Nature's Way Vitamin D3 1000IU helps maintain healthy Vitamin D levels and prevent dietary deficiency when sunlight exposure or dietary intake is inadequate in healthy adults and adolescents. Vitamin D is a key nutrient to help: - Maintain bone health, strength and density. - Support immune system health. - Maintain muscle health and function when sun exposure is inadequate Vitamin D also helps calcium absorption and a diet deficient in calcium can lead to osteoporosis in later life.