Summary: For those who find it difficult to exercise, taking a hot bath can help improve inflammation and glucose levels, a new study reports.
Hot water treatment may help improve inflammation and blood sugar (glucose) levels in people who are unable to exercise, according to a new study. The findings are published ahead of print in the Journal of Applied Physiology.
Physical stress such as exercise can cause the short-term elevation of inflammatory markers. After exercise, the level of an inflammatory chemical (IL-6) rises. In a process called the inflammatory response, this activates the release of anti-inflammatory substances to combat unhealthily high levels of inflammation, known as chronic low grade inflammation. Recent research has shown that raising body temperature augments the inflammatory response, which has provided a rationale for identifying alternatives to exercise to reduce low-grade inflammation in the body. Previous studies have also found a connection between a spike in body temperature and nitric oxide production, a substance that aids blood flow and helps carry glucose throughout the body.
Researchers studied markers of inflammation and blood sugar and insulin levels in a group of sedentary, overweight men. The volunteers participated in both hot-water immersion and ambient room temperature (control) trials separated by at least three days. The researchers took blood samples before and after the participants rested in an 80-degree F room for 15 minutes. After the rest period, the participants either remained seated in the room or entered a hot-water bath for 60 minutes. In the hot water trial, the volunteers sat immersed up to their necks in 102-degree F water. The research team measured the men’s heart rate, blood pressure and body temperature every 15 minutes throughout both the control and immersion conditions. Blood samples were taken again two hours after each session.
The researchers found that a single hot-water immersion session causes the elevation of Il-6 levels in the blood and increased nitric oxide production, but did not change the expression of another protein (heat shock protein 72) suggested to be important for health. However, a two-week treatment period in which the men participated in daily hot-water baths showed a reduction of fasting blood sugar and insulin levels as well as improved low-grade inflammation at rest.
The men reported a level of discomfort during the hot water immersion trial, which could be due to the high temperature of the water or the length of time they were required to remain immersed. The researchers acknowledge that these conditions may make it difficult for people to commit to this type of alternative treatment. However, the positive results of decreased inflammation and improved insulin sensitivity suggest that hot-water immersion may “improve aspects of the inflammatory profile and enhance glucose metabolism in sedentary, overweight males and might have implications for improving metabolic health in populations unable to meet the current physical activity recommendations,” the researchers wrote.
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Original Research: Abstract for “The acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults” by Sven P. Hoekstra, Nicolette C. Bishop, Steve H. Faulkner, Stephen J. Bailey, and Christof Andreas Leicht in Journal of Applied Physiology. Published October 18 2018.
The acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults
Regular exercise-induced acute inflammatory responses are suggested to improve the inflammatory profile and insulin sensitivity. As body temperature elevations partly mediate this response, passive heating might be a viable tool to improve the inflammatory profile. This study investigated the acute, and chronic effects of hot water immersion on inflammatory and metabolic markers. Ten sedentary, overweight males (BMI: 31.0±4.2 kg/m2) were immersed in water set at 39°C for 1 h (HWI) or rested for 1 h at ambient temperature (AMB). Venous blood was obtained prior to, immediately post and 2 h post-session for assessment of monocyte intracellular heat shock protein 72 (iHsp72) and plasma concentrations of extracelullar heat shock protein 72 (eHsp72), interleukin-6 (IL-6), fasting glucose, insulin and nitrite. Thereafter, participants underwent a 2-week intervention period, consisting of 10 hot water immersion sessions (INT). Eight BMI-matched participants (BMI: 30.0±2.5 kg/m2) were included as control (CON). Plasma IL-6 and nitrite concentrations were higher immediately following HWI compared to AMB (IL-6 p<0.001, HWI: 1.37±0.94 to 2.51±1.49 pg/ml; nitrite p=0.04, HWI: 271±52 to 391±72 nM), while iHsp72 expression was unchanged (p=0.57). In contrast to resting iHsp72 expression (p=0.59), fasting glucose (p=0.04, INT: 4.44±0.93 to 3.98±0.98 mmol/l), insulin (p=0.04, INT: 68.1±44.6 to 55.0±29.9 pmol/l) and eHsp72 (p=0.03, INT: 17±41% reduction) concentrations were lowered after INT compared to CON. HWI induced an acute inflammatory response and increased nitric oxide bioavailability. The reductions in fasting glucose and insulin concentrations following the chronic intervention suggest that hot water immersion may serve as a tool to improve glucose metabolism.