Comparison of symptoms after the consumption of milk or lactose-hydrolysed milk by people with self-reported severe lactose intolerance.

BACKGROUND Ingestion of a large dose of the milk sugar lactose--for example, the 50 g load in 1 liter of milk--causes symptoms such as abdominal pain, diarrhoea, bloating and flatulence in the majority of people with lactose malabsorption. It is uncertain whether the ingestion of more common doses of lactose, such as the amount in 240 mol (8 oz) of milk, causes symptoms. Some people insist that even smaller quantities of milk, such as the amount used with cereal or coffee, cause severe gastrointestinal distress. METHODS In a randomized, double-blind, cross-over trial, we evaluated gastrointestinal symptoms in 30 people (mean age, 29.4 years; range 18-50) who reported severe lactose intolerance after ingesting less than 240 ml of milk. The ability to digest lactose was assessed by the subjects' end-alveolar hydrogen concentration after they ingested 15 g of lactose in 250 ml of water. Subjects then received either 240 ml of lactose-hydrolysed milk containing 2% fat or 240 ml of milk containing 2% fat and sweetened with aspartame to approximate the taste of the lactose-hydrolysed milk; each type of milk was administered daily with breakfast for a 1-week period. Using a standardized scale, subjects rated the occurrence and severity of bloating, abdominal pain, diarrhoea, and flatus and recorded each passage of flatus. RESULTS Twenty-one participants were classified as having lactose malabsorption and nine as being able to absorb lactose. During the study periods, gastrointestinal symptoms were minimal (mean symptom-severity scores for bloating, abdominal pain, diarrhoea, and flatus between 0.1 and 1.2 [1 indicated trivial symptoms, 2 indicated mild symptoms]). When the periods were compared, there were no statistically significant differences in the severity of these four gastrointestinal symptoms. For the lactose malabsorption group, the mean (+/- SEM) difference in episodes of flatus per day was 2.5 +/- 1.1 (95% confidence interval, 0.2-4.8). Daily dietary records indicated a high degree of compliance, with no additional sources of lactose reported. CONCLUSIONS People who identify themselves as severely lactose-intolerant may mistakenly attribute a variety of abdominal symptoms to lactose intolerance. When lactose intolerance is limited to the equivalent of 240 ml of milk or less a day, symptoms are likely to be negligible and the use of lactose digestive aids unnecessary.