> But when you supplement Vitamin D seems to lower your blood pressure as much as it makes your team win the Superbowl
Because you need UVA to convert the vitamin D to nitric oxide, and if you're getting enough UVA to do that then you're also more likely to already be getting enough UVB to create sufficient vitamin D in the first place.[1] Not super complicated.
Taking vitamin D supplements is probably still better than not taking them if you're deficient, but if you understand the mechanism of action then it should be obvious as to why the science is always equivocal.
[1] Or, more precisely, vitamin D regulates nitric oxide synthesis.
Because you need UVA to convert the vitamin D to nitric oxide, and if you're getting enough UVA to do that then you're also more likely to already be getting enough UVB to create sufficient vitamin D in the first place.[1] Not super complicated.
Taking vitamin D supplements is probably still better than not taking them if you're deficient, but if you understand the mechanism of action then it should be obvious as to why the science is always equivocal.
[1] Or, more precisely, vitamin D regulates nitric oxide synthesis.