Five Theories on the Mechanisms of Acupuncture: How it Works from a Western Physiological Perspective

Thus, as scientific inquiry and research studies steadily increase, so too have the mechanisms of acupuncture become elucidated. What has been found is that acupuncture has three main effects: it restores homeostasis, it reduces inflammation, and it relieves pain.

By Cody McBeath

​As acupuncture has emerged into mainstream medicine as a treatment option for a wide variety of conditions and disorders, it has garnered a great deal of attention from the western medical community. Curiosity, investigation, and scientific inquiry into this ancient modality has steadily increased ever since New York Times reporter James Reston received pain relief after an appendectomy during President Nixon’s visit to China in the early 1970’s.                            (https://www.nytimes.com/1971/07/26/archives/now-about-my-operation-in-peking-now-let-me-tell-you-about-my.html). Since this time, many theories have been proposed as to the exact physiological mechanisms behind acupuncture’s efficacy. Thus, as scientific inquiry and research studies steadily increase, so too have the mechanisms of acupuncture become elucidated. What has been found is that acupuncture has three main effects: it restores homeostasis, it reduces inflammation, and it relieves pain. The scope of this article is to look at five specific theories that have been proposed and review their findings on acupuncture’s mechanism of action in brief detail.
 
1. Neurotransmitter & Endorphin Theory
 
Acupuncture needle insertion stimulates the release of specific neurotransmitters, such as serotonin, norepinephrine & GABA, and endogenous opioids, such as endorphins and enkephalins.  It has been proposed that the release of these neurotransmitters and endogenous opioids lead to the analgesic, pain reducing, mood improving qualities often experienced during acupuncture sessions. Studies have shown that the use of low frequency electro-acupuncture leads to an increased release of endorphins and enkephalins that act to block our perception of pain and relieve stress. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC442119/)
 
2. Gate Control Theory
 
Acupuncture regulates our pain physiology system. We have two types of pain receptors (A- fibers & C- fibers) that carry pain signals to our spinal cord and central nervous system. Needle stimulation may inhibit the transmission of pain signals from A- fibers during acupuncture treatment. The basis of this theory is rooted in competition of pain signaling to the brain. Thus, when acupuncture activates receptors at a distal point on the body, these other pain- signaling mechanisms are “gated out” and unable to elicit a pain response.
 
3. Circulatory/Blood Chemistry Theory

Acupuncture affects the circulatory system by dilating the blood vessels through nitric oxide release, ultimately increasing blood flow and oxygenation to local tissues and muscles. The insertion of needles creates a “micro-trauma” to the body that increases the amount and migration of white blood cells to the area that helps improve immune function, removes metabolic waste, and reduces inflammation in the local area. As blood flow is increased, more nutrients and inflammatory mediators are circulating which leads to a faster healing response time after injury.
 
4. Growth Control Theory
 
It is believed that acupuncture points have a high correlation to areas on the body known as organizing centers that form during our embryonic development. Further, it has been shown that acupuncture points are areas where there is a high level of electrical conductivity as opposed to adjacent tissue. So, by stimulating an acupuncture needle we are regulating this growth control system of the body that is responsible for cellular adaptation and tissue growth and regeneration.                          (https://www.ncbi.nlm.nih.gov/pubmed/11388686)
 
5. Connective Tissue Model
 
While the previous theories represented biological models of acupuncture, this theory presents a bio-mechanical mechanism of acupuncture. This model looks at the interaction between the muscles, connective tissue, and fascia, in response to the acupuncture needle. By stimulating what are known as trigger points (taut bands of connective tissue) or the muscle spindle (motor nerve innervation into muscle belly), acupuncture can release these tight bands of tissue and re-establish proprioceptive communication between the muscle and the central nervous system. When the strands of fascia wrap around the needle, leading to what’s called tissue-needle coupling, the body elicits a response to allow these areas to relax. This communication between the muscle spindle, or motor point, and the central nervous system assists in resetting muscle tone and increasing muscle strength.

The research into the mechanisms of acupuncture show us that there isn't one unifying theory as to why it works. Rather, the efficacy of acupuncture is seen when we assess it from a panoramic lens. The stimulus of an acupuncture needle signals various responses from the body, as the circulatory, endocrine, muscular, and nervous systems all seem to be involved. Due to the physiological response from these multiple systems, we can begin to explain how and why acupuncture can be effective for such a wide variety of medical conditions. As research into acupuncture evolves, a greater clarity will begin to emerge as to the exact "how" and "why" that underlies acupuncture's magic.