Reduced spinal bone mineral density in adolescents of an ultra-Orthodox Jewish community in Brooklyn

Objectives. Bone mass increases throughout childhood, with maximal bone mas s accrual rate occurring in early to mid-puberty and slowing in late pubert y. Prevention of osteoporosis and its morbidities depends primarily on the establishment of adequate peak bone mass. Physical activity, calcium intake , and vitamin D stores (from sunlight conversion of precursors of vitamin D and to a lesser degree from dietary intake) are vital determinants of bone mineral density (BMD). BMD is further controlled by genetic and environmen tal factors that are poorly understood. Observance of ultra-Orthodox Jewish customs may have a negative effect on t he factors that promote bone health, and there have been anecdotal reports of higher fracture rates in this population. The ultra-Orthodox Jewish life style encourages scholarly activity in preference to physical activity. Add itionally, modest dress codes and inner-city dwelling reduce sunlight expos ure. Orthodox Jews do not consume milk products for 6 hours after meat inge stion, leading to potentially fewer opportunities to consume calcium. Foods from the milk group are some of the best sources of dietary calcium. Our aims are to examine BMD in a group of healthy ultra-Orthodox Jewish ado lescents in an urban community and to attempt to correlate it to physical a ctivity and dietary factors. Design and Methods. We recruited 50 healthy, ultra-Orthodox Jews, ages 15 t o 19 years (30 males and 20 females). None were taking corticosteroids or h ad evidence of malabsorption. All girls were postmenarchal and nulliparous. Pubic hair Tanner stage for boys and breast Tanner stage for girls were de termined. Weight and height standard deviation scores were calculated. Calc ium, phosphorus, protein, vitamin D, and calorie intake were assessed using a comprehensive food questionnaire referring to what has been eaten over t he last year. Hours per week of weight-bearing exercise and walking were de termined. Serum levels of calcium, intact parathyroid hormone (PTH), 25 hyd roxyvitamin D (25[OH]D) and 1,25 dihydroxyvitamin D (1,25[OH](2)D) were mea sured. Lumbar spine (L) BMD was assessed by dual energy radiograph absorptiometry. The pediatric software supplied by Lunar Radiation Corporation, which cont ains gender- and age-specific norms, provided a z score for the lumbar BMD for each participant. L2 to L4 bone mineral apparent density (BMAD) was cal culated from L2 to L4 BMD. Results. BMD of L2 to L4 was significantly decreased compared with age/sex- matched normative data: mean z score was -1.25 +/- 1.25 (n = 50). The mean L2 to L4 BMD z score 6 standard deviation was -1.71 = 1.18 for boys and -0. 58 +/- 1.04 for girls. Eight boys (27%) had L2 to L4 BMD z scores < -2.5, w hich defines osteoporosis in adulthood. Twenty-seven adolescents (54%), 16 boys and 11 girls, had Tanner stage V. Two participants (4%) had delayed de velopment of Tanner stage V. Mean consumption of calcium by participants un der 19 years old was 908 +/- 506 mg/ day (n = 46), which is lower than the adequate intake of 1300 mg/day for this age. The consumption of phosphorus was 1329 +/- 606 mg/day, and the consumption of vitamin D was 286 +/- 173 I U/day (n = 50). The mean serum 25(OH)D level was 18.4 +/- 7.6 ng/mL, and the mean serum 1,2 5(OH)(2)D level was 71.1 +/- 15.7 pg/mL (n = 50). Boys had significantly hi gher serum levels of 1,25(OH)(2)D than did girls (74.9 +/- 16.46 pg/mL vs 6 5.25 +/- 12.8 pg/mL, respectively). The serum levels of PTH, calcium, and p rotein were (mean 6 standard deviation): 33 +/- 16 pg/mL, 9.5 +/- 0.69 mg/d L, and 7.8 +/- 0.6 g/dL, respectively (n = 50). L2 to L4 BMD z score had positive correlation with walking hours (r = 0.4). L2 to L4 BMD z score had negative correlation with serum level of 1,25(OH) (2)D) r = -0.33; n = 50). We could not find significant correlation between L2 to L4 BMD z scores for the entire cohort and any of calcium, vitamin D, phosphorus, or protein intake. However, the L2 to L4 BMD z scores of boys had positive correlation with calcium, phosphorus, and protein intake (r = 42, r = 44, and r = 43, respectively). After adjustment for Tanner stage, b oys who had Tanner stage V (n = 16) had stronger positive correlation betwe en L2 to L4 BMD z scores and calcium and protein intake (r = 0.55 and r - 0 .57, respectively), as was the correlation between L2 to L4 BMD z score and weight-bearing activity and walking hours (r = 0.77 and r = 0.72, respecti vely; n = 16). By multiple regression analysis with stepwise selection, sex, walking hours , weight-standard deviation scores, and serum PTH predicted 54% of the vari ability in L2 to L4 BMD z score. Sex, walking hours, and age predicted 65% of the variability in L2 to L4 BMAD. Conclusions. Lumbar BMD is significantly decreased in ultra-Orthodox Jewish adolescents living in an urban community. Boys had profoundly lower spinal BMD than did girls. Previous studies have introduced estrogen as a critica l factor in bone mineralization. However, the role of estrogen is still con troversial. Our investigation of the significant determinants of BMD proved that sex is an important predictor of z score in this group, which may ind icate the importance of sex hormones. Walking activity was positively associated with L2 to L4 BMD z score and wa s a significant predictor of L2 to L4 BMD z score and L2 to L4 BMAD. Additi onal studies are needed to investigate whether walking activity is lacking or is a causal factor of low BMD. The high normal levels of 1,25(OH)(2)D may represent a compensatory mechani sm to absorb more calcium from the intestine, and the low normal 25(OH)D le vels may represent relatively poor total body stores of vitamin D in this g roup of adolescents. This group is at great risk for the morbidities of poo r bone health if no bone mineral recovery happens later in their life. We encourage additional longitudinal studies to evaluate the bone mineral s tatus of the elder generation of this community and possible interventions that will lead to improved BMD. We recommend an increase in calcium intake to reach the adequate intake and an increase in walking activity. However, our study provides no evidence t hat following these recommendations will improve the BMD of this particular population.