Lactose and milk intolerance: clinical implications.
Level 4 - case-series / case-control
Cross-sectional observational study of tolerance testing and symptom provocation
PubMed 1173192 · doi:10.1056/NEJM197505292922205
What was done
Researchers evaluated 166 hospitalized male patients (98 Black men, 59 white men of Scandinavian or Northwestern European extraction, and 9 non-European white men) with lactose tolerance tests. A subset of lactose-intolerant (n = 44) and lactose-tolerant (n = 18) men were challenged with 240 ml of low-fat milk and an equivalent amount of lactose to record gastrointestinal symptoms (gaseousness or cramps). Milk refusal rates during hospital meals were also compared between tolerant and intolerant patients.
What was found
Abnormal lactose tolerance tests were present in 81% of 98 Black men, 12% of 59 Northwestern European white men, and 3 of 9 non-European white men. Prior awareness that milk induced abdominal symptoms was noted by 72% of lactose-intolerant participants. In symptom testing, 240 ml of low-fat milk induced gaseousness or cramps in 59% of 44 lactose-intolerant men, and equivalent lactose provoked symptoms in 68%; 0% of 18 lactose-tolerant men developed symptoms from either challenge. Refusal to drink 240 ml of milk with meals occurred in 31.4% of lactose-intolerant men compared to 12.9% of lactose-tolerant men.
Why it matters
This study provides early clinical evidence that laboratory-identified lactose intolerance is common in specific adult populations and leads to perceptible symptoms and reduced milk intake at standard serving sizes (240 ml).
Limits
The study was restricted entirely to hospitalized male inpatients, limiting generalizability to healthy individuals and women. Some subgroup sample sizes were small (n = 9 for non-European whites). The abstract does not specify whether symptom provocation testing was blinded or placebo-controlled.
Cited by
- supports Seventy-five percent of African Americans are lactose intolerant.