Does eating fish increase the risk of melanoma?

Frequent consumption of fish may be associated with an increased risk of melanoma, according to a study just published in the journal Cancer Causes & Control, from the Nature group. The findings of this research have sparked intense controversy because they are not well established and may help divert attention from the real risk factors for more aggressive skin cancer, which are not related to diet.

This is demonstrated by the controversial work done by American scientists the risk of malignant melanoma was 22% higher in people who ate an average daily of 42.8 grams of fish compared to those who consumed an average of 3.2 grams per day. He also found that those whose average daily intake was higher had a 28% increased risk of developing early stage (stage 0) melanoma, which is melanoma. on site.

To examine the relationship between fish consumption and melanoma risk, the study authors analyzed data from 491,367 American adultswho reported how often they have eaten fried fish, non-fried fish and tuna, in addition to servings, over the past year (a standard serving is about 140 grams of cooked fish).

The incidence of new melanomas over a median of 15 years was calculated using data obtained from the US cancer registries. The researchers also took into account the sociodemographic factors, body mass index (BMI), and physical activity levels of the participants. They also looked at their smoking history, daily alcohol and coffee intake, calories consumed each day, family history of cancer. and the average levels of ultraviolet (UV) radiation in the area where each of them lived. During that time, around 5,000 participants developed malignant melanoma, while another 3,200 were diagnosed with stage 0 cancer.

Possible explanation: arsenic, mercury and other contaminants in fish

Lead researcher, Eunyoung Cho, of Brown University (Rhode Island, United States), presented the hypothesis that her team considers most plausible: “Let’s assume that our findings could be attributed to fish contaminants such as polychlorinated biphenyls, dioxins, arsenic and mercury. Previous research has found that increased fish intake is associated with higher levels of these contaminants within the body, and associations have been identified between these contaminants and an increased risk of skin cancer. ”However, he acknowledges that his studydid not study the concentrations of these pollutants in the participants’ bodiestherefore more research is needed to confirm this relationship. “

The limitations of this study are not limited to the absence of these data. The same researchers warn that the observational nature of the research does not allow for a causal relationship between fish intake and melanoma risk to be established. It’s more: they also did not take into account in their analysis of the fundamental risk factors for melanoma, such as the number of moles (nevi) of each individual, the color of the hair, the history of severe sunburn or the habits of exposure to the sun. Additionally, since the average daily fish intake was calculated at the start of the study, it may not be representative of the participants’ diets over time.

Strengths and weaknesses of the study

The study authors acknowledge this its results cannot lead to any change in the current recommendations aimed at the prevention of melanoma. This is confirmed by dermatologist Eduardo Nagore, clinical chief of the Dermatology Service of the Valencian Institute of Oncology (IVO), who believes that the work “has some virtues”, including the power it “uses many thousands of patients” gives. , as well as “a structured questionnaire and sufficient development time”.

However, believes that conclusions should be viewed with great caution because “the risk factors that are well established in melanoma have not been included: number of nevi, type of skin, burns…”, underlines the doctor. Disregarding these crucial elements, interpretations can be very conflicting. “For example, if a person with many moles is told that she has a greater predisposition to melanoma, she may decide to start taking better care of herself and eat a healthier, more balanced diet with more fish and less meat. “. If that person develops melanoma, the real reason will be that she was more at risk because of her numerous nevi and not because of her eating habits. But since it was something that was not evaluated in the study, it will be concluded that the intake of fish in abundance may have influenced.

Miguel Angelo LuruenaPhD in Food Science and Technology and author of the blog gummy candies with petroleumindicates another possible explanation: “Are people who eat more fish more likely to develop melanoma from any component of this type of food? or maybe it’s because they live in coastal areas and sunbathe more often compared to those in inland areas, where people tend to eat less fish and sunbathe less?

Guidelines for preventing melanoma

A healthy diet contributes to better health and helps prevent cancer, but there is no specific recommendation for the prevention of melanoma and skin cancer in general. On the other hand, there are some very clear risk factors that provide very valuable clues for the prevention of this type of cancer. These are the main tips:

  • Protection against excessive sun exposure: avoid the hours of maximum UV radiation, always look for shade, use photoprotective creams, wear a t-shirt and a cap or hat, protect especially babies and small children …
  • Moles review through self-examination and periodic visits to the dermatologist.

Recommendations on the consumption of fish

As for fish, it should be remembered that its usual consumption fits perfectly into the model of the Mediterranean diet and nothing suggests that this consideration will change soon. Both white and blue provide very valuable nutrients. The current recommendations of the Ministry of Health limit its consumption only in some segments of the population particularly vulnerable to the presence of contaminants.

“The legislation sets limits for the most important pollutants, such as mercury,” confirms Lurueña. However, as there are fish in which mercury can be found in quantities that may exceed those considered safe in particularly vulnerable populations, “it is recommended that pregnant and lactating women, as well as children under the age of 10, avoid the consumption of swordfish, shark, pike and bluefin tuna “. Also, it is advisable to alternate the consumption of fatty fish species with other white fish. “Fatty fish contains more fat and this is where some polluting compounds, such as heavy metals, accumulate,” explains the food technologist.