Vitamin D is essential for a healthy life. But it's the only vitamin that acts more like a hormone. While we can get increased amounts of it from foods like fatty fish and nuts, mostly we rely on sun exposure to change a compound in our body's cholesterol in order to get what we need. But vitamin D deficiencies are increasingly common—or at least increasingly diagnosed. If you experience more than a few of these symptoms, you may want to get your levels checked.
If you are getting seven to eight hours of sleep a night, but find yourself feeling deeply fatigued throughout the day, it may be a sign of a vitamin D deficiency.