Thanks for the detailed reply.
My understanding is that there are still significant unknowns on the exact mechanisms of entrainment, and I don’t dispute that yellow-blue (YB) contrasts play a role. I considered mentioning it in this post, but my understanding is that it is more of a secondary point compared to the significance of the timing of bright, blue light exposure. Curious to see any evidence for your/Huberman’s assertion that early morning light exposure in the absence of YB contrasts has little effect on entrainment. This seems to contradict most of the literature I’ve seen.
The balance of my post more closely reflects this 2021 summary of the state of the art by... (read more)
Melatonin (particularly at higher doses) has a fast-acting sedative effect, so if you want to use it to help you fall asleep, then taking it 30 minutes before bed makes sense.
However, if you want to use it to advance your circadian rhythm (i.e., be inclined to be more of a morning person), then it has the greatest effect when taken 9–11 hours before your sleep midpoint (so very roughly at 6 p.m.). Below is a graph of the effect it has on the circadian rhythm.
^https://www.timeshifter.com/jet-lag/melatonin-for-jet-lag-type-dose-timing
Thanks a lot, Seth!
I agree with you on the importance of Vitamin D—it has helped me enormously. Most studies on Vitamin D focus on achieving levels similar to those experienced during summertime. However, few of the bright light studies come anywhere close to replicating the typical lux levels experienced in summer. From my anecdotal experience, I’ve found that spending several hours under 10,000 lux+ artificial lights can totally transform my mood.
You are correct in your understanding of things to try as a night owl. One other thing you might consider is supplementing with 0.5mg of melatonin around 6pm [1]. Exogenous melatonin also has a phase response curve for affecting your circadian rhythm. It’s important to stick to a low dose; otherwise, you’re likely to feel drowsy in the evening.
You may have heard that you 'shouldn't use screens late in the evening' and maybe even that 'it's good for you to get exposure to sunshine as soon as possible after waking'. For the majority of people, these are generally beneficial heuristics. They are also the extent of most people's knowledge about how light affects their wellbeing.
The multiple mechanisms through which light affects our physiology make it hard to provide generalisable guidance. Among other things, the time of day, your genetics, your age, your mood and the brightness, frequency and duration of exposure to light all interrelate in determining how it affects us.
This document will explain some of the basic mechanisms through... (read 2970 more words →)
So glad to hear!