Saunas and cold plunges are often sold together as health habits, but the evidence behind them is quite different. Sauna use has a long-running population study linking it with better heart outcomes. Cold water has many small studies with mixed results, real safety risks, and one clear downside for people training for strength. This piece is part of our guide to stress management.
| Sauna | Cold water | |
|---|---|---|
| Strongest evidence | A 20-year study of 2,315 Finnish men | Many small studies, often of one sex |
| What it shows | More frequent use linked with lower heart-related and all-cause death | Some effects on body fat and insulin sensitivity; still debated |
| Main caution | An association, not proof of cause | Cold shock can be dangerous; may blunt strength training gains |
What does the research on saunas show?
The best-known study followed "a population-based sample of 2315 middle-aged (age range, 42-60 years) men from Eastern Finland" for a median of 20.7 years. Published in JAMA Internal Medicine in 2015, it compared men by how often they used a sauna.
Compared with men who used a sauna once a week, those who used it 4 to 7 times a week had a lower risk of sudden cardiac death after accounting for other heart risk factors, and similar patterns held for heart disease and death from any cause. The authors concluded that "Increased frequency of sauna bathing is associated with a reduced risk" of these outcomes.
The limits matter. The study was observational and included only men from one region where sauna use is part of everyday life. It shows a link, not that saunas cause the lower risk, and the authors themselves said "Further studies are warranted to establish the potential mechanism."
What does the research on cold water show?
It is suggestive but unsettled. A 2022 review in the International Journal of Circumpolar Health looked at 104 studies of voluntary cold water exposure, such as winter swimming and cold water immersion. It reported that cold water "seems to reduce and/or transform body adipose tissue" and to "reduce insulin resistance and improve insulin sensitivity."
The reviewers were cautious. Clear conclusions were "hampered by the fact that they were carried out in small groups", "often of one gender and with differences in exposure temperature and salt composition of the water", and "Whether winter swimmers as a group are naturally healthier is unclear." Their conclusion: "Some of the studies indicate that voluntary exposure to cold water has some beneficial health effects. However, without further conclusive studies, the topic will continue to be a subject of debate."
Do ice baths after a workout help or hurt?
If your goal is strength and muscle, regular ice baths straight after training may work against you. In a 2015 study in The Journal of Physiology, 21 active men strength-trained for 12 weeks, followed by either cold water immersion or an active cool-down. "Strength and muscle mass increased more in the ACT group than in the CWI group", meaning the active cool-down group gained more.
The authors concluded that "The use of CWI as a regular post-exercise recovery strategy should be reconsidered." If you enjoy cold water, keep it separate from your strength sessions, for example on rest days, rather than straight after training. For building strength, see the workout plan builder.
Is cold water immersion dangerous?
It can be. A 2017 review titled "Cold water immersion: kill or cure?" examines cold water "as a precursor to drowning, cardiac arrest and hypothermia", and describes it as something that "can be either good or bad, threat or treatment, depending on circumstance." It also notes that for some claims made about cold water, "the supporting data remain at the level of anecdotal speculation."
The first moments in cold water bring a gasp and fast breathing, which is most dangerous in open water. Sensible precautions:
- Never swim or plunge in open cold water alone.
- Get in slowly rather than jumping or diving in, and keep your head above water.
- Keep sessions short and get out if you start shivering hard or feel unwell.
- Warm up gradually afterwards with dry clothes and a warm drink.
Who should check with a doctor first?
Both heat and cold put real strain on the heart and circulation. Talk to a doctor before trying saunas or cold plunges if you have a heart condition, high or low blood pressure, are pregnant, or have been told to avoid strenuous exercise. Our articles on normal resting heart rate and low blood pressure cover related topics.
If you are drawn to cold water mainly to feel calmer, slower and lower-risk options have their own evidence: see breathwork for beginners and what actually happens in your body when you are stressed.
