There are a few things I constantly see around the Internet that really irk me. One of those things is the meme that soy causes feminization in males. Some people may see a picture of a guy with soft facial features and they’ll say ‘oh that’s a soy boy.’ They do not show a good understanding of soy and its chemicals. As usual, overblown claims from people who have no specialty in what they’re talking about have an answer—just one they do not want to hear.
I have no idea when this craze of blaming soy and other foods on ‘feminization of males’ (I have done so a few years ago, though I realize my error now), but it’s starting to get out of hand. I see this around Twitter a lot; ‘oh it’s the soy making men beta’ or ‘they know exactly what soy does to men and they still push it!’. The whole scare about soy is that soy has phytoestrogens called isoflavones, and these phytoestrogens then may mimic estrogen production in the body. (It’s worth noting that phytoestrogens do not always mimic estrogens, despite some people’s protesting to me that “It has estrogen right in the name!”.)
Many men have blamed soy and phytoestrogens/isoflavones on their growing breasts, having a flaccid penis, slow beard growth (that’d be enough motivation for me to do something about it, to be honest), loss of hair on his arms and legs, and, he says “Men aren’t supposed to have breasts … It was like my body is feminizing.” So this man went to an endocrinologist and was told that he had gynecomastia—enlarged breasts in men. He got tested for a whole slew of maladies, but they all came back negative. Then the doctor told him to be very specific with his diet. The man then said that he was lactose intolerant and that he drank soy milk instead of cow’s milk. The doctor then asked him how much soy milk he drank per day, to which the man responded 3 quarts. Was soy the cause of his gynecomastia and other negative health effects? I don’t think so.
For men and boys, soy does not seem to have an effect on estrogen and other hormone levels, nor does it seem to have an effect on development and fertility:
A handful of individuals and organizations have taken an anti-soy position and have questioned the safety of soy products. In general, this position latches to statistically insignificant findings, understates how powerfully the research refutes many of the main anti-soy points, and relies heavily on animal research studies, which are medically irrelevant to human health.
Most of those people are ‘activists’ who do not understand the intricacies of what they are talking about. In the field of nutrition, it’s dumb to take studies done on animals nd then extrapolate that data to humans. It does not make sense.
There are reasons not to eat soy that do not go along with this dumb hysteria from people who do not know what they are talking about. One reasons is that, when compared to casein protein, soy protein is inferior (Luiking et al, 2005). Further, data is “inconsistent or inadequate in supporting most of the suggested health benefits of consuming soy protein or ISF” (Xiao, 2008). People may cite studies like Lephart et al (2002) where they write in their article Neurobehavioral effects of dietary soy estrogens:
Whether these observations hold true for the human brain remains to be established and will only become apparent from long-term clinical studies. One point that needs clarification relates to the timing of brain development in the rat, which differs from that in the human. (pg. 12)
Rats and humans are different; I don’t think I need to say that. Though people who cite these studies (uncritically) as ‘evidence’ that soy lowers T, causes infertility problems, and feminization just look to grab anything that affirms their fearmongering views.
Jargin (2014) writes in his article Soy and phytoestrogens: possible side effects:
Feminizing effect of phytoestrogens and soy products may be subtle, detectable only statistically in large populations; it can be of particular importance for children and adolescents. This matter should be clarified by independent research, which can have implications for the future of soy in the agriculture.
If it’s only identifiable in statistically large populations, then it is meaningless. Though, East Asians seem to be adapted to soy and so (like all studies should note), these results should not be extrapolated to other races/ethnies (Jargin, 2014). I do agree with that assessment; I do not agree with the claim that these phytoestrogens would cause problems that would only be seen in statistically large populations.
If people want to use rat studies to show that soy supposedly raises estrogen levels, then I will use a rat study showing the opposite (Song, Hendrich, and Murphy, 1999). They showed that the effects of the isoflavones from soy were only weakly estrogenic. Further, Mitchell et al (2001) write in their article Effect of a phytoestrogen food supplement on reproductive health in normal males:
The phytoestrogen supplement increased plasma genistein and daidzein
concentrations to approx. 1 µM and 0.5 µM respectively; yet, there was no observable effect on endocrine measurements, testicular volume or semen parameters over the study period. This is the first study to examine the effects of a phytoestrogen supplement on reproductive health in males. We conclude that the phytoestrogen dose consumed had no effect on semen quality.
The men in this study took a daily isoflavone supplement containing 40 mg of isoflavone every day for two months and still did not show negative effects. Looking at rat studies and then extrapolating that to humans doesn’t make sense.
Finally, there was a large meta-analysis by Messina (2010) who writes:
The intervention data indicate that isoflavones do not exert feminizing effects on men at intake levels equal to and even considerably higher than are typical for Asian males.
And from the conclusion:
Isoflavone exposure at levels even greatly exceeding reasonable dietary intakes does not affect blood T or estrogen levels in men or sperm and semen parameters. The ED-related findings in rats can be attributed to excessive isoflavone exposure and to differences in isoflavone metabolism between rodents and humans. Thus, men can feel confident that making soy a part of their diet will not compromise their virility or reproductive health.
Now, I know that proponents of the hypothesis of soy feminizing males would say to me “Why don’t you just eat a bunch of soy and see what happens then, if it is fine for you?” Well, unlike most people, I eat a strict diet and soy is not part of it.
Soy isoflavones are currently being researched in regards to the prevention and treatment of diabetes, cardiovascular disease, cancer, osteoporosis, and neuroprotection (Kalaiselven et al, 2010), while the nutritional and health benefits of soy isoflavones are currently being studied (Friedman and Brandon, 2001; McCue and Shetty, 2004). Soy foods may also be optimal for bone health (Lanou, 2011).
In conclusion, as you can see, the claims of soy causing feminizing effects on men are largely overblown. People extrapolate data from rat studies to humans, which doesn’t make any sense. To paraphrase Dr. Jason Fung, imagine 2 lions are watching a deer eat. They see how strong and in shape the deer are eating grass. So the lions, noticing that the deer are healthy eating grass, begin to eat grass too thinking it is healthy and they die. One hundred years later, 2 deer are watching a lion eat meat and sees how strong, fast, and healthy it is. They then draw the conclusion that eating meat is healthy and will do the same for them and they eat meat and die. The point of the analogy is that just because studies on animals show X and therefore Y, that does not mean that it will hold for humans! This is something very simple for people to understand, though most do not.
Most people search for things to prove their assumptions without having an actual understanding of the biological mechanisms of what they’re talking about. People should learn some of the literature before they cite studies that supposedly back their biases, because they would then see that it is not as nuanced as they believe.
(Note: Diet changing under Doctor’s supervision only.)