A fine, say, Bordeaux wine, the product of fermentation by Saccharomyces cerevisiae and other fungal species, will age over years, developing scents, flavors, and nuances that a young wine just off the press or barrel will not have. The differences can be substantial and worth a lot of money to some people. Similarly, food fermentation by lactic acid-fermenting species proceeds for days to weeks to generate the desired end-product. Perhaps it won’t have the nuances of a fine wine, but it will be altered in taste, texture, and biological effects from its starting material. And, made correctly, it too can have enormous value, not financially, but in health benefits.
And so it goes with the products of bacterial fermentation to create yogurt, fermented dairy that involves conversion of lactose to lactic acid. I’ve discussed this in a previous Wheat Belly Blog post entitled “The Arithmetic of Yogurt.” But it bears repeating to make the point: fermentation times matter, i.e., the amount of time that a food is fermented, plays a big role in determining bacterial counts and other properties of the yogurt. And it matters hugely in terms of health effects. Too little time allowed for yogurt to ferment will yield low bacterial counts and thereby limit health effects upon consumption, or even provide no health benefits at all.
Let’s take our favorite bacteria, Lactobacillus reuteri, that we use to make yogurt that yields age-reversing effects. The doubling time of L. reuteri, i.e., the amount of time required for, say, 1000 microorganisms to become 2000 microorganisms, is around 3 hours. This means 8 doublings over the course of 24 hours.
So let’s say that you start your yogurt-making experience with 100 million microorganisms (“CFUs”) of L. reuteri. Three hours later, you will have 200 million. Six hours later, 400 million. Nine hours later, 800 million, and so on. Let fermentation proceed for 24 hours and you now have 6.4 billion. (We are not accounting for bacterial death for simplicity, so real numbers will be lower. And, anyway, L. reuteri does not have to be alive to exert oxytocin release from the hypothalamus.) But look at the numbers after the initial 24 hours:
27 hours: 12.8 billion
30 hours: 25.6 billion
33 hours: 51.2 billion
36 hours: 102.4 billion
Compare this to conventional commercial yogurt you buy at the grocery store that is typically fermented for 4-6 hours (and usually starting with low counts at the start) and thereby has relatively trivial numbers of bacteria, often in the tens to hundreds of millions—sounds like a lot but, in the world of bowel flora, it is little better than none. Some yogurts are also heated after fermentation to extend shelf-life, a step that kills all bacterial species.
It’s when we get to tens and hundreds of billions that we obtain truly meaningful biological effects such as favorable shifts in bowel flora composition, reductions in fatty liver and insulin resistance, and other benefits. This is why I advise fermenting L. reuteri yogurt for 36 hours. And we ferment in the presence of prebiotic fibers to ensure super-duper high bacterial counts. (Our latest analysis revealed 90 billion CFUs per 1/2 cup serving.) Some Wheat Belly L. reuteri yogurt consumers have fermented for even longer: 40-48 hours. There are other desirable effects of extended fermentation longer than that used commercially that include:
- Maximal exhaustion of lactose–thereby minimizing potential for lactose intolerance and reducing carb count
- A drop in pH to around 3.5 that denatures, or breaks down, casein beta A1 (the potentially immunogenic form of casein. There may be potentially immunogenic peptides that remain, but they are reduced in number).
- A thick end-product that has a wonderfully thick texture, similar to Greek yogurt even if the whey is not strained out, particularly if you begin with full-fat half-and-half. Remember: We NEVER use low- or non-fat products, including dairy products, in the Wheat Belly lifestyle. While dairy products do indeed have issues, the fat is the healthiest component of all–ironically, given the last 30 years of pushing low-fat dairy products. You can also strain the whey out to generate an even thicker end-result and reduce whey content.
I don’t generally advise fermenting past 36 hours, however—there is no harm in doing so, but you will generate greater sourness and risk emergence of fungal contamination (that you can recognize by orange, pink, or green colors on the top).
If you do consume commercial yogurt, make sure there are live cultures within (specified on the label—if not specified, assume it contains none). You can also amplify bacterial counts by either leaving it on the countertop or in your choice of heating vessel, e.g., yogurt maker, sous vide, Instant Pot (provided it does not exceed 108 degrees F) for 24 hours before consumption. (Transfer to a glass or ceramic vessel first so that you are not fermenting in heated plastic.)
In future, I shall be discussing fermentation of other bacterial species and strains to obtain specific health benefits, as well as combinations of various species.