There is a new fad circulating the internet.  This fad is the cold shower movement.  The cold shower movement is accompanied by claims that cold morning showers will help bring you to your peak performance by releasing all the right neurotransmitters and suppressing all of the bad ones.  They claim cold showers will cure depression and unleash your inner genius as if cold showers were the drug from the 2011 thriller limitless.

Lets take a pragmatic approach by looking at the facts that we can back up with real science based studies:

The Good: Improved Circulation

To say circulation is improved by cold showers is a bit misleading.  Cold showers in fact cause the constriction of blood vessels.  Think of this like squeezing a dirty sponge.  When the sponge is squeezed, the water exits the sponge and takes the dirt with it.  When you release the sponge into clean water, the sponge soaks up the fresh water.

In the case of cold showers, the sponge is our cardiovascular system near the surface of our body, and the water is our blood.  The dirt is analogous to by-products like lactic acid and carbon dioxide.

It is important to release our cardiovascular sponge into clean water by warming the water up so our blood can get flowing and resupply our tissues with a fresh supply.

The Bad: Increased Cortisol

Many articles will claim cold showers will reduce cortisol levels.  This simply isn’t true.  Immersion in cold water has shown to increase cortisol levels.  Cortisol is a stress hormone that can take a real toll on the body if cortisol levels are elevated over an extended period of time.  Habitually taking cold showers every morning may in fact cause chronic elevation in cortisol levels.  Side effects of high cortisol levels include poor sleep, compromised immune system, increased fat gains, and breakdown of muscle mass.

The Myth: Increased Testosterone

Increased testosterone is a commonly cited benefit of cold showers.  But where is the evidence?  In fact, there was a study conducted that measured the testosterone levels of men before exercise, between exercise and cold water stimulation, and then after cold water stimulation.  It was shown that the exercise increased testosterone levels, but the cold water stimulation did not exhibit similar effects.  Cold water stimulation in fact decreased the testosterone levels by 10%.

Conclusion

Engineering is the art of trade-offs and lifestyle engineering is no different.  We must balance the pros and cons to fit our application.  Then, we must test our design, improve our design, and repeat.  See how cold showers effect your life.  Do you notice improved skin quality, lack of depression, or increased cortisol?  Share your experience in the comments below.