How much lactose is low lactose?

J Am Diet Assoc. 1996 Mar;96(3):243-6. doi: 10.1016/S0002-8223(96)00074-0.


Objective: To test the hypothesis that complete elimination of lactose is not necessary to ensure tolerance by lactose maldigesters.

Design: Double-blind, randomized protocol in which challenge doses of 0, 2, 6, 12, and 20 g lactose in water were fed to subjects after a 12-hour fast.

Subjects: 13 healthy, free-living adults who were lactose maldigesters.

Main outcome measures: Breath hydrogen production (a measure of maldigestion) and symptom response to each challenge dose.

Statistical analysis: Analysis of variance was done to determine overall differences in mean hydrogen gas production (peak and sum of hours 1 through 8). Friedman's test was used to determine overall differences in the mean ranks for each symptom. Fisher's least significant difference test was used for multiple comparisons for hydrogen and symptom and data.

Results: Hydrogen production after consumption of the 0- and 2-g lactose doses was not significantly different. Hydrogen production increased with the 6-g dose. Intensity of abdominal pain increased when the dose of lactose was 12 g. Episodes of flatulence did not increase until the dose reached 20 g. No significant differences in the occurrence of diarrhea were observed after the five treatments.

Conclusions: No significant increase in breath hydrogen production or intolerance symptoms occurred after consumption of a 2-g dose of lactose. Up to 6 g was tolerated, even though maldigestion could be measured at the 6-g dose. Thus, lactose maldigesters may be able to tolerate foods containing 6 g lactose or less per serving, such as hard cheeses and small servings (120 mL or less) of milk.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdominal Pain
  • Adult
  • Breath Tests
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Flatulence
  • Humans
  • Hydrogen / analysis
  • Lactose / administration & dosage*
  • Lactose Intolerance / physiopathology*
  • Male


  • Hydrogen
  • Lactose