As promised a few weeks ago when I wrote my article on declining testosterone in men, I decided to cover the topic of phytoestrogens more fully.
There’s a lot of hype out there that particularly soy is bad for you, because it’s estrogenic. Men avoid it out of fear that it may cause them to develop breast tissue (gynecomastia). Women avoid it out of fear that it may throw their already precarious thyroid numbers out of balance, or that it may increase the risk of hormone-based cancers.
For the moment, however, let’s separate the issue of soybeans specifically from phytoestrogens generally (which, in addition to soy, also include isoflavones such as lentils and chickpeas, lignans such as flaxseeds, and coumestins such as red clover, alfalfa, and a number of other botanicals).
What is a Phytoestrogen?
The prefix phyto- means plant, so phytoestrogens are plant-based estrogens, as opposed to the estrogens your body naturally produces, bioidentical estrogens (which are physically indistinguishable from those produced by your body), or animal-based estrogens such as Premarin (which is derived from horse urine, and far from side-effect free).
Phytoestrogens are 100 to 1000 times weaker than the estrogen your body produces. What this means: both types of molecules bind to estrogen receptors the same way a key might fit into a lock – but the resulting effects of this match will be very different between the two.
- If you have too few natural estrogen molecules in your body, such as in menopause, these phytoestrogens will bind to those estrogenic receptors and weakly stimulate them, which may help improve symptoms of too little estrogen.
- If you have too much estrogen relative to progesterone, however (such as in endometriosis, PMS, some menstrual migraines, etc), then a phytoestrogen will still stimulate that estrogen receptor, but it will do so 100 to 1000 times less than the estrogen molecule that otherwise would have occupied that spot!
In other words, phytoestrogens function can be either estrogenic OR anti-estrogenic, depending on which one your body needs.
Soy as a Goitrogen
The connection between soy and thyroid suppression has nothing to do with its status as a phytoestrogen, however. Several other foods considered to be thyroid suppressants (aka goitrogens) include millet, peanuts, radishes, turnips, and raw cruciferous veggies (such as cauliflower, brussels sprouts, and broccoli).
These are very healthy foods overall, and it would be a mistake to completely avoid them! Goitrogens are only a problem for thyroid function if you’re already iodine deficient. Iodine is one of the minerals necessary for the formation of thyroid hormone, and goitrogens compete with thyroid hormone for iodine. So as long as your iodine status is not a problem, you need not avoid these foods – including soy. Even if you are iodine deficient, fermenting, cooking, or steaming these goitrogens renders them safe for consumption. (Fermented soy products include natto, miso, soy sauce, and tempeh.)
Soy as a Genetically Modified Organism (GMO)
However (and this is a big however): soy is one of the foods that is most commonly genetically modified – we’re talking 94% of the soy in the U.S. It still isn’t absolutely clear what sorts of ramifications genetic modification may have on health, but because there is plenty of evidence to suggest there might be a problem, I choose to play it safe and avoid GMO soy.
This isn’t always as easy as it sounds, though. Companies are not required to label GMO foods as such, and soy is ubiquitous in our food – it’s hiding in lots of things you’d never expect. So read your labels (here’s a list of ingredients that contain soy), and assume that if it doesn’t specifically say it’s not GMO, then it is. Non-GMO will either contain a non-GMO label on the package, or it will be labeled organic.
- As a general rule, phytoestrogens are balancing, not dangerous.
- Goitrogens should be consumed with iodine-containing foods, or else cooked, steamed, or fermented IF you already have low thyroid function. Otherwise, enjoy them in moderation!
- Consume non-GMO soy.
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