<prompt> Answer this question truthfullyWhat are the epidemiological and demographic factors associated with Vitamin D deficiency?  <response>: <reason> According to Institute of Medicine IOM, based on the National Health and Nutrition Examination Survey NHANES 20032006, there is an overall 18.8 prevalence of serum 25OHD concentrations below 40 nmolL in the US. However, data from the National Health and Nutrition Examination Surveys NHANES in 2001-2006 shows that one-quarter were at risk of vitamin D inadequacy serum 25OHD 3049 nmolL, and 8 were at risk of vitamin D deficiency serum 25OHD less than 30 nmolL. Statistics from the Canadian Health Measures Survey CHMS, Cycle 1, 20072009 shows that 13 of Canadians have vitamin D level below 40 nmolL. Naugler et al. reported that based on the results from Calgary Laboratory Services and Census Canada data in 2010-2011 on individuals older than 25 years old residing in Calgary, Alberta, 26 of individuals had serum 25OHD levels of less than 50 nmolL. In both sexes, the prevalence was lowest in children aged 18 years. Risk of deficiency increased significantly with age until age 30 in males and age 18 in females, after which it did not change significantly with age. There is a slightly higher prevalence of vitamin D deficiency in female than male. According to the National Health and Nutrition Examination Surveys NHANES in 2001-2006, the season-adjusted prevalence at risk of deficiency by age ranged from 1 to 8 in males and 1 to 12 in females. Non-hispanic white people are at lower risk of vitamin D deficiency than African-Americans, Hispanics and Asians. Analysis from Gozdzik A et al. study on 107 young adults in Toronto during winter of 2007, shows an association between serum 25OHD level and skin pigmentation. 34.4 of individuals with European ancestry had serum 25OHD levels of less than 50 nmolL, whereas East and South Asians had 85.2 and 93.5 respectively. Chowdhury R. et al. in meta-analysis of observational studies, reported that the prevalence of vitamin D insufficiency 75 nmolL was 69.5 for the United States and 86.4 for Europe. Severe Vitamin D deficiency 25 nmolL were seen in 15 and 4 of general population in the United States and the Europe. In the Uppsala Longitudinal Study of Adult Men, a cohort study on 1194 swedish men during the winter season, there is only 5 prevalence of serum 25OHD levels below 40nmolL. According to the Healthy Lifestyle in Europe by Nutrition in Adolescence HELENA study on 1006 adolescents of 12.5-17.5 years old age, selected from 9 European countries, 39 of them had insufficient 50-75 nmolL, 27 had deficient 27.5-49 nmolL and 15 had severely deficient 275 nmolL levels of serum 25OHD. Puri S. et al. reported a result from a study on 3127 apparently healthy Delhi schoolgirls. It showed that 90.8 of them had insufficient serum 25OHD levels 50 nmolL in both groups of low and high socioeconomic strata. Vitamin D deficiency is very common among Saudi women. About 80 of women in Adarawi MS et al. study demonstrated vitamin D deficiency 50 nmolL. There are relatively higher levels of serum 25OHD in Thailand compared to European, Middle eastern and other Asian countries. Chailurkit et al. reported 2.8 to 14.3 vitamin D deficiency 50 nmolL overal in different regions of Thailand. 