Reference; https://mbp-japan.com/jijico/articles/32356
Modified and translated by CFJA
It seems not widely known, but activities that appear to warm the body, such as long baths, extended showers, spas(sauna), and hot yoga, actually consume physical energy.
Since many Japanese people feel that long baths are beneficial, the following Dr. Seino’s article is recommended.
“Is a long soak bad for your health? Are hot baths dangerous? What is the safe way to bathe?”
Table of Contents
Japanese People Who Believe Long Baths Are Good for the Body
Japan is home to hot springs scattered throughout the country. Most Japanese likely think, “Hot springs are the best way to relieve fatigue.” I am one of them. Enjoying the scenery while soaking in a hot spring and having a beer (or a cold drink) after sweating a lot feels exceptional. Although it’s a common part of everyday life, there are many people who get sick from spending too much time in hot springs. Listening to patients, they generally believe that longer baths are better for their health. Despite maintaining a regular lifestyle and getting enough sleep, those who still feel unwell may need to reconsider how they bathe. For over 40 years, I have been asking detailed questions about bathing habits at the first consultation and have noticed a pattern. Those who bathe for over 30 minutes daily tend to show symptoms of declining kidney function. Also, there seems to be a correlation with how long they have maintained this lifestyle. From my observations, people start to feel unwell after maintaining the same lifestyle for the following periods:
1. Daily 30-minute baths for about 23 years
2. Daily 45-minute baths for about 17 years
3. Daily 60-minute baths for about 13 years
4. Daily 90-minute baths for about 7 years
5. Daily 120-minute baths for about 3 years
There are slight differences between individuals with more or less physical strength, but generally, those with less strength do not take long baths, so the estimates are fairly accurate. Many have been taking long baths since their school days, but it is more common among working adults. Various reasons are cited for long baths, but stress relief is a common one. Assuming one started taking longer baths at around 23 years old after graduating from university, they might start feeling unwell around the age of 45. The initial symptoms typically include feeling sluggish and easily tired. Since baths tend to be refreshing, people gradually increase their bathing time. As symptoms progress, one might notice a heavy feeling in the back of the neck, reduced hearing, occasional tinnitus, and women might frequently develop cystitis. After eating, one might quickly feel full, leading to reduced food intake. Joint strength decreases, making ligament tears in the knee joints, fractures, and sprains more likely. If this article resonates with you, I advise immediately reducing your bath time to three minutes or less to focus on recovering your physical strength. Additionally, exercise during or after bathing increases the likelihood of sprains.
Are Hot Baths Good for Your Health?
Many Japanese believe that sweating in a hot bath is beneficial for the body, which leads to a preference for increasingly hotter baths. Kusatsu Onsen, ranked as the top destination for foreigners in 2024, is famous for its very hot water, ranging from 50°C to 90°C. To cool the water, a traditional technique called “Yumomi” is used, which involves stirring the water to cool it down. Initially, the water feels too hot to enter without adding a considerable amount of cold water, but it seems that people can get used to temperatures around 44°C to 46°C.
I have made house calls twice for individuals who collapsed in the bath and could not move. One person had spent two hours in a 44°C bath, and another had spent one hour in a 46°C bath. These are instances of what is known as “Yuatari,” heat stroke from the bath, and even for those with good physical strength, this seems to be the limit for temperature and duration.
Humans have polymodal receptors that transmit heat sensation. At temperatures of 44°C to 45°C, these receptors convey heat stimuli, so if someone regularly baths at these temperatures, it may disrupt the normal transmission of heat sensation, making it harder to feel the heat. While I wouldn’t recommend 43°C, considering that the typical setting for bath water heaters is 42°C, this seems to be a reasonable temperature. When you fill the tub, the water cools down due to exposure to the air, usually settling to around 40°C to 41°C after a while.
Is it really good for your body to warm up with long baths? 02