On June 14, 2011, the Washington Post published an article by Lenny Bernstein on the unknown cause of the popular experience of “runners high” and whether or not this often reported “state of euphoria” is in fact related to the release of endorphins; or if it in fact actually exists.

While countless runners report the experience of an almost altered state of being after a vigorous or strenuous run, researchers have not been able to identify a link to this experience from endorphins to explain this feeling experienced by trained distance runners.

In 2009, researchers Rod K. Dishman and Parick J. O’Connor wrote regarding this now well accepted sports-lore that “The hypothesis that endorphins are responsible for changes in euphoria and other moods during or after acute exercise remains plausible, but it has been perpetuated with little evidence.” In other words, there is currently no known cause or evidence-based science demonstrating why runners experience a reported “high” from the activity.

If endorphins are being eliminated from the cause and effect of this elevated sense of well-being and pleasure that many runners experience than what can be creating such a state? In my 20 years as a 10K runner I can attest that something occurs in the body that is both pleasurable and desirable after one has run a few miles, most noticeably if the running is consistent.

For possible clues, let’s look at the evidence-based science of what might be causing his elevated sense of well-being and, for some runners, euphoria? The blood brain barrier (BBB) is an important mechanism which controls the passage of substances from the blood into the cerebrospinal fluid and, as a result, into the brain and spinal cord. This is a highly selective and extremely important process to protect our brain and central nervous system function.

Hormones, neurotransmitters, viruses, bacteria and even many drugs are denied entry into this critical region of our neurology. Molecules that are larger than 500 daltons, a unit that is used for indicating mass on an atomic or molecular scale, are denied access unless the BBB is lowered by chronic hypertension, microwaves, radiation or injury.

What does easily cross the BBB that might account for the “runner’s high” experience? While more research into this fascinating brain function is required to accurately identify the specific cause, if we look at oxygen, glucose and white blood cells, we may have the answer.

With an increase in the uptake, during strenuous exercise, of glucose and oxygen, two of the most critical brain function factors, as well as white blood cells which are produced in enormous amounts during exercise, it is easy to understand why we may have an enhanced feeling of well-being or euphoria.

These substances are critical to brain function. It may be that during the “runner’s high” when they are being absorbed in higher quantities they may be part of - or be the reason for - this unidentified feeling of well being. Whatever the cause, those who run know it exists, and no doubt medical science will soon identify the how and why of this pleasurable experience.

Dr. Georgianna Donadio