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Comment by markenqualitaet | Hacker News Reader

There is no threshold for harm*. It's a cost:benefit consideration. From a cancer/aging perspective, any amount of UV exposure is bad. Tanning is a consequence of DNA damage. If your skin gets darker from sun exposure, you see evidence of your skin cells reacting to increased DNA repair signals. Malignant transformation/senescence is a stochastic event of course, but age markers pretty much suffer in a dose dependent manner.

* Of course exhausting antioxidant capacity will greatly increase damage at a certain point. I am not exactly sure if UV light can cause single strand breakage by itself, or via ROS, but antioxidants are no "shield" in any case - more like a minefield.

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The antidote for damage from UV light is the pro-metabolic effects of red light. Red light hits the red metal (copper) in the Cytochrome C Oxidase enzyme [0] in our mitochondria and refreshes this enzyme. When the cells have enough energy (ATP) they can repair the damage from UV light.

[0] https://en.wikipedia.org/wiki/Cytochrome_c_oxidase (no mention of red light therapy in this article).

UV light from the sun comes with plenty of red light. UV light from the tanning bed does not have any red light. In the winter I used to go tanning, then would spend 12 minutes in the bright-light room [1].

[1] at Planet Fitness. The company website doesn't have any information, but I found this page: https://thelifevirtue.com/total-body-enhancement-pros-and-co...

This explains the therapeutic benefits of red light on retinal tissue.

I was curious so performed a brief search. What are your thoughts on this study, which suggests that cytochrome c oxidase is not involved in the effect?: https://doi.org/10.1016/j.jphotobiol.2019.03.015

I think your link is interesting, in that the group without the copper enzyme also benefited from red light exposure. The copper enzyme explanation seemed reasonable to me, but perhaps there’s better explanation for why people seem to benefit from red light exposure. Maybe the benefit from red light it multifaceted.

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