One point made frequently in the NIH state-of-the-science conference on Lactose Intolerance (LI) was that people often misinterpreted the symptoms they got from food. Having symptoms, even when having dairy products, didn't necessarily mean that lactose was the cause.
Another larger and better test of this notion just appeared in the medical journal Clinical Gastroenterology and Hepatology. "Subjective Perception of Lactose Intolerance Does Not Always Indicate Lactose Malabsorption," by Francesc Casellas et al., Volume 8, Issue 7 , Pages 581-586, July 2010.
Background & Aims
Symptomatic lactose intolerance is common; however, abdominal symptoms that patients experience after ingestion of lactose-containing foods can have causes beyond lactose malabsorption. We aimed to determine whether symptoms that patients usually attribute to lactose intolerance are comparable to symptoms provoked by a controlled lactose challenge and whether these symptoms are related to lactose absorption capacity.
We performed an observational, prospective, transverse study of 353 patients referred for a lactose hydrogen breath test (HBT). Patients completed a validated questionnaire about symptoms associated with consumption of dairy products at home (home symptoms). After a 50-g lactose breath test, they completed the same questionnaire again (lactose challenge symptoms). Patients were assigned to groups of absorbers or malabsorbers according to HBT results and tolerants or intolerants according to the results of the questionnaire.
The total symptom score was significantly higher for home symptoms than for the lactose challenge (16 vs 8, P < .01). Symptoms perceived at home were reported to be more intense than those that followed the lactose challenge for lactose absorbers compared with malabsorbers (16 vs 4, P < .01) and lactose tolerants compared with intolerants (12 vs 2, P < .05). Overperception of lactose intolerance at home was similar in men and women.
Daily life symptoms that patients associate with lactose intolerance are often unrelated to lactose malabsorption. Even among true lactose malabsorbers, symptom recall tends to be amplified by the patient. Thus, conventional anamnesis is a highly unreliable tool to establish symptomatic lactose malabsorption.
A 50 gram lactose challenge is enormous. That's the amount of lactose in four 8-ounce glasses of milk, more than almost anybody normally gets from food. So much lactose should create enormous and violent symptoms in anyone who is truly LI.
Yet the symptoms reported at home from normal food intake were more numerous and more severe than the symptoms reported from the lactose challenge. That's impossible to explain except subjectively. People either are getting their symptoms at home from foods other than lactose (or non-food reasons entirely) or else they simply report symptoms worse than they really are.
LI is real and people do get symptoms from it. But it's not the fault of the most or the worst symptoms for most people. Hard as that may be to believe, here's another test - and of a large number of patients - that replicates that claim.