RESUMEN
BACKGROUND: The main symptoms of lactose intolerance are bloating, abdominal cramps, increased flatus and loose watery stools. These symptoms are similar to those of irritable bowel syndrome (IBS), which is a prevalent entity in the community. OBJECTIVE: As there was no data available on the prevalence of LI and the correlated factors, this study aimed to determine these correlations and their relation to IBS symptoms in an apparently healthy population in Shiraz, southern Iran. MATERIALS AND METHODS: A survey among 1,978 individuals older than 35 years was conducted in Shiraz, southern Iran, using a questionnaire that consisted of items regarding demographic data, life style, subjective gastrointestinal symptoms of LI and IBS symptoms according to ROME II criteria. RESULTS: A total of 562 subjects reported LI (28.41%). The prevalence was significantly higher in females, in subjects taking NSAIDs or acetaminophen and in cases reporting IBS symptoms. Subjects with LI avoided certain foods and drinks; and in order to relieve their symptoms, they used OTC drugs, herbal medicine or visited a physician. On the other hand, no relation was found between LI and age, smoking or the number of meals per day. CONCLUSIONS: Although we found that individuals with IBS had significantly more subjective LI than those without IBS, in the absence of documented lactose malabsorption, it is hard to tell whether the reported symptoms indeed are those of LI or simply those of IBS. So, a period of dairy product avoidance and/ or requesting a test for lactose malabsorption may be beneficial in this area.