Two hormone-like compounds linked to the consumption of soy-based foods can cause irreversible changes in the structure of the brain, resulting in early-onset puberty and symptoms of advanced menopause in research animals, according to a new study by researchers at North Carolina State University.Another part of the puzzle, indicating the importance of even relatively small doses of hormones on the development of the hypothalamus during gestation.
The study is the first to show that the actual physical organization of a region of the brain that is important for female reproduction can be significantly altered by exposure to phytoestrogens – or plant-produced chemicals that mimic hormones – during development. Specifically, the study finds that the compounds alter the sex-specific organization of the hypothalamus – a brain region that is essential to the regulation of puberty and ovulation.
While the study examined the impact of these compounds on laboratory rats, neurotoxicologist Dr. Heather Patisaul – who co-authored the study – says the affected "circuitry" of the brain is similar in both rats and humans. Patisaul is an assistant professor in NC State's Department of Zoology. Her co-author is Heather Bateman, a doctoral student in the department.
Patisaul says this finding is extremely important because, while the changes in brain structure cannot be reversed, "if you understand what is broken, you may be able to treat it."
Patisaul says that this study is also "a step towards ascertaining the effects of phytoestrogens on developing fetuses and newborns." Patisaul adds that these phytoestrogenic compounds cross the placental barrier in humans and that, while many people are concerned about the effects of man-made compounds on human health, it is important to note that some naturally occurring substances can have similar effects.
Patisaul explains that the brains of both female rats and female humans have a region that regulates ovulation. "That part of the brain," Patisaul says, "is organized by hormones during development – which is the neonatal stage for rats and during gestation for humans." Patisaul says the new study shows that the female brain is "critically sensitive" to genistein and equol during this crucial stage of development – and that this may indicate that the brain is also especially sensitive during this period to all phytoestrogens and possibly other man-made chemicals, such as bisphenol-A.
Phytoestrogens are very mild, and very ineffective. The many patent "breast enlargement" cremes made using them are 99.99% Snake Oil, with effective doses 1/10,000 that used in Hormone Replacement Therapy. In those particularly sensitive, there may be some measurable clinical effect: but dissolving one birth control tablet in a full bath, and taking a teaspoonful of the resultant liquid would have a greater effect.
It does lead to some concern though - the possible pollution of the water supply with oestrogen. Most of the contents of birth control pills are excreted in urine, and end up unchanged in the environment. Most is quickly broken down, or at least, we think it is. It should be. There are experts keeping an eye on the situation, and it's a topic at every conference on endocrinology.
Phytoestrogens appear to be just one of the defence strategies that various plants have evolved to stop over-predation by animals. Many plants produce toxins. But a few produce significant quantities of hormones that interfere with the predators' reproductive systems.
Never trust a vegetable. They're sneaky.