Sauna and cold plunge claims face the research
The science and hype behind heat & cold therapies.
Podcasts and ads promise a lot from a hot room and a cold tub. We trace each promise back to the study it came from and show you how far it drifted on the way.
96°H · Hot air
“Infrared sauna sweat is 20% toxins, where a normal sauna's is only 3%.”
Read the verdict →Each ladle reads another claim
The board
Every claim falls somewhere between solid and hot air
Every dot is a claim at its reading on the dial, and the ones about cold hang below the scale. Hover or tap a dot to read the claim, then open it to see the studies behind the number.
- Solid 1
- Likely 7
- Unsettled 16
- Stretched 18
- Hot air 13
TLDR
The findings to act on
Stories
These stories rebuild the studies behind the headlines
Story · Heat
A scientific look at Bryan Johnson's sauna experiment.
Bryan Johnson spent a year and a half measuring what a daily sauna does to his body, and he posted the results as he went. We laid his tests out on one calendar and read them the way a scientist would, to see what one carefully measured person can show.
9 min readStart scrolling →
Story · Heat and cold
Watch a sauna and a lake dip work on a body minute by minute.
Sixteen adults sat through two rounds at 85°C in a lakeside sauna in Wales on two separate days. On one of those days, each break opened with a 90-second lake dip. Scroll through the session and watch their core temperature and heart rate move.
7 min readStart scrolling →
Story · Heat
Watch the verbs heat up as a sauna study becomes news.
The 2015 Finnish sauna paper found frequent sauna use was associated with fewer deaths. Scroll through the week of coverage that followed and watch each headline climb a ladder of verbs toward a promise.
7 min readStart scrolling →
Story · Cold
Most cold plunge rules come from studies that kept people cold for hours.
Cold plunge advice keeps repeating a few famous numbers. We traced each one back to its study, then plotted every study by how cold it got and how long each session lasted.
8 min readStart scrolling →
Solid ground
The research backs these claims best
How we rate
Four questions set every reading on the dial
Each question can add up to 25 degrees of hype. A claim reads near zero when strong human trials keep finding exactly what it says.
Read how we rate claims →01 · Evidence
What kind of human evidence exists?
02 · Consistency
Have other studies found the same thing?
03 · Magnitude
Does the claim match the size of the effect?
04 · Dose
Does the studied dose match how people use it?
- claims on the dial
- 55
- studies explained
- 56
- interactive stories
- 5
- sources cited
- 445
From our sister magazine
Sauna Monthly reviews the saunas and plunge tubs worth buying
When you're ready to build a sauna or buy a tub, our sister magazine compares prices and specs across every brand it covers.
Sauna Monthly · Shop
These outdoor saunas reach Finnish temperatures
Sauna Monthly compares barrels and cabins that run hot-rock heaters.
Sauna Monthly · Guide
These cold plunge tubs are worth buying
Sauna Monthly picks its favorites and names the spec that decides between them.
Nootka Saunas
Nootka 8ft Barrel Sauna
Almost Heaven
Almost Heaven Salem 2-Person Barrel
Ice Barrel
Ice Barrel 500
Sun Home Saunas