What’s the deal with all the hate on soy recently?
For some reason, it’s been part of a popular term used in a way to emasculate others. Supposedly you’re less of a man if you eat soy regularly because soy kills your testosterone. Before we even dive into it yes, it’s a ridiculous claim born entirely out of hyperbolic reactions and sheer ignorance of the sciences.
The main issue stems from soybeans containing something called phytoestrogens. Phytoestrogens do in fact interact with our sex hormones, notably estrogen and testosterone, and also their respective receptors.
It can bind to estrogen receptors, wherein men it can mean a greater estrogenic effect. In the same breath, it’s interaction with androgen receptors might ultimately lead to a reduction in testosterone. These phytoestrogen properties are in fact true, particularly the phytoestrogens in soy known as isoflavones.
The only problem is that the imposed effects are rather weak compared to the effects of estrogen and androgens themselves. And that’s where we see the testosterone-killing claim of soy fall short in the research.
A 2001 paper in Japan showed that compared to a control, drinking roughly one and a half cups of soymilk per day for 8 weeks did not have any statistical effect in total and free-testosterone levels.
A 2007 study looked at young men split into four groups consuming either 50 grams of soy concentrate, soy isolate, a soy isolate and whey blend, or a whey blend only. After 12 weeks, total and free testosterone, as well as lean mass gains, were similar across all groups.
Much of the same is seen in a longer 3-month study in 2006 done on older men (>50), where eating soy at amounts similar to Asian countries did not affect testosterone.
And once more, this time in high-quality papers, found that soy protein or isoflavone intake had no significant effects on free and total testosterone.
However, having too much soy might still pose a problem.
In 2008, a study found that exposing rats to 20 milligrams of isoflavones per kilogram of bodyweight did lower plasma testosterone by 35% compared to control.
When we adjust the amounts of isoflavone consumption to equal that of a 180-pound male, that adds up to 1,636 milligrams of isoflavones per day. Or on a simpler scale, that adds up to 54 and a half cups of soymilk daily.
As mentioned earlier, consuming amounts equivalent to that of Asian countries, where soy consumption is the most prevalent, did not cause any testosterone dips.
That amount if roughly 65 milligrams of isoflavones, well below the amount in the rat study. Suffice to say, the testosterone-killing claim looks to be effectively quashed.
But if you’re even remotely concerned about it, then just remember, like everything else, moderation is key. Based on the research, it looks like a safe bet to consume up to 50 grams of soy protein per day without any problems.
As for the type of soy foods, fermented soy or tofu are decent choices, containing fewer phytoestrogens than raw or whole soybeans.
If you want to use soy protein supplements, shoot for soy concentrates or isolates that are alcohol washed, which removes almost all of the phytoestrogen content.
As long as you’re not getting all of your protein from soy, then chances are things will be fine. But to reiterate, soy does not kill your testosterone despite what the media might tell you.
Practice moderation and enjoy your soy milk or tofu curry from time to time. It’s going to be okay.