Skeletal Muscle Strength Including Its Energy Metabolism, Bone Mineral Homeostasis and Th1/Th2 Cytokines Expression in Asian Indians With Chronic Hypovitaminosis D Before and After Oral Cholecalciferol Supplementation

Vitamin D is an essential nutrient that plays an important role in calcium metabolism and bone health. In recent years, biomarkers like PTH, calcium absorption have been used to define relevant biological indices of vitamin D nutritional status.

Prevalence of 25(OH)D in Asian Indians Several studies from India have shown wide prevalence of vitamin D deficiency (VDD) in India, Goswami et al studied serum 25 (OH)D levels and its functional significance in apparently healthy subjects residing in Delhi. In this study three groups of subjects (soldiers, depigmented person and physicians and nurses) were studied in winter. Other three groups namely pregnant women, newborns and physicians and nurses were studied in summer. All the groups except one with maximum sunlight exposure (soldiers) had subnormal concentration of serum 25(OH) D levels. Vitamin D deficient groups tended to have an imbalance in bone mineral homeostasis when exposed to winter and low dietary calcium and high dietary phytate, with significantly low serum calcium and elevated PTH.On the basis of the studies related to the intestinal calcium absorption, inverse relation with serum iPTH concentration and protection from fracture risk, a recent consensus has suggested that an ideal health based normal cutoff of circulating serum 25(OH) D would at least be 32 ng/mL. Interestingly, using the above consensus, recent studies conducted at AIIMS, by Goswami et al , have shown that 94.3% of the apparently healthy northern Indian subjects residing in Delhi were vitamin D deficient (AJCN 2006, BJN 2008).

Functional Significance of 25(OH)D deficiency Though there have several studies highlighting widespread prevalence of 25(OH)D in Asian Indians, there is paucity of data on its functional significance. Relevant studies assessing functional significance of VDD in Asian Indians are summarized below (Am J Clin Nutr 2000).

A) Effects on Serum PTH levels Goswami et al while reporting low serum 25(OH) D concentrations in healthy subjects in Delhi, showed a higher serum PTH levels & significant inverse relation between serum 25(OH) D and PTH levels ( r = -0.6303, p < 0.001) in all the three groups (soldiers, physicians & nurses, depigmented persons) studied in winter (Am J Clin Nutr 2006) B) Effects on BMD Recently,we have analyzed relationship between BMD and serum 25(OH) D in 105 apparently healthy Asian Indian. The cohort of 105 subjects was split into 2 groups at a serum 25(OH) D cutoff of 9.0 ng/mL. The mean serum iPTH was significantly higher in the group 1 (<9.0 ng/ml)than in the group 2 subjects (53.1±31.3 and 39.3±17.5 pg/mL, respectively; P=0.012).The mean BMD values of the total hip, including femoral neck, trochanter, and intertrochanter, were significantly (P = 0.001) lower in group 1 than in group 2.

C) Effects on intestinal calcium absorption Effect of VDD on intestinal calcium absorption in Asian Indians with chronic hypovitaminosis D and its change after cholecalciferol supplementation was studied recently at our Department of Endocrinology and Metabolism. Study subjects were 29 apparently healthy volunteers [17 M, 12 F, mean (SD) age = 28.4 ± 6.4 year] with low serum 25(OH)D levels [mean (SD) = 7.6 ± 4.8 ng/ml]. Intestinal calcium absorption was assessed by 'calcium load test' (PAK test) (10) using 1 gm of oral elemental calcium load before and after (n = 26) supplementation with oral cholecalciferol (60,000 IU/week for eight weeks). This study showed that the vitamin D Deficiency is physiologically relevant in terms of intestinal calcium absorption in Asian Indians.