Cod Liver Oil with Vitamin A and D3 may be the ultimate combination of nutrients for immune and brain health. Cod liver oil is a rich source of omega-3 fatty acids which may be critical in supporting brain heath. One of the fatty acids, DHA, is also important for the development and ongoing health of the central nervous system and brain function throughout life. Vitamin A is involved in the development of the immune system and plays regulatory roles in cellular immune responses and humoral immune processes. Meanwhile vitamin D3 is a popular supplement because it may play a protective role with the brain. Also, without D3, important immune cells such as T-lymphocyte (T-cells) would not develop fully or function properly. Having a supplement that contains fish oil (cod liver) plus vitamin A and D3 all together in one easy-to-swallow softgel can save you time and money.