Your body needs Vitamin D. It is necessary for your body to be able to absorb calcium and promote bone growth. If you are deficient in Vitamin D you are more likely to have soft, fragile bones.
Vitamin D deficiencies have been linked to multiple types of cancer, including: breast, colon, prostate, and heart. A lack of Vitamin D is also linked to depression, weight gain and other diseases.
There are multiple ways to increase your Vitamin D levels the best being from the sun. If you are outside for 10-15 minutes a day in the midday sun with no sunscreen your body will absorb a good deal of Vitamin D.
There are many foods rich in Vitamin D as well. Fatty fish, such as tuna and salmon. Cheeses, egg yolks, milk, almond milk, yogurt, and orange juice.