Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors.

BACKGROUND Increased awareness of the importance of vitamin D to health has led to concerns about the prevalence of hypovitaminosis D in many parts of the world. OBJECTIVES We aimed to determine the prevalence of hypovitaminosis D in the white British population and to evaluate the influence of key dietary and lifestyle risk factors. DESIGN We measured 25-hydroxyvitamin D [25(OH)D] in 7437 whites from the 1958 British birth cohort when they were 45 y old. RESULTS The prevalence of hypovitaminosis D was highest during the winter and spring, when 25(OH)D concentrations <25, <40, and <75 nmol/L were found in 15.5%, 46.6%, and 87.1% of participants, respectively; the proportions were 3.2%, 15.4%, and 60.9%, respectively, during the summer and fall. Men had higher 25(OH)D concentrations, on average, than did women during the summer and fall but not during the winter and spring (P = 0.006, likelihood ratio test for interaction). 25(OH)D concentrations were significantly higher in participants who used vitamin D supplements or oily fish than in those who did not (P < 0.0001 for both) but were not significantly higher in participants who consumed vitamin D-fortified margarine than in those who did not (P = 0.10). 25(OH)D concentrations <40 nmol/L were twice as likely in the obese as in the nonobese and in Scottish participants as in those from other parts of Great Britain (ie, England and Wales) (P < 0.0001 for both). CONCLUSION Prevalence of hypovitaminosis D in the general population was alarmingly high during the winter and spring, which warrants action at a population level rather than at a risk group level.