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| Cita: | Misinformation regarding soy’s relationship to cancer largely stems from confusion around the presence of phytoestrogens in soy. Phytoestrogen is not estrogen. Estrogen and testosterone are steroid hormones, and occur naturally in both sexes of humans, as well as in animals used for food. They help regulate s*xual function and secondary s*xual characteristics, in addition to s*xual cellular functions. While estrogen plays many important beneficial roles in humans, it also naturally promotes proliferation of cells, and, at high levels, can increase risk of some cancers by encouraging cells to multiply more than they usually would. Hormone replacement therapy in postmenopausal women (specifically, taking only estrogen) has also been implicated in cancer growth. (2)
While soy does not contain estrogen, animal foods do. Many consumers are aware that animals used for meat and dairy are commonly supplemented with synthetic growth hormones, but what they don’t consider is that animal flesh and cow milk also contain their own naturally occurring estrogen— and this is true even of “grass-fed” and “organic” animals. Furthermore, meat, dairy and eggs all contain phytoestrogens; they are pervasive in our food, both plant and animal-derived, and you are not avoiding them entirely by avoiding soy.
Phytoestrogen is just a catchall term for numerous naturally occurring plant compounds which are structurally similar to mammalian estrogen, and functionally are weakly estrogenic (weakly mimicking estrogen) or antiestrogenic (blocking estrogen’s effects). The metabolism and functionality of phytoestrogens are incredibly complex, and vary between individuals. The concern over soy and cancer stems from the fact that soy-based foods contain phytoestrogens (specifically, isoflavones) in varying amounts (depending on the preparation), and these react with the estrogen receptor. There are two types of estrogen receptors in humans: alpha and beta. Alpha are distributed widely throughout the body, whereas beta are localized in the ovary, prostate, lung, and epididymis (testicle). While isoflavones, like estrogen, bind to both alpha and beta receptors (preferentially to beta), isoflavones do not have the estrogenic effect of inducing tumor growth. In fact, isoflavones have demonstrated a protective benefit against hormone-dependent cancers.
The inverse relationship between soy consumption and risk of developing premenopausal breast cancer has been clearly established. In other words, higher rates of soy intake are associated with lower rates of breast cancer. (3) However, large clinical trials have not yet been conducted regarding the effect of phytoestrogen consumption on tumor growth in established cancer patients. (4) To date, such studies have utilized small sample sizes, and the methods for obtaining data were highly variable. There have been ‘promising’ results from multiple animal models, demonstrating a reduction in tumor size with consumption of soy protein. Yet, aside from the immorality of artificially inducing cancer in unwilling participants, it is dangerous to compare laboratory animals to humans. We are not mice. Even within our species, there is tremendous variability in the metabolic processing of phytoestrogens and pharmacological agents, thus establishing the difficulty and complexity of this area of research. Instead, attention should be placed on the already available mass of epidemiological data which compares Asian cultures to those consuming a Western diet.
- See more at: http://freefromharm.org/health-nutrition/vegan-doctor-addresses-soy-myths-and-misinformation/#.dpuf |
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