You have probably heard about a recent study 1 from Stanford University that compared digestion of raw milk to the digestion of pasteurized milk among a small group of people who had been determined to be lactose intolerant. The study was published in the March/April issue of the Annals of Family Medicine. There was much media fanfare touting the failures of raw milk to overcome lactose intolerance. Headlines included Study: Raw milk no help for lactose intolerance, Raw Milk Doesn’t Help Lactose Intolerance, Study Shows, Is Lactose Intolerance Relieved By Raw Milk? Scientists Find These Claims Untrue. As far as I know this is the first and only serious study to compare the digestibility of raw milk to pasteurized and soy milks. Let’s look at what we can learn from the study.
The study was conducted by researchers at Stanford University. This is the study’s stated conclusion:
Raw milk failed to reduce lactose malabsorption or lactose intolerance symptoms compared with pasteurized milk among adults positive for lactose malabsorption. These results do not support widespread anecdotal claims that raw milk reduces the symptoms of lactose intolerance. 1
The study does not appear to be biased in favor of pasteurized milk because at least two of the study’s sponsors–the Weston A. Price Foundation and the Raw Milk Institute–certainly were expecting and hoping for a different result. One of the study’s authors did say that “When I heard that claim it didn’t make sense to me because, regardless of the bacteria, raw milk and pasteurized milk have the same amount of lactose in them . . .” 2
As with most studies, it can be difficult to account for all variables and to find a sample size large enough to produce a definitive result. This study is no exception. There are several problems that might have caused misleading results.
The number of study participants was very small–only sixteen people were selected out of a pool of 440 applicants. The sixteen were chosen based on the results of hydrogen (H2) breath testing. Although it is the preferred method of testing for lactose intolerance, 3 there are several conditions that can produce incorrect results.
As noted by Mark McAfee, chairman of the board at the Raw Milk Institute, “The study actually shows that the H2 breath test is insufficient to diagnose milk sugar digestion problems in 97 percent of the study applicants. Most people are not overtly lactose intolerant but are better described as pasteurization intolerant, something for which medical science may not have an appropriate test.” 4
Notice that the study rejected 97% of the applicants who thought they had problems digesting milk. The preferred test may not be adequate for determining difficulty in digesting pasteurized milk.
Hydrogen (H2) Breath Test
The breath test used to select participants is “based on the fact that there is no source for hydrogen gas in humans other than bacterial metabolism of carbohydrates.” To be accurate the tests “are performed in the fasting state after at least one day of a low fibre diet.” 5
However, the test can produce incorrect results under several conditions:
The hydrogen breath test depends on the presence of hydrogen producing bacteria. However, a considerable proportion of non‐hydrogen producing bacteria, which can yield false negative results, has been observed in some but not all studies. Several other potential sources of error exist, such as carbohydrate malabsorption in chronic pancreatitis and coeliac disease, with false positive tests for SIBO [small intestinal bacterial overgrowth] due to colonic fermentation and gas production, and gastrointestinal motor disorders, where delayed gastric emptying may cause false negative tests and rapid transit through the small bowel will produce false positive breath tests. False positive results may also be due to the oral bacterial flora and if the subject has failed to adhere to a low fibre diet the day before the test. 5
Soy Milk Control
Another problem with the study may be in the use of soy milk as a control, since soy can be difficult to digest. Unfermented soy foods, including soy milk, contain “powerful protease inhibitors that inhibit our digestive enzymes and overwork the pancreas.” These inhibitors make it difficult for the body to break down soy protein, causing bloating, indigestion, and even constipation. 6 With the known problems digesting unfermented soy, it is difficult to accept the validity of the study when the following results are found:
By day 7 of drinking, lactose intolerance symptoms were equally as severe, whether raw milk or pasteurized milk was consumed. The symptoms reported by people who had consumed either the raw or pasteurized milk were significantly worse than the symptoms reported by the patients who drank soy milk.1 [emphasis added]
Length of Study
Improvements or other changes to digestion may not be discovered in the short period of time this study was conducted. The study consisted of a crossover trial of three periods of eight days each. Each of three groups were randomly given raw milk, pasteurized milk, or soy milk for eight days then switched to another milk, etc. Improvement in beneficial gut bacteria which might result from drinking milk raw probably takes longer than 8 days to become apparent. 4
The study is interesting and certainly worth additional investigation; however, there are too many unanswered questions and too much room for error to accept these results at face value. Even the study authors admitted that the short period of time and limited number of participants were limitations. 7
With 97% of study applicants rejected, maybe problems digesting pasteurized milk encompass far more than simply lactose intolerance, as suggested by Mark McAfee. Maybe the H2 breath test isn’t adequate for determining study participants.
In the end, if no further studies are undertaken, you may be the best, and only, judge of whether raw milk is easier for you to digest. You can try drinking raw milk, starting with a small amount. If tolerated, you may increase the amount gradually. I did not grow up drinking raw milk, but I have been drinking it now for over eight years and thoroughly enjoying it. I have had no problems digesting raw milk, but then I did not have problems with the digestion of pasteurized milk either. I just didn’t like the taste of processed milk. Now I enjoy drinking milk again!
1 Effect of Raw Milk on Lactose Intolerance: A Randomized Controlled Pilot Study, Annals of Family Medicine, by Sarah Mummah, MPhil, Beibei Oelrich, MD, PhD, Jessica Hope, MSN, NP, Quyen Vu, BAH and Christopher D. Gardner, PhD
2 Claim that raw milk reduces lactose intolerance doesn’t pass smell test, study finds, Stanford School of Medicine
3 Lactose tolerance tests, MedlinePlus
4 Stanford Study on Raw Milk Digestibility: Conflicting Interpretations, the Weston A. Price Foundation
5 Use and abuse of hydrogen breath tests, International Journal of Gastroenterology and Hepatology
6 The Whole Soy Story by Kaayla T. Daniel, PhD, CCN
7 Raw Milk Not Better for Lactose Intolerance, Daily Rx
This post is shared on Fight Back Friday @FoodRenegade.