The case for raw milk’s benefits for the lactose intolerant soured a little bit today, after a study showed that it seems to be no more easily digestible than pasteurized milk.
The study was small, with just 16 volunteers, all adults with lactose intolerance. But the results pretty much broke in one direction: Raw milk (nonpasteurized, nonhomogenized, probably seen at a farmer's market near you) was no better at easing symptoms of lactose intolerance than pasteurized milk; nor was the lactose in raw milk more easily absorbed.
There might be some beneficial qualities in raw milk, “but it’s not anything to do with lactose intolerance,” senior author and Stanford University physician Christopher Gardner said in a phone interview.
A person with lactose intolerance doesn’t have the enzyme, lactase, which allows the body to break down the milk sugar lactose into glucose and galactose. Instead, undigested lactose passes into the colon, where it’s fermented by bacteria and broken down to fatty acids and gases – resulting in symptoms like bloating, diarrhea and abdominal pain.
Some natural food advocates claim that raw milk can ease lactose intolerance systems – supposedly because it contains helpful bacteria (thanks to the lack of pasteurization) that make their own lactase, giving a person’s digestive system a helping hand. There are studies showing that unpasteurized yogurt can reduce symptoms when compared to pasteurized yogurt. But this claim hasn't been fully tested -- and whether milk can match yogurt is a bit doubtful. Gardner and colleagues note that because yogurt is thicker, digesting it takes longer, which may give the yogurt bacteria time to go to work. Milk passes through your tract quicker, meaning that perhaps the little microbiotic helpers don’t have enough time to gear up.
In Gardner and colleagues’ study, published Monday in the Annals of Family Medicine, participants drank steadily increasing amounts of pasteurized, raw, or soy milk for three eight-day periods, separated by a week of dairy abstinence. The researchers examined the participants’ reactions to the various milks both through reported symptoms of gastric distress and by measuring the amount of hydrogen gas in the subjects’ breath. A spike in hydrogen gas after milk drinking is a sign that the lactase isn’t getting properly digested, and is instead fermenting in the colon.
On the hydrogen gas breath test, raw milk actually performed worse than pasteurized milk at the start of the eight-day period. By day seven of milk-chugging, lactose intolerance symptoms for raw milk and pasteurized milk were basically the same.
Overall, the study “provided no evidence that raw milk is better tolerated by adults” with lactose intolerance, the authors wrote.
Overall, the scientific literature on raw milk is still relatively slim. Raw milk advocates sometimes point to the 2007 PARSIFAL study published in the journal Clinical and Experimental Allergy, which found that European children who drank milk bought straight from farms (versus from a store) were less likely to have allergies and asthma.
But the “farm milk” examined in the PARSIFAL study isn’t synonymous with raw milk; in fact, around half the farm milk examined in the research was boiled. As such, it was impossible for the researchers to evaluate the effects of pasteurized vs. unpasteurized milk consumption.
“Dietary interventions are an attractive means for primary prevention” of allergies, the PARSIFAL team wrote. “However, raw milk may contain pathogens such as salmonella … and its consumption may therefore imply serious health risks … at this stage, consumption of raw farm milk cannot be recommended as a preventive measure.”
Gardner isn’t anti-raw milk; he’s actually very interested in encouraging the consumption of whole foods – based on solid evidence of the benefits.
“Food’s complicated,” he says. “I think we need to be more willing to take on these questions and do real science on it.”
Interestingly enough, Gardner found anecdotal evidence that some people might be misdiagnosing themselves with lactose intolerance. Of the 63 people reporting lactose intolerance symptoms that initially responded to their call for volunteers, 37 “failed” the hydrogen breath test and didn’t meet the standard definition of lactose intolerance.
That, he says, might explain why some people will claim raw milk is good for what ails them – because what’s ailing them might not be lactose intolerance. Perhaps some other health issue is at play, but it’s a medical mystery for another study.
Gardner doesn’t have any immediate plans to do another raw milk experiment. But he is doing work on the interplay of nutrition and the human microbiome – the collection of bacteria and other microorganisms in our guts. Scientists think that the state of the microbiome could be a key factor in health. And dairy products – particularly of the fermented kind – are thought to help shape that tiny ecosystem (hence all the “probiotic” yogurts crowding health food store shelves).
“Maybe I’ll make a cocktail of yogurt and tempeh and raw milk and throw all of those at once at someone,” Gardner mused.
SOURCE: Mummah et al. “Effect of Raw Milk on Lactose Intolerance: A Randomized Controlled Pilot Study.” Annals of Family Medicine 12: 134 – 141, March/April 2014.