Seafood linked to higher risk of melanoma


Does what you eat contribute to your risk of skin cancer? Seafood lovers might be concerned about 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 know about the diet linked to skin cancer,” Cho told TODAY. “You never think about diet (being) linked to skin cancer.”

Still, she and other experts cautioned against changing the amount of fish eaten based on the results, which simply showed correlation, not causation. The main melanoma risk factors remain the same: exposure to ultraviolet rays, the presence of numerous moles and a family history of the disease.

“Single” correlation

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

After being followed for 15 years, the researchers looked at diagnoses of melanoma – the deadliest form of skin cancer – among the participants. When grouped by the amount of seafood they ate, the group that ate the most fish was found to have a 22% higher risk of malignant melanoma compared to the group that ate the least amount of fish, according to the study.

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

It is well established that arsenic is carcinogenic to the skin, said Cho. A previous study found that 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 such a way that we could assess which specific components of the 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 yet groundbreaking.”

The “unique” correlation would require many more studies to even suggest that eating more fish could lead to a higher risk of melanoma, he noted.

“Investigators unfortunately did not take into account many established risk factors, such as number of moles, hair color – red hair is important – number of past burns or sun protection behaviors, that 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 this data to his diet.”

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

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

The US government recommended adults eat at least 8 ounces of seafood per week.

Eating fish and seafood regularly is associated with a lower risk of cardiovascular disease, according to the American Heart Associationwho recommends eating two servings of it — especially oily fish, which is a good source of omega-3 fatty acids — a week.

But consuming large amounts of fish increases a person’s exposure to mercury, a naturally occurring metal that is toxic to living things. People can get in 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 City, 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. A higher consumption of citrus and alcohol has also been associated with an increased risk in previous studies.

Alcohol is the least surprising of all these factors, as it is linked to many different types of cancer, Cho said.


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