That warm, fuzzy feeling you get from sitting in a sauna isn't in your imagination — and it may also help your heart. People with chronic heart failure who took saunas five times a week for three weeks improved their heart function and the amount of exercise they could do. Meanwhile, neurons that release the "happiness molecule" serotonin respond to increases in body temperature, perhaps explaining the sauna's pleasurable effects.
Heart failure occurs when the heart is unable to supply enough blood to the body, resulting in shortness of breath and difficulty exercising. Previous studies have hinted that saunas might boost health. To investigate, Takashi Ohori at the University of Toyama in Japan and colleagues asked 41 volunteers with heart failure to take 15-minute saunas five times per week, using a blanket for 30 minutes afterwards to keep their body temperature about 1°C higher than normal.
Sauna treatment increased the heart's ability to pump blood, and boosted the distance participants could walk in 6 minutes from 337 metres to 379 metres. The team also noticed improved function of the endothelium - the membrane lining the inside of the heart that releases factors controlling the diameter of blood vessels, and clotting.
The researchers also found more circulating endothelial progenitor cells - adult stem cells that can turn into endothelial cells (The American Journal of Cardiology, DOT: 10.1016/ Lamjcard.2011.08.014). In a separate study, the same group temporarily cut off blood supply to rats' hearts to mimic a heart attack, then gave them a sauna every day for four weeks. Later examination saw fewer of the changes to the heart's chambers that usually occur after heart attacks in rats not exposed to a sauna. In addition, the sauna rats showed increases in endothelial nitric oxide synthase, an enzyme that regulates blood pressure and the growth of new blood vessels (AJP: Heart and Circulatory Physiology, DOI: io.1152/ajpheartoolo3.2on).
"We think that repeated saunas trigger pathways that produce nitric oxide and other signalling molecules that eventually reduce resistance to the pumping capacity of the heart," says Tofy Mussivand at the University of Ottawa Heart Institute in Ontario, Canada, who was not involved in the research. Heating might have other benefits, says Christopher Lowry of the University of Colorado at Boulder. He has identified a group of serotonin-releasing neurons in a region of the brain called the dorsal raphe nucleus, which fire in response to increases in body temperature.
They seem to initiate cooling, but these neurons also project into a region of the brain that regulates mood, which may account for the pleasure of a sauna. Intriguingly, these same neurons feed into the sympathetic nervous system. Activation of the SNS boosts blood pressure and heart rate, but "by heating up the skin you inhibit the sympathetic nervous system, which is probably a good thing if you've had a heart attack", says Lowry. Mussivand cautions against people with heart failure rushing to the nearest spa, though. "Cardiologists currently don't recommend that heart failure patients should be exposed to heat, so this has to be done under medical supervision," he says.
SOURCE : NEW SCIENTIST MAGAZINE NOVEMBER 2011