Vitamin D and calcium are well known for their synergistic roles in supporting bone mass. Calcium is used to form part of our bone structure, and vitamin D helps increase calcium absorption from foods and supplements. In recent years, calcium has also garnered a lot of press for its potential role in fat loss. Mounting evidence now suggests that vitamin D may be important for optimizing physique gains — the vitamin plays a role in muscle growth and strength.

Scientists first became intrigued with the role of vitamin D in muscle growth when it was discovered that muscles have receptors for the vitamin. These receptors appear to affect muscle in several different ways. When vitamin D interacts with its muscle receptors, changes can occur at the genetic level that can increase growth. Additionally, vitamin D can boost calcium levels in muscle, which is important for muscle function.

Studies have linked different types of vitamin D receptors to increased grip strength, as well as increased hamstring and quadriceps strength. Although we can't alter the type of vitamin D receptors we are born with, we can increase vitamin D intake to ensure that all of our receptors are activated.

There are two types of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D3 is the more potent form. To maximize vitamin D3 levels, eat fatty fish, such as salmon, and take a vitamin D3 supplement.

Vitamin D3 is also produced in the skin upon exposure to the sun; however, scientists warn that the risk of skin cancer outweighs the benefits of getting the vitamin that way and, therefore, suggest dietary intake as the primary source of this nutrient.

taken from Flex Magazine, June 2006