Fish consumption can increase risk of melanoma: Study

According to a large study of US students, eating more fish, particularly tuna and non-fried fish, appears to be associated with an increased risk of malignant melanoma.

Eunyoung Cho, the accompanying author, stated: “Melanoma is the sixth most common cancer in the United States, with a lifetime risk of one in 38 for whites, one in 1,000 for Blacks, and one in 167 for Hispanics1. Although fish intake has increased in the United States and Europe in recent decades, previous research on the association between fish diet and melanoma risk has produced inconsistent results. Our studies have indicated a link that requires additional investigation.”

Researchers from Brown University in the United States discovered that those with a median daily fish consumption of 42.8 grammes had a 22% greater risk of malignant melanoma than those with a median daily fish intake of 3.2 grammes. They also discovered that individuals with a median daily consumption of 42.8 grammes of fish had a 28% higher chance of having abnormal cells just in the outer layer of the skin, known as stage 0 melanoma or melanoma in situ, than those with a median daily intake of 3.2 grammes of fish. A serving of fish is around 140 grammes of fried fish.

The scientists examined data from 491,367 people recruited from throughout the United States for the NIH-AARP Diet and Health Study during 1995 and 1996 to assess the connection between fish intake 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 their portion sizes.

Using data from cancer registries, the researchers determined the incidence of new melanomas that occurred over a median of 15 years. They took into account sociodemographic characteristics, as well as participants’ BMI, physical activity levels, smoking history, daily intake of alcohol, caffeine, and calories, cancer family history, and average UV radiation levels in their local region.

During the research period, 5,034 people (1.0 percent) acquired malignant melanoma and 3,284 (0.7 percent) developed stage 0 melanoma.

The researchers discovered that eating more non-fried fish and tuna was linked to an elevated incidence of malignant melanoma and stage 0 melanoma. Those with a median daily tuna consumption of 14.2 grammes had a 20% greater risk of malignant melanoma and a 17% higher risk of stage 0 melanoma than those with a median daily tuna intake of 0.3 grammes.

In comparison to a median consumption of 0.3 grammes of non-fried fish per day, a median intake of 17.8 grammes of non-fried fish per day was related with an 18% greater risk of malignant melanoma and a 25% higher risk of stage 0 melanoma. The researchers found no significant links between fried fish consumption and the incidence of malignant melanoma or stage 0 melanoma.

According to Eunyoung Cho: “We hypothesise that our findings are due to pollutants in fish such as polychlorinated biphenyls, dioxins, arsenic, and mercury. Previous study has discovered that eating more fish is connected with greater levels of these pollutants in the body, as well as connections between these contaminants and an increased risk of skin cancer. However, because our study did not look at the quantities of these pollutants in the individuals’ bodies, more research is needed to validate this link.”

The researchers emphasise that the study’s observational nature precludes drawing inferences regarding a causal association between fish consumption and melanoma risk. They also did not account for several melanoma risk variables in their analysis, such as mole count, hair colour, history of severe sunburn, and sun-related behaviours. Furthermore, because the average daily fish intake was estimated at the start of the trial, it may not be indicative of the individuals’ lifelong diets.

Future study, according to the authors, is needed to examine the components of fish that may contribute to the observed connection between fish intake and melanoma risk, as well as any molecular processes underpinning this. They do not yet advocate any adjustments to fish eating.