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Study Examines Relationship Between Raw Milk and Lactose Intolerance

Despite claims sometimes made about the health benefits of drinking raw milk, evidence does not suggest that drinking raw milk will relieve or lessen the symptoms of lactose intolerance, according to a study conducted by nutritionists at Stanford University and published this week in Annals of Family Medicine.

But, according to the dairy owner who supplied the raw milk and aided in the study, the design had several limitations that were not obvious until after the data had been collected. As a result, he says, the study raises more questions than answers and should be seen as paving the way for a more complete analysis.

The relatively small study required 16 individuals with the clinical definition of lactose intolerance to drink raw milk, pasteurized milk and soy milk exclusively over eight-day periods, separated by a week of zero milk consumption each time. As each phase progressed, the test participants reported on their level of physical discomfort as they went through bouts of diarrhea, cramping, flatulence and audible intestinal sounds.

The results found no noticeable difference between the severity of lactose-intolerance symptoms faced when participants drank raw milk compared to pasteurized milk, said Christopher Gardner, Ph.D., professor of medicine at the Stanford Prevention Research Center and senior author of the study.

Gardner said, however, that the test did not account for whether or not the eight-day phase of drinking raw milk was a long enough time for bodies to adjust to the bacteria in raw milk, as theorized by Mark McAfee, the owner of Organic Pastures, a prominent raw milk dairy and the supplier of raw milk to the study.

Gardner said that he became personally interested in the subject of raw milk and lactose intolerance when a student in one of his nutrition classes said that drinking raw milk did not cause him to suffer from symptoms of lactose intolerance such as diarrhea and abdominal cramping, but he did suffer those symptoms when he drank pasteurized milk. In fact, the student said he had developed severe intestinal problems from drinking pasteurized milk since moving to the U.S. from Africa, but was able to nurse himself back to health with raw milk, which he was accustomed to drinking back home.

At first, that claim didn’t make sense to Gardner. Raw milk and pasteurized milk contain the same amount of lactose and should therefore both require a person to produce the lactase enzyme in order for them to digest it.

“Raw milk has just as much lactose in it, but it also has probiotics,” Gardner said, explaining his thought process. “Does that make a difference? It sounded like something I could test.”

Gardner told Food Safety News that he is personally a big proponent of whole foods and studying how whole foods influence nutrition, as opposed to studying isolated nutrients. He said that he understands the attraction to whole foods as a response to the abundance of refined and highly processed foods found in grocery stores, and that’s why his nutrition studies focus on whole foods.

How the study worked

Participants were asked to rate the severity of their symptoms on a scale of 0 to 10 for each of the eight days they drank progressively larger servings of each type of milk. A rating of 10 indicated “unbearably severe” symptoms.

The ratings of symptom severity for raw milk and pasteurized milk matched up almost identically on day seven of each phase – the day when participants consumed the largest serving of milk.

On average, participants rated the severity of their flatulence at a little more than 4 out of 10 after drinking both raw and pasteurized milk. For diarrhea, severity averaged around 3 for both, while it also averaged around 3 for intestinal sounds and 2.5 for abdominal cramping.

By comparison, when the participants drank soy milk for a week, on average they rated flatulence at less than 2, while diarrhea, intestinal sounds, and cramping hovered around 1. Soy milk has no lactose.

Figure 4

To prevent participants from easily identifying which milk they were drinking during each phase – and therefore potentially influencing the results – the milk samples were supplemented with sugar-free maple syrup flavoring, provided in unlabeled containers, and distributed in a randomized order.

At the end of each phase, participants were asked to try to identify which milk they had just consumed. When it was over, 40 percent (6 participants) correctly guessed each of the dairy milks, while 80 percent (12 participants) correctly guessed the soy milk.

Finding real lactose-intolerant participants

One of the biggest challenges of the study, Gardner said, was finding participants who fit the clinical definition of lactose intolerance by proving with a hydrogen breath test that they could not digest lactose.

While Gardner said that lactose intolerance is not a binary condition and there are degrees to which someone can or cannot digest milk, the clinical definition of lactose intolerance occurs when a person is a malabsorber of lactose, along with exhibiting the usual symptoms of digestion problems such as diarrhea and cramping. When someone does not produce enough lactase enzymes to break down the lactose in milk, the lactose passes on to the colon, where bacteria feed on it and produce hydrogen as a byproduct.

In short, when clinically lactose-intolerant people drink milk, they exhale hydrogen. When people can digest lactose, they don’t.

