You may be up to speed on vitamin C and even know a bit about the various B vitamins, but what about vitamin D? Well, some are calling it the "super supplement." Here is what you need to know.

Vitamin D is a fat-soluble vitamin, which means it needs fat to be absorbed by the body. This is one of the many reasons why it is important to have fat in your diet. In October 2008, the American Academy of Pediatrics doubled the amount of vitamin D recommended for infants, children and adolescents (from 200 IU to 400 IU). This drastic change made many people take a closer look at this vitamin.

Vitamin D plays an important role in calcium absorption and bone growth. For children, it helps prevent rickets, which is a softening of the bones characterized by knocked knees and bowed legs. In adults, this condition is known as osteomalacia and is characterized by bending of the bones, especially the spine. Vitamin D is also involved in nerve and muscle function and helps reduce inflammation in the body. Recent research suggests that it may also play a role in immune system function and protection against high blood pressure.

Vitamin D is one of the only vitamins that your body can make on its own! Your skin can actually synthesize vitamin D when it is exposed to sunlight (how cool is that?). Foods such as eggs, fish, mushrooms and fortified milk products also contain vitamin D. Since it is not present in a wide range of foods, supplements are also available. Look for vitamin D in a multi-vitamin or a separate supplement in the form of vitamin D3.

It's important to note that you cannot overdose on vitamin D with too much sun exposure, but too much from supplements can be toxic. Always talk with a registered dietitian or your doctor before taking a supplement. Signs of overdoing it include nausea, confusion and fatigue.