Is your shower cold enough?
A man by the name of Wim Hof has been exploring how freezing water and extreme environmental conditions can serve to awaken our lost evolutionary strength.
As Wim is located in the north of Poland, my own experiments are nowhere near as extreme as his, but I feel as though the benefits of simply engaging in a moderate amount of willful environmental disturbance are compelling nonetheless.
You essentially have the ability to manipulate your environment 100% to your liking. Physiologically, this had made you, well, weak. Extreme environmental conditions are what modifies gene expression - this elicits physiological adaptations that make you better equipped to handle difficult conditions.
But it's much more than that. Cold water shunts blood to your internal organs, thereby bathing your immune system with nutrient rich blood and improving your digestion. Approximately 80% of your immune system resides in your gastrointestinal tract.
The reason for this is that the G.I. tract is actually outside of your body - meaning it interacts directly with the outside world. Until the nutrients you have consumed are broken down and absorbed, they're still considered to be outside your body, and your immune system is your last line of defense against any and all pathogens attempting to enter circulation.
In addition to this, some people will claim that cold showers or cold plunges function to boost testosterone levels. Although it's not out of the realm of possibility, my belief is that cold does not "boost" T as much as it simply allows for more favorable conditions for its production.
In the context of improving fertility, this study showed that hot baths/showers functioned as an effective contraceptive, and the cessation of hot baths/showers increased sperm count by 491% - essential knowledge for young men trying to conceive.
But, as my primary interests lie with proper lifestyle and optimizing normal physiological function, I will simply echo Dr. Mercola's statement that,
"a robust immune system is your number one defense system against ALL disease."
If cold showers/plunges can improve Testosterone calculus, reduce depression, and improve circulation as well as skin and hair health, in addition to strengthening the immune system thereby improving gut health, I see every reason to include cold water therapy as part of a regular routine.