Patients who identified themselves as lactose intolerant recalled symptoms experienced at home as being much more severe than symptoms following a 50-gram lactose challenge, Dr. Francesc Casellas and colleagues reported.
In addition, more than half of these self-identified lactose intolerant individuals were not, in fact, lactase deficient, based on a hydrogen breath test conducted after the lactose challenge.
This means that “symptoms patients believe related to lactose are aggravated by the home environment or, more likely … are not due to lactose malabsorption but to other causes,” they wrote.
Dr. Casellas of the Digestive System Research Unit at the Hospital Universitari Vall d'Hebron in Barcelona looked at 353 white patients referred to their unit for evaluation of suspected lactose maldigestion. The cohort included 240 women, and the median age was 41 years (Clin. Gastroenterol. Hepatol. 2010 July [doi:10.1016/j.cgh.2010.03.027]).
Patients were asked to complete a questionnaire that assessed five symptoms common among lactose malabsorbers: diarrhea, abdominal cramping, vomiting, audible bowel sounds, and flatulence.
“Patients completed the validated questionnaire on lactose intolerance symptoms twice,” wrote Dr. Casellas and coauthors. The first time occurred before patients underwent a lactose hydrogen breath test: The questionnaire asked exclusively about symptoms occurring after “usual consumption of milk-based products at home,” or what the investigators referred to as “home symptoms.” The second time patients completed the questionnaire was following completion of the breath test; this time, they were asked to rate symptoms experienced in the laboratory after they ingested a 50-gram lactose test load.
Only 164 out of the 353 patients (46%) were found to be true lactose malabsorbers following the hydrogen breath test. Among all 353 patients, at-home symptoms were ranked as being much worse than were symptoms following the lactose challenge, with the median score for home symptoms being 16 (range, 8-26) and the median score for symptoms in the laboratory being 8 (range, 2-18).
However, patients with true lactase deficiency according to the breath test reported more severe symptoms following the challenge than did patients with normal lactase levels: Malabsorbers reported a median of 15 for symptoms on the second, in-laboratory questionnaire (range, 7-25), compared with a median score of 4 on that survey among lactose absorbers (range, 0-11).
“These results suggest that, despite patient manifestations, symptoms experienced at home were unlikely to be directly related to lactose-containing foods,” especially among those patients without true lactase deficiency, the authors wrote. They speculated that the reported increased severity could be caused by the fact that “patients at home ingest lactose with other nutrients, such as fat, that could in themselves cause symptoms.”
In any case, “A record of symptoms does not suffice to establish lactose malabsorption,” they wrote. “Specific procedures such as the lactose breath test should be performed to confirm it.”
Disclosures: The study was supported in part by grants from the Generalitat de Catalunya and the Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas. The individual authors declared that they had no competing interests to disclose.