A study suggests that a higher consumption of fish may be associated with a higher risk of melanoma

In 2021, 5,767 new melanomas were diagnosed in Spain, as indicated by the observatory of the Spanish Association against Cancer (AECC). Although cases are reported at virtually any age, most are detected between 40 and 70 years old.

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The main risk factors are family backgroundthe pigmentary features and exposure to ultraviolet radiation. In addition, several epidemiological studies suggest that some dietary factorssuch as coffee, citrus fruits and alcohol, can also affect its prevalence.

However, studies on the associations between eating fish and melanoma risk have so far been sparse and have yielded inconsistent results.

Although fish consumption has increased in the US and Europe, previous studies on the associations between this food and melanoma risk have been fragile. Our findings have identified a relationship that requires further investigation

Eunyoung Cho — Main Author

Thus a prospective study 2011 –based on the Diet and Health Study of the National Institute of Health (NIH) from the USA in 491,367 adults recruited between 1995 and 1996– evaluated the fish intake and different types of cancer. His results showed that melanoma was the only type of tumor that was associated with higher consumption.

now one new research led by experts from brown university (USA) examines, based on the same figures, the associations between total and specific intake of fish and the risk of melanoma, with extended follow-up.

"Melanoma is the deadliest type of skin cancer, with few forms of prevention," explains Eunyoung Cho, lead author of the study published in Cancer Causes & Control, to SINC. “Although fish consumption has increased in the US and Europe in recent decades, previous studies on the associations between food and this skin cancer have been fragile. Our findings have identified a relationship that requires further investigation,” she adds.

While this study doesn't describe how eating fish might increase that risk, researchers found that compared with those whose average daily fish intake was 3.2 grams, the risk of developing malignant melanoma was 22% higher among those whose average daily intake was 42.8 grams. Keep in mind that a serving of fish is approximately 140 grams.

Melanoma is the deadliest type of skin cancer, with few forms of prevention. In 2021, 5,767 new cases of melanoma were diagnosed in Spain, the majority between 40 and 70 years of age

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

“These results are surprising. The estimated effect of fish consumption on risk is small. Just a 1,200% increase in median consumption is associated with a 22% increased risk of melanoma,” he says. UK SMC Stephen Duffy, professor at the Queen Mary University From london. "Estimation of diet-associated risks is fraught with difficulties due to the possibility of multiple association of dietary factors with other risk factors."

More studies needed

To examine the relationship between fish intake and melanoma risk, the participants, who had a mean age of 62 years, reported how often they ate fried fish, non-fried fish, and tuna in the past year, as well as the size of your portions.

The researchers calculated the incidence of new melanomas that developed over a median period of 15 years. They took into account sociodemographic factors, as well as their body mass index, physical activity levels, smoking history, daily intake of alcohol, caffeine, and calories, family history of cancer, and average levels of UV radiation in their home. local area.

Among all of them, 5,034 participants (1.0%) developed a malignant melanoma during the study period and 3,284 (0.7%) developed a stage 0 melanoma.

The data presented in this study are by no means convincing enough to cast doubt on current recommendations on fish intake, generally included in a healthy and balanced diet

The experts found that a higher intake of non-fried fish and tuna was associated with an increased risk of malignant melanoma and stage 0 melanoma. Those whose median daily intake of tuna was 14.2 grams had a 20% higher risk of malignant melanoma and a 17% increased risk of stage 0 melanoma, compared with those whose median daily intake of tuna was 0.3 grams.

A mean intake of 17.8 grams of non-fried fish per day was associated with an 18% increased risk of malignant melanoma and a 25% increased risk of stage 0 melanoma, compared with a mean intake of 0.3 grams of non-fried fish per day. The researchers found no significant associations between fried fish consumption and the risk of malignant melanoma or stage 0 melanoma.

“Our results could be attributed to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic and mercury. Previous research has found that higher intakes are associated with higher levels of these pollutants in the body and has identified associations between them and an increased risk of skin cancer,” says Eunyoung.

"However, our study did not investigate the concentrations of these pollutants in the body of the participants, so more work is needed to confirm this relationship," he points out.

No causal relationship

The authors caution that the observational nature of the study does not allow conclusions to be drawn about a causal relationship between fish consumption and melanoma risk. The research also has other important limitations.

“We were unable to take into account factors such as number of moles, hair color, history of severe sunburn, and sun-related behaviors. Also, as the average daily intake of fish was calculated at the beginning of the study, it may not be representative of the participants' diet throughout their lives," Eunyoung said.

The authors caution that the observational nature of the study does not allow conclusions to be drawn about a causal relationship between fish consumption and melanoma risk.

The data presented is by no means convincing enough to cast doubt on the current recommendations on fish intake, generally included in a healthy and balanced diet.

“For now we do not recommend changing the fish consumption and we hope that our article will motivate more studies to replicate these findings and find out which components of the fish are responsible for the positive association”, concludes the author.

Yufei Li, Linda M. Liao, Rashmi Sinha, Tongzhang Zheng, Terrence M. Vance, Abrar A. Qureshi, Eunyoung Cho. Fish intake and risk of melanoma in the NIH-AARP diet and health study. Cancer Causes & Control

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