The Emerging Science of Saunas: New Study Review

Changes in Sperm, Release of Harmful Metals, 65% RR in MCI

September 14, 2021

Neuro Athletes, 

The use of saunas has exploded in popularity this year. The market was valued at 420 Million USD in 2020 and is projected to reach 480 Million USD by 2025, at a CAGR of 2.1% during the forecast period.

In a recent review, ‘Sauna Use as a Lifestyle Practice to Extend Healthspan’, Rhonda Patrick summarises many fascinating studies on the use of saunas that we ave talked about many times in the Neuro Athletics Newsletter.

Here, you can see the psychological response to heat stress eliciting a rapid, robust response that affects primarily the skin and cardiovascular system.

And this diagram which shows that heat stress from saunas in particular, robustly increases intracellular levels of HSPs (heat shock proteins) in humans.

So what exactly is driving all this interest in sauna use? The short answer is that saunas increase longevity and decrease cognitive decline. The cost of owning your own sauna can range from $5000-$12000 but the positive effects of this far outweighs the investment.

The mere fact that we can step into a box and heat our bodies up to potentially mmic the effects of cardiovascular fitness, increase blood flow, decrease inflammation by way of Interleukin-6 (IL-6) and other pathways is just one of the reasons why people are affording to buy this hot box.

One thing I talk about profoundly is sleep. I have spent the better half of my career focused on the fundamentals of sleep physiology and how it relates to performance and longevity. I mention quite often that growth hormone is secreted in the early stages of sleep during deep SWS sleep and this hormone is specifically involved in protein synthesis, it also stimulates growth, cell reproduction, and cell regeneration. Well, it appears that entering environments that is very hot, like in a sauna, for very short periods of time anywhere from 20-30 minutes at a temperature of 80-100 degrees celsius or 175-210 degrees Fahrenheit has been shown to increase growth hormone release 16 fold. 

Amongst the benefits of sauna use also lies some concerns. Let’s dive into the literature.

  1. Male fertility - CONCERN 🛑

Heat exposure has notable, but reversible, effects on male sperm and fertility measures. In a study involving 10 healthy men who underwent two 15-minute sauna sessions at 80 °C to 90 °C (176 °F to 194 °F) every week for 3 months, the men experienced reduced sperm counts and motility. These measures returned to normal, however, within 6 months of sauna use cessation (Garolla et al., 2013).

  1. Release of Harmful Metals - BENEFIT ✅

Sweating also facilitates higher excretion of some heavy metals including aluminum (3.75-fold), cadmium (25-fold), cobalt (7-fold), and lead (17-fold), compared to elimination via urine (Genuis et al., 2011). Repeated sauna use acclimates the body to heat and optimizes the body's response to future exposures, likely due to a biological phenomenon known as hormesis, a compensatory defense response following exposure to a mild stressor that is disproportionate to the magnitude of the stressor. 

  1. Risk Reduction in Mild Cognitive Impairment - BENEFIT ✅

What to read

  1. Sauna use as a lifestyle practice to extend healthspan (LINK)

  2. Effectiveness and safety of Bifidobacterium and berberine in human hyperglycemia and their regulatory effect on the gut microbiota: a multi-center, double-blind, randomized, parallel-controlled study (LINK)

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