What is cod liver oil? Cod liver oil is a nutritional health product extracted from the livers of deep-sea fish such as sharks and cod. It is rich in vitamins A, D, E, K and other nutrients and unsaturated fatty acids. It can not only enhance human immunity and improve skin quality, but also help prevent cardiovascular and cerebrovascular diseases, enhance bone health and other multiple effects. Effects of cod liver oil 1. Enhance immunity: Cod liver oil is rich in nutrients such as vitamins A and D, which can enhance the body\’s immune function, improve the body\’s resistance, and prevent colds and other diseases. 2