by Joshua Soll

Shark liver oil is used as a dietary or health supplement in many countries. Some of these supplements also contain squalene, a derivative of shark liver oil. While certain components of shark liver oil, such as omega-3, are important to the human body, the risks of these supplements may outweigh their benefits. Many other supplements that are safer and more sustainable than shark liver oil exist. There is little research on shark liver oil as a supplement and the results of the existing research are somewhat contradictory. Some research in this field demonstrates that shark liver oil can be harmful due to the presence of pollutants while other research claims that it could be beneficial to human health.

Multiple studies have found large quantities of harmful pollutants in the liver of different shark species (Venugopal et al. 2016 May 31; Cotronei et al. 2018; Salvo et al. 2020). Tsutsumi et al. (2018) tested the dioxin concentration of 46 supplements made from shark liver oil, marine mammals, egg yolk, or mixtures of these ingredients. 43 out of 46 supplements tested in their research contained dioxins, which are a persistent environmental pollutant with a high toxic potential. Additionally, shark liver oil supplements had some of the highest concentrations of dioxins compared to the others. Furthermore, the dioxin concentration in many of these products were well above the determined Japanese tolerable intake of this harmful pollutant. In another study, multiple pollutants and chemicals have been found at worrying levels in the liver of sixgill sharks, including dioxin-like and non-dioxin-like PCBs, pesticides, and plasticizers (Salvo et al. 2020). The concentration of DDT, a persistent chemical, of 15 greenland sharks was identified in one study (Cotronei et al. 2018).  DDT was highest in the muscle tissues of this shark species but still present in the liver. 

There is little existing literature that researches the effect of shark liver oil on the human body. However, the small body of research that does exist studies the effect of shark liver oil in the potential for cancer treatment (Gómez de Cedrón et al. 2019) and on the vascular system (Hamadate et al. 2015). Hamadate et al. (2015) aimed to assess the effect of shark liver oil as a supplement on arterial stiffness and peripheral microvascular function in otherwise healthy middle-aged and older males with slightly increased arterial stiffness. They found that shark liver supplements can have some small beneficial health benefits. However, the exact ingredient(s) in shark liver oil that may benefit the human body is unknown. Gómez de Cedrón et al. researched the safety and tolerability of a dietary supplement containing rosemary extract and shark liver oil enriched in bioactive alkylglycerols on the human body. They found a lack of adverse effects of this treatment on the human body, indicating that it could potentially be used as a co-adjuvant in different diseases following further research. 

The field of research on supplements containing shark liver oil is new and requires more studies for the advancement of knowledge on its effects on human health. Without concrete scientific evidence on the effect of shark liver oil, cosmetics, or any supplement, how can we be certain that they are safe for consumption? Shark liver oil supplements not only harm sharks, but could be unsafe to humans as well.

There are several alternative ways to obtain your daily omega-3s and healthy fats that don’t contribute to the decimation of shark populations or that may harm your health. Make some overnight chia pudding, add flaxseed to your mid afternoon smoothie, eat some nuts or sustainably caught fish. Whatever you do, please don’t supplement with sharks!