The lower the level of vitamin D, the more likely that calcium will build up in fatty plaques in the coronary arteries. The inverse relationship also holds: the higher the level of vitamin D, the less likely calcium will build up in atherosclerotic plaque. The relationship was unexpected, because -- at least in bones -- the higher the vitamin D level, the more likely calcium is to accumulate.
Researchers thought that development of atherosclerotic calcification would respond in the same way as bone -- that high vitamin D would lead to higher calcium absorption, but serum vitamin D seems to have an opposite effect on the skeleton as it does on the vessels. About 90% of patients with coronary heart disease have deposits of calcium in the fatty plaques clogging their arteries.
Circulation September 1997;96:1755-1760
This information is particularly important in that in a few weks all of us who live in the northern latitudes (which certainly includes me near Chicago) should be taking 400 units of supplemental vitamin D. Normally sun exposure on our skin will generate vitamin D. However from October to March the angle of the earth's atmosphere changes so that the effective penetration of the ultraviolet rays become significantly diminished. In the middle of the winter they are so low that two years ago I heard the chairman of Harvard's endocrinology department explain that one could stand stark naked on the roof from dawn until dusk and there would not be enough photons present to cause the production of vitamin D in our skin. So this new study provides an additional reason for taking vitamin D in the winter. Not only will it help protect against heart disease but it will help prevent hardening of our arteries.