It has rich protein, calories, calcium, vitamin B. It has 200 times of vitamin A compared to beef.  Rich vitamin A and vitamin B are especially good for the stamina of male. It was known as health food since long time ago. Eels cooked with herbs are loved dearly by males.
It has much vitamin B, also called tocopherol, controls oxidation of unsaturated fatty acids. It strengthens blood vessels and gives energy. It helps blood circulation and ovarian move of females. It prevents forming of wrinkles and aging.

Eel contains healthy unsaturated fatty acid(DHA 1,322mg and EPA742mg). Also, it has much lecithin. It's a main element composing the cell membrane. There was a research saying that lecithin elevates memories and learning ability about 20%.
Vitamin A, vitamin E, calcium, iron and such ingredients necessry for the growth is contained much more than beef.