Vitamin D: How to Increase Your Energy, Revitalize Your Skin and Improve Your Health Today, the deficiency of vitamin D is very common. In the United States alone, there are more than 200 million people (men, women and kids) who lack this crucial vitamin and hence are suffering from chronic health conditions like fatigue, diabetes, heart ailments, cancer, skin related issues and various autoimmune diseases. Almost 70% of Americans apply sunscreens and avoid the sun for fear of sunburns and rashes. This phobia has led to a deficiency of this vital vitamin. Vitamin D is often commonly called as the 'sunshine vitamin'. This is because natural sunlight is one of the best sources of this vitamin.