Circadian rhythms and prostate cancer


Incidence of prostate cancer is higher among pilots, flight attendants, and rotating shift workers than the general population (RR as high as 3.0 in some cases!).

Circadian rhythms of androgens is absent & clock genes are disrupted in prostate cancer; the latter of which is reversible with melatonin which also suppresses prostate cancer progression.

Interestingly, radiation treatment is significantly more effective before 5pm than after.  I don’t know why this is; could be a spurious correlation.  Or not.



Circadian rhythmicity and the influence of clock genes on prostate cancer (Kiss and Ghosh, 2016)




Two key players are the circadian proteins Per1 and Per2. They’re supposed to exhibit diurnal fluctuation but are suppressed in prostate cancer cells, and genetic overexpression inhibits tumor progression. 



And similar to Bmal2 SNPs and breast cancer progresssion, Bmal and Period SNPs are associated with prostate cancer incidence and severity.




High levels of melatonin at night, which can be relatively easily achieved by avoiding artificial light and rocking hot blue blockers, are associated with lower incidence and severity of prostate cancer.



In rodent models of prostate cancer, administration of melatonin suppresses tumorigenesis.  Importantly, this is only seen with properly timed doses and not chronic infusions (ie, physiological melatonin exposure).  Circadian rhythms are clearly of great import.  Even specific dose-timing of anti-cancer drugs shows superior efficacy and lower toxicity over chronic infusions.




I’m not crazy. Light and food during the day, dark and sleep at night.  This is just how it needs to be.  QED.


Entraining central and peripheral circadian clocks


calories proper


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  • Charles Richardson

    So basically, to supplement, take melatonin at night, right?

    • better to see sunlight early in the day and avoid artificial light or wear blue blockers at night

      • Charles Richardson

        Not always easy to do @ 48 degrees north ;=)

  • Matt Neibaur

    After age 60, the melatonin production is negligible. Interesting that cancers increase with age. Is there any point in trying to boost endogenous melatonin with increasing age vs a supplement?

    • reduced, not negligible, and yes definitely still worth it to boost endogenous melatonin production.

      • Matt Neibaur

        I found this article for reference to best dosing – 0.3 mg (300 micrograms) was the most effective and physiological dose in helping elderly with sleep problems.

        Age-Related Decreases in Melatonin Secretion—Clinical Consequences

        • Seems specific to insomniacs, not age or low mel per se (like you said lol). Interesting. Thanks!

          “the hormone had no discernable effect on sleep among the
          noninsomniac subjects, even though those subjects, like the insomniacs,
          had nighttime plasma melatonin levels that were well below those seen in
          younger adults: apparently, the age-related decline in nocturnal plasma
          melatonin is not sufficient, in itself, to cause insomnia in all