While contorting my body into a spinal twist at a recent yoga class I couldn't help but groan when the teacher remarked that the pose helps to "release toxins from the body." I've heard this dubious claim in other yoga classes, especially hot yoga, where teachers blithely state that the heat helps you to sweat out toxins.
But those claims have no scientific or medical basis according to Dr. Pam Peake, a Fellow of the American College of Sports Medicine and its national spokesperson. "Detox is a hot issue," Peake told CBS News. "It needs to be corrected in a serious sort of way."
The idea that twisting in yoga can detox the body was popularized by master yoga teacher B.K.S. Iyengar, who touted the "squeeze and soak" theory. According to Iyengar, twisting the spine compresses muscles and organs, which blocks the flow of blood. When you release the pose, blood flows back into those areas bringing with it nutrients and improving circulation.
But the theory has no scientific evidence to back it up.
"Second by second, nanosecond by nanosecond, the human body is detoxing," Peake said. "It's part of what it does, it never stops doing that. The squeeze and soak theory is very inaccurate and the assumption that we're somehow beneficially increasing this detoxification process is not accurate, either."
So how does the body really detox?
Peake said that detoxification takes place naturally in the body through the lungs, the digestive system, the kidneys and the liver.
The lungs remove gases and volatile chemicals when you exhale. As food passes through the gastrointestinal tract, it either gets broken down into smaller molecules for use in the body or passes through the large intestine as waste. The liver and the kidneys also process toxins and excrete them as urine or stool.
"All physical activity -- not just yoga -- increases the motility and mobility of the organs to perform their normal detoxifying functions," Peake said.
And the notion of sweating out toxins?
It is true that some toxins can dissolve in sweat, but only a trivial amount; Peake said 1 percent of toxins at most get removed from the body through sweat.
According to an education site sponsored by Texas A&M University and the National Institute of Environmental Health Sciences, "it is a common belief that stimulating sweat with intense exercise or heat will help clean the body of toxins. But there is not much medical evidence that this is practical. And, excess sweating can cause loss of water, which may be more hazardous than the toxins."
Peake noted that activities like hot yoga and drinking more water do help support the body's natural detoxification process.
"Yoga and all physical movement support the natural process of detoxification in the human body," Peake said. "Detox is happening anyway. You and I are talking and detoxing away. Let's not insult the body, it's doing a nice job."