Large study found strange link between eating fish and skin cancer

More than 3 billion people around the world depend on fish for their food. Fish is a favorite source of protein and healthy fats in highly recommended diets, such as Mediterranean and Nordic

But new research suggests that, as with all things, too much good fish can also be a bad thing.

A large, long-term study of nearly 500,000 people found that people who ate more fish than the equivalent of half a can of tuna a day were 22 percent more likely to contract malignant melanoma.

“Melanoma is the fifth most common” cancer in the [US] and the risk of developing melanoma throughout life is one in 38 for white people, one in 1,000 for black people, and one in 167 for Hispanic people,” explains Brown University dermatologist Eunyoung Cho.

It is important to note that this does not mean that we should avoid eating fish at all. This study shows a trend, not an underlying cause, that has prevented researchers from directly demonstrating that eating more fish increases your risk of skin cancer. Even if there appears to be a direct link, benefits of eating fish would probably still outweigh total avoidance.

However, such a strong link within a large sample size, which makes sense in the broader context of our current environment, begs for further investigation.

“While the results are from a cohort study, meaning they are observational and thus do not imply causation, they cannot be ignored,” say University of Newcastle dietitian Clare Collins, who was not involved in the study. “The role of contaminants that may be present in some fish should be considered.”

It is well known that toxins in our environment, including those known to directly cause cancer, such as heavy metals, accumulate through the food chain.

For example, Mercury broadