More on the Circadian Rhythm of the Gut Bacteria…and Its Relationship to Melatonin

Several months ago a very dear friend of mine had a cancer relapse. Coincidentally, I had been doing a little reading about new ideas surrounding cancer, including the causes and the treatment, and it turned out that my friend had been doing the same, with both of us stumbling across the concepts forwarded by Dr. Thomas Seyfried.  (If you know anyone with cancer, this video is more than worth 54 minutes of your time.  It was actually pointed out to me by my friend, Dr. Derrick MacFabe, whose research I have covered so extensively on this blog.  (Here and here and here, as just a few examples.))

Along these lines, my friend with cancer also asked me to watch this video of Dr. Frank Shallenberger, which is about using high dose melatonin as an added therapy in cancer.  I was mesmerized.  Again, I believe it is more than worth the hour of your time, even if you do not have cancer because the global health benefits of melatonin are really astounding.

Melatonin, for those less familiar, is a hormone created from serotonin in the pineal gland in the brain which makes you sleepy.  The gland is activated by the dark, typically starting around 9:00 pm.  As melatonin levels rise, you begin to feel drowsy and less alert.  As levels of melatonin fall over night, the level of it in the blood becomes barely detectable and you wake. (A little side note:  the pineal gland is only stimulated by complete dark.[i]  This is why nightlights are such an awful idea!)  It also turns out that melatonin has a vast host of other incredibly important functions in the body, including acting as an antioxidant, has antiaging properties, modulates the immune system (thus, its role in treating cancer, for one), and many more.  It is crucial for good health.

For me, of course, there was not only the objective interest in hearing new ways of thinking about maintaining health and treating disease:  as always, there was also a huge biome connection.  Just a week ago, I wrote about the circadian (daily) rhythms of the microbiome and how these fluctuations can actually be used to assess the risk of developing diabetes.

It turns out, according to new research out of the University of Kentucky, that a particular species of gut bacteria called Enterobacter aerogenes has its own circadian rhythm in response to melatonin.  It reproduces much more rapidly when melatonin is present, and this effect was dose dependent.  (The higher the dose of melatonin, the more it reproduces.)  Other bacteria were also tested and did not exhibit this same behavior when exposed to melatonin, but undoubtedly, this is not the only bacteria so highly dependent on the presence of the hormone. The take-away message:  “This work indicates the circadian clock of the host may give out hormonal signals that elicit responses from the circadian clocks of commensal gut bacteria.”[ii]  That is, your body – your pineal gland’s secretion of melatonin – has a direct effect on inducing those normal rhythms of the gut bacteria that it’s turning out are absolutely critical for the normal functioning of you bacterial microbiome.  And we all know the consequences of altering that organ.

I did my usual snooping around and found that this phenomenon is really undergoing a great deal of scrutiny now in the scientific world.  This article in particular jumped out at me:  “Effects of Melatonin on Intestinal Microbiota and Oxidative Stress on Colitis Mice.”[iii]  Two groups of mice had colitis chemically induced in them, but one group was also treated with melatonin.  The group who were not treated with melatonin had “…significantly less antioxidant capability” (i.e. much higher levels of oxidative stress) than the melatonin group.  There were also differences in their microbiome profiles:  the melatonin group had higher levels of Firmicutes species, which are known to be at lower levels in those with inflammatory bowel diseases.  The researchers state that, “The results support the use of melatonin for prevention of intestinal bowel disease due to its modulatory effect antioxidant capability and microbiota in mice with colitis…” and the paper’s concluding sentence:  “This evidence supports our finding that melatonin has a highly beneficial therapeutic effect in mice with colitis.”

In the meantime, after reading all this and listening to that lecture twice, I have added melatonin into my daily regimen, am wearing an eye shade to prevent any kind of light to get into my eyes at night…because it seems to me that it’s something I can do now for my own health.




[iii] Zhu, D, Ma, Y, Ding, S, Jiang, H, Fang, J.  Effects of melatonin on intestinal microbiota and oxidative stress in colitis mice. BioMed Research International. 2018.

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