More than 400 people who said they suffered digestion problems from drinking milk expressed interest in participating in the study. Out of 63 people who were ultimately tested, only 27 passed the hydrogen test for clinical lactose intolerance. Of those 27 qualifiers, 11 chose to drop out of the study when they learned they would be asked to drink milk for several weeks. That left behind the relatively small sample size of 16 lactose-intolerant participants.

Gardner said he could not say why more than half of the people who claimed to have lactose intolerance proved to not be lactose malabsorbers. They could have just had a bad experience with milk and misdiagnosed themselves, or they could be affected by milk in another way that isn’t related to lactose.

“I couldn’t explain it, but I’m not going to look someone in the eye and tell them they don’t have cramps and diarrhea when they drink milk,” Gardner said.

McAfee questioned the high selectivity of the criteria for the participants. With so many people complaining of problems when they drink pasteurized milk, he said, there is reason to believe that lactose may not be the only thing wrong. That, or the hydrogen breath test may not be the definitive way to diagnose if someone has problems digesting milk.

From McAfee’s personal observations, he said that new raw milk customers who cite pre-existing symptoms of lactose intolerance usually say that they experience the same symptoms when they begin drinking raw milk, but the symptoms fade away after several weeks on raw milk. To him, that suggests that it may take some time for lactose-degrading bacteria to colonize the intestines and ease the symptoms.

Criticism about study’s flaws and limitations

The study was funded in part by the Weston A. Price Foundation, an organization which promotes traditional practices of food, farming and healing arts, including the consumption of raw milk for health benefits. When contacted by Food Safety News, a spokeswoman for the foundation referred questions to McAfee.

But the spokeswoman did cite a survey conducted by the foundation in 2007 that found that 81 percent of Michigan raw milk drinkers who say they were diagnosed with lactose intolerance reported that they did not suffer from symptoms after switching to raw milk.

McAfee said that conducting this study identified two main flaws, which Gardner agreed were limitations. The first was that the hydrogen breath test may have excluded a number of participants who have legitimate digestion problems when it comes to drinking milk. The second was that eight days on raw milk was not enough time to judge whether or not the body could adapt to any new bacteria.

“If the study would have continued for another two or three weeks, I propose you would see a decline in the severity of symptoms from raw milk,” McAfee said. “That’s exactly what we see happening in the marketplace.”

Gardner said his study could not account for those limitations, in part because he wasn’t willing to ask participants with clinical lactose intolerance to drink raw milk for weeks or months. Participants were asked to drink 16 ounces on days one and eight of each phase, while, on days two through seven, they drank progressively larger servings, starting with four ounces on day two and working up to 24 ounces on day seven.

Figure 1

Participants were permitted to quit drinking the milk at any time if their symptoms ever became too unbearable. To Gardner’s surprise, however, 13 of the 16 participants drank all the way up to the 24-ounce level for both raw and pasteurized milk.

Of course, experiences varied, and some participants couldn’t handle the symptoms.

“One guy wrote us a very graphic email explaining how he soiled everything in his house,” Gardner said.

Taking what they have learned from this study, McAfee expressed interest in conducting a similar study in the future that would involve participants drinking the milk over a longer duration.

“This study has taken us to a place where we can ask the right questions,” McAfee said. “I have a theory that there’s some sort of maldigestion syndrome going on here that should be analyzed and evaluated. There’s something going on with the people who complain of tummy aches that isn’t indicated by the hydrogen breath test.”

The study was turned down by four peer-reviewed journals before finally making it into Annals of Family Medicine. The two main reasons given for rejection were that the sample size of 16 participants was too small and that the study was answering too obvious of a question, implying that there should be no expected difference in effects between raw milk and pasteurized milk since the lactose levels would be the same.

“At the end of the day, it’s a small study and not intended to be the final word on the issue,” Gardner said. “Maybe I recruited 13 freaks out of the whole population of lactose-intolerant people.”

Read the full study: “Effect of Raw Milk on Lactose Intolerance: A Randomized Controlled Pilot Study”

© Food Safety News
  • http://burningbird.net Shelley Powers

    I think we can safely say that, even if they extended the study for months, it wouldn’t have made a difference: the supposed claim that raw milk is fine for those who are lactose intolerance is a myth.

    • Joanne

      Shelley, However, my son became pasteurized milk intolerant (lactose intolerant) after two large doses of antibiotics to combat two bouts pneumonia. He can drink raw milk without a problem. Regular butter also gives him a problem. He uses Lactaide (?) as a solution when coming in contact with ice cream and butter. So everyone is different.

      • http://burningbird.net Shelley Powers

        Your comment makes little sense. What you’re saying is your son is lactose intolerant, period. And he uses Lactaide to help him digest dairy products.

