Cod liver oil and vitamin AD have the same main ingredients, but the difference is that the former is natural and the latter is synthetic. Cod liver oil is a product extracted directly from the liver of fish, so it is an internal component of the animal’s body that supplements the body with vitamin AD. It is a natural ingredient. Vitamin AD, it belongs to the synthetic products, its main ingredients and the composition of cod liver oil is the same, used to supplement the human body’s vitamin A, D, usually the ratio of vitamin A and D to 3:1 synthesis. Vitamin AD is “synthetic vitamin AD oil”. However, for some people who are allergic to seafood, cod liver oil cannot be used, but only direct vitamin AD or vitamin D supplementation. Cod liver oil and vitamin AD should be used under the supervision of a doctor, as unauthorized use can lead to side effects.