I am still surprised every time I see researchers discover yet another function that vitamin D plays in its “repair and maintenance” role in the human body.
Take the eye, more specifically the cornea; the clear barrier between the outside, with all its germs and dirt, and the front part of the eye, with all its delicate instruments, like the lens. Scientists from the University of Tennessee just discovered that the cornea has all the requisite vitamin D machinery to make and bind activated vitamin D.
More importantly, they found that the barrier function of the cornea (that keeps bad stuff out of the eye) is directly related to vitamin D levels. They tested corneal barrier function in the test tube to see if vitamin D increased the ability of the cornea to keep bad stuff out. It did; both 25(OH)D and 1,25(OH)D enhanced the barrier function of the eye.
Add one more organ, the cornea, and one more function, keeping bad stuff out of the eye, to the list of responsibilities for vitamin D, the chief of the repair and maintenance section in the human body.
It is also only fair to remember who predicted just such a role for vitamin D way back in 2004: Professor Martin Hewison, of the University of Birmingham in England, one of the giants of vitamin D research.