        The use of pasteurization or not is irrelevant in this context.

    • Raye

      Shelley, what you said:
      “I think we can safely say that, even if they extended the study for months, it wouldn’t have made a difference: the supposed claim that raw milk is fine for those who are lactose intolerance is a myth.” Based on what evidence did you reach those conclusions? You can say that, but your position isn’t believable w/o facts. Who believes what someone says just because they said it? “There’s absolutely no proof whatsoever that a person can more easily digest milk just because it happens to be raw.” Shelley, how much research did you do? Maybe you have a financial interest in the pasteurization process of milk; I can understand that. Plenty of falsehoods are written about raw milk, and studies such as this one are flawed, first, because the participant numbers were too small, and the length of the study, contrary to your “opinion”, was not long enough, leading to bias and made to look objective when not. Maybe you’re a scientist, clinician, holistic physician, dietician, etc., and just keeping it secret? Joanne’s comments make perfect sense based on “facts” in her living experiences. She said her son can drink raw milk, but needs help using Lactaid to consume other dairy products made from pasteurized milk, not raw milk (underlined). You said, “The use of pasteurization or not is irrelevant in this context.” Again, you present no facts, just your opinion.
      “. . . suggestible people who have been told something and they allow that to influence their perception of benefit.”? It’s all in their head, those thousands upon thousands of people who drink raw milk without problems they have with pasteurized milk?
      Shelley, some real facts about pasteurized/raw milk and choice – just replace the word “dot” with a period and copy/paste in case this site doesn’t permit web addresses here:

  • john mark carter

    The scientific paradigm is that lactose intolerant people have problems because their small intestine passes lactose to the colon, where a subpopulation of normal bacteria binges on this sugar. McAfee hypothesizes that there are special probiotic bacteria, present in raw milk but not pasteurized milk, which can colonize the colon. There they either substantially displace the problematic normal bacteria, allowing fecal excretion of lactose, or else they sequester and metabolize all of the lactose without causing cramps, diarrhea, and flatulence. I found one publication that suggests, while tolerance to milk can develop in lactose intolerant humans after 3 weeks of feeding, the effect has nothing to do with bacteria or lactose (http://gut.bmj.com/content/41/5/632.full). Other more well-publicized recent studies report that eating meat changes intestinal bacterial populations quite dramatically, within only a day or two.

    I reckon the interesting finding in Gardner’s paper is the confirmation that self-reporting “lactose intolerant” people are not all alike. Some probably have a food allergy, have bowel problems not specifically related to milk, or are even completely normal but nervous/superstitious about milk. It’s tough to do research when your study population is so poorly defined. Kudos to Gardner for using the hydrogen breath test to at least try.

  • AlanComments

    Not a myth. Worked for an office mate. She hadn’t been able to drink milk for years. She tried raw milk and was able to resume drinking milk again. People need to do their own research. Everyone else has an agenda.

    • Guest

      AlanComments, you are absolutely correct that people have an agenda, and that includes people who are both for and against raw milk. I know many people with who are lactose intolerant. They tried raw milk, and it didn’t help them at all. In fact, a few of them got food poisoning instead (E.coli). That being said, anecdotal evidence is just that — anecdotal. We need scientific evidence to prove there is a link; otherwise, it’s safe to assume there is no benefit for lactose intolerant people to drink raw milk.

      • Guest

        The simple facts surrounding the need for pasturization should direct the attention to the milk consumer to inquire much deeper into the health issues surrounding pasturized milk. Regardless of a persons position on raw milk, the liquid thats sold in grocery stores should be given a cold hard look at how it got there. After establishing that info, it seems rather ignorant to take such a hard line stance against raw milk.

  • juliusaugustus

    You CAN drink pasteurized milk if you are lactose intolerant, there are ways of curing it.

  • Gordon S Watson

    16 people over the course of 8 days, and you call this “science”?! it takes at least 21 days for a human being to adjust to any new habit, let alone diet. Contrast this pretended “evidence” with how scientific study is conducted in every other area. This is an exercise in propaganda of the first order … designed to generate 7 words as a headline, so it can be disseminated as “fact”, when it’s the very opposite
    in our cowshare, about 1/4 of the 500 plus households, were people who sought us out, after learning about REAL MILK, in order to be able to have dairy products, after being UNable to do so for many years. Every one of whom reported – independent of each other – being sickened by the stuff on retail store shelves, mis-labelled “milk”, when it’s cooked, broken-down to micro-particles, then re-constituted with Milk Protein Concentrate brought in from the 3rd World.

