Background & Aims
Lactose intolerance is a common cause of abdominal discomfort, manifesting in a spectrum of symptoms ranging from pain to non-painful manifestations such as bloating, flatulence, nausea, and diarrhea. Traditionally, lactose malabsorption was thought to be the sole cause of lactose intolerance, but recent research suggests that it may also be caused by visceral hypersensitivity or dysbiosis of the gut microbiome. Recently, the adult Carbohydrate Perception Questionnaire (aCPQ) was developed, the first and only questionnaire to provide an unbiased assessment of symptoms following lactose ingestion. Our aim in the present study was to characterise pain and non-painful symptoms induced by lactose ingestion in patients with lactose intolerance, depending on the presence or absence of malabsorption, utilizing the aCPQ.
Methods
536 patients with abdominal symptoms suggestive of lactose intolerance underwent lactose (25 g) hydrogen breath and intolerance testing using the aCPQ and an electrochemical hydrogen detector to quantify end-expiratory breath hydrogen. Malabsorption (M+) was defined as an increase in end-expiratory H2 of >20 ppm over baseline (as opposed to M-), and lactose intolerance was defined as an increase in symptom scores on any of the five VAS scales of >20 cm over baseline within the 180-minute test period. A p-value <0.05 was considered significant.
Results
289 patients (53%) had lactose intolerance, of whom 160 patients (55.4%) had malabsorption (M+), and 129 patients had no malabsorption (M-). Another 66 patients (22.8%) had M+ but no intolerance. Pain was reported by 149 intolerant patients (51.6%) and non-painful symptoms by 264 patients (91.3%). The table shows the frequency of painful and non-painful symptoms in patients with lactose intolerance, depending on the presence of malabsorption. Pain was the most bothersome symptom in 24 patients (15.0%) in the M+ group and in 22 patients (17.0%) in the M- group (p>0.05).
Table:
Lactose intolerance (n=289)
pain nausea bloating flatulence diarrhea
M+ 64.4 29.4 59.4 64.4 51.9
M- 35.7 38.8 45.0 38.8 16.3
p-value >0.001 0.09 0.01 >0.001 >0.001
Conclusions
This study highlights the important role of visceral pain as a symptom in patients with lactose intolerance. In particular, the study shows that patients with both lactose intolerance and concurrent malabsorption are almost twice as likely to experience pain as those with lactose intolerance but normal lactose absorption. In addition, individuals identified as malabsorbers with lactose intolerance also show a significantly higher propensity to report non-pain symptoms, with the exception of nausea.
References
Hammer J, Hammer HF. Gastroenterology 2019; 156:1220-1221
Hammer J et al. Eur J Gastroenterol Hepatol 2021;32:171-177
Hammer HF et al. United European Gastroenterol J 2022;10:15-40
Hammer HF, Hammer J. Dig Dis Sci 2024; in press