Alteration of Vitamin D metabolism in mexican‐Americans

Studies were performed to investigate vitamin D metabolism in Mexican‐Americans. Groups of 15 whites and 16 Mexican‐Americans ranging in age from 18 to 41 years were evaluated. All of them were within 25% of their ideal body weight. Each of them was admitted to the Clinical Research Center of the University of Texas Health Science Center and placed on a daily diet estimated to contain 400 mg calcium and 900 mg phosphate. It was found that whereas serum vitamin D (1.8 ± 0.5 versus 7.6 ± 1.3 ng/ml, P < 0.001) and serum 25‐hydroxyvitamin D (9 ± 1 versus 17 ± 2 ng/ml, P < 0.01) were significantly lower and serum 1,25‐dihydroxyvitamin D (37 ± 2 versus 28 ± 2 pg/ml, P < 0.001) was significantly higher in the Mexican‐Americans than in the whites, serum calcium (9.1 ± 0.1 versus 9.2 ± 0.1 mg/dl), magnesium (1.84 ± 0.07 versus 1.80 ± 0.07 mEq/liter), and Gla protein (19 ± 3 versus 21 ± 2 ng/ml) were not different in the two groups. Urinary calcium (144 ± 14 versus 124 ± 16 mg/day), phosphate (672 ± 51 versus 683 ± 44 mg/ day), sodium (110 Ω 8 versus 99 ± 9 mEq/day), potassium (43 ± 4 versus 49 ± 3 mEq/day), and magnesium (7.3 ± 0.7 versus 7.7 ± 0.5 mEq/day) and creatinine clearance (173 ± 14 versus 154 ± 7 liters/day) were not different in the two groups. Serum immunoreactive PTH (390 ± 25 versus 299 ± 21 pg/ml, P < 0.02) was significantly higher in the Mexican‐Americans than in the whites and urinary cyclic AMP (2.64 Ω 0.27 versus 2.59 ± 0.39 nM/dl GF) was not different in the two groups. The results indicate that Mexican‐Americans are depleted of vitamin D and, as a result, have low serum 25‐hydroxyvitamin D and compensatory increases in serum immunoreactive PTH and 1, 25‐dihydroxyvitamin D. The depletion of vitamin D in Mexican‐Americans is attributed to increased skin pigment