Most people don't realize your body is literally built to get a shit ton of sunlight. Pretty much every part of the spectrum has a job waiting for it: ⠀ • UVB gets your skin making vitamin D • UVA frees up nitric oxide stored in your skin, which relaxes your blood vessels and brings blood pressure down • UV also switches on p53 in your skin cells, which kicks off your tan through alpha-MSH and releases beta-endorphin, a feel-good molecule that likely helps explain why the sun feels so damn good • Blue light hits special cells in your retina that don't help you see at all. Their job is measuring brightness and setting your body clock • Red and near-infrared get absorbed right in your mitochondria's energy-making machinery, and near-infrared passes all the way through your body ⠀ Even the timing is built in. Sunrise is loaded with red and infrared with zero UV, and the UV ramps up as the morning goes on. Your melanin builds with regular exposure too, which is why someone outside every day can handle sun that would torch someone stuck inside since winter. ⠀ For almost all of human history we lived outdoors and every one of those systems got used daily. Now about 90% of our time is spent inside under electric light that's roughly 100 times dimmer than daylight, and missing most of that spectrum entirely.