Sundown Naturals Vitamin D3 is a potent and active form of Vitamin D.* Our fast acting liquid softgels are easy to swallow, and are a convenient way to get your daily intake of this essential vitamin. Our Vitamin D3 supports healthy bones and teeth, and helps keep your immune system healthy year-round.* Vitamin D3 is the form naturally produced in the body from sunlight. Your body can produce Vitamin D when your skin is directly exposed to sunlight. If you’re not getting enough Vitamin D every day, you may not be able to adequately absorb Calcium from the foods you eat, and your body will have to take Calcium from your bones.