Fish and fish products are commonly regarded as the most important natural food sources of vitamin D. Vitamin D contents differ greatly between species. It also varies with season as to be expected but also varies with environmental conditions and diet.
Various cooking method such as frying in oil can reduce vitamin D content by as much as half.
In general, the higher fat content of the fish meat, the higher is the vitamin D content. Oily fish such as mackerel and herring contain a higher level of vitamin D than learner fish like flounder and sea trout.
Oils extracted from the livers of shark, cod and halibut are very rich in vitamin A. These fatty acid fish obtain vitamin A by ingesting plankton living near the surface of the sea, and get exposed to sunlight.
Vitamin E functions as a natural antioxidant to prevent lipids from becoming rancid. Fish flesh is only a low to modest source of vitamin E.
Relatively few values for the vitamin K content of fish are available.
Vitamin B complex, especially niacin is present in good amount. Two other water soluble vitamins, folic acid and vitamin C are found in very small amounts in the edible portions of fish and shellfish.
Though a good amount of vitamin C is present in raw fish, it is destroyed in cooking. Most fish foods begin to lose some their potency in processing and continue to lose it.
Fish source of vitamin