Of all the important vitamins and minerals, Vitamin D has been getting a much deserved special attention during the last few decades in North America due to its high prevalence of deficiency. Some studies cite insufficient levels of 25-hydroxyvitamin D (marker for vitamin D blood levels) in as high as 40 percent of individuals tested. Although this vitamin is naturally synthesized by the body when the skin gets exposed to ultraviolet radiation from sunlight, use of sunscreen blocks this method of production but in turn protects against skin cancer and burns. Although governments and health authorities have tried implementing policies such as fortifying dairy products with vitamin D, deficiency in the following vitamin still remains at high levels amongst North Americans which highlights the imminent need for supplementation.

There are two different forms of vitamin D: D2 which is produced by plants, and D3 which is produced by humans and animals after exposure to ultraviolet radiation from the sun. Since the D3 form is more effective in raising blood levels of vitamin D, it is considered the activated form of this vitamin and is the form used in almost all vitamin D supplements. Research has shown vitamin D to play numerous roles throughout the body including the following: ensuring optimal bone health through regulation of calcium and phosphorous absorption in the intestines and maintaining blood levels of both minerals; supporting the immune system; and aiding in cell growth and differentiation. Current research is examining potential roles of this vitamin in autoimmune diseases such multiple sclerosis (MS), inflammatory diseases like arthritis, cardiovascular health, and cognitive decline.

Since vitamin D is a fat soluble vitamin, it is highly recommended to take with food containing fat to ensure higher absorption. However, it is also important to note that vitamin D supplements that contain fat within the capsule or gel will additionally increase the absorption of this vitamin by the body. Therefore, even though these supplements tend to cost more than their non-fat containing counterparts, the amount absorbed will also differ greatly.