DEAR DR. BLONZ: I’m under the impression that vitamin D requires fat in order to be absorbed well. If I drink a glass of nonfat milk by itself, will I absorb less of its vitamin D? Also, is that why cod liver oil is one of the best ways to get vitamin D -- because of the fat in the oil? Vitamin D is a fat-soluble vitamin, and it requires some fat to facilitate its passage through the absorptive surface of the intestines. Cod liver oil does contain vitamin D and fat, but it can also contain a lot of vitamin A, which is harmful in large doses.