Vitamins

Fish and shellfish are well known as sources of the fat soluble vitamins A and D.

Fat Soluble Vitamins

Fish and shellfish are well known as sources of the fat soluble vitamins A and D. Vitamin A can occur in two different forms - as retinol, which is easily absorbed by the body, or as carotenoids, which are less easily absorbed and have only 50% of the absorption rate of retinol. Carotenoids are converted to vitamin A once absorbed by the body. The easily absorbed retinol is the type of vitamin A found in fish.

Vitamin A has a number of functions in the body - it is needed in the eye for the transmission of light stimuli to the brain and is important for night vision. It promotes the growth and health of all cells and is particularly important for endothelial cells. It is important for reproduction and embryo development and acts as an antioxidant, helping to reduce risks of some cancers and heart disease.

Vitamin A is found in quite high amounts in oil-rich fish such as herring and mackerel and in shellfish. 4oz/100g portions of these fish provide around 10 to 15% of the adult recommended daily amount (RDA) for retinol. Oil-rich fish are also excellent dietary sources of vitamin D3, (cholecalciferol) providing 50 to 200% of the RDA in a 4oz/100g portion.

Vitamin D promotes the absorption of calcium and phosphorus from the intestine and regulates blood calcium levels. Without vitamin D the small intestine absorbs no more than 10 to 15% of dietary calcium. Vitamin D is also important in bone metabolism, helping to control bone formation and resorption and it may also play a role in preventing some cancers.

The flesh of oil-rich fish is a better source of vitamin A and D than white fish, but the livers of both white fish and oil-rich fish are very high in both vitamins A and D. This is important to note as pregnant women may be exceeding their vitamin A requirement by taking supplements such as cod liver oil. Too much vitamin A can be dangerous especially during pregnancy when it may be linked with an increased risk of miscarriage.

Vitamin E is present in significant amounts in many seafoods, for example salmon and some shellfish, providing up to 15% of the RDA for vitamin E in a 4oz/ 100g portion. Vitamin E acts as an antioxidant protecting polyunsaturated fats and Low Density Lipoprotein (LDL) cholesterol from oxidation by free radicals and may also have anti-inflammatory effects.

Water Soluble Vitamins

Most fish are a source of some B vitamins, particularly thiamine, riboflavin and pyridoxine. A 4oz/100g portion of most fish will provide approximately 10% of the RDA for these vitamins. Fish are especially rich in vitamin B12, supplying 100% or more of the adult RDA in a 4oz/100g portion. B vitamins are essential for the metabolism of food, particularly carbohydrate. B12 is important for the formation of red blood cells. Fish generally provide little or no vitamin C.