As people's life and work gradually enter high-rise buildings, people have less exposure to daylight. It is found that sunlight is a necessary condition for the synthesis of vitamin D, and vitamin D is a key factor to promote calcium absorption. 
People with osteoporosis spend the same amount of time exposed to sunlight as others
 some people have come to the conclusion that modern people are more likely to suffer from diseases such as osteoporosis caused by calcium deficiency.