Cod liver oil is a nutritional supplement derived from liver of cod fish. Cod liver oil contains more vitamin A and more vitamin D per unit weight than any other common food. One hundred grams of regular cod liver oil provides 100,000 IU of vitamin A, almost three times more than beef liver, the next richest source; and 10,000 IU vitamin D, almost four times more than lard, the next richest source. Of course, cod liver oil is only consumed in small amounts, but even a tablespoon (about 15 grams) provides well over the recommended daily allowance for both nutrients. It has high levels of the omega-3 fatty acids, EPA and DHA, and very high levels of vitamin A, vitamin D and vitamin E. It is widely taken to ease the symptoms of arthritis, and also seen to be helpful in alleviating symptoms of autism, as well as other health benefits. It was once commonly given to children, because the high levels of vitamin D in cod liver oil have been shown to prevent rickets. Other Uses: Cod Liver oil has also been shown to have a positive effect on the heart, bone, and brain, as well as helping to nourish skin, hair, and nails. It's also been listed as treating long-term multiple sclerosis. Cautions: because it's high in Vitamin A, it's possible to exceed the recommended daily limits of Vitamin A, which can reach unhealthy levels when accumulating in body fat. This is called hypervitaminosis. This risk is reduced depending on the level of purity of the cod liver oil. Pregnant women should not take as high doses can lead to birth defects.