That warm, fuzzy feeling you get from sitting in a sauna isn鈥檛 in your imagination 鈥� 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 鈥渉appiness molecule鈥� serotonin respond to increases in body temperature, perhaps explaining the sauna鈥檚 pleasurable effects.
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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, 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鈥壜癈 higher than normal.
Sauna treatment increased the heart鈥檚 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 鈥� 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 鈥� adult stem cells that can turn into endothelial cells (The American Journal of Cardiology, ).
In a separate study, the same group temporarily cut off blood supply to rats鈥� 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鈥檚 chambers that usually occur after heart attacks in rats 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, ).
鈥淲e 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,鈥� says at the University of Ottawa Heart Institute in Ontario, Canada, who was not involved in the research.
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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 鈥渂y heating up the skin you inhibit the sympathetic nervous system, which is probably a good thing if you鈥檝e had a heart attack鈥�, says Lowry.
Mussivand cautions against people with heart failure rushing to the nearest spa, though. 鈥淐ardiologists currently don鈥檛 recommend that heart failure patients should be exposed to heat, so this has to be done under medical supervision,鈥� he says.
When this article was first posted, in the paragraph beginning 鈥淚n a separate study鈥︹��, the second sentence incorrectly read 鈥淟ater examination saw fewer of the changes to the heart鈥檚 chambers that usually occur after heart attacks in rats not exposed to a sauna.鈥�
