Soy must be the most recognised and vilified food stuff amongst Men looking for optimal T levels. The term, ‘Soy Boy’, which is used to label weak, effeminate Men, encapsulates the current polarised thoughts surrounding Soy.
Soy contains several isoflavones, the main of which is called Genistein. It is these isoflavones that are responsible for Soy’s Oestrogenic effects in the body.
Genistein is an ‘endocrine disruptor’. This makes complete sense under an evolutionary lens. Disrupt the endocrine system that controls fertility in the creatures that like to eat you, and you will prevent their numbers from increasing, thus managing predation.
This phenomenon was initially observed in sheep grazing heavily on red clover. Red clover is rich in xenoestrogens, Genistein amongst them, and it significantly reduces their fertility (Morley 1966).
In humans, a dose of just 30g of soy flour per day has shown frank Oestrogenic effects in Women (Doerge 2009). But will Soy intake affect Male hormone levels?
Well, several animal studies exist showing dietary Soy reducing androgen levels (Weber 2001) In humans, a study of 42 males who had their lean meat replaced with tofu (Soy protein) for only 4 weeks had a lower Testosterone : Oestrogen ratio, lower free androgen index and higher SHBG (Habito 2000) Another study also showed Soy protein Powder reduced T levels in young Men by up to almost 20% - this effect subsequently reversed two weeks after stopping the Soy intake (Goodin 2007).
Perhaps this is why Men consuming soy foods twice or more per week had 41,000,000 fewer spermatoza per mL of semen than men who did not consume soy foods (Minguez et al 2015)
It isn’t just actual Testosterone levels that may be affected. Soy has been shown to actually reduce Androgen Receptor expression (Hamilton-Reeves 2007, Mahmoud 2014). Your circulating T levels are irrelevant unless they have Androgen receptors to bind to.
It is important to note that data on this topic is mixed. But regardless of Soy’s effect on your Male health, there are several other points to consider before reaching for the Soy protein powder.
Soy is a well-known goitrogenic agent – it is toxic to the thyroid gland. Not ideal for something marketed as a health food. Reportedly, manufacturers began adding iodine to soy infant formulas as far back as the 1960’s in order to mitigate this goitrogenic effect. Soy has also been shown to be a developmental toxicant (Doerge 2009).
The serum/plasma concentration of Genistein achieved in infants fed Soy formula exceeds the concentration seen in lab studies using doses that were toxicologically active (Chen 2004). That is correct, large corporations push Soy infant formulas in doses that animal studies have shown to be toxic.
We have digressed somewhat, but if you are not concerned about its effects on your Male health, perhaps the logical sentiment on Soy consumption is best summarised in two recent scientific reviews.
Cederroth et al (2014) cautioned against drawing firm conclusions on this topic, due to the usual paucity of data on factors affecting Male health, and the presence of several conflicting study results. However, it went as far as to highlight that there were indications that Soy could indeed alter reproductive hormones and fertility (Cederroth 2014) and it also reiterated avoiding exposing infants to Soy based formula feeds.
In another recent, in depth review article, Rietjens et al (2017) concluded that, “the literature overview presented in this paper illustrates that the beneficial health effects (of Soy) are not so obvious that they clearly outweigh the possible health risks”
There are plenty of superior protein sources available, many of which positively contribute to your Testosterone levels. Choose wisely.
We’ve also written before about Iron and iron overload. It seems that Testosterone and Iron are closely interrelated. In fact, Iron stores are negatively related to serum T levels, that is, the higher your Iron levels climb, the lower your T (Gabrielsen 2018).
This is an area that needs more research. however, after you have checked your iron levels, if they are high, it may be possible to increase your T, simply by donating blood! A win-win situation for all involved.
The effects on your Testosterone levels of some over-the-counter drugs for that sore back, a few beers (and a few more) with the lads, the Tofu you’ve been misled into eating by the food industry, may alone and of themselves be small.
We have additionally already noted how poor sleep, excess body fat, stress, chronic high carb or calorie intake and high intake of PUFA’s can negatively impact your T. (see here, here and here)
When you start to stack combinations of the above together, the effects become very real and significant. This is partly why scientists have struggled to pinpoint the exact cause of the Testosterone and fertility decrease in the last few generations of Men. It is a multi-pronged assault.
Men, forewarned is forearmed!
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