Calcium phosphate is not the best choice because the average diet is already too high in phosphorus. Calcium lactate and calcium gluconate have only a small amount of calcium per tablet. Avoid supplements derived from oyster shell, bone meal, or dolomite, since these may contain heavy metals. Always check with your doctor before taking any dietary supplement. The best natural food sources of vitamin D are fish oils, butter, cream, egg yolk, and liver.
Milk is the only food fortified with appreciable amounts of the vitamin.
Still, you'd need to drink four glasses to get your day's vitamin D needs. There's a precursor of vitamin D in the skin that gets converted to the vitamin upon exposure to ultraviolet light. Dark-skinned people don't make as much vitamin D, probably because melanin in the skin blocks more ultraviolet rays. In that case, it's important to get the vitamin from your diet. If you don't drink milk, take a multivitamin or a vitamin D supplement.