title: Vitamin D status and its seasonal variability in healthy young adults in an Asian Indian urban population.
abstract: OBJECTIVE
  To assess the vitamin D status and its seasonal variability in healthy young adults in Chandigarh, a city in northern India.
  
  
  METHODS
  The history was elicited and examination was performed pertaining to metabolic bone disease in 329 young adults (18 to 25 years of age) at the end of summer and 237 subjects from the same cohort at the end of winter. The calcium profile, 25-hydroxyvitamin D [25(OH)D], and intact parathyroid hormone were measured during both the seasons.
  
  
  RESULTS
  Among the young adults in this study cohort, 25(OH)D sufficiency (≥ 30 ng/mL) was found in 72.5% in summer and in 50.7% in winter. A significantly higher number of men were 25(OH)D sufficient in comparison with women in summer (P = .001). The mean (standard deviation) serum 25(OH)D levels were significantly higher at the end of summer-52.9 (33.7) ng/mL-in comparison with that at the end of winter-31.8 (21.1) ng/mL; P<.001. The intact parathyroid hormone levels were significantly lower in the 25(OH)D-sufficient group (P = .001) and began to increase at 25(OH)D levels below 25 ng/mL. The serum 25(OH)D levels correlated positively with the duration of exposure to sunlight during summer (r = 0.111; P = .05) and also the calcium intake during summer (r = 0.129; P = .03).
  
  
  CONCLUSIONS
  Vitamin D sufficiency may be a reality with a combination of young skin, optimal and effective exposure to sunlight, and adequate calcium intake.
authors.affiliation: Department of Endocrinology, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India.
authors.forename: Santosh
authors.initials: S
authors.lastname: Ramakrishnan
authors.forename: Anil
authors.initials: A
authors.lastname: Bhansali
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Bhadada
authors.forename: Ravikant
authors.initials: R
authors.lastname: Sharma
authors.forename: Rama
authors.initials: R
authors.lastname: Walia
authors.forename: Muthuswami
authors.initials: M
authors.lastname: Ravikiran
authors.forename: Gopal
authors.initials: G
authors.lastname: Shanmugasundar
authors.forename: Padala
authors.initials: P
authors.lastname: Ravikumar
mesh_terms: D000368:Aged; D044466:Asian People; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D