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Study finds link between eating lots of seafood and skin cancer

One dermatologist called the findings “interesting, but not game changing as of yet.”
Contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury, could be part of the explanation, the authors wrote.
Contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury, could be part of the explanation, the authors wrote.Leonid Sneg / Getty Images
/ Source: TODAY

Does what you eat contribute to your risk of skin cancer? Seafood lovers may be concerned by new research that found eating more fish was associated with a higher risk of melanoma.

It’s one of the first studies to make that connection, said co-author Eunyoung Cho, an associate professor of dermatology and epidemiology at Brown University in Providence, Rhode Island.

“Not many people are familiar with diet related to skin cancer,” Cho told TODAY. “You never think about diet (being) related to skin cancer.”

Still, she and other experts cautioned against changing how much fish people ate based on the findings, which simply showed a correlation, not causation. The major risk factors for melanoma remain the same: ultraviolet light exposure, having lots of moles and a family history of the disease.

'Unique' correlation

For the study, published in Cancer Causes & Control, Cho and her colleagues examined the fish eating habits of 491,367 participants in the NIH-AARP Diet and Health Study — a large cohort of Americans 50 to 71 years old who described their diet in a questionnaire in the mid-1990s.

After they were followed over 15 years, the researchers looked at the diagnoses of melanoma — the deadliest form of skin cancer — among the participants. When they were grouped by how much seafood they ate, it turned out the group that consumed the most fish had a 22% higher risk of malignant melanoma compared to the group that ate the least fish, the study found.

That may be due to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury, the authors wrote.

It’s well established that arsenic is a skin carcinogen, Cho said. A previous study found higher blood mercury levels were associated with a higher prevalence of non-melanoma skin cancer.

“But at this point, we don’t really know which contaminant may be responsible. And this study was not designed in a way that we could evaluate which specific components of fish would be responsible for the association,” she noted. “There should be more studies to address this topic.”

Should you change your diet?

Dermatologist Dr. Adam Friedman, who was not involved in the new research, called the study “interesting, but not game changing as of yet.”

The “unique” correlation would require much more study to even suggest eating more fish might cause the higher melanoma risk, he noted.

“The investigators unfortunately did not account for many established risk factors, such as number of moles, hair color — red hair is an important one — number of past burns or sun-protective behaviors, which really impair our ability to interpret this data,” said Friedman, professor and chair of dermatology at the George Washington School of Medicine and Health Sciences.

“Therefore, I would recommend caution in translating these data to one’s diet.”

Cho also advised people to stick with their current seafood menu.

“My recommendation would be: Don’t change your fish intake habit now. People should really wait for more studies,” she said.

The U.S. government recommends adults eat at least 8 ounces of seafood per week.

Regularly eating fish and seafood is associated with a lower risk of cardiovascular disease, according to the American Heart Association, which recommends eating two servings of it — particularly fatty fish, which is a good source of omega-3 fatty acids — per week.

But consuming large amounts of fish does increase a person’s exposure to mercury, a naturally-occurring metal that’s toxic to living things. People can run into trouble when they hear fish is healthy and think they should eat as much of it as possible, Lisa Young, a registered dietitian nutritionist in New York, previously told TODAY.

Related: What is mercury poisoning?

Fish with the highest mercury levels include king mackerel, shark, swordfish and tuna.

Seafood may not be the only dietary factor affecting melanoma risk. Higher consumption of citrus fruit and alcohol has also been associated with increased risk in previous studies.

Alcohol is the least surprising of all of those factors because it’s related to a lot of different types of cancer, Cho said.