A new study has linked fish consumption to an increased risk of melanoma, a serious form of skin cancer.
Melanoma is widely considered the most dangerous variety of skin cancer. it is the most invasive and the highest risk of death. Melanoma is rare and a significant number of cases are caused by the sun. In fact, a British study found that exposure to ultraviolet rays from the sun was responsible for 86% of melanomas.
Additionally, a person’s risk of developing melanoma doubles if they have had more than five sunburns. (However, a single severe sunburn in childhood or adolescence can also double the risk).
But what we eat could also play a role, according to a recent analysis by a Brown University team.
skin cancer research
The study was published in the journal Cancer causes and control. It included 491,367 adults in the United States with an average age of 62.
Participants reported their consumption (including frequency and portion size) of fried fish; unfried fish or seafood (such as lobsters, crabs, clams, and shrimp); and tuna, including products packaged in oil and water.
Using data from cancer registries, researchers tracked participants’ new melanomas over a median of 15 years. They took into account socio-demographic factors as well as smoking, body mass index, physical activity, family history of cancer and average levels of ultraviolet radiation in each participant’s area.
They also accounted for participants’ daily alcohol, caffeine, and calorie consumption.
During the study period, 1% of participants (5,034 people) developed malignant melanoma. Meanwhile, 0.7% (3,284) developed stage 0 melanoma (also called in situ), in which the cancer cells are still confined to the outermost layer of the skin and have not spread into the second layer.
Researchers found that eating more fish or unfried tuna increased the risk of developing both forms of melanoma.
Compared to people who ate 0.3 grams (0.01 ounces) of tuna every day, those who ate 14.2 grams (0.5 ounces) had a 20% higher risk of malignant melanoma. They also had a 17% higher risk of stage 0 melanoma.
For unfried fish, eating 17.8 grams (0.62 ounces) – compared to 0.3 grams – was associated with an 18% higher likelihood of malignancy and a 25% higher risk of stage 0 melanoma.
The researchers found no significant association between fried fish and melanoma risk.
mercury and fish
Study author Eunyoung Cho is an associate professor of dermatology and epidemiology at Brown, an Ivy League research university in Rhode Island.
Cho theorizes that the link between seafood consumption and cancer may be due to the presence of biocontaminants, such as mercury.
“We speculate that our findings could possibly be attributed to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury,” Cho said in a statement. “Previous research has shown that high fish consumption is associated with higher levels of these contaminants in the body and has identified associations between these contaminants and a higher risk of skin cancer.”
“Mercury consumption in the United States comes primarily from fish,” Cho noted. “So if mercury is linked to skin cancer, it stands to reason that fish consumption may also be linked.”
Almost all fish today contain traces of mercury, and humans are largely responsible. According to a 2018 United Nations Environment Program report, human activities have increased total mercury concentrations in the atmosphere by about 450% above natural levels.
High levels of mercury can damage the kidneys and liver, as well as the nervous, digestive and immune systems. It can also become deadly.
Cho noted that the study did not investigate mercury or other contaminants. Therefore, “further research is needed to confirm this relationship.”