Normal Vitamin D Levels Will NOT Tell the Whole Picture

The Institute of Medicine (IOM), however, considered blood levels of 50 nmol/L (20 ng/ml) to be sufficient and therefore recommended only 600 to 800 units a day for those with little or no sun exposure. Why so low? Because the IOM was only considering bone health. Even if we cared just about our bones and not our lifespan, we’d still probably want to shoot for a 75 nmol/L (30 ng/ml) threshold, because there’s evidence from hundreds of autopsies of people who died in car accidents, for instance, showing osteomalacia, or softening of the bones, in 18 to 39 percent of people who reach the IOM target of 50 nmol/L, but failed to make it to 75 nmol/L.The natural level, however, isn’t necessarily the optimal level. Maybe the body would have thrived with less, so we still have to look at what levels correspond to the lowest disease rates. And, when we do, the higher levels do indeed seem to correlate with less disease.
https://nutritionfacts.org/2019/04/30/what-is-the-optimal-vitamin-d-level/