Does Excessive Fish Consumption Linked to Increased Risk of Melanoma?

It is often assumed that the increased consumption of fish implies a lower risk to health, but recent research suggests that the relationship between fish intake and melanoma risk is complex and may be influenced more by the associated toxins than by the fish itself. While some studies have indicated a positive correlation between fish intake and melanoma risk, further and more thorough investigations are needed to draw conclusive findings.

Key Findings from Recent Research

According to a large, long-term study involving approximately 500,000 participants, higher total fish intake, including tuna, and non-fried fish, was positively associated with the risk of both malignant melanoma and melanoma in situ. Specifically, the study found that those consuming a median daily intake of 42.8 grams of fish had a 22% higher risk of malignant melanoma and a 28% increased risk of developing abnormal cells in the outer layer of the skin (melanoma in situ) compared to those whose daily intake was 3.2 grams. A serving size of cooked fish is roughly 140-170 grams, which is equivalent to a can of tuna.

Study participants' fish intake over a long term period.

The lead author, Eunyoung Cho, an associate professor of dermatology and epidemiology at Brown University, emphasized that despite the study's large scale and prospective design, it does not establish a causal relationship between fish intake and melanoma risk. This is due to the observational nature of the study, which does not control for all possible confounding factors.

Role of Bio-Contaminants in Melanoma Risk

Cho's previous research has shown an association between higher levels of mercury and skin cancer, leading her to speculate that bio-contaminants like mercury, polychlorinated biphenyls (PCBs), dioxins, and arsenic in fish may be the underlying cause of the cancer link. Cho stated, "We speculate that our findings could possibly be attributed to contaminants in fish such as polychlorinated biphenyls, dioxins, arsenic, and mercury." However, she also highlighted the need for further research to investigate the specific components of fish that may contribute to the observed association.

Focusing on Contaminants Rather Than Fish Itself

It is important to distinguish between the potential risks associated with consuming fish and the fish itself. In a recent study, the results showed that the risk of melanoma may not be the same for all types of fish. Fried fish seemed to carry a lower risk than canned fish. This suggests that the type of preparation and the types of contaminants present may play a significant role. Tuna, as a top predator, is more likely to have higher levels of contaminants such as mercury, which accumulates in the bodies of fish at higher trophic levels.

Future Research and Recommendations

The authors of the study recommend that more research is needed to investigate the specific components of fish, particularly contaminants, that may contribute to the observed association between fish intake and melanoma risk. They do not currently advise changes to fish consumption, as the current findings are not sufficiently robust to support such recommendations.

Conclusion

While there is a correlational link between fish consumption and melanoma risk, the evidence is not yet strong enough to warrant changing dietary habits. The focus should be on understanding the specific contaminants in fish that may pose a risk and developing strategies to reduce exposure to these harmful substances.

References

[1] Y. Liao, L.M. Sinha, R. et al. Fish intake and risk of melanoma in the NIH-AARP diet and health study. Cancer Causes Control 33, 921-928 (2022).