Researchers in Japan have managed to turn male catfish 100% female by using a soy compound.

Soy and soy compounds are ubiquitous in modern diets, with most prepackaged and processed foods contain soy and soy compounds.

The purpose of turning the catfish from male to female was for financial motives as female catfishes are more valuable than males.

Female catfish grow quicker than males, providing the researchers with the extra incentive.

Professor Toshinao Ineno said: “by making them all female, production efficiency will rise.”


Catfish, Soy, and Changing Sex


According to Mainichi:

“…In catfish cultivation, which has been attracting attention as an alternative to increasingly scant eel, females grow to shipping weight — at least 600 grams — in six to 10 months after hatching. Males, which grow more slowly, are often discarded. Though it has been known that administering female hormone turns male catfish into females, this method is banned for fish for human consumption. So Ineno came up with the idea of using soybean isoflavone, which is sold commercially as a dietary supplement.

“The experiment was conducted with catfish divided into five different tanks; one of regular fish farming water; three with different concentrations of “genistein,” a chemical component of soybean isoflavone; and one with female hormone dissolved in the water. The team kept 150 fry in each tank for 15 days, before transferring them to ordinary water until they were 150 days old. While 68% of catfish in the ordinary water tank were female, 96% of the catfish kept in the water with genistein at a concentration of 100 micrograms per liter were female. A concentration of 400 micrograms per liter yielded a 100% female group, the same as in the female hormone-treated water group.”

The Problem With Soy

avoid soy products

The effects of phytoestrogens, such as soy, have been well-documented and even believed to cause a drop in testosterone levels as well as fertility.

From our article on Soy:

Although soy is a potent phytoestrogen — something we have written about in the past — it has other deleterious effects besides lowering your testosterone. Drinking a diet of liquid soy will damage your facial physiognomy, and large-scale soy cultivation, despite what the activists for vegetarianism and veganism say, is also massively damaging to the environment.

As noted in our article on 5 Foods That Lower Testosterone:

Scientific research has shown that regular consumption of soy products like edamame, tofu, soy milk and miso may also lower testosterone levels.

For example, one study in 35 men found that drinking soy protein isolate for 54 days resulted in lower testosterone levels [R].

As well as lowering testosterone levels, soy consumption has also been found to reduce male fertility [R].

Be in no doubt: soy is bad for your testosterone levels and fertility if you’re a man.

But hang on: what’s so important about testosterone?

Testosterone is the hormone most associated with masculinity, and although it’s also important to women’s bodies and their health, the increased levels of testosterone in the male body are responsible for the host of traits that make men men, rather than women. 

Body hair, muscle mass, bone density, strength, aggression, dominance and competitiveness – increases in all of these things are associated with increased testosterone in men. 

Falling testosterone levels are a fact of life for all men as they age. After the age of 30, a man can expect to lose 1% of his testosterone every year for the rest of his life. 

But the natural reduction all men can expect to suffer pales in comparison with the society-wide collapse in testosterone levels that has occurred over the second half of the twentieth and the first quarter of the twenty-first century.

Men today have considerably less testosterone than men of the same age even a single generation ago. 

A 2007 study in the Journal of Clinical Endocrinology and Metabolism showed a significant reduction in the testosterone levels of men since the 1980s. A 60-year-old American man in 2004, for example, had 17% less testosterone than a 60-year-old American man in 1987.

These findings were corroborated in a study of Danish men, who displayed a two-digit decline between the 1920s and the 1960s.

Soy and Phytoestrogen Consumption in the Animal World

On Monday, we reported on a largely unreported study on the effects of long-term soy consumption on the behaviour of some of our closest evolutionary cousins. The study from 2004, which can be accessed here, showed that macaque monkeys which were fed a diet of soy isoflavones over a 15-month period exhibited significant increases in aggressive and submissive behaviour, as well as drastical reductions in the time spent socialising with their fellow monkeys. In short, they became aggressive loners.

Our report seems to have struck a chord and soon Twitter was ablaze with discussion of soy monkeys and possible parallels with the behaviour of certain groups in the human world. Even Joe Rogan picked up on the report, commenting on his Instagram profile ‘This explains Twitter’. At the time of writing, the article is our most popular, and continues to rack up views.

People are talking about… aggressive soy monkeys

Our suggestions that the monkey study could have human implications was not meant to be a throw-away one, however. Although we acknowledged in the article that proving a relationship between changing social behaviour and changing diet is a tall order, it’s clear that the last 70-or-so years have seen massive changes to human lifestyles, behaviour and diets. Hypothesising links between these changes is far from absurd, even if the links are hard to prove definitively.

Catfish and Monkeys weren’t the only creatures affected by soy.

A study from last year showed that consumption of soybean oil caused weight gain and genetic dysregulation in mice, leading to potentially serious neurological problems, including dysfunction of the oxytocin system, which helps governs empathy and bonding. 

Could the massive increase in soybean oil consumption be responsible, at least in part, for the massive obesity epidemic in the US? And what about the neurological effects: could changing patterns of mental health and increasing social alienation and anxiety also be the result?

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