Additive risk factors in atherosclerosis.

The tissues of human subjects assayed for a higher level of vitamin D than the tissues of 6-month-old swine which had been fed a commercial ration containing 14 times more vitamin D3 than the National Research Council recommended requirement for growing swine. Bioassays of commercial livestock feeds indicate much higher vitamin D contents than the National Research Council recommendation. High levels of vitamin D activity are demonstrable in tissues from the animals on such livestock feeds. The grossly normal areas of the aorta of weanling swine fed 100,000 IU of vitamin D3/pound of basal ration during the initial 6 weeks had a higher frequency of degenerated smooth muscle cells than the grossly normal areas of the aorta of swine fed the commercial ration, or 7.43+/-0.45 and 5.60+/-0.27/100 cells, respectively, at the age of 3 months. Tbe addition of 13 pounds of hydrogenated fat and 200 g of cholesterol/100 pounds of the commercial ration further increased the frequency of degenerated smooth muscle cells by 0.53 (P less than 0.05) or to 7.96 +/- 0.39/100 cells in the grossly normal areas of the aorta of weanling swine fed this fat-supplemented ration to 3 months of age.