Vitamin D is an important hormone in the prevention of osteoporosis and rickets but beyond that has major functions in the prevention of heart disease, cancers, diabetes and in the regulation of the immune system. Foods naturally rich in vitamin D are all from animal sources: cod liver oil, finfish, and shellfish. The only naturally occurring plant sources of vitamin D are certain mushrooms, in which it is present in only small amounts. There has been concern that vegetarians would have lower blood levels of vitamin D than non-vegetarians.
AHS-2 looked at the vitamin D status of vegetarians, partial vegetarians and non-vegetarians. The results demonstrated that a vegetarian diet was not associated with lower levels of vitamin D. Other factors, such as vitamin D supplementation, degree of skin pigmentation, and amount and intensity of sun exposure had a greater influence on vitamin D levels in blood than diet.
Of the factors mentioned above, degree of skin pigmentation caused the greatest difference in vitamin D concentrations. Regardless of dietary preferences, the percentage of subjects with deficiencies was much higher among Blacks (75.4%) than among Whites (47.5%). This was shown even though other areas, such as vitamin D intake and amount of exposure to the sun, were equal. The reason cited for this outcome is that, when exposed to sufficiently strong sunshine, lighter-skinned persons’ skin can produce relatively high amounts of vitamin D in a relatively short amount of time. Nevertheless, Black subjects generally have good bone health. Whether lower blood vitamin D levels affect other aspects of their health is not yet clear.