I have two related questions about soy allergies and possible reactions.

  1. What is it that are humans who have soy allergies actually allergic to? What is the allergen?
  2. If an animal eats soy, are those allergens broken down or retained? Can the consumption of that animal cause an allergic reaction similar to direct soy consumption?
  • $\begingroup$ I think this is a worthy and interesting question. I've rewritten it to try and make to not personally medically related. $\endgroup$ – kmm Mar 6 '13 at 20:48

There are multiple soy protein allergens. This has a pretty good review in the introduction. Here is a list of some of the allergens (same paper).

Chickens on soy diets do lay eggs with higher concentrations of soy isoflavones than chicken on non-soy diets. (Edit: higher concentrations of soy isoflavones are also found in chicken tissues -- see ref 4 below.) References (originally found here) are:

  1. Saitoh, S.; Sato, T.; Harada, H.; Takita, T. Transfer of soy isoflavone into the egg yolk of chickens. Biosci. Biotechnol. , Biochem. 2001, 65, 2220-2225.
  2. Saitoh, S.; Sato, T.; Harada, H.; Matsuda, T. Biotransformation of soy isoflavone-glycosides in laying hens: intestinal absorption and preferential accumulation into egg yolk of equol, a more estrogenic metabolite of daidzein. Biochim. Biophys. Acta 2004, 1674 (2) 122-130.
  3. Lin, F.; Wu, J.; Abdelnabi, M.; Ottinger, M.; Giusti M.M. Effects of dose and glycosylation on the transfer of genistein into the eggs of the japanese quail (Coturnix japonica). J. Agric. Food Chem. 2004, 52, 2397-2403.
  4. Vargas Galdos, Dante Miguel Marcial. Quantification of Soy Isoflavones in commercial eggs and their transfer from poultry feed into eggs and tissues. Thesis. Ohio State University, Food Science and Technology Graduate Program, 2009; http://etd.ohiolink.edu/send-pdf.cgi/Vargas%20Galdos%20Dante%20Miguel%20Marcial.pdf?osu1236706764.

However, I do not know whether this is enough to cause an allergic reaction if consumed. (There's plenty of anecdotal evidence, but no clinical studies that I know of.)

  • $\begingroup$ Are soy isoflavones among the allergens listed, though? $\endgroup$ – octern Mar 9 '13 at 5:24
  • $\begingroup$ @octern: they're not listed, but that table references only the major allergens (as per the authors of that paper, there are around 20, although only 7 are in the table). Hence, my last statement - anything I can find regarding this is anecdotal evidence from not necessarily reputable sources. $\endgroup$ – blep Mar 9 '13 at 5:58

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