The Solar Pendulum
For the past months, I've been enjoying doing a deep dive into the optics of human health and the central role light plays in our health and vitality. It's probably still the most overlooked area of physiology, even in Functional, natural & Chinese medicine. I've come to see that biochemistry is downstream of light exposure and that if you don't understand how light interacts with biology, you cannot understand biochemistry.
At the forefront of the sun worshipping movement are those who refer to themselves as practitioners of Quantum Biology. My best assessment is that their philosophy when it comes to the sun is the more the better. Yes, people will need to build up their levels of sun exposure overtime but this is the main tool in the toolkit.
Having been looking into the literature on light, optics and biology for months now, what I'm seeing is a course correction very similar to what proponents of the "Keto Diet for All" folks are to low-fat. A low-fat diet as a prevention for cardiovascular disease was a catastrophic idea that caused and continues to cause an untold amount of harm. It was created by the sugar industry (1) and while disproven many times over, it still has its toe-holds in modern medicine.
I suppose it's human nature to overcorrect. The "Keto-diet for all" folks argue not just that dietary fat is important to health but that we should all be in ketosis. To me, this view is a logical response to the Low-fat diet for all but is not reality based and not based on accurate first principles.
The range of dietary fat intake in hunter gatherer tribes ranged from 25%-90%. So first, I would accept proposed recommendations any where in that range but not lower (the How not to Die vegans advocate 15% dietary fat). That said, fat intake varied based on geographical location. And pre-industrial hunter-gatherers didn't just have different diets. They had different everything. So while I think it's helpful to look at these diets as a clue (especially for what none of them included), we'd be wise to not leave out important context, like everything else about how they lived.
When it comes to sunlight exposure, we're seeing something similar. The overwhelming majority of modern people are devastatingly deficient in natural sunlight, which may be one of the most important inputs for health. Some of that is by default. Wake up inside, hop in a car, go to work inside, drive home in a car, go back inside. Rinse and repeat.
But then there's the recommendations to avoid the sun. This is a very efficient way to make people ill, for which you can sell them treatments. A large scale study conducted in Sweden found that the risk of all-cause mortality in those with the lowest sun exposure was twice that compared to the group with the highest sun exposure, after controlling for all the things that you would control for (2). The increased risk of death from avoiding the sun is similar to that of smoking.
That said, it does not follow that "more is better" for everyone. Like with everything, exposures need to be balanced with someone's current level of health and someone's constitution. Constitution is interesting because while we're an extremely adaptable species, when it comes to adaptations to sun exposure this can take years and in some cases generations.
So, if you are not currently optimizing your light exposure - whatever healthy amounts of natural light based on your health, your constitution, and your geography - are for you as well as avoiding the artificial stuff, then this is going to be the bottleneck to vibrant health for most people reading this. You almost certainly want to prioritize addressing this.
And, "the more sunlight the better" messaging will mess a lot of folks up. It's not unlike exercise in this regard, another stimulus with outsize effects on health that you certainly can overdo and can harm yourself with. You can get too much sun exposure.
So I think the key message here, just like with everything else, is taking an accurate inventory of your current baseline and then improving from there.
References
1) Kearns, Cristin E., Laura A. Schmidt, and Stanton A. Glantz. “Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents.” JAMA Internal Medicine 176, no. 11 (November 1, 2016): 1680. https://doi.org/10.1001/jamainternmed.2016.5394.
2) Lindqvist, P G, E Epstein, M Landin-Olsson, C Ingvar, K Nielsen, M Stenbeck, and H Olsson. “Avoidance of Sun Exposure Is a Risk Factor for All‐cause Mortality: Results from the Melanoma in Southern Sweden Cohort.” Journal of Internal Medicine, 2014, 10.