Utility of sun-reactive skin typing and melanin index for discerning vitamin D deficiency.

BackgroundSkin color, a vitamin D status determinant, can be assessed subjectively by Fitzpatrick sun-reactive skin typing (FST) and objectively by melanin index (MI). FST was validated against MI for discerning vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) <20 ng/ml) in children.MethodsWe measured FST, MI, and serum 25(OH)D in healthy, 8- to 18-year-old children from one of two vitamin D trials. MI from forehead, hand, and upper arm split at the median of the more racially balanced study cohort and FST (I-III vs. IV-V) were used for discriminating vitamin D deficiency.ResultsA total of 296 participants (mean age, 12.3±2.3 years; black, 208; FST IV-V, 209; 25(OH)D <20 ng/ml, 159) were studied. MI and FST had a strong positive association. Serum 25(OH)D was negatively associated with MI and FST. Sensitivity, specificity, and predictive values were similar for discriminating vitamin D deficiency between higher vs. lower MI and between FST I-III vs. IV-V. ROC area under the curves for FST (0.59) and MI (forehead (0.63); hand (0.62); and arm (0.64)) were similar.ConclusionsFST is comparable to MI for discerning vitamin D deficiency and can be deemed as an inexpensive, useful surrogate measure of skin color in the context of vitamin D research.

Estimations of dietary vitamin D requirements in black and white children.

BACKGROUND: The Institute of Medicine (IOM) dietary guidelines for vitamin D are based on limited pediatric data. Our objective was to estimate the dietary vitamin D requirements for maintaining serum 25-hydroxyvitamin D [25(OH)D] concentrations at the various IOM-considered thresholds of vitamin D status (12, 16, and 20 ng/ml) during fall and winter in children. METHODS: Ninety-six healthy 8- to 14-y-old Pittsburgh-area black and white children enrolled in a randomized, placebo-controlled trial of vitamin D3 1,000 IU daily for 6 mo with baseline and 2-mo follow-up assessments completed during October through April were studied. Vitamin D intake from diet and study supplement adjusted for adherence and serum 25(OH)D were measured. RESULTS: The vitamin D intakes needed to maintain serum 25(OH)D concentrations at 12, 16, and 20 ng/ml in 90% of the children were 581, 1,062, and 1543 IU/day, respectively. The estimated vitamin D intakes needed to maintain serum 25(OH)D concentrations at 20 ng/ml in 97.5% of the children was 2,098 IU/day. CONCLUSION: Our data suggest that the current vitamin D recommended dietary allowance (RDA) (600 IU/day) is insufficient to cover the skeletal health needs of at least 50% of black and white children.

Determinants of 25-Hydroxyvitamin D Concentrations in Infants and Toddlers.

BACKGROUND: Resurgence of rickets and recognition of excessive prevalence of hypovitaminosis D among all age groups in the western hemisphere have refocused attention on vitamin D nutrition. OBJECTIVE: To examine the prevalence of hypovitaminosis D [25-hydroxyvitamin D [25(OH)D] <30ng/mL] and characterize the determinants of 25(OH)D concentrations in 8- to 24-month-old healthy infants and toddlers living in Pittsburgh, Pennsylvania. METHODS: Serum 25(OH)D concentrations were measured and dietary intake of vitamin D, mode of feeding, summertime sun exposure characteristics, and skin color (sun-reactive skin type and melanin index) were assessed. RESULTS: A total of 111 healthy 8- to 24-month-old children (mean age [±SD] 14.4 [±3.5] months; male, 51%; black, 67%) were studied. Serum 25(OH)D concentration was <30 ng/mL in 16% (n=18) of the children. Median (interquartile) 25(OH)D concentration was lower in children who were ≥ 13 months vs. <13 months of age [35 (31, 40.5) vs. 40 (35.8, 44.3) ng/mL, p=0.013]; with sun-reactive skin type IV and V vs. I, II, and III [36 (31, 41) vs. 44 (36.5, 48.5) ng/mL, p=0.001]; and examined during fall/winter vs. spring/summer [35.5 (32.5, 38.5) vs. 39 (32.5, 44) ng/mL, p=0.05]. Age and skin type were significant independent predictors of 25(OH)D. CONCLUSIONS: Concentrations of 25(OH)D tend to be lower in infants and toddlers during fall/winter, and in children who are older (≥13 months vs. <13 months of age) and have darker skin tone. Benefits of enhancement of 25(OH)D concentrations during fall/winter and in children with higher sun-reactive skin type need further exploration.

Effect of Vitamin D3 Supplementation in Black and in White Children: A Randomized, Placebo-Controlled Trial.

