And once again I will point out that bacteriology.com is a Trevor Marshall website with slanted pick-and-choose articles by his shill Amy Proal like the one referenced, as well as articles by her boyfriend and fellow Marshall shill and board member Paul Albert. The Marshall Protocol that they all profit from depends on scaring people about Vitamin D.
One also notes that the Duke study the article refers to included people who had high intakes of dairy and other vitamin D fortified foods. The form of vitamin D used to fortify dairy and other foods: Vitamin D2, an artificial form of Vitamin D and not at all the same as natural Vitamin D3.