss TR, McKee D, et al. Efficacy of individualised diets in patients with irritable bowel syndrome: a randomised controlled trial. BMJ Open Gastro 2017;4:e000164. doi:10.1136/ bmjgast-2017-000164