Study claims those who eat tons of fish more likely to get deadliest type of skin cancer

By Stephen Beech via SWNS

People who eat a lot of fish are more likely to develop the most deadly form of skin cancer, suggests a new study.

Researchers found that eating higher levels of seafood - including tuna and non-fried fish - appears to be associated with a greater risk of malignant melanoma.

Study corresponding author Doctor Eunyoung Cho said: “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.”

Dr. Cho and colleagues at Brown University found that, compared to those whose average daily fish intake was 3.2 grams, the risk of malignant melanoma was 22 percent higher among those whose average daily intake was 42.8 grams.

They also found that those whose average daily intake was 42.8 grams of fish had a 28 percent increased risk of developing abnormal cells in the outer layer of the skin only – known as 'stage 0 melanoma' or melanoma in situ – compared to those whose average daily intake was 3.2 grams of fish.

A portion of fish was defined as around 140 grams of cooked fish.

To examine the relationship between fish intake and melanoma risk, the researchers analyzed data collected from more than 490,000 American adults.

The participants, who had an average age of 62, reported how frequently they ate fried fish, non-fried fish, and tuna during the previous year as well as their portion sizes.

The researchers calculated the incidence of new melanomas that developed over an average period of 15 years using data obtained from cancer registries.

They accounted for socio-demographic factors, as well as the participants’ body mass index (BMI), physical activity levels, smoking history, daily intake of alcohol, caffeine and calories, family history of cancer, and the average UV radiation levels in their local area.

A total of 5,034 participants developed malignant melanoma during the study period and 3,284 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 average daily tuna intake was 14.2 grams had a 20 percent higher risk of malignant melanoma and a 17 percent higher risk of stage 0 melanoma, compared to those whose median daily tuna intake was 0.3 grams.

The findings, published in the journal Cancer Causes and Control, showed that an average intake of 17.8 grams of non-fried fish per day was associated with an 18 percent higher risk of malignant melanoma and a 25 percent 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.

They said that the observational nature of the 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 - including mole count, hair color, history of severe sunburn and sun-related behaviors in their analyses.

However, Dr. Cho, an Associate Professor and Director of Research in the Department of Dermatology at Brown, added: “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.”

She suggested 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 that may link them.

However, the researchers do not recommend any changes to fish consumption at present.