How healthy is your store-bought yogurt?

Yogurt is the product of bacterial fermentation of sugars such as lactose. By FDA regulations, to label something as “yogurt,” it must be fermented with the bacterial species Lactobacillus bulgaricus and Streptococcus thermophilus, even though there are many other fermenting bacterial species (such as our favorite, Lactobacillus reuteri).

Here’s an issue you rarely hear discussed: It’s not just a matter of which bacterial species you choose, but also how long the yogurt is allowed to ferment. This is a critical aspect of the potential health and probiotic properties of yogurt, as well as any other fermented product.

Remember the story we heard as kids about how, if you begin with a penny on day 1 of the month and double the amount every day for the rest of the month, you would be a millionaire many times over after 30 days? That is the power of doubling: enormous, exponential increases over time.

The same principle applies to yogurt fermentation. The doubling-time of bacteria, i.e., the time required for one microorganism to become two, two to become four, four to become eight, etc. varies widely depending on species, temperature, nutrient availability and other factors, ranging from minutes to days. But a typical bacterial doubling time for yogurt-fermenting organisms is 3-4 hours. So let’s play a mind game and say that we begin our yogurt with 100 million bacteria (“CFUs” or colony-forming units) at the start, then allow our bacteria to double for 6 hours:

Hour 0: 100 million
Hour 3: 200 million
Hour 6: 400 million

(For simplicity, we assume that bacteria do not die and all continue to procreate.)

Most commercial yogurts are fermented for 6 hours, rarely more than 8 hours. This also explains why various thickening agents and emulsifiers are added, especially to ridiculous low- or non-fat yogurts: to improve texture and mouthfeel, since there is a lack of fat and very few bacteria.

Let’s allow bacterial fermentation to proceed for a longer period:

Hour 0: 100 million
Hour 3: 200 million
Hour 6: 400 million
Hour 9: 800 million
Hour 12: 1.6 billion
Hour 15: 3.2 billion
Hour 18: 6.4 billion
Hour 21: 12.8 billion
Hour 24: 25.6 billion
Hour 27: 51.2 billion
Hour 30: 102.4 billion
Hour 33: 204.8 billion
Hour 36: 409.6 billion

In other words, fermenting for an additional 30 hours (as we do with our L. reuteri yogurt) increases bacterial count by 400-fold, an exponential increase.

It also means that your expectations for health benefits from commercial yogurt should be low, given the relatively trivial counts of bacteria, not to mention the limited health benefits of the fermenting species chosen. This is why you can do SO much better by fermenting yogurt and other foods on your own. You are not limited by production schedules, as commercial factories are. After all, think how much factory production would be limited if it required 36 hours to produce a product rather than 6 hours? From a business standpoint, that is a crippling difference. But that is not your primary concern. Health is your primary concern. By fermenting your own yogurt, you can also choose the fermenting species and strains obtaining, for instance, the huge age-reversing oxytocin boost of our L. reuteri yogurt or B-vitamin augmentation by fermenting with L. rhamnosus (an issue I shall discuss in future).

If you are not interested or too lazy to ferment on your own, you can also improve commercial yogurt by purchasing a brand that contains live cultures (labeled “live cultures” and/or with bacterial species listed in the ingredients), then either leaving it out on the counter at room temperature or, even better, putting it into whatever vessel you have to maintain at 100-112 degrees F to allow additional fermentation to proceed for another 24 or so hours. That is how you obtain real benefits from yogurts.

Stay tuned to the Wheat Belly conversations about these issues as the health benefits of specific bacterial species become clearer and we are able to amplify via extended yogurt fermentation.

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