The Yin & Yang of Acupuncture:
A New Theory of Acupuncture
and Its Relationship to Inflammation
There is no definitive word on the physiologic effects of acupuncture. The treatment principles laid down in the first recorded texts from 2500 years ago conformed to an ancient Chinese view of the world in which doctors envisioned a body with a network of canals, similar to the canals constructed by the Emperor's corps of engineers that permitted barge traffic throughout the empire. These principles, elaborated through time, are still in use, as is the Grand Canal from Beijing to Hangzhou, but medical science in today's world requires different lenses through which to view this ancient system.
An article in the journal Mediators of Inflammation, "Anti-inflammatory actions of acupuncture"  outlines various ways one essential mechanism of acupuncture may be how it stimulates both the body's inflammatory and anti-inflammatory activities.
What is inflammation?
Inflammation is associated with pain, redness, swelling, heat and loss of function, which anyone with a sprained ankle can testify to. Inflammation is one way in which the body fights disease, but inflammation, when uncontrolled, is often implicated in disease. Any disease ending in -itis involves inflammatory processes, although the list is not limited to that; much chronic illness involves inflammation. The public is generally aware of the significance of inflammation in health; a recent Amazon search for "inflammation" in book titles since 2002 came up with 53 hits.
Acupuncture and inflammation
One jumping-off point for examining the relationship between acupuncture and inflammation is to look at how it first stimulates inflammation. Puncture by an acupuncture needle mobilizes the body's own defenses, improves blood flow to organs, activates cell growth, and influences the movement of substances in and out of cells. Among the chemicals stimulated by the insertion of an acupuncture needle are neuropeptides such as calcitonine gene-related peptide (CGRP), which is a substance that both prevents and promotes some forms of inflammation, and is also involved in "migraine, thermal injury, circulatory shock, pregnancy and menopause, hypertension and heart failure." In some circumstances, CGRP helps to protect the heart. Another neuropeptide, Substance P, works in conjunction with CGRP to create edema and inflammation, both of which are important in containing an injury and bringing red and white blood cells and nutrition to the site of injury.
Acupuncture stimulates or otherwise influences the production of other substances involved in inflammation. Beta-endorphins, another group of neuropeptides, promote the analgesic (pain-reducing) effects of acupuncture. Cytokines, produced by white blood cells, "provide signals to regulate immunological aspects of cell growth and specific immune response" mostly local to their production but sometimes systemically.  Nitric oxide (NO), used by the body to expand the size of blood vessels (vasodilatation), is another component of the inflammatory process that brings blood where it is needed. Acupuncture's initial effect is thus to engage the body's own defenses.
A yang & yin explanation of acupuncture's action: inflammation/anti-inflammation
Given the body's complexity and how much we still have to learn, the precise mechanism of acupuncture is strictly conjecture. Zijlstra, et al. offer an interesting hypothesis, which is offered here in considerably abbreviated fashion. Insertion of an acupuncture needle initially stimulates the production of beta-endorphins, CGRP and substance P, leading to further stimulation of cytokines and NO. The beta-endorphins help combat the feeling of pain. The other substances are involved directly in inflammation, stimulating the body's defense mechanisms against a variety of pathogenic processes.
But while "high levels of CGRP have been shown to be pro-inflammatory , . . . CGRP in low concentrations exerts potent anti-inflammatory actions . . . . Therefore, a well-performed and frequently applied 'low-dose' treatment of acupuncture could provoke a sustained release of CGRP with anti-inflammatory activity, without stimulation of pro-inflammatory cells." This dual action, inflammatory and anti-inflammatory, yang and yin, may explain why acupuncture, effective in the short term for acute disorders, is also effective in the long term for chronic illness.
1. Anti-inflammatory actions of acupuncture. Mediators of Inflammation, 12(2), 59-69 (April 2003). Freek J. Zijlstra, Ineke van den Berg-de Lange,Frank J. P. M. Huygen1 and Jan Klein.
2. Tabor's Medical Dictionary, 18th Edition.
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