Vitamin D3 is the key to optimal health, plus it supports strong bones, muscles, teeth and immunity. Unfortunately, a large number of individuals are lacking this essential vitamin. Zahler's Vitamin D3 is the safe option for receiving the benefits of Vitamin D, instead of risking unprotected sun exposure. More about Vitamin D3: The "sunshine vitamin" can be acquired from sunbathing, but also from certain foods like eggs, fish, and fortified milk. Unfortunately, many people have inadequate Vitamin D3 levels and need supplements..