Sunday, 25 May 2008

Nutrition, better than steak, milk, spinach or liver

Oysters would have been an ideal food for sailors, settlers and early nomadic natives. A dozen oysters can amount to less than 100 calories but are worth as much in protein as 100g of steak and contain as much calcium as a glass of milk. Unusually for any living animal or marine food, they are also a source of vitamin C.

Precise calculations vary from creek to creek, but overall even now they are a superb dietary source of food. Their fat is glycogen and starch. The glycogen, stored glucose, would have been an important source of energy especially useful for people acing long hard days of labour building new settlements.

So too, especially for the sailors, the cocktail of vitamins an oyster provides would have been a viable alternative to fruit and vegetables and help stave off diseases like scurvy.

Vitamin B12 was thought only to originate in fungi and bacteria, but it is the most pronounced of all the vitamins found in an oyster. B12 influences nerve cell activity, the metabolism in general, DNA replication, and affects moods positively. It is often prescribed as a top up for depression.

In lesser amounts in descending order the oyster will have Vitamin B1 (thiamin) which helps convert the glycogen to energy, Vitamin B2 (riboflavin), Vitamin C, niacin, Vitamin A, Vitamin B6 and Vitamin E.

The highest quantity of mineral in an oyster is zinc, which protects the immune system, helps wounds to heal, supports general growth especially in pregnancy and childhood. It also is linked to fertility. Curiously the next largest mineral is copper. Zinc often inhibits the absorption of copper into the body, which in turn allows the body to absorb and use iron. Iron and selenium are the other main minerals among a supporting cast that also include magnesium, phosphorus, manganese and calcium.

Only liver can equal an oyster in terms of the levels of iron and copper it delivers in the diet. Only spinach has as much folic acid.

The shells too have had medicinal and nutritional roles beyond the more obvious role they have played in building roads and footpaths; filling for wharfs, fortifications, and railway embankments. They were raw material for lime, an enricher for arable land They were fed to laying chickens to harden the egg shell. The pharmaceutical industry has also used ground oyster shell, incorporating it in pills to prevent osteoporosis because of its high level of calcium