A study finds that high fish consumption is associated with an increased risk of melanoma.
According to a large study of US adults published in the journal Cancer Causes & Control, eating more fish—including tuna and non-fried fish—seems to be linked to a higher risk of malignant melanoma.
Eunyoung Cho, the corresponding author said: “Melanoma is the fifth most common cancer in the USA and the risk of developing melanoma over a lifetime is one in 38 for white people, one in 1,000 for Black people, and one in 167 for Hispanic people. Although fish intake has increased in the USA and Europe in recent decades, the results of previous studies investigating associations between fish intake and melanoma risk have been inconsistent. Our findings have identified an association that requires further investigation.”
The incidence of malignant melanoma was 22% greater among individuals whose median daily consumption of fish was 42.8 grams as compared to those whose median daily intake was 3.2 grams, according to researchers from Brown University. Additionally, they discovered that individuals with a median daily consumption of 42.8 grams of fish had a 28% higher chance than those with a median daily intake of 3.2 grams of fish of having abnormal cells in just the outer layer of the skin, often known as stage 0 melanoma or melanoma in situ. An average serving of cooked fish weighs around 140 grams.
The scientists analyzed data from 491,367 people who were recruited from all across the USA to the NIH-AARP Diet and Health Study between 1995 and 1996 to investigate the association between fish consumption and melanoma risk. Participants, who on average were 62 years old, answered questions on their consumption patterns and portion sizes of fried, non-fried, and tuna throughout the previous year.
Using information from cancer registries, the researchers determined the incidence of new melanomas that appeared during a median period of 15 years. They also took into consideration the individuals’ BMI, degree of physical activity, history of smoking, daily calorie and caffeine consumption, family history of cancer, and the average UV radiation exposure in their neighborhood. During the research period, 5,034 participants (1.0%) developed malignant melanoma and 3,284 (0.7%) developed stage 0 melanoma.
The researchers found that a higher intake of non-fried fish and tuna was associated with increased risks of malignant melanoma and stage 0 melanoma. Those whose median daily tuna intake was 14.2 grams had a 20% higher risk of malignant melanoma and a 17% higher risk of stage 0 melanoma, compared to those whose median daily tuna intake was 0.3 grams.
A median intake of 17.8 grams of non-fried fish per day was associated with an 18% higher risk of malignant melanoma and a 25% higher risk of stage 0 melanoma, compared to a median intake of 0.3 grams of non-fried fish per day. The researchers did not identify significant associations between consumption of fried fish and the risk of malignant melanoma or stage 0 melanoma.
Eunyoung Cho said: “We speculate that our findings could possibly be attributed to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic, and mercury. Previous research has found that higher fish intake is associated with higher levels of these contaminants within the body and has identified associations between these contaminants and a higher 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 caution that the observational nature of their study does not allow for conclusions about a causal relationship between fish intake and melanoma risk. They also did not account for some risk factors for melanoma, such as mole count, hair color, history of severe sunburn, and sun-related behaviors in their analyses. Additionally, as average daily fish intake was calculated at the beginning of the study, it may not be representative of participants’ lifetime diets.
The authors suggest that future research is needed to investigate the components of fish that could contribute to the observed association between fish intake and melanoma risk and any biological mechanisms underlying this. At present, they do not recommend any changes to fish consumption.
Reference: “Fish intake and risk of melanoma in the NIH-AARP diet and health study” by Yufei Li, Linda M. Liao, Rashmi Sinha, Tongzhang Zheng, Terrence M. Vance, Abrar A. Qureshi and Eunyoung Cho, 9 June 2022, Cancer Causes & Control.