L. reuteri yogurt FAQ’s | Dr. William Davis


The Lactobacillus reuteri yogurt we make to boost oxytocin and obtain its unique profile of upper gastrointestinal probiotic benefits is truly one of the most fascinating things we’ve stumbled across in the Wheat Belly and Undoctored worlds. Using the unique fermentation process that I introduced, we develop a wallop of benefits due to exceptionally high bacterial counts of the L. reuteri strains.

But there seems to be continual confusion on the reasons, species/strains, methods, etc. surrounding our unique “yogurt.” I didn’t stumble on all these ideas at once, but gradually evolved my understanding of how and why this thing achieves such extraordinary effects and how to best put it to use, chronicled in at least a dozen Wheat Belly Blog posts. If you read through them chronologically starting with my appreciation for making yogurt with higher fat content and fermenting with prebiotic fibers and using probiotic species, rather than conventional yogurt species, you can chart the line of thinking. Apparently, most people do not do this. So I though a Frequently Asked Question, FAQ, post would be helpful, as the same questions come up over and over again.


Q: What is so special about Lactobacillus reuteri? And why do you insist on these two strains?

A: The two strains of L. reuteri used, DSM 17938 and ATCC PTA 6475, are the two strains that have been shown to exert the skin, muscle, bone, hormonal, and probiotic benefits in both experimental and human clinical trials. Of the nearly 200 known strains of L. reuteri, these are the only two that have been shown to exert this wide range of effects. Other strains may indeed do so likewise, but this has not yet been documented. (This is among the projects that we are likely going to undertake ourselves.)

But a word about strain specificity and why choice of strain is critical. You have E. coli in your gut; I have E. coli in my gut. But if we are exposed to E. coli from lettuce contaminated by cow manure, you can die of kidney failure and sepsis—same species, different strain. Strain can therefore make a life-death difference. So, until we know better, we stick to the strains that we know are safe, effective, and generate the benefits we desire.


Q: I’ve made yogurt before and this is not how we do it. We use shorter fermentations times, e.g., 6-12 hours, don’t add prebiotic fibers, and ferment at 108-114 degrees F. Why is the L. reuteri yogurt-making process different?

A: It is purposefully different. The longer fermentation time of 36 or so hours is used to cultivate higher bacterial counts for more pronounced oxytocin-boosting and probiotic effects. We add the prebiotic fibers also for greater bacterial counts, since bacteria feed on the fibers, as well as for better texture and mouthfeel. (I find it surprising that all yogurt makers don’t do this, rather than add thickening agents and emulsifiers.) And L. reuteri “prefers” human body temperature, actually starting to die at the temperatures used for conventional yogurt making. This is why some people have experienced repeated failures using yogurt makers or Instant Pot devices that are sometimes set at higher temperatures. (You can figure this out by turning the device on with a thermometer inside and see what the eventual temperature reaches. Unfortunately, unless you have a variable temperature control, you will have to resort to a new device such as a sous vide device or something like the Luvele yogurt maker with adjustable temperature control that you can find in the Wheat Belly Marketplace.)


Q: Can I make the yogurt with commercial store-bought yogurt and still obtain all the benefits?

A: No. The effects have nothing to do with yogurt. In fact, if I were producing it commercially, I couldn’t even call this thing we make “yogurt”—even though it looks like yogurt and tastes like yogurt, it’s not really yogurt. We specifically need Lactobacillus reuteri, one or two of the strains that we know generate these extravagant effects. (There may be other strains that do likewise, but we have no evidence that they do or do not–see above.) But you can make yogurt by combining L. reuteri with the microoganisms from a live-culture commercial yogurt. Doing so yields lower counts of L. reuteri which thereby does not have the potency of our usual L. reuteri yogurt, but is something you could serve to younger people, including menstruating females, who lack L. reuteri. This is how we make our mixed-culture yogurt suitable for younger people.


Q: Early in the L. reuteri experience, you advised menstruating females and people younger than 45 to not consume the yogurt, but then you changed your mind. Why did you change your mind?

A: My initial concern was that, because oxytocin is known to induce uterine contraction (injected intravenously to induce delivery of a term infant), it is uncertain what a menstruating female with menstrual cramps might experience. (Interestingly, however, a number of younger women reported having dramatically less severe menstrual cramps, bleeding, and emotional turbulence, but this is purely anecdotal from a handful of women.) And, of course, a pregnant woman should not make the full-strength yogurt. In addition, oxytocin is already present at higher levels in younger people who have not yet experienced the age-related decline in oxytocin levels and the same benefits likely do not apply when there is higher levels of endogenous oxytocin present.

BUT it also became clear that L. reuteri is meant to be carried by most, if not all, humans, obtained via breast milk as an infant. L. reuteri has also been administered in dozens of clinical trials in hundreds of millions to several billion CFUs to children with no ill-effect, only benefits such as reduced infant colic, regurgitation of milk or formula, and faster recovery from post-antibiotic diarrhea. This is why I devised the simple method of making a mixed-culture yogurt that delivers L. reuteri in lower counts and is suitable for children and younger people, including menstruating females.

But anyone consuming our high-potency yogurt needs to accept that this is a work in progress and that we are learning lessons along the way, in addition to planning limited clinical trials to further explore some of the effects, especially those on hormonal status.


Q: Can I use raw milk?

A: VERY bad idea. While raw milk has its benefits, you cannot chance even a minuscule amount of contamination by pathogenic organisms like Listeria or Staphylococcus aureus because, if present, their numbers will be amplified by the yogurt-making process. This can make the yogurt a potentially fatal product—not good. So NO raw milk or other raw dairy.