  • Sappho

    WHO paid for the study? And, no a real study is not a few days with a few people. How narrow minded to look at just one ingredient instead of the whole food.

  • cheeibelle

    How about the concept that cows milk isn’t meant for humans and some can tolerate it and some can’t. But ultimately humans are drinking a fluid coming from bovines meant for baby bovines. Adults have no need to consume milk!

  • http://burningbird.net Shelley Powers

    No, it does not. There’s absolutely no proof whatsoever that a person can more easily digest milk just because it happens to be raw.

    What you have is suggestible people who have been told something and they allow that to influence their perception of benefit. And that includes parents and the perceived influence on their children.

  • Anna

    My son and husband are severely lactose intolerant and my daughter and I are not. I laugh when people tell me their symptoms of supposed lactose intolerance when they have no idea what they are talking about in their self diagnosed rambles. I’m a big milk drinker and grew up in a dairy farming community in Wisconsin. I’ve seen the process of procuring milk up close and personal. I have drank both raw and pasteurized growing up and I will never drink raw again. Do you know how much poop and dirt that is around and near the utters even with the best practices to keep it all clean?! Would you feed your kid a sandwhich that’s been sitting on the rim of your toilet?! True, some, but very little, nutrients may be extracted, but I’d rather that than get sick. But, it wouldn’t matter if my son had raw or pasteurized milk, either way it had lactose and no other enzymes or good bacterias are going to cute that! As for those people on here who think the studies should just be longer in order to check for sure you are just either sadists or stupid! What parent in their right mind would make their kid suffer for that long to try to get them to tolerate something instead of just get that nutrient from something else! My breast milk is about as pure of a milk as you can get for a human baby but my son couldn’t even handle that! He was in pain, has explosive liquid diapers at least 10 times a day and when we changed to formula and or had him on a milk based antibiotic when he got really sick he ended up with acid burns on his bottom that would not even let desatin stick to it. Obviously at that point we realized he was intolerant:). He was my first kid. I had no idea other babies didn’t have that problem. Then I changed him to a soy based formula and it all went away! Even lactose free formula and it went away. Even with lactaide products it may help a little bit so he can have a bite of ice cream but it just lessons the symptoms and doesn’t take them away. Raw milk can not fix that! You either have the enzyme in your body or you don’t! Why try to get someone to drink milk in any form if that can’t?! Believe me I’ve tried 6 ways to Sunday! I LOVE dairy and have tried to sneak it in anyway I can to see if he can tolerate it thinking he needs the nutrients from it. But when my husband explained that he can not absorb any of it because the enzyme will not allow it be be broken down at ALL then I realized it was an exercise in futility. Now, I just give him other nutrients that he could otherwise get from milk and he is healthier for it. My daughter and I continue to live off of milk daily and we are fine! I would NEVER give her raw milk! I don’t need to experiment with her having the chance of getting e-coli. I’m a social worker with special needs kids. I know what e-coli can do to a kid! If you want to chance your kids dying or being left as profoundly mentally and physically retarded, go ahead and take the chance. I see no need to chance it. If pasteurization is so bad, I recommend getting your nutrients from a different source all together and not drinking raw milk either!

  • fangirlno23

    As a child, my mother could not eat cottage cheese without suffering major, flu-like symptoms, and it led to an aversion of all cheese for her (she’ll order pizza with no cheese, for example). As a young adult, she married my dad, who was a farmer. They had one milk cow. They would take the milk straight from the cow, and my mom, once again, grew extremely ill after consuming the raw milk. When she didn’t drink the milk, she was fine. Eventually, she also had the same reaction drinking pasteurized, store-bought milk. Unlike the usual 30 minute-to-2-hour window of time you hear about from consumption to reaction, my mom’s reactions to dairy were always delayed a day or two. Then, she’d have her reaction, said it “felt like a bad case of the flu” and that it would take another 2-3 days to feel better. After years of this, she went to the Mayo Clinic for a diagnosis, and while they didn’t formally announce “lactose intolerance” (maybe they didn’t have the breath test back in the early-to-mid-1980s??) they did advise her to avoid dairy. She returned home and found out about Lactaid, tried that, and her symptoms went away. Now, in her mid-60s, she still will not eat cheese to this day. She tends to avoid dairy, but will occasionally eat small amounts (like ice cream) without Lactaid and not react. Meanwhile, I’ve had food-related reactions to dairy, as well, and my reactions are also delayed –usually I will have a digestive issue 12-24 hours after I ingest dairy. I have considered that we might be dealing with something else (casein intolerance? I also get congested sinuses) –but if that was the case, why would Lactaid work?