Endocrine Abstracts

Background: Our previous study revealed a high prevalence of abnormal mineralization markers namely low 25 hydroxyvitamin D (47.9%); high serum alkaline phosphatase (3.7%) and low calcium-phosphate product (9.8%) suggestive of biochemical signs of osteomalacia (OM, defined as any two of these risk factors). OM was more prevalent in girls (11.2%) compared to boys (5.0%). In this follow-up study, we aimed to evaluate if biochemical OM was associated with low intakes of calcium and phosphorous.

Methods: Saudi adolescents (n=2938, 57.8% girls), aged 12-17 years from 60 different secondary and preparatory year schools in Riyadh, Saudi Arabia were included in this study. A dietary recall for daily intakes of nutrients/minerals using a validated computerized food database “ESHA—the Food Processor Nutrition Analysis program” was collected. Compliance to reference daily intake (RDI) was calculated. Fasting blood samples were collected and circulating levels of 25 hydroxyvitamin D, alkaline phosphatase, calcium, phosphate, and C-terminal telopeptide (CTX) were analyzed.

Results: A total of 1703 Saudi adolescents (991 girls, 712 boys) provided the dietary recall data. A major proportion (89.6%, 92.2%) of the participants failed to achieve the RDI of 1000 mg/day and 10 mg/day of dietary calcium and vitamin D respectively. The average daily dietary calcium intake was significantly lower in girls compared to boys (median levels of 294.3 and 345.5 mg/day respectively, P<0.001). In contrast, boys reported lower dietary intakes of phosphorous compared to girls (P<0.01). Interestingly, no significant correlation in status of biochemical OM or its individual risk factors with dietary calcium intake was found, irrespective of sex. However, circulating 25 hydroxyvitamin D and alkaline phosphatase levels correlated negatively with daily dietary intakes of phosphorous in girls (r=-0.18, P<0.001) and boys (r=-0.14, P<0.05) respectively.

Conclusions: This study suggests a need for vitamin D fortification and increased dietary calcium in the diet of Saudi adolescents. The results also show that all adolescents exceeded the RDI for dietary phosphorous but none met the RDI for dietary calcium and vitamin D, and none had sufficient 25 hydroxyvitamin D levels (>50nmol/l). We speculate that the high phosphate diet may somehow compensate for the insufficient supply with calcium and vitamin D. This insufficient supply would otherwise have caused a much higher prevalence of biochemical OM than the 6.2% we observed.