Thermal therapy has been around quite some time—from Native American sweat lodges to Turkish steam baths to the Finnish dry sauna, it's a tradition from the BC days. Yet the health benefits remain controversial. So what's the true story about risks versus rewards of sauna, backed by science?

Sauna Myths
Sauna is a great detox tool. Despite modest findings in small preliminary studies, no large-scale studies have proven this claim. One Japanese study found that people who took a sauna released 12 trace elements—but one was zinc, an essential mineral for healthy immunity. So even if you sweat out the bad stuff, beneficial minerals could escape too.

Saunas will make me infertile. While sperm production slows when the scrotum heats up, everything goes right back to normal as soon as the body cools down.

Saunas will help me lose weight. Sadly, sweating out a pint of fluid at a time will not help you lose pounds permanently.

Sauna Truths
Saunas might help fight colds and flu. Some older studies have found a connection between sauna and cold relief—researchers link the improvements to sauna's benefits for drainage. Others believe sauna can actually prevent colds or flu by heating the air you inhale, killing any virus before it could make you sick. More research is needed to understand how it all works.

Some saunas are better than others. The far-infrared sauna (FIRS) uses radiant heaters similar to those found in neonatal incubators. Radiant heat penetrates skin more deeply and produces more sweat at a lower temperature (140 degrees) than in a traditional convection-style sauna (185 degrees)—so it's more comfortable.

Sauna can be good for people with heart problems. Surprisingly, one group traditionally advised against sauna—heart patients—should take another look. A Canadian review of nine studies on FIRS found it helped regulate heart rhythms, treat congestive heart failure, lower markers for inflammation, and reduce systolic blood pressure by up to 15 points. (Just check with your doctor—who knows your personal health—before trying.)

You can (sometimes) swap your workout for a sauna. Your circulatory system works hard to regulate your internal temperature—sweating, dilating blood vessels, increasing heart rate. And those are many of the cardiovascular effects you'd get from a brisk walk. If you're sidelined by osteoarthritis or breathing problems, FIRS may help you get a cardio "workout" to help your heart and lungs stay fit.

Sauna's relaxation can be powerful. In one study, mildly depressed adults were treated with FIRS for 15 minutes and then put to bed with a warm blanket for another 30 minutes. After doing this treatment five times a week for four weeks, they experienced significantly less pain, better appetites, and greater relaxation than patients who'd not been treated.

Safe Sauna
Check with your doctor before taking a sauna, especially if you have abnormal heart rhythms, advanced heart disease, heart valve disease, poorly controlled blood pressure, or unstable angina. And always be smart:

• Skip the alcohol—it slows the blood flow and cancels out any benefits to your circulation.
• Keep it to less than 20 minutes (go shorter if you're over 65).
• Drink 16 to 32 ounces of water to rehydrate.
• Transition to cooler temperatures as gradually as possible, especially if you have high blood pressure. (Skip the cool pool afterward.)
• Bring a friend. And. if you start to feel woozy or uncomfortable in any way, just get out—above all, sauna should feel good.