Soy is definitely causing more controversy than any other bean. Red kidney beans are certainly safe from rumor. And the pinto’s place is secure in the Mexican cuisine. Leave it to the soybean to give us something to talk about for many years to come. What makes soybeans different nutritionally from other beans is:
* They have a high isoflavone (plant estrogens) content
* They are a complete protein (they contain all the essential amino acid building blocks).
I think there is synergy within the soybean, which means, the power is in the package, not necessarily the individual components. Here are a few examples of possible synergy in soy:
Soybeans contain many beneficial active phytochemicals, besides isoflavones, all having antioxidant activity, including lignans (phytoestrogens) and phenolic acids. Genistein, the main isoflavone in soy, has possible anti-tumor activity, but there are other bioactive anti-cancer components in soy as well (protease inhibitors, lignans, phytosterols and saponins). Researchers suspect that these bioactive anticancer components exert their anti-cancer activity in different stages of the carcinogenesis process. This means, there is value in eating your soy as close to whole form as possible instead of getting just one of the valuable components in soy.
Here’s another reason to eat your soy in close to “whole” form. Soy contains “inactive” components along with the “active” ones we’ve just been talking about. It is even possible that some of these “inactive” components are required for the “active” components to be useful. And it’s “dietary” soy that has been shown to improve blood pressure by making it less likely that our blood vessels will constrict in the presence of two hormones (angiotensin II or phenylephrine). In female rats, it was dietary soy again that exerted a vasodilator effect (opening up and relaxing the blood vessels) similar to the effect fish oil seems to have.
Soy In Synergy With Radiation Therapy. Here’s a way most of us never thought soy could help – Eating soy (under certain conditions) may actually make radiation more effective during prostate cancer treatment by making the cancer cells more susceptible to radiation (or more radiosensitive), according to some new research by Dr. Gilda Hillman, PhD, with the Karmanos Cancer Institute.
But here’s the fascinating news that suggests to me that soy has synergy and that the best way to get soy is probably as a whole food–as close as possible to whole soybeans. When Dr. Hillman used the isolated soy isoflavone, genistein, in her study, it showed the potential to stimulate the spread of tumor cells from the prostate to the lymph nodes. But when she switched to dried powder of whole soy, she got the same exciting radiosensitization effect on the prostate cancer cells but without the negative effect of the tumor spreading to the lymph nodes. “It’s intriguing that whole soy did not stimulate prostate cancer cells to metastasize while a single soy component did,” said Dr. Hillman.
First of all, that’s over-the-top exciting. But secondly, more clinical data in human subjects are needed before advice about soy and supplements during treatment can be made, advises Dr. Hillman. So we’ll just have to stay hopeful while we await more research. [AICR Press Release June 28, 2006 "Laboratory Studies Reveal How Components
of Diet Help Therapies Target Cancer Cells"]