Abstract
Many studies showed Vitamin D deficiency is highly prevalent in healthy individuals. We planned to study the normal levels of Vitamin D in healthy individuals and make recommendation for defining deficiency of 25(OH)D in Indian population. Normal healthy subjects 18 to 60 years of age were included. Estimation of serum calcium, serum phosphorus, iPTH and bone alkaline phosphatase levels with vitamin D (25(OH)D) levels were done to study the normal 25(OH)D levels and make recommendation for defining deficiency of 25(OH)D in Indian population. Meta-analysis was performed of studies which estimated the mean vitamin D levels in healthy individuals. There was significant positive correlation of serum 25(OH)D levels with calcium levels (r = 0.148; p-value = 0.003). The normal mean values of 25(OH)D levels in total population was 13.5 ± 7.83 ng/ml, iPTH was 59.8 ± 28.84 pg/ml, bone ALP was 14.6 ± 6.66 microg/ml. The normal upper bound of 25(OH)D in 97.5% of total population in our study is less than 33.19 ng/ml. The normal upper bound of iPTH and bone ALP in 97.5% of total population in our study was less than 123.97 pg/ml and 32.19 microg/ml, respectively. Pooled analysis of 33 studies revealed overall mean 25(OH)D levels in total population to be 13.95 ng/ml (95%CI - 12.37-15.54). The concept of initializing treatment based on serum Vitamin D levels using the RDA (20ng/ml) and EAR (16ng/ml) values as "cutoff-points" is not recommended as per Institute of Medicine Committee on Dietary Reference Intakes, Washington DC. Vitamin D levels less than 12.5ng/ml in a symptomatic individual should be the sole criteria for treatment rather than Vitamin D levels alone. Trial Registration: CTRI/2018/02/011820; CTRI/2018/02/011913.