Nature’s Bounty Vitamin D3 (2000-IU) of Vitamin D in its most active form, cholecalciferol. This supplement is designed to support overall health by helping maintain bone strength and immune system function. Vitamin D3 is the form of vitamin D naturally produced in the body through sunlight exposure. Aids calcium absorption for strong bones and teeth. Enhances immune defense by supporting immune cell activity. It may help maintain muscle strength, especially in older adults. Adequate Vitamin D levels are associated with emotional well-being.