I always get a good chuckle when I hear men say that they can’t have soy products for fear of increasing estrogen levels and then growing man boobs. My response to implausible statements like this, without a poignant question directed toward me is, “that’s interesting” with a sarcastic, yet supportive nod. If they ask what I think, then I have to give it to ‘em, because: 1) soy lattes (and soy, in general) are delicious and men should not be deprived; 2) research is extremely limited to conclusively say that estrogen levels are affected by soy; 3) someone made a weak, illogical, non-empirically supported, unsubstantiated (get my drift?) claim about soy that spread like rapid fire, and it’s extremely hard to recover from the incessant slandering; and 4) even though “dad bods” are in, there should be no fear – your chest will still look the same with or without the soy latte.
Alright, my “burn my bra” session is over. Whoa! Pun totally intended.
So, what’s the deal?
Well, soy is typically consumed when people are restricting animal products like cow’s milk from their diets – perhaps during times when they are trying vegetarianism or veganism. What \ happens when people try these dietary lifestyle changes is that there is also a shift in macronutrient – carbohydrates, proteins and fats – consumption. People generally consume much more carbohydrates and much less protein compared to what they were eating before they made the change. When this happens, there is a shift in body composition, and most people gain some fat – and get a bit soft. I hear this complaint quite often from people trying vegetarian/vegan diets.
However, instead of seeing the shift in macronutrient consumption, people have learned to blame soy!
So, what’s the science?
Soy contains this compound called phytoestrogens. Phytoestrogens are implicated in a litany of great health benefits, but may also affect hormone status negatively. However, just like in all research, the direct effects of soy (and thus these phytoestrogens) on hormonal status are not implicitly understood – it depends on age, health status, etc…
Most notably today, the phytoestrogens in soy are blamed for increases in estrogen content, or perhaps an offsetting of the testosterone to estrogen ratio. However, you cannot deduce that estrogen levels will be raised if the study that you are looking at is in rats that are fed a diet consisting of 10 times the amount of soy that a human would consume for 20 straight days. Know your population.
In fact, in a recently published review of the existing research on the effects of soy on hormones, researchers found only a handful of studies that even examined these effects in men (Kurzer, 2012). The studies that they found in men showed that the present data do not support concerns about the effects of soy products on reproductive hormones (i.e. estrogen and testosterone). Added bonus: semen quality is also unaffected! Furthermore, in women, specifically post-menopausal women, soy may help the balance of hormones! Although more research is warranted all around, the effects of soy on hormonal status do not look to be negative!
Furthermore, in these studies that showed no effects, men consumed an average of 40-70 mg of soy isoflavones (a class of phytoestrogens) per day. In 1 cup of soy, there are about 6 mg of soy isoflavones. And in a grade soy latte, there are about 2 cups of soy milk. That equates to only 12 mg of phytoestrogens, which is MUCH lower than the 40-70 mg that were examined in the study. Realistically, guys – you can have 4-6 soy lattes and be ok! But then you’d be broke.
So now that we have dispelled the myth of soy causing man boobs, what are some other potential benefits of consuming soy on body composition? Most notably, soy may positively affect muscle protein synthesis and therefore muscle building. Just like other proteins, soy can increase protein building – it’s a protein, after all! However, it is important to note that compared to animal sources like whey and casein protein, soy will likely not increase protein synthesis to the same level. However, if you want a different option, or if you are a vegetarian/vegan – soy should be able to do the trick!
Guys - the only growth that your chest will be doing if you take soy protein is from muscle-building after National Chest Day on Monday.