Shark liver oil is an extract derived from the livers of various shark species, commonly those inhabiting deep-sea environments. For centuries, communities in coastal regions, such as Scandinavian fishermen, used this oil as a traditional remedy. Its historical applications included promoting the healing of wounds and addressing various general health concerns. The oil served as a folk remedy for a range of ailments before modern scientific investigation.
Key Components of Shark Liver Oil
Shark liver oil contains unique compounds that set it apart from other marine oils. A prominent component is squalene, a natural organic compound classified as a triterpenoid. This lipid serves as a precursor in the body’s synthesis of cholesterol and is also a natural constituent of human skin sebum, where it contributes to hydration and serves as an antioxidant. The concentration of squalene can vary significantly, sometimes comprising up to 90% of the oil, depending on the shark species from which it is extracted.
Another notable group of compounds found in shark liver oil are alkylglycerols (AKGs). These are a type of ether lipid naturally present in various biological systems. Alkylglycerols are involved in the formation of cell membranes. The presence of both squalene and alkylglycerols distinguishes shark liver oil from more common fish oils, which are typically rich in omega-3 fatty acids.
Reported Health Applications
Shark liver oil has been associated with several purported health applications. Its alkylglycerol content is believed to support the immune system by stimulating white blood cells, such as macrophages, and enhancing antibody production. Preliminary studies suggest that these compounds may play a role in the body’s defense mechanisms against infections.
The squalene found in the oil is thought to contribute to skin health and wound healing. Squalene helps maintain skin hydration and has been applied topically for various skin conditions. Animal and test-tube studies indicate that alkylglycerols may also offer anti-tumor potential by activating certain white blood cells and by restricting the formation of new blood vessels that could feed tumor growth. Squalene has been investigated for its potential to reduce inflammation caused by some anti-cancer treatments.
Sourcing and Environmental Impact
The primary source of shark liver oil is deep-sea sharks, including species like the gulper shark, dogfish shark, and basking shark. These sharks are targeted because their livers are exceptionally large, often accounting for 5% to 25% of their total body weight, and are rich in the desired oil. The global demand for shark liver oil, which is used in dietary supplements, cosmetics, and even vaccine adjuvants, drives significant fishing pressure on these species.
Deep-sea sharks are particularly susceptible to overfishing due to their unique biological characteristics. They are known for their slow growth rates, delayed sexual maturity, and low reproductive output, with some species giving birth to only one or two pups every few years. The expansion of deep-water fishing technologies has exacerbated these issues, leading to a substantial increase in the number of threatened deep-water shark and ray species, with about one in seven currently facing extinction.
Potential Risks and Side Effects
Shark liver oil can present certain potential risks and side effects. Common, milder side effects reported by users include an unpleasant taste or odor, nausea, upset stomach, and diarrhea. Some studies also suggest that high doses of shark liver oil may lead to increased blood cholesterol levels.
A more concerning issue is the potential for bioaccumulation of environmental toxins. As apex predators, sharks can accumulate high levels of contaminants like mercury and polychlorinated biphenyls (PCBs) in their tissues over their long lifespans. While some analyses of commercially available shark liver oil supplements have shown low levels of mercury, the presence of such toxins remains a consideration. Additionally, there have been rare reports of shark liver oil-induced pneumonia in humans, and excessive intake could lead to vitamin A toxicity due to its natural content. Individuals considering taking shark liver oil should consult with a healthcare provider, especially if pregnant, nursing, or managing pre-existing medical conditions.