Vitamin D deficiency (and while we're at it, B12 deficiency and iron deficiency) are real deficiency issues that have risen in numbers across Western societies for quite the time now - IIRC, a large contributor is our change in diets and living habits.
Basically, we're spending far less time working out in the open so our body doesn't generate vitamin D on its own in sufficient quantities, and the trend towards highly processed, nutritionally inflexible diets on one side and vegetarianism/veganism on the other side leads to a whole host of malnutrition issues.
Unfortunately, the "malnutrition" levels in bloodwork are mostly calibrated on white European males... so similar to BMI [1] and a few medications and diseases [2], there is a "vitamin D paradox" in Black people who seem to not be that sensitive to lower vit-D levels than White people [3].
Human bodies and genetics are fascinating, even if you're not an expert in it.
Basically, we're spending far less time working out in the open so our body doesn't generate vitamin D on its own in sufficient quantities, and the trend towards highly processed, nutritionally inflexible diets on one side and vegetarianism/veganism on the other side leads to a whole host of malnutrition issues.
Unfortunately, the "malnutrition" levels in bloodwork are mostly calibrated on white European males... so similar to BMI [1] and a few medications and diseases [2], there is a "vitamin D paradox" in Black people who seem to not be that sensitive to lower vit-D levels than White people [3].
Human bodies and genetics are fascinating, even if you're not an expert in it.
[1] https://pubmed.ncbi.nlm.nih.gov/9877251/
[2] https://academic.oup.com/ehjcvp/article/8/7/738/6644872
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5954269/