Natural Factors Vitamin D3 is carefully blended with organic flaxseed oil to deliver a dietary supplement to help with bone, muscle, and immune health.

Known as the sunshine vitamin, D3 is essential for bone development, is required for calcium and vitamin C absorption, and supports your nervous system.

Anyone who lives far away from the equator may not make sufficient vitamin D in their skin during long, gloomy winters.

People who do not get enough vitamin D may develop soft, thin, brittle bones -- called rickets in children and osteomalacia in adults.

As well as playing a critical role in bone health, vitamin D is also needed to

• Maintain healthy teeth

• Move muscles

• Carry messages between the brain and body parts

• Maintain a healthy immune system to fight off invading bacteria and viruses

• Help regulate cell growth

D-2 or D-3?

Vitamin D-3 is one of two forms of vitamin D, the other being D-2.

Vitamin D-2, or ergocalciferol, is commonly used to fortify milk.

But it is vitamin D-3, or cholecalciferol, that your body synthesizes in your skin after exposure to sunlight.

Previously, vitamins D-2 and D-3 were considered interchangeable. Today, however, vitamin D-3 is believed to be better at raising levels of vitamin D in your blood.

When you see vitamin D mentioned without a number, it is generally referring to vitamin D-3.