The mission of the International Dark-Sky Association is “to preserve and protect the night time environment and our heritage of dark skies through quality outdoor lighting.” They’re all about stressing the importance of lighting on health, light pollution, and some really interesting stuff.
For more on the topic, check out their website, darksky.org, and Paul Bogard’s book, The End of Night: Searching for Natural Darkness in an Age of Artificial Light.
Humans have a peculiar relationship with light: differences in brightness, wavelength, and even circadian timing all have biologically meaningful effects.
The right combination of timed light exposure and hot Blue Blockers is probably not only the solution to jet lag, but also to a whole host of other health problems. Maybe you can’t completely escape the bane of the modern condition, but there are some tools, widely available, accessible, and even free in some cases (eg, sun), that may be of benefit.
The frequency of light impacts circadian rhythms.
Wright showed this in 2004. The subjects wore special glasses with LEDs that emitted light of varying frequency for 2 hours, from 6 to 8 in the morning (65 uW/cm2). Salivary melatonin measurements commenced at 7 pm. As seen in the figure below, blue but not red light induced a significant phase advance in melatonin onset:
And for the whole group:
I’ve adapted much of this chart from Howell-Skalla (2002) and Tsubota (1998).
Canadian polar bears: bona fide seasonal breeders.
The light cycle increases until June, then decreases until December. Melatonin goes in the exact opposite direction. Testosterone peaks around the onset of breeding season (springtime, April/May), coinciding with LH (as expected). There is also a lot of bear-on-bear violence at this time due to: 1) testosterone-induced aggression; and 2) the high female:male ratio –-> females rear their cubs and are thus out of the game for about 3 years, but males like to breed every year.
Females followed a similar pattern, with estrogen peaking around breeding season and prolactin following the light cycle.
The authors mentioned that prolactin levels mirrored day length, and according to Wiley this would be the prolactin peak that normally occurs when you’re sleeping, but has spilled over into the daytime due to short sleep / long light cycle… not total prolactin levels (24h AUC?), which should be highest in winter (see below).
Posted in Advanced nutrition, Bromocriptine, circadian, Dopamine, fertility, sex
Tagged circadian, dopamine, light, melatonin, Paleo, prolactin, sex