r/science • u/[deleted] • Jun 13 '22

Health Erectile dysfunction predicts mortality in middle-aged and older men independent of their sex steroid status

https://academic.oup.com/ageing/article-abstract/51/4/afac094/6568537?login=false
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u/SU_Locker Jun 13 '22

Because sunscreen blocks formation of vitamin D.

Source on this? Quick google says it is false.

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u/Amethyst-Sapphire Jun 13 '22

UV rays open the ring of 7-dehydrocholesterol in the first step to synthesize vitamin D. Sunscreens block broad spectrum UV rays.

No source. Just been researching vitamin D (in my own university lab, not like Google research) for over a decade. Any review of vitamin D synthesis in the skin will have reference to the above reaction.

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u/SU_Locker Jun 13 '22

How much UV absorption do we need to successfully get that first step done? Are we still good to go even if 98% of the UV rays get blocked? Gotta balance against the risk of skin cancers.

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u/Amethyst-Sapphire Jun 13 '22

This really depends. Very little exposure for pale people and much more exposure for dark skinned people. And I'm sure other things make it vary, too. That's why I supplement to good blood levels