It appears that consuming more fish, such as tuna and other non-fried seafood, is linked to an increased risk of malignant melanoma, finds a major US adult study published in the journal Cancer Causes & Control.
Melanoma is the sixth most frequent cancer in the United States, and the risk of having melanoma during a lifetime is one in 38 for white individuals, one in 1,000 for Black people, and one in 167 for Hispanic people1.
Melanoma is the sixth most frequent cancer in the United States, and the risk of having melanoma during a lifetime is one in 38 for white individuals, one in 1,000 for Black people, and one in 167 for Hispanic people1.
Although fish consumption has risen in the United States and Europe in recent decades, the results of prior studies looking into the link between fish consumption and melanoma risk have been mixed.
“Our findings have identified an association that requires further investigation,” said Eunyoung Cho, the corresponding author
Researchers at Brown University in the United States found that people who ate an average of 42.8 grams of fish every day were 22 percent more likely to get malignant melanoma than those who ate an average of 3.2 grams of fish every day. They also discovered that people people who ate 42.8 grams of fish per day had a 28 percent higher risk of having abnormal cells just in the outer layer of their skin – known as stage 0 melanoma or melanoma in situ – than people who ate 3.2 grams of fish per day. A portion of cooked fish is around 140 grams.
The investigators looked at data from 491,367 adults who participated in the NIH-AARP Diet and Health Study during 1995 and 1996 to see if there was a link between fish consumption and melanoma risk. Participants, who were on average 62 years old, indicated how often they ate fried fish, non-fried fish, and tuna in the preceding year, as well as the portion sizes they consumed.
Using data from cancer registries, the researchers determined the incidence of new melanomas that occurred over a median of 15 years. Participants’ BMI, physical activity levels, smoking history, daily intake of alcohol, caffeine, and calories, family history of cancer, and average UV radiation levels in their local area were all taken into account. During the study period, 5,034 people (1.0 percent) acquired malignant melanoma, while 3,284 (0.7 percent) developed stage 0 melanoma.
Researchers discovered that consuming more non-fried fish and tuna was linked to a higher incidence of malignant melanoma and stage 0 melanoma. People who ate an average of 14.2 grams of tuna every day had a 20 percent higher risk of malignant melanoma and a 17 percent higher risk of stage 0 melanoma than people who ate an average of 0.3 grams of tuna every day. In comparison to a daily diet of 0.3 grams of non-fried fish, a median intake of 17.8 grams of non-fried fish was linked to an 18 percent greater risk of malignant melanoma and a 25 percent higher risk of stage 0 melanoma. The researchers found no significant links between fried fish consumption and the risk of malignant melanoma or stage 0 melanoma.
“We speculate that our findings could possibly be attributed to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury,” Eunyoung Cho added.
The previous study has linked higher fish consumption to higher levels of these pollutants in the body, as well as links between these contaminants and an increased risk of skin cancer.
“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 researchers point out that because their study was observational, they can’t draw any conclusions about a causal association between fish consumption and melanoma risk. They also failed to account for some melanoma risk factors in their analysis, such as mole count, hair color, a history of severe sunburn, and sun-related behaviors. Furthermore, because participants’ average daily fish intake was estimated at the start of the trial, it may not be indicative of their lifetime diets.
Future research is needed, according to the authors, to investigate the components of fish that may contribute to the observed link between fish diet and melanoma risk, as well as any molecular mechanisms underpinning this. They do not propose any adjustments to fish consumption at this time.
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