Vitamin A is a fat-soluble vitamin that is naturally present in many foods. Vitamin A is important for normal vision, the immune system, skin, bones, and reproduction. It helps the heart, lungs, kidneys, and other organs work properly. There are two different types of Vitamin A, carotenoids and retinyls. Retinyls are ready for use by the body so are preferred over carotenoids which must be activated in the body.
It is obtained from the diet either as all-trans-retinol, retinyl esters or ß-carotene. All-trans-retinol is esterified to retinyl esters and stored in the liver, mostly in the stellate cells
Vitamin D3 (cholecalciferol) helps regulate the amount of calcium and phosphate in the body. These nutrients are needed to keep bones, teeth, and muscles healthy, and aid with cognitive health and immune support. A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults.
It is synthesized in the skin from a process which depends on sunlight. Alternatively, it can be acquired in the diet or in vitamin supplements. Vitamin D3 is converted in the liver. It can also be metabolized in the kidneys to a physiologically active VD3 metabolite. In addition to being processed in the liver and the kidneys, VD3 can also be metabolized by cells of the immune system
Vitamin A and Vitamin D work in partnership that has been has been refined through time. They must be supplemented together so that a “functional” deficiency is not created. The pairing of Vitamin A and Vitamin D allows these two nutrients to balance, enhance, and contain each other, through a receptor called RXR. The result, which cannot be achieved with either nutrient alone, is a balanced, functioning immune system that does not swing into autoimmune disease, or have trouble handling pathogens. Healthy immune systems are linked to healthy nervous systems.