Studies related to vitamin D supplementation are the most important because in many cases the correlation between low vit D and "lots of bad stuff" is established. But what's not always known is if supplementation helps or not.

Now as I'm a simple man and as I know that there aren't side-effects to vit D supplementation [1], I take my supplements.

[1] except in the mind of intellectually dishonest people who shall take that one case of a person who took 10 000 IU of vit D per day for 10 years and ended having this or that (non-life threatening) issue. But these intellectually dishonest people would have no problem telling you to "be careful while drinking water, for one person who drank 20 liters of water per day got into trouble!", so do like me: ignore these pharma-lab paid shills.

it makes sense since vit d acts

Related:

Study finds vitamin D supplements with or without Omega-3s decreased risk of autoimmune diseases (2022): https://medicalxpress.com/news/2022-01-vitamin-d-supplements...

Researchers find low magnesium levels make vitamin D ineffective (2018): https://medicalxpress.com/news/2018-02-magnesium-vitamin-d-i...

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It would seem that there is a pharma-inspired cabal of users trying hard to suppress the info that vitamin D3 is highly relevant for autoimmune matters. Due to such suppression across the internet, most people with autoimmune issues find out the connection too late if ever.