With people's life and work gradually entering high-rise buildings, people have less chance to contact with sunlight. The study found that sunlight is a necessary condition for the synthesis of vitamin D, and vitamin D is the key factor to promote calcium absorption. 
Patients with osteoporosis can be relieved or cured by more exposure to the sun
 it was concluded that modern people are more likely to suffer from diseases caused by calcium deficiency such as osteoporosis.