Cod is the common name for the demersal fish genus Gadus, belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus Gadus is commonly not called cod (aAlaska Pollock). The cod family is a huge family.  There are 3 suborders, including 12 families, 85 genera and 482 species. The two most common species of cod are the Atlantic cod, which lives in the colder water and deeper sea regions throughout the North Atlantic, and the Pacific cod, found in both eastern and western regions of the northern Pacific.
Cod is popular as a food with a mild flavor and a dense, flaky, white flesh. Many countries in the world eat cod as main food fish.  Cod is rich in nutrients, such as protein, vitamin A, vitamin D, calcium, magnesium, selenium and other nutrients.
The protein content of cod is higher than that of salmon, crucian carp, pomfret and hairtail. Cod livers are high-quality raw materials for extracting cod liver oil.  The proportion of these nutrients in cod liver oil is the optimal proportion of the human body's daily requirements.  In addition, cod meat is rich in magnesium, which is beneficial to prevent cardiovascular diseases such as hypertension and myocardial infarction, and cod has a good protective effect on the cardiovascular system.  As a result, cod is known as "gold in the sea" and "nutritionist on the table" in Europe.