More than 3 billion people around the world rely on fish for food. Fish is a good source of protein and healthy fats in highly recommended diets such as the Mediterranean and Scandinavia.
But new research shows that, like all things, too many good fish can be bad.
A large, long-term study of nearly 500,000 people found that people who ate half a can of tuna a day had a 22 percent higher risk of developing melanoma.
“Melanoma is the fifth leading cause of cancer [US] and lifetime melanoma risk is 1 in 38 for whites, 1 in 1,000 for black people, and 167 for Spaniards, ”said Yunyon Cho, a dermatologist at Brown University.
Significantly, this does not mean that we should avoid eating fish. This study shows a trend, not a underlying cause, so researchers have not directly shown that eating more fish increases the risk of skin cancer. Also, even if there is a direct connection, the benefits of eating fish may still outweigh the overall avoidance.
However, such a strong reference to a large sample that is relevant in the broader context of our current environment requires further investigation.
Claire Collins, a nutritionist at the University of Newcastle who did not participate in the study, said: “Although the results are from a cohort study, they do not represent an observational and therefore causal relationship.” “The role of contaminants that may be present in some fish needs to be considered.”
It is known that toxins in our environment, including heavy metals, which are directly responsible for cancer, accumulate through the food chain.
For example, mercury Substances released through industrial processes, such as burning coal, enter our waterways, and microbes convert it into methyl mercury.
This is absorbed by the plankton and accumulates in the tissues of the shrimp that eat that plankton, and then in the fish that eat the shrimp, and so on, as the food chain rises higher and higher. This is called biomagnification.
“We suspect that our findings may be related to pollutants in fish such as polychlorinated biphenyls, dioxins, arsenic and mercury,” Cho said.
“Previous studies have found that higher consumption of fish is associated with higher levels of these pollutants in the body, and have linked these pollutants to the risk of skin cancer.”
Researchers led by Brown University epidemiologist Yufei Lee used data from the NIH-AARP diet and health study of participants between 1995 and 1996. They compared it with the National Mortality Index and state cancer registers and found a risk of melanoma. Those who ate fish up to about 43 grams per day were 22 percent higher than the average size (about 3 grams per day).
This relationship was linear, with the amount of tuna consumed increased cancer incidence and was consistent across several demographic and lifestyle factors, taking into account other risks such as mole count, hair color, history of severe sunburn, and sun-related behaviors.
Fish intake was calculated only at the beginning of the study, so this may change over the life of the participants.
These findings do not alleviate any other known causes of skin cancer.
Matthew Brown, director general of the Australian Institute of Melanoma, commented on the study, “It’s very important that we don’t confuse or cloud the prevention message.” “Scientific evidence is clear – sun exposure is the biggest risk factor for the development of melanoma.”
However, the level of these pollutants increases due to increased land use and even climate change (increasing precipitation increases mercury concentrations in some waterways), and this potential cause of skin cancer cannot be ignored. Lee and his colleagues are demanding further investigation.
This study was published Cancer causes and control.