Q: Do I have to re-inoculate the yogurt with additional tablets with each batch? 

A: No. I am on my 60th or so batch and have never reinoculated yet all the benefits are maintained, as well as the same taste and texture. It doesn’t hurt to re-inoculate, but it does not seem to be necessary to propagate your live cultures.


Q: The BioGaia Gastrus tablets have mango flavoring? Is this the wrong product? 

A: No, this is fine. The yogurt will not have any mango flavoring, as it is diluted in the yogurt-making process, then virtually gone with subsequent batches.


Q: I tried making the yogurt and the first batch was lumpy with separation into curds and whey. Why did this happen and is it okay to consume?

A: This is the expected result with everyone’s first batch. Subsequent batches tend to be thicker and more uniform, with separation in to whey only through straining and/or with removal of some of the curds. And, yes, the first batch is safe to consume.


Q: Should I remove the liquid whey?

A: That’s your call. But remember: Whey is the fraction of dairy that provokes insulin and can thereby block weight loss and contribute to insulin resistance. My advice is to at least pour off the whey when it separates and save it to use as starter for your next batch or just discard. Some people also strain their yogurt through cheesecloth to more thoroughly remove the whey and generate the thicker Greek-style yogurt.


Q: Why is the L. reuteri yogurt so tart or sour?

A: The prolonged fermentation time we use—36 hours, compared to the 6-8 hours typically used in commercial yogurt-making, or 6-24 in home yogurt-making–allows maximal fermentation of lactose sugars to lactic acid, the component that confers the tart or sour taste. We do this, of course, to generate higher bacterial counts but also to 1) exhaust lactose to as low a level as possible and 2) reduce the pH of the yogurt to 3.0-3.5, a level that denatures (breaks down) the casein beta A1 protein and reduces its immune-stimulating potential. So the increased tartness or sourness simply reflects the greater lactic acid content from prolonged fermentation time. You can add some berries, a teaspoon of inulin, a squirt of stevia liquid or other safe natural sweetener to conceal the tartness, if you like.


Q: My yogurt developed a greenish/pinkish discoloration on top. What is this?

A: This is fungal contamination. We remove the discolored area and discard.

However, should this happen, take steps to more meticulously clean your utensils (bowls and spoons) with hot soap and water. Also, be sure that your yogurt is not in the path of airflow from your air condition, heater, or other device. The yogurt mixture should also be lightly covered, e.g., plastic wrap, during the fermentation process.


Q: What’s the best device to use to maintain the 100 degree F temperature for fermentation?

A: As discussed above, not all yogurt making devices or Instant Pots get the job done because of temperatures pre-set at temperatures suitable for conventional yogurt-making, not for fermentation of L. reuteri that prefers human body temperature. My choices for devices include sous vide devices (basin and stick) and yogurt makers with adjustable temperature such as the Luvele device. You can find these devices in the Wheat Belly Marketplace. Some people have even devised their own homemade devices, such as an incandescent lightbulb mounted in a covered box, or just turning on the oven light on a closed oven. Don’t make this harder than it should be.


Q: Can I feed the L. reuteri yogurt I make for myself to my children/grandchildren? 

A:  Occasional consumption by young people is safe. What is not known is whether chronic or repeated consumption is safe, given the potent oxytocin-boosting effect of the yogurt. This is why I devised the mixed-culture yogurt that delivers lower numbers of L. reuteri because it is combined with several other yogurt-fermenting bacterial species. Whenever I’ve made the mixed-culture yogurt, I found it to be surprisingly tasty, certainly far tastier than anything you buy in the store.


Q: How long with the yogurt keep in the refrigerator?

A: The shelf-life of yogurt is longer than non-fermented dairy and is generally up to 4 weeks.


Q: What if I have repeated failures in my yogurt-making efforts?

A: See this Wheat Belly Blog post on troubleshooting the yogurt-making process. Identify the problem—contaminated utensils, too high fermenting temperature, etc.—and you can join the ranks of people obtaining the extravagant health benefits of the L. reuteri yogurt. But, if you go through all the issues and are still having trouble, then consider taking the new BioGaia Osfortis product with 10 billion CFUs of one L. reuteri strain, available as a probiotic capsule without needing to ferment to yogurt to generate higher counts. What is unclear is what dose to take to mimic the effects of the yogurt. Anecdotally, it required two capsules per day for me to re-experience the anorexigenic and deep sleep-cultivating effects. You can find the Osfortis product in the Wheat Belly Marketplace.


Q: My experience with consuming the L. reuteri yogurt is somewhat different than you describe. For instance, I obtain the appetite-suppressing effect and greater skin moisture, but not the skin thickening/wrinkle-smoothing effects. Why is this?

A: This is likely due to such factors as variation in oxytocin receptors. So individual experiences can vary. Also, factor in time: some effects will require a longer time period in some people. There may be other factors that influence response, and I hope that these will become clearer as our understanding of this phenomenal thing progresses.


Q: If consuming one-half cup yields effects, will consuming an entire cup yield more effect?

A: We have no formally quantified this response, i.e., performed bacterial counts on the yogurt, then observed such factors as blood oxytocin levels on consuming increasing quantities of yogurt. Anecdotally, however, some people have indeed reported a better response to greater quantities. Interestingly, these same people have reported no rise in blood sugar with the somewhat greater carb exposure of greater yogurt portions.

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