There are generally two kinds of liver oil supplements that people take — cod liver oil and shark liver oil. Unfortunately, both have much to be desired.
Cod liver oil is a much more common liver oil, and has been taken traditionally for health reasons. The primary benefits of cod liver oil are omega-3 fatty acids and very high levels of Vitamin A and Vitamin D. The presence of these vitamins is what differentiates cod liver oil from omega 3 fish oil. In fact, too much Vitamin A from cod liver oil has been shown to produce hip fractures in various studies, so it’s probably not good to take cod liver supplements.
Shark liver oil also contains omega-3s, but has other additional benefits like Alkylglycerols (AKGs) and squalene. AKG’s have been associated with better immune function and have demonstrated a reduced need for chemotherapy and radiation treatment by keeping levels of white blood cells up (because of how eicosanoids work). AKGs are also taken for colds, flu & chronic infections. They’re also taken to speed up wound healing, and to improve inflammation-based conditions such as asthma, psoriasis and arthritis.
However, some shark liver oils were found to have high levels of toxic pollutants such as PCBs (Polychlorinated biphenyl), so you have been warned!