A recent study conducted by Brown University has found eating two portions of fish per week creates an increased risk of malignant melanoma, the deadliest type of skin cancer.
The study, "Fish intake and risk of melanoma in the NIH-AARP diet and health study," published in the journal Cancer Causes and Control, involved 491,367 adults in from the United States Participants in the study averaged 62 years of age, and reviewed how frequently participants consumed portion sizes of fried fish, non-fried fish, and tuna over the duration of a year.
The research showed a person who consumed 42.8 grams of fish per day had a 22 percent higher risk of malignant melanoma in comparison to a daily intake of a person consuming 3.2 grams per day.
Brown University Department of Dermatology Associate Professor and Director of Research Eunyoung Cho said it would be beneficial for further research to be conducted on the topic.
“Previous research has found that higher fish intake is associated with higher levels of these contaminants within the body and has identified associations between these contaminants and a higher risk of skin cancer," Cho said. "However, we note that our study did not investigate the concentrations of these contaminants in participants' bodies and so further research is needed to confirm this relationship."
The NHS recommends people eat at least two portions of fish weekly, with portion sizes of approximately 140 grams, which includes oily fish.
Results of the study also concluded humans consuming more fish had 28 percent increased risk of stage-zero melanoma, which looks like an abnormal skin development. In the study, 5,034 people developed malignant melanoma and 3,284 people developed stage-zero melanoma.
The study found those who consumed larger amounts of tuna had a 20 percent higher risk of malignant melanoma in comparison to those with a more typical intake of 0.3 grams per day.
Institute of Cancer Research London Senior Staff Scientist in Genetics and Ppidemiology Michael Jones, who was not involved in the study, said based on a review of the data, its findings were conclusive.
"The authors found a higher intake of non-fried fish and tuna was associated with melanoma. These results were statistically significant and therefore unlikely due to chance," Jones said. "It is possible people who intake more non-fried fish or tuna have other lifestyle habits that increase their risk of melanoma. The authors considered this and adjusted for some potentially confounding factors.”
Aston Medical School Senior Lecturer Duane Mellor said the potential link between fish contaminants and cancer increase would affect more than skin cancer.
"This study does not have a clear mechanism of how fish intake could increase risk of melanoma risk – there is no clear evidence that eating fish can lead to an increased risk of developing skin cancer," Mellor said. "It is important to remember eating two portions of fish per week ... can be a way of including important nutrients such as omega-3 fatty acids as part of a healthy diet and this study should not discourage people from including fish as part of a healthy diet."
Cho told Medscape the study likely reveals moderate health implications due to contaminants found in fish.
"I already published an article showing that total mercury level is related to skin cancer, and we know very well that in the U.S., fish consumption is the major source of mercury contamination," Cho said. "So, I naturally thought that fish consumption may be associated with increased risk of skin cancer too."
Cho told The New York Times she wouldn’t discourage people from eating fish just because of the study's finding, as eating fish is associated with a lower risk of cardiovascular disease and potentially other cancers.
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