Effects of Raw Milk vs Paseurized Milk on Lactose Maldigestion and Symptoms of Lactose Intolerance Among Lactose Intolerant Adults

An increasing number of Americans are choosing to consume raw, unpaseurized milk rather than conventional pasteurized milk.  Several health calims are made by raw milk enthusiasts.  Many or most of those claims are anectdoatal and remain untested, including the claim that lactose intolerant adults can enjoy raw milk with minimal to no symptoms. 

The objective of this study was to determine if lactose maldigestion and symptoms of lactose intolerance are lower when consuming Raw milk vs. conventional pasteurized milk.

Eligible Participants

The adults recruited had reported experiencing hte standard symptoms (e.g., flatulence, abdominal sounds, abdominal cramping) of lactose intolerance after exposure to a 25 g dose of lactose and who have a positive test of lactose maldigestion as determined by a standard hydrogen breath test (HBT). 

Study Design

Three way crossover.  The three treatment arms were:

  • Organic, full-fat, pasteurized milk
  • Organic, full-fat, raw milk
  • Organic, soy milk


All three milks were "flavored" with small amounts of vanilla in an effort to "blind" the study participants.  Study staff were also blinded (i.e. double blind).  Each milk phase was 8 days in duration, with 1-week wash-outs in between, and the entire protocol was preceded by a 1-week dairy-free run-in period.  A hydrogen breath test was conducted on days 1 and 8 of each milk phase using 16 oz of the milk specific to that study phase.  In the intervening days, participants were instructed to consume increasing amounts of milk, from 4 oz on day 2 to 24 oz on Day 7 (i.e., increasing by 4 oz each day) until such time that symptoms were so severe that they were unwilling to continue.  On each of days 2-7 participants recorded the severity of symptoms.


  • HBT values on Day 1 and Day 8 of each of the three study milks
  • Symptom severity on Day 7 of each of the three study milk phases (i.e., the day of consuming 24 oz of milk)


383 participants completed an on-line survey to determine initial eligibility.  63 continued to participate in a screening HBT test.  27 of the 63 tested positive for lactose maldigestion (HBT) and reported standard symptoms in response to 25 grams of lactose.

16 of the 27 agreed to and were available to enroll.  All 16 participants completed all three milk phases.  13 of the 16 participants completed the full protocol, including consuming 24 oz of milk, on all three milk phases (3 participants were not willing to tolerate consuming 24 oz for at least one of the milk types).  15 of 16 participants completed the HBT's on both days 1 and 8 for all three study milks.

To learn more about the details of this study, read: