Although the amount of vitamin D adults get from their diet is often less than what’s recommended, exposure to sunlight can make up for the difference. However, not all people are living in regions that will provide enough exposure to the sun. Older adults and people with dark skin may not get enough vitamin D. The recommended dietary allowance (RDA) for adults is 600 IU of vitamin D a day which increases with age Some foods rich in vitamin D would be milk and yogurt and fatty fish such as salmon or tuna. If your doctor suspects that you are not getting enough vitamin D, a supplement or a multi-vitamin containing vitamin D may be recommended. The following link offers a good discussion on the value of vitamin D.
http://www.health.harvard.edu/newsweek/Vitamin-D-Enjoying-its-day-in-the-sun.htm