Saturday, May 28, 2011

Digest This! Fermented Soybean Liquid Destroys Proton Pumps and Thus Impairs Nutrient Absorption

Image 1: Natto, a traditional Japanese food made
from soybeans fermented with Bacillus subtilis.
Does not even look healthy, does it?

(image from Wikipedia.de, uploaded by Gleam)
As a studious visitor of the SuppVersity, you have probably banned all conventionally processed soy-containing products from your homes, already (at least I would hope so). Yet, those of you who frequent the various nutrition blogs from the paleo- and similar "healthy-eating" spheres, will probably have come across information about the miraculous benefits that are ascribed to "traditionally fermented" soy products. And, yes indeed, a recent study published in the Journal of Agricultural Food Chemistry (Wang. 2011) was able to reproduce the results of previous studies, which had shown  that fermented soybean liquid alleviates peptic ulcers. Yet, what your soy-friendly nutrition-guru from the XYZ-Blog did not tell you, the fermented soybean liquid does this by destroying your proton pumps.

Edit: Ola just made a comment on some possible flaws in the study design (cf. bottom of the page) which made me re-read the whole study with the interesting result that what I already took for an hypothesis, only (the "destruction of the proton pump"), is re-phrased in the summary of the paper as destruction of "the acidic microenvironment created by PP [proton pumps]". If this is actually the correct version and the formulation "destruction of the proton pumps" rather the result of incompetent translation, this would put into question, whether the fermentation process really created a toxic variety of soy, or not. As studies dating back to the late 1980s show, there is yet a potential issue with "gut irritants" or rather antigenic foods such as soy and damages to the intestinal wall / epithelium. In how far this holds true for the variety of available soy products (and other antigen containing products, including milk!), would warrant individual investigation, though.
Wang and his co-workers tested the effects of fermented soybean liquid (FSL), which - other than some Internet sources would have it - "exhibit[s] higher contents of isoflavonoids (2.5-17.3-fold) and essential amino acids (1.5-4.0-fold) than the nonfermented" soybean liquid, on Helicobacter pylori over a 3 month period in 37 volunteers with gastric peptic ulcers (GPU) and found that "FSL administered at 1 g/20 mL tid [...] eradicated Helicobacter pylori (HP) by 82%".
Image 2: Electron micrograph of H. pylori possessing multiple flagella (negative staining)
(image by Yutaka Tsutsumi, Fujita Health University School of Medicine)
Interestingly, though, further experiments including kinetic analysis and the chyme-shelter testing revealed that "direct infection by bare HP [Heliobacter plyori]  cells is unlikely" in gastric peptic ulcer (GPU) patients. So, if fermented soybean liquid alleviates GPU, the mechanism must be one that is independent of its effects on HP - put simply, fermented soybean liquid "destroys" [I am citing from the study here] the proton pumps!

For those of you, who have not yet read of the nasty effect even over the counter proton pump inhibitors have on nutrient absorption: The proton pumps are those parts of your gut which release H+ ions into the stomach juice, thus acidify it and allow for the first step of digestion to take place. Many of the enzymes involved in this process are released or activated exclusively in an acidic milieu. And optimal PH-control, which is obviously impossible with blocked or even destroyed proton pumps, is a vitally important requisite for optimal nutrient absorption (esp. vitamins, minerals and protein).

So, a potential of permanently impaired digestion and a higher isoflavonoid load than in the "evil" conventional soy-products? Are you still sold on the idea that fermentation has been practiced for centuries and thus must be a valid way of transforming a "poisonous" food into a panacea?