A major study published on June 8 found an astonishing link between eating fish and developing melanoma, the most serious type of skin cancer.
The findings raise questions about the possible links between diet and melanoma, but the lead author and other experts have warned that this should not be a reason to avoid fish. The results also do not change the most important tip for reducing the risk of melanoma: limiting exposure to the sun or ultraviolet (UV) rays from tanning.
A new study, published in the journal Cancer Causes & Control, evaluated data from more than 490,000 adults between the ages of 50 and 71 in the United States who were enrolled in the NIH-AARP Diet and Health Study. American Association of Retired Persons).
At the beginning of the study, participants completed specific questionnaires, including information on fish consumption. They were followed for about 15 years to test their cancer diagnoses. Compared to people who ate almost no fish, the group that ate the most — an average of 287 grams, or about three servings a week — had 22% more cases of malignant melanoma, according to the researchers.
It is unclear why eating fish may increase the risk of developing melanoma, said Eunyoung, associate professor of dermatology at Cho Brown University and lead author of the study. “We think it’s not the fish itself, but it’s probably one of the contaminants in the fish,” he said.
Other research has found that people who eat more fish have higher levels of heavy metals in their bodies, such as mercury and arsenic. These contamination factors are linked to an increased risk of skin cancer, Chok said. However, his research did not measure the level of contamination of the participants, and more research is needed to examine that link, he said.
“I wouldn’t recommend people to eat fish just because of our discovery,” Chok said. Eating fish is associated with a lower risk of cardiovascular disease and possibly other cancers, he said. ,
The American Cancer Society recommends eating fish, poultry, and beans more often than red meat, and the AHA (American Heart Association) recommends eating two fish a week for heart health. (One fish is the same as 86 grams of cooked fish, according to the AHA, or about three-quarters of a cup of fish flakes).
Other experts were also cautious in interpreting the findings of the study. “It doesn’t change the recommendations for eating fish as part of a heart-healthy, anti-inflammatory, or general cancer prevention diet,” Carrie Daniel-MacDougall, an associate professor of epidemiology at MD Cancer Center, wrote in an email. Email. Anderson University of Texas.
Dr. Daniel-MacDougall led an early analysis of the same NIH-AARP group included in the final study, with a shorter follow-up time and fewer variables.
His work, published in 2011, also found a correlation between catching fish and the risk of melanoma. However, the NIH-AARP study was initially designed to study a variety of cancers and did not measure important and known risk factors for melanoma, such as a history of sunburn or increased lifetime UV exposure, Daniel wrote. -MacDougallek.
He pointed out that people with these risk factors may have spent more time in the sun, perhaps on the beach or fishing, and may also be more likely to consume seafood. Without further information, it is impossible to determine whether the fish is at increased risk for melanoma, its time in the sun, or any other factor.
Sancy Leachman, director of the Melanoma Research Program at Oregon University of Health and Science, said the new research was well-designed and said the findings were “intriguing.” But “when you process such large data sets,” he said, what you find are correlations between factors, not evidence that one affects the other.
These types of research are good for developing new hypotheses — for example, the contaminants found in fish may increase the risk of melanoma — but they need much more research to see if they can be sustained.
“Science is evolving, and you can’t do everything from one day to the next. That’s just part of the process,” said Dr. Leachman.
Many studies have identified correlations between certain foods and the type of cancer, but in general, when more tests are done and the results are seen as a whole, the effects are smaller or completely disappear.
In the case of melanoma in particular, limited research has revealed some strange and surprising relationships with certain foods. Eating more citrus fruits has been linked to an increased risk of melanoma in some, but not all, studies. And red and processed meat has been linked to a lower risk of melanoma, but a higher risk of developing other cancers.
As for the correlations between cancer risk and specific foods, “don’t be afraid of the incomplete data that has yet to be proven,” Leachman said. “Keep up with the tried and true things: eat well, sleep well, exercise, everything in moderation,” he said. “This gives you the greatest resilience you can have against any type of disease, including cancer.”
And in the case of melanoma, in particular, “the most effective prevention practices we have are to limit sun exposure – throughout life, starting in childhood – and to screen for skin cancer,” wrote Dr. Daniel-MacDougall.
Compared to the limited data on fish and other dietary factors, there is much more evidence to support this advice, Drs. Leachman. Having five or more sunburns in your life doubles your risk of melanoma, and using a tanning bed can increase your risk by 75%, according to the Skin Cancer Foundation.
Check your skin regularly for new, changing, or unusual looking blemishes, and see if you find anything about the doctor, Leachman said. “If you see something that looks different, don’t throw it away,” he said. – The sooner you study, the better.
Translated by Luiz Roberto M. Gonçalves