CONTEXT: Dosages of vitamin D necessary to prevent or treat vitamin D deficiency in children remain to be clarified. OBJECTIVE: To determine the effects of vitamin D3 1000 IU/d on serum 25-hydroxyvitamin D [25(OH)D], PTH, and markers of bone turnover (osteocalcin and collagen type 1 cross-linked C-telopeptide) in black children and white children, and to explore whether there is a threshold level of 25(OH)D associated with maximal suppression of serum PTH concentration. DESIGN: Healthy 8- to 14-year-old Pittsburgh-area black (n = 84) and white (n = 73) children not receiving vitamin supplements, enrolled from October through March from 2008 through 2011, were randomized to vitamin D3 1000 IU or placebo daily for 6 months. RESULTS: The mean baseline concentration of 25(OH)D was <20 ng/mL in both the vitamin D-supplemented group and the placebo group (19.8 ± 7.6 and 18.8 ± 6.9 ng/mL, respectively). The mean concentration was higher in the supplemented group than in the placebo group at 2 months (26.4 ± 8.1 vs 18.9 ± 8.1 ng/mL; P < .0001) and also at 6 months (26.7 ± 7.6 vs 22.4 ± 7.3; P = .003), after adjusting for baseline 25(OH)D, race, gender, pubertal status, dietary vitamin D intake, body mass index, and sunlight exposure. Increases were only significant in black children, when examined by race. The association between 25(OH)D and PTH concentrations was inverse and linear, without evidence of a plateau. Overall, vitamin D supplementation had no effect on PTH and bone turnover. CONCLUSIONS: Vitamin D3 supplementation with 1000 IU/d in children with mean baseline 25(OH)D concentration <20 ng/mL effectively raised their mean 25(OH)D concentration to ≥20 ng/mL but failed to reach 30 ng/mL. Vitamin D supplementation had no effect on PTH concentrations.

Impact of seasonal flux on 25-hydroxyvitamin D and bone turnover in pre- and early pubertal youth.

BACKGROUND: Seasonal fluxes in 25-hydroxyvitamin D (25(OH)D) in children can affect bone turnover, and in turn potentially affect bone accrual and peak bone mass. The aim of this study was to examine the effect of seasonal flux on the association among 25(OH)D, parathyroid hormone (PTH) and markers of bone turnover in pre- and early pubertal black children and white children. METHODS: Data were collected during summer (June-September) and winter (December-March) in 6-12-year-old children. Measurements included serum 25(OH)D, PTH, osteocalcin (OC), collagen type 1 cross-linked C-telopeptide (CTx), dietary intake of vitamin D and calcium, skin color, sunlight exposure, and body mass index (BMI). RESULTS: A total of 138 children (mean age, 9.1 ± 1.7 years; black, n = 94; male, n = 81) were studied. 25(OH)D was higher (41.2 ± 13 vs 34.5 ± 11.1 ng/mL; P < 0.001) and CTx was lower (0.8 ± 0.3 vs 0.9 ± 0.5 ng/mL; P < 0.001) in all participants during summer when compared to winter. Furthermore, seasonal differences in CTx were more pronounced in black children (summer, 0.7 ± 0.3 vs winter, 1.0 ± 0.5 ng/mL; P < 0.001). PTH was a significant predictor of serum CTx and OC after adjusting for race, season, Tanner stage, dietary calcium, skin color and BMI. CONCLUSION: 25(OH)D declined significantly in both black children and white children during winter. CTx significantly increased during winter in black children compared to white children, suggesting increased rates of resorption in black children during winter. Benefits of enhancement of wintertime vitamin D status on bone health need further exploration.

The effectiveness of a short food frequency questionnaire in determining vitamin D intake in children.

Previous studies have found a high prevalence of vitamin D deficiency in children, yet few validated dietary vitamin D assessment tools are available for use in children. Our objective was to determine whether a short food frequency questionnaire (SFFQ) can effectively assess vitamin D intake in children. Vitamin D intake ascertained by a SFFQ was compared with assessments by a previously validated long food frequency questionnaire (LFFQ) in a population of 296 healthy 6- to 14-y-old children (54% male, 60% African American) from Pittsburgh, PA. The questionnaires were completed at two points 6 mo apart. Median reported daily vitamin D intake from the SFFQ (baseline: 380 IU, follow-up: 363 IU) was higher than the LFFQ (255 IU and 254 IU, respectively). Reported median dairy intake, including milk, cheese, and yogurt, was 3.7 cups/day, which meets the USDA recommendation for children. Vitamin D intake reported by the 2 questionnaires was modestly correlated at baseline and follow-up (r = 0.35 and r = 0.37, respectively; p < 0.001). These associations were stronger in Caucasians (r = 0.48 and r = 0.49, p < 0.001) than in African Americans (r = 0.27 and r = 0.31; p = 0.001). The sensitivity of the SFFQ for predicting daily vitamin D intake, defined as intake of ≥ 400 IU on both the SFFQ and LFFQ, was 65%. Specificity, defined as intake of < 400 IU on both questionnaires, was 42%. Vitamin D requirements may not be met despite adequate consumption of dairy products. The SFFQ was found to be a modestly valid and sensitive tool for dietary assessment of vitamin D intake in children.

Impact of season and diet on vitamin D status of African American and Caucasian children.

Seasonal variation of vitamin D status and adequacy of dietary vitamin D and impact of race on maintaining vitamin D sufficiency was assessed in 140 healthy 6- to 12-year-old African American (AA) and Caucasian (C) children residing in Pittsburgh, Pennsylvania during summer and winter. Vitamin D insufficiency was not rare in either group (AA vs C, summer, 17.2% vs 14.3%, nonsignificant; winter, 34.1% vs 32.5%, nonsignificant) despite a mean dietary intake of vitamin D above the American Academy of Pediatrics (AAP) recommended intake (400 IU/d; AA vs C, summer, 421 vs 456 IU/d, nonsignificant; winter, 507 vs 432 IU/d, nonsignificant). Race/season and dietary vitamin D were predictors of serum 25-hydroxyvitamin D [25(OH)D] concentrations. However, dietary vitamin D influenced 25(OH)D only in Caucasians during winter. Current AAP recommended daily intake for vitamin D is inadequate for maintaining vitamin D sufficiency in children.