Summary of Key Points
Biohackers have packaged the traditional practice of alternating hot and cold baths (such as Finnish saunas and Roman baths) as an anti-aging “contrast therapy,” claiming it can activate heat shock proteins, increase norepinephrine levels, and improve blood circulation. However, there are significant flaws in the scientific evidence: the effective dosages for cold water baths do not match the recommendations made, and the combined effects have not been verified. This is essentially a business that exploits scientific concepts; from the methodology to the equipment, there is a complete monetization chain. In China, due to cultural habits and public perception (such as the impact of saunas on fertility), such practices are not widely adopted. The truly reliable methods for anti-aging remain basic lifestyle choices like getting enough sleep, exercising regularly, and maintaining a healthy weight.
Traditional Baths as Anti-Aging Techniques? Just a New Scientific Labeling
Traditional hot and cold baths (e.g., jumping into an ice lake after a Finnish sauna or using a Japanese onsen) were originally intended for cleansing, relaxation, or social interaction. For example, Finns use saunas to relax, which they refer to as “sauna happiness.” Biohackers have attached a fancy scientific label to each step:
- Hot water baths/saunas = activation of “heat shock proteins” (which are said to repair cells);
- Cold water baths = increase in “norepinephrine” (which is said to burn fat and improve mood);
- Alternating baths = a “vascular pump effect” (improving blood circulation).
In essence, it’s still just alternating hot and cold water, but the narrative has shifted from being about comfort to promoting anti-aging, instantly elevating these ordinary bathing practices to something scientific.
Scientific Evidence: Inadequate Dosages and Unverified Combined Effects
While individual hot or cold baths do have some health benefits, they are far from being effective for anti-aging:
1. Sauna evidence: A Finnish cohort study showed that men who used saunas 4–7 times a week had a 40% lower overall mortality rate, but this was based on long-term adherence and did not include any combination with cold water baths.
2. Cold water bath data: In experiments, participants’ norepinephrine levels only increased by fivefold after soaking in 14°C water for one hour, while biohackers recommend soaking in 10–15°C water for 2–3 minutes—a 20-fold difference in duration! Using data from a one-hour experiment to claim benefits from a two-minute bath is like using a marathon result to prove that walking 100 meters can help with weight loss.
3. Combined effects unproven: No studies have tracked the impact of alternating saunas and cold water baths on lifespan; the so-called “synergistic anti-aging effect” is merely a hypothesis without any empirical evidence.
The Hoax of Scientific Claims
Biohackers use clever tactics:
- **Misappropriating the concept of “contrast therapy”: In rehabilitation medicine, contrast therapy is used to relieve muscle soreness after exercise (local alternation of hot and cold with precise timing), but biohackers apply it to the whole body for anti-aging purposes—same name, completely different application.
- Piecing together studies: For example, they cite research on winter swimming and saunas as evidence for the benefits of “cold bath + sauna,” or use a PNAS study on acute inflammation in just 24 people to claim anti-aging effects. They combine unrelated studies to create an illusion of scientific support.
The Business Behind the Anti-Aging Trend
There is a lucrative business behind this trend:
- High-end services: People like Hof in the Netherlands offer certified courses, apps, and books on breathing techniques combined with cold baths; Gary Brecka sells his own brand of cold water tubs and saunas.
- Celebrities driving demand: Influencers like Joe Rogan and Tim Ferriss promote these baths as part of their morning routines, attracting many followers and boosting sales.
- Equipment sales: Cold water tubs were virtually non-existent 10 years ago but generated $2.4 billion in global sales in 2024; infrared saunas have also become a “longevity gadget,” with prices inflated by 5–10 times. Companies repackage the idea of “feeling refreshed after bathing” as an anti-aging solution, turning ordinary tubs into high-end products.
Why Isn’t This Trend Popular in China?
In China, this trend has not caught on due to cultural and educational factors:
- Cultural habits: People prefer keeping warm; they may find winter swimming unusual and unattractive, and the potential health risks (like catching a cold) deter them from trying it.
- Public perception: Scientific studies in China warn that high temperatures (such as those in saunas) can affect male fertility. Therefore, saunas and cold baths are not promoted as anti-aging methods.
Final Warning: Don’t Be Fooled by the Anti-Aging Myth
Using saunas or cold baths alone can have some benefits (e.g., relaxation or invigoration), but there is no evidence to support their combined use for anti-aging. The truly reliable ways to stay healthy include getting enough sleep, exercising regularly, maintaining a healthy weight, not smoking, and controlling blood pressure and cholesterol levels. If you don’t follow these basic principles, soaking in hot and cold water won’t make much difference.
(Note: This article does not provide medical advice; for health-related issues, consult a professional doctor.)