High doses of vitamin D rapidly reduce arterial stiffness
I'm old enough to remember when the fad was taking supplemental Vitamin A and E as 'antioxidants' to reduce cancer risk. Then long term studies in Sweden on Vitamin A showed it actually increased risk, at least for lung cancer. I would be hesitant to go all-in on Vitamin D loading until such studies have been done here. There is a good reason why medicine is conservative - first, do no harm.