HELPS SUPPORT HEALTHY BONES & TEETH. Vitamin D is needed to promote calcium absorption, which helps support healthy bones and teeth and provides 125 mcg (5000IU) per serving. PROMOTES IMMUNE HEALTH. Windmill Natural Vitamins Vitamin D3 plays an important role in the immune function. NON-GMO, GLUTEN FREE. Windmill Natural Vitamins Vitamin D3 is non-GMO and Gluten Free. ABOUT WINDMILL NATURAL VITAMINS. Windmill offers cutting edge, clinically based formulas to satisfy a variety of market needs, including multi and single vitamins and minerals, whole food supplements, greens, proteins, specialty formulas, anti-aging nutrition, condition specific, performance nutrition, and herbals.