Vitamin D

Vitamin D is essential for health, maintaining strong bones, and aiding in the absorption of calcium and phosphorus. Vitamin D helps regulate the calcium in the blood and helps protect against the loss of bone mass. Without vitamin D, the muscles would not be able to function, and the brain would not be able to communicate through the nerves. Vitamin D is important for the immune system because it helps fight off the invading bacteria and viruses. Here are three ways you can absorb vitamin D:

From the Sun

When the sunlight makes contact with unprotected skin it gets converted to vitamin D. However, make sure to apply sunscreen in order to be safe against ultraviolet radiation. 

From Food and Drinks

Vitamin D is not commonly found in food, but salmon and mackerel are excellent choices for foods that contain high amounts of vitamin D. To increase consumption, try looking for foods and drinks that have been fortified with vitamin D.

From Supplements

Certain individuals may need to increase consumption such as older adults, breastfeeding infants, people with dark skin, and compromised immune systems. Make sure to consult a registered dietitian about taking a vitamin D supplement.

Source: https://www.eatright.org/food/vitamins-and-supplements/types-of-vitamins-and-nutrients/what-is-vitamin-d