Can baths improve your health? Scientists find a surprisingly positive effect

One mainstay in millions of people's daily routines? Soaking in a hot bath.

Scientists say that, in addition to relaxing us and getting us squeaking clean, baths may be a vital tool capable of staving off cardiovascular diseases like heart disease, high blood pressure, and type 2 diabetes.

In a recent study, including 1,297 patients with type 2 diabetes, those who bathed more frequently had greater blood sugar control, lower blood pressure, and lower body mass indices. These are all metabolic risk factors when at unhealthy levels.

These latest findings were presented on Tuesday at the Annual Meeting of the European Association for the Study of Diabetes (EASD), and build on growing evidence on the therapeutic potential of heat therapy — regularly taking hot baths and tubs or using saunas. The study has not yet been published or peer-reviewed.

Past research suggests baths are also associated with a lower risk of dying from heart disease and stroke, along with having a lower body fat percentage.

Hisayuki Katsuyama is a co-author of the new study and a physician at Kohnodai Hospital in Ichikawa, Japan.

"The development of pharmacotherapy has contributed to a better quality of life and longer life span of patients with type 2 diabetes, but daily habits are still important for patients," Katsuyama tells Inverse. "Aside from diet and exercise, heat therapy might be promising."

To determine if baths make a meaningful difference, diabetes-wise, researchers recruited 1,297 patients with type 2 diabetes who regularly visited an outpatient hospital unit in Ichikawa, Japan between October 2018 and March 2019.

The group documented their bathing habits through questionnaires and noted the temperature of the water, frequency of bathing, and duration of each session. The patients were divided into three groups:

• Group one: four or more baths per week.
• Group two: between one and four baths per week.
• Group three: less than one bath per week.

The researchers also took blood samples and medical histories documenting the group's history of heart attack and stroke. They measured each person's height, weight, waist circumference, body mass index (BMI), blood pressure, cholesterol levels, and blood sugar.

On average, the group bathed 4.2 times a week for about 16 minutes at a time.

Across the board, people who bathed more often had lower body mass indexes (BMI), diastolic blood pressure, and glycated hemoglobin (a risk factor for type 2 diabetes).

Group one (with the highest bathing frequency) had an average glycated hemoglobin of 7.10 percent, group two was measured at 7.20 percent, and group three at 7.36 percent. Group one also had the lowest average BMI (25.5 kilograms per meter squared) followed by group two (26.0) and group three (26.7).

"These findings suggest that daily heat exposure by hot-tub bathing can contribute to improvements of glycemia, hypertension, and obesity, and thus, can be a therapeutic option for patients with type 2 diabetes," Katsuyama and the team write in their presentation materials.

Why does bathing seem to work? — Katsuyama expects patients may benefit from heat therapy similar to the way people benefit from exercise.

Previous animal studies suggested that heat stimulation could improve insulin sensitivity and enhance energy expenditure, which can also be observed during exercise, Katsuyama says.

Other researchers suggest bathing increases blood circulation, body temperature, and the production of nitric oxide in the body, which appear to confer the positive benefits.

The correlations between bathing and positive health outcomes are promising, but they don't yet point to cause and effect.

"This was a cross-sectional study," Katsuyama explains. "To build the evidence of the benefits of heat therapy, a prospective study will be needed."

LONGEVITY HACKS is a regular series from Inverse on the science-backed strategies to live better, healthier, and longer without medicine.

HOW THIS AFFECTS LONGEVITY — Researchers discover people with type 2 diabetes who bathe regularly have greater blood sugar control, lower blood pressure, and lower BMIs.

WHY IT'S A HACK — Although the evidence is preliminary, it suggests a regularly soaking in hot water may help people with type 2 diabetes better manage their disease.

SCIENCE IN ACTION — Heat therapy including bathing is a relatively promising and cheap intervention to help treat obesity and diabetes. Researchers suggest bathing a few times per week for at least 15 minutes at a time at 40 degrees Celsius, or 104 degrees Fahrenheit.

HACK SCORE OUT OF 10 — 💦💦💦💦💦💦 (6/10 water lovers)