Intolerance in the Land of Milk and Honey – Is It All In Your Head?

Most people are born with the ability to digest lactose — the major carbohydrate in milk. But, as they age, many people lose this ability and report lactose intolerance, which can significantly impair quality of life owing to uncomfortable symptoms. A new study reports, however, that, while the inability to adequately digest lactose is a true physiological condition for some, many suffer from symptoms that may be more psychological than physiological.

The latest research, conducted by Italian gastroenterology experts, explains that lactose intolerance, a subjective experience, is often attributed to lactose malabsorption, an objective, diagnosed condition. However, the relationship is far from proven, and the presentation of lactose intolerance symptoms varies with the type and amount of dairy product ingested. For the study, 102 patients underwent a lactose hydrogen breath test — the most reliable method for diagnosing lactose malabsorption. The patients also reported symptoms of lactose intolerance on a subjective scale and they completed a psychological symptom checklist and a health-related quality of life survey.

Lactose malabsorption was diagnosed in 18% of the patients, while lactose intolerance was reported in 25% of patients. The two conditions were not associated with each other. Interestingly, the severity of intolerance symptoms was the lowest among patients with malabsorption. Somatization (the presence of clinically relevant symptoms with no identifiable cause) is blamed for the intolerance-related complaints. Patients with a high level of somatization reported the lowest quality of life. Patients with malabsorption did not report poor quality of life.

Lactose malabsorption is the inability of the body to completely digest lactose due to a deficiency of the enzyme lactase. This condition may occur as a primary disorder or secondary to a gastrointestinal disease. Lactase activity may also decline with age, resulting in nearly 75% of the world’s adults losing the ability to digest lactose at some point during their lives. However, not all of these people will experience symptoms consistent with lactose intolerance such as bloating, abdominal pain, diarrhea, and vomiting. A lactose-restricted diet often leads to decreased symptoms of intolerance, but it also carries the nutritional disadvantages of reduced calcium and vitamin intake.

True lactose malabsorption is difficult to diagnose, and, as new research points out, symptoms are not a reliable indicator of absorption ability. Symptoms associated with lactose intolerance may be little more than psychological manifestations that can lead to impaired quality of life. Subjective, non-pathological health complaints are common among the general population, and gastrointestinal symptoms account for many of these complaints. Somatization disorders are often difficult to identify and the authors of the current study do not recommend a therapeutic approach for patients complaining of lactose intolerance. But, they suggest that a cognitive approach may prove more useful than a medical or pharmacological approach.


Mattar R, de Campos Mazo DF, & Carrilho FJ (2012). Lactose intolerance: diagnosis, genetic, and clinical factors. Clinical and experimental gastroenterology, 5, 113-21 PMID: 22826639

Olivier CE, Lorena SL, Pavan CR, Dos Santos RA, Dos Santos Lima RP, Pinto DG, da Silva MD, & de Lima Zollner R (2012). Is it just lactose intolerance? Allergy and asthma proceedings : the official journal of regional and state allergy societies, 33 (5), 432-6 PMID: 23026186

Tomba C, Baldassarri A, Coletta M, Cesana BM, & Basilisco G (2012). Is the subjective perception of lactose intolerance influenced by the psychological profile? Alimentary pharmacology & therapeutics, 36 (7), 660-9 PMID: 22860690

Usai-Satta P, Scarpa M, Oppia F, & Cabras F (2012). Lactose malabsorption and intolerance: What should be the best clinical management? World journal of gastrointestinal pharmacology and therapeutics, 3 (3), 29-33 PMID: 22966480

Image via Gayvoronskaya_Yana / Shutterstock.

Jennifer Gibson, PharmD

Jennifer Gibson, PharmD, is a practicing clinical pharmacist and medical writer/editor with experience in researching and preparing scientific publications, developing public relations materials, creating educational resources and presentations, and editing technical manuscripts. She is the owner of Excalibur Scientific, LLC.
See All Posts By The Author