Whole Body Heat Therapy - Guest Blog by Dr. Scott Gerson
Therasage would like to thank Dr. Scott Gerson, Director of The Gerson Institute of Ayurvedic Medicine, for his time, experience, and thoughtful contributions to educating us all on Ayurvedic Medicine and Swedana. Blessings and good health to Dr. Gerson and his team at GIAM.
Our amazing full spectrum infrared sauna format adheres to the ayurvedic principles of not over heating your brain. To learn more about swedana and the use of whole-body heating please enjoy Dr. Gerson's article below.
Swedana or Sarvanga Swedana
(Ayurvedic Heat Therapy or Whole-Body Heat Therapy)
By Dr. Scott Gerson
Sarvanga Swedana (whole-body heating) is a treatment modality common in Ayurvedic clinical practice. Practiced either as a purvakarma (preparatory component) to Panchakarma (five detoxification procedures) or as an independent intervention, Swedana is an important part of Ayurvedic detoxification and rejuvenation treatments. The procedure can produce between 0.4 to 2.0 liters of sweat per treatment. Since water is the main content of sweat, many water-soluble waste products can be eliminated through swedana.
And when swedana is administered directly following herbalized whole-body oil massage (snigdhaswedana), many lipid-soluble substances can be exchanged through the skin, though in minute quantities. To understand more about the mode of action of any therapy which involves sweat, a thorough knowledge of thermal homeostasis mechanism in human body is very essential. Its really not that complicated.
Thermoregulation is an important aspect of human homeostasis. Most body heat is generated by metabolic processes in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles. Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid. This is possible only through the mechanism of thermoregulation. So the skin plays an important role in homeostasis.
It does this by reacting differently to hot and cold conditions so that the inner body temperature remains more or less constant. Arterial vasodilatation and sweating are the primary modes by which humans attempt to lose excess body heat. The mechanism of thermoregulation in hot and cold environments are described below.
In hot conditions
- Vasodilatation occurs allowing increased blood flow through the arteries. This redirects blood into the superficial capillaries in the skin increasing heat loss by convection and conduction.
- Eccrine sweat glands under the skin secrete sweat which travels up the sweat duct, through the sweat pore and open directly on the surface of the skin. This causes heat loss via evaporative cooling. When environmental temperature is above core body temperature, sweating is the only physiological way for humans to lose heat.
In cold conditions
- Sweat production being stopped.
- Arterioles carrying blood to superficial capillaries under the surface of the skin constrict, thereby redirecting blood away from the skin and towards the warmer core of the body.
- Muscles can also receive messages from the thermo-regulatory center of the brain to cause shivering. This increases heat production.
These are the physiological events taking place under heat and cold stimulus. In swedana, we are inducing sweating by the application of heat. Sweating is achieved by cutaneous vasodilatation which activates the sweat glands to secrete sweat. There are two types of sweat glands: eccrine and apocrine. Apocrine sweat glands are mostly limited to the armpits and groin area and do not play a significant role in cooling, although (as we all know) they do produce sweat. Eccrine sweat glands are distributed all over the body, are about 2-3 million in number, and are the primary organ responsible for thermoregulation (cooling) in humans.
So now lets get a little more technical to better understand the mechanisms of thermoregulation.
Increases in internal core and/or skin temperatures are sensed by an area of the hypothalamus in the brain known as the preoptic nucleus. The preoptic nucleus then generates nerve impulses back to the skin to create cutaneous vasodilation, sweating and increased heat dissipation which corrects the body temperature. The influence of internal core temperature is several times that of skin temperature in the control of these effectors.
Resting skin blood flow in thermoneutral environments is approximately 250 mL/min, which results in a heat dissipation of approximately 80 to 90 kcal/h, about the level of resting metabolic heat production.
With hyperthermia in humans, skin blood flow can increase to as much as 6 to 8 L/min (that’s a 3000% increase!) or 60% of cardiac output. The large increases in skin blood flow are mediated primarily (80%-90%) by activation--via the preoptic nucleus of the hypothalamus--of sympathetic vasodilator nerves in the skin. This sympathetic active vasodilator system in humans is not tonically active in normothermia and is only activated during increases in internal temperature, such as those that occur during exercise, environmental heat exposure, or therapeutic sauna.
Although heat therapies are generally safe for the vast majority of people, it still must be regarded as a para-medical treatment and administered with due caution. Because of its dramatic effects on cardiac output, I carefully evaluate every patient prior to Sarvanga Swedana. Heat therapies are contraindicated in cases where hemodynamic functions are altered owing to some pre-existing pathologies. The most common examples are hypothyroidism, recent myocardial infarction, unstable angina, cerebral infarct, stroke, cardiomyopathy, congestive heart disease, bundle branch block, and moderate to severe anemia.
The value of heat therapies for detoxification is both under-appreciated and under-utilized. Our environment is much more toxic than ever before. Between petroleum-like compounds such as gasoline, diesel and jet fuels to flame retardants to phthalates and PCBs, glyphosate, and methane and many more, we’re exposed thousands of more toxins than our grandparents. Chemicals are big business, an industry valued at $750 billion, and as of 2015, there were 85,000 “legal” chemicals used in the U.S.
From the Ayurvedic detoxification perspective, the most interesting and valuable effects of sauna therapy occur after the therapy stops and the patient emerges from the cabinet into the room temperature environment. When the stimulus, i.e. the heating, is withdrawn, the body will try to keep the thermal homeostasis by quickly stopping cutaneous vasodilatation and causing cutaneous vasoconstriction. The net effect is a great increase in the blood flow away from the skin and towards the internal organs-- particularly to the GIT (gastrointestinal tract). In the GIT a process known as retrograde intestinal absorption occurs, whereby substances in the blood can re-enter the small intestines and eventually be excreted in the stool. This route of excretion for many lipophilic toxic substances in the blood can be substantially enhanced by increasing the lipophilicity of the GIT by preceding sauna therapy (swedana) with the administration of ghee or other oil (snehana). Retrograde absorption is known to occur via both passive diffusion and active transport mechanisms.
Some toxic substances are more readily excreted through sweat (i.e., arsenic, cadmium, lead, mercury, phytates, and bisphenol A). But others are not able to be excreted in that way. So, apart from causing the excretion of some substances through the skin, swedana (heat treatment) also causes many unwanted materials to secrete from the blood into the GIT, so that they can be eliminated out by the main sodhana (purification) procedures (i.e. laxative and enema therapies).
In short, we can consider swedana as a procedure of two-phase elimination, i.e., during the heating procedure itself elimination is through the skin and after the procedure the elimination is from the blood into the GIT via retrograde intestinal absorption.
Steam sauna presents a heat load of 300-600 W/m2 of skin surface area. This increases mean skin temperature to 40-41 degrees C, causes strong heat sensations and starts thermoregulatory mechanisms. Evaporative heat transfer by sweating is the only effective mechanism for dissipating heat from the body in sauna therapy.
Difference between Steam and Infrared Sauna (IR): Why IR is Superior
Heat treatment with steam is equivalent to IR with respect to inducing the initial vasodilatation which is mediated via local neuropeptide release from cutaneous sensory nerves. However, this local component is estimated to account for only approximately 20% of the total vasodilatation and sweating effect. The other 80% is due to visceral and whole-body heating which is sensed by the hypothalamus as warmed blood permeates it. Because IR penetrates further into the body (up to 30 mm) as compared to steam heat which is effective only to a depth of 1-2 mm, far more tissue mass and blood is heated far more quickly. Thus, the hypothalamus-mediated vasodilatation occurs more robustly with IR. With infrared sauna, we are heating the body more deeply, heating more body mass and raising the core temperature of the body, rather than just heating the skin with hot steam.
A 30-minute stay in an infrared sauna with a temperature of 52⁰ C (125⁰ F) increases core temperature by about 0.9⁰ C (1.6⁰ F) in adults. The body cannot compensate for the heat load of IR through local mechanisms and the temperature of viscera begins to increase. The rate of sweating with IR has been measured to be from 0.5-0.9 kg/h (1-2 lb/hr!) and represents a heat loss of about 200 W/m2.
With either type of either sauna, you will experience deep relaxation, reduced muscle soreness, and relief from body aches. More importantly, heat treatment promotes detoxification through the mechanisms described above. Also, the metabolic processes which produce perspiration burns some calories, although the quantity of calories burned is debatable and is dependent upon the individual. Most of the weight lost in a sauna is water loss and is re-gained upon re-hydrating. However, without a doubt sauna can be an important part of a healthy weight loss program. Finally, lets acknowledge a statement attributed to Hippocrates observed nearly 2000 years ago “Give me the power to create a fever and I can cure any disease.” While certainly an exaggeration, it points to the health benefits of deliberately and carefully increasing the body heat.
- Melody Besner