Science / Fertility

Sauna, cooling & sperm health.

A small human sauna study, a review of cooling research and one personal experiment. Here is what each can tell us.

The sauna study, at a glance.

A 2013 study followed semen measures during repeated sauna use and after it stopped.

10

men in the study

Normal semen measures at the start.

3

months of sauna

Two sessions a week. Sperm count and motility fell.

6

months after stopping

Sperm count and motility returned to baseline.

Garolla et al., 2013 · Human Reproduction

No pregnancy outcomes or Arctic Nut products were tested.

What it cannot establish

A small study of men with normal starting measures does not establish an individual’s fertility risk or a safe sauna schedule.

What about cooling?

A 2013 systematic review of eight articles found insufficient evidence for firm conclusions about scrotal cooling and male fertility. The authors called for better randomized trials. That uncertainty remains important when interpreting a personal experiment or a product claim.

Nikolopoulos et al., 2013 · Systematic review

General education, not personal medical advice. The studies linked here have not tested Arctic Nut products.

Personal experiment · One participant

Bryan Johnson’s sauna experiment.

Johnson’s published table reports sperm motility before sauna, after 27 sessions with ice, and after 15 sessions without ice. It records one person’s experience, not a controlled clinical trial.

Bryan Johnson’s protocol · Original results table

Reported sperm motility

Before saunaReported pre-sauna average
46%
Sauna with iceAfter 27 sessions
53%
Sauna without iceAfter 15 sessions
23%

Observed percentages, not relative changes. Transcribed from the protocol’s published table, accessed 20 September 2026.

Self-reported observations in one person cannot isolate the effect of cooling or establish protection of sperm motility, pregnancy outcomes or safety. This was not a test of Arctic Nut, and Johnson has not endorsed our product.

The Arctic Nut concept

Where the brief fits.

The Cooling Brief provides a padded pocket for removable packs. Its design explores the question of cooling during sauna.

Johnson’s personal method used packs between clothing layers. It does not establish a safe sauna temperature, wear duration or cooling performance for Arctic Nut. Sperm protection has not been demonstrated.

If fertility is a concern, discuss heat exposure with a qualified clinician. Cooling is not a reason to extend a sauna session.

Explore the Cooling Brief