THIS

I often use the analogy of HRT, taking a hormone like testosterone as a supplement will provide benefits in studies, but it will disrupt dozens of tightly regulated feedback loops

Vitamin D is a hormone as well, and when supplementing it we see the exact same issue https://twitter.com/brittsliladvice/status/1328206737648857089

Vitamin D produced from sunlight is not just one compound, there's actually 12+ analogs of vitamin D, as well as hundreds of other compounds produced in response to sunlight!

The supplement form is the storage form of the hormone, which is normally only produced as needed

When we artificially jack up the body's vitamin D stores it can cause disturbances by breaking the body's normally tight regulation

These can range from depletion of nutrients like magnesium and retinol, to a chronic increase in serum calcium concentration

If that's not enough to put you off, vitamin D blood tests don't even measure the active form

Serum vitamin D measures only the storage form which has only a limited correlation with the active form, so if your storage vitamin D is low your active may be high!

All things considered, I see no reason to take vitamin D supplements, it's far easier to get it from sunlight, food, or even a UV-B lamp over the winter

Invest in your health, a single pill may seem easy, but it won't actually solve a complex issue like hormone D imbalance