Lactose Malabsorption Is Associated with Early Signs of Mental Depression in Females (A Preliminary Report)

Abstract

Lactose malabsorption is characterized by adeficiency of mucosal lactase. As a consequence, lactosereaches the colon where it is broken down by bacteria toshort-chain fatty acids, CO₂, andH₂. Bloating, cramps, osmotic diarrhea, and other symptoms ofirritable bowel syndrome are the consequence and can beseen in about 50% of lactose malabsorbers. Having madethe observation that females with lactose malabsorption not only showed signs of irritable bowelsyndrome but also signs of premenstrual syndrome andmental depression, it was of interest to establishwhether a statistical correlation existed betweenlactose malabsorption and mental depression. Thirtyfemale volunteers were analyzed by measuring breathH₂ concentrations after an oral dose of 50 glactose and were classified as normals or lactosemalabsorbers according to their breath H₂concentrations. All patients filled out a Beck'sdepression inventory questionnaire. Of the 30 femalevolunteers, six were lactose intolerant (20%) and 24were normal lactose absorbers (80%). Subjects with lactosemalabsorption showed a significantly higher score in theBeck's depression inventory than normal lactoseabsorbers did. The data thus suggest that lactosemalabsorption may play a role in the development of mentaldepression. In lactose malabsorption high intestinallactose concentrations may interfere with L-tryptophanmetabolism and 5-hydroxytryptamine (serotonin)availability. Lactose malabsorption should be considered inpatients with signs of mental depression.