Impact of Work Environment Absent of Natural Light on Vitamin D Levels

Inclusion Criteria: * people employed in their current work place at least 6 months, Exclusion Criteria: * people who consume food additives containing Vitamin D. * people who have a chronic illness which harms the Vitamin D absorption, such as Celiac, chronic Pancreatitis, Cystic Fibrosis and IBS. * people who have a chronic illness which harms Vitamin D metabolism, such as chronic hepatitis, kidney insufficiency and Nephrotic Syndrome. * pregnant women. * people who require prescribed medicine like steroids, anti-convulsion, and HIV treatments.