The importance of Vitamin D to optimum health and the widespread deficiency crisis has achieved top billing in the past couple of years. Another vitamin looms on the horizon as the next superstar, though, and that vitamin is A. Most Americans possibly know Vitamin A as an antioxidant and as an important nutrient for eye health, but this vitamin also plays an invaluable role in gut health.  Vitamin A is a necessary factor in healthy mucus lining from sinus to lungs to stomach