What Is the Physiological Basis for Acupuncture?

acupuncture dummySociety in the United States has been long focused on what we call Western medicine. We treat medical conditions, often conditions identified by analytical blood tests or characterization of symptoms, with drugs. These drugs are developed based on rigorous research and development and their risks:benefit ratios have been determined to be acceptable by the Food and Drug Administration. However, in the age of increasing stress and development of chronic conditions such as chronic pain and digestive disorders, people have begun to turn to techniques that are rooted in what we call Eastern medicine, such as acupuncture.

Acupuncture is a technique used in traditional Chinese medicine usually used to treat pain. This is done by inserting long, thin needles into the skin in strategic locations. Chinese medicine explains that our bodies have channels through which energy flows that is responsible for our life force. This energy is called Chi or Qi and the channels are called Meridians. Meridians originate in our organs and connect to a particular point in the skin. When a person is ill, Chinese medicine says that Chi has been disrupted. Acupuncture needles are used to clear the obstruction and allow Chi to flow in a balance manner. A very good description of these principles can be found here: http://www.drmanik.com/chap2.htm.

Being a spiritual person, the concepts of energy and life-force do make sense under certain circumstances; however, such forces still must be able to be explained when it comes to physiological effect on the body. Of course, the physiologist and Western upbringing in me says, “Okay, that’s cool and all, but what exactly are these needles doing to body systems and biochemistry?”

I was a bit surprised that during my brief literature review of acupuncture, very few articles have been published in major journals on the subject. It would seem that a technique that has been growing in popularity in Western medicine over the past few decades, presumably with favorable results, would get more research funding. Alas, that is a discussion for another post, and I digress…

Although there are a handful of plausible theories as to why acupuncture works. I have not found an explanation I am completely comfortable with. Current research seems to relate to the idea that these needles must be targeting some kind of tissue system that connect pain signals to internal organs and/or modify the biochemical signaling related to pain. I’ve found three major theories that could show promise in the future: needles targeting concentrated areas of interstitial connective tissue, c-fibers that specifically transmit pain signals or an entirely unique circulatory system that handles pain signals.

Studies supporting the concept of needles targeting concentrated areas of connective tissue have been done looking at the force required to pull acupuncture needles out of the skin when they are inserted at acupoints or at random locations. This force is called “needle grasp.”  Langevin and Yandow (1) have reported that needle grasp is 18% higher at acupoints compared to random locations. To properly insert acupuncture needles, the needles are rotated to ensure they are inserted correctly. Langevin and Yandow assert that this causes connective tissue to wind around the needle, thus increasing the force required to remove the needle. Needle grasp, they say, is not unique to acupoints, but it is enhanced at these points, suggesting a larger connective tissue network. These connective tissue networks are believed to be associated with the acupuncture meridians. Still, it is a bit unclear how association with connective tissue relates to pain relief.

neuronAnother assertion for why acupuncture eases pain is associated with C fibers. There are two types of nervous tissues associated with pain: C fibers and Aδ fibers. Aδ fibers are generally active when you prick your finger on something sharp or touch a hot stove. These fibers deliver a signal to your spinal cord and brain rapidly and produce the “reflex” action, for example, of pulling your hand away from the stove. C fibers transmit signals much more slowly and  are generally thought to be involved with a dull, burning type of pain, and related to inflammation (click here for a quick overview of the pain system). Electrical analysis of skin surfaces led Morry Silberstein (2) to assert that acupoints correlate to locations where C fibers bifurcate and diverge along acupuncture meridians. It is unclear whether inserting needles at this bifurcation point leads to inhibition or excitation of the pain pathway. Nevertheless, Silberstein hypothesizes that inserting needles at acupuncture points essentially short circuits the pain pathway preventing the spinal cord from receiving the pain signal.

One especially interestng explanation for the way acupuncture works is through the discovery of a novel circulatory system termed Bonghan channels. These channels or ducts are thin, thread-like structures that were discovered originating from acupoints by Korean scientist, Bong Han Kim in the 1960s (3). His work was discounted by many scientists because it was difficult to determine whether this new tissue he discovered was distinct from the lymphatic system, and because it was difficult for others to reproduce his findings because he would not reveal the recipe for the dye he used to stain the tissues. Bong Han’s findings were not reproduced until the late 2000 when scientists used both dye-based histology (4) and magnetic ferrite nanoparticles (5) to visualize these “floating thread-like structures” within and distinct from lymphatic vessels. It is still unclear how, exactly, the Bonghan system interferes with the pain pathway.

All of these hypotheses raise many questions, but I believe they provide enough compelling evidence for further study of this popular therapy. Bottom line at this point in history is that if it works for you, do it! And if you have a condition that Western medicine has failed to remedy, there is no harm in at least trying an alternative therapy as long as you thoroughly research any potential risks and discuss them first with your doctor.

Thanks to Joe Ramos for suggesting this topic for a blog post!

  1. Langevin, H. M. and Yandow, J. A. (2002) Relationship of acupuncture points and meridians to connective tissue planes. Anat. Rec., 269: 257–265.
  2. Silberstein, M.  (2009) The cutaneous intrinsic visceral afferent nervous system: A new model for acupuncture analgesiaJournal of Theoretical Biology 261, 637–642, ISSN 0022-5193.
  3. Kim, B.H. (1963) On the kyungrak system. J Acad Medi Sci10,1–41.
  4. Lee, B.-C., Yoo, J. S., Baik, K. Y., Kim, K. W. and Soh, K.-S. (2005) Novel threadlike structures (Bonghan ducts) inside lymphatic vessels of rabbits visualized with a Janus Green B staining method. Anat. Rec., 286B, 1–7.
  5. Johng, H-Y, Yoo, J-S, Yoon, T-J, Shin, H-S, Lee, B-C, Lee, C, Lee, J-K, Soh, K-S. (2007) Use of Magnetic Nanoparticles to Visualize Threadlike Structures Inside Lymphatic Vessels of Rats. Evid. Based Complement Alternat Med4, 77–82.
  6. Leung, L. 2012. Neurophysiological Basis of Acupuncture-induced Analgesia: An Updated Review. Journal of Acupuncture and Meridian Studies.
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Karen Reece

Karen served as a Senior Research Scientist in Nucleic Acid Technologies at Promega before switching careers. She has a BS in Biochemistry and MS and PhD in Physiology, all from University of Wisconsin-Madison. Karen was born and raised in Madison, WI.


  1. a nice attempt to join different worlds….the major problem most of the developing nations is failure to join the two ends, the modern scientist/medical practitioner sees everything as superstition or magic or barbarism…!
    keep it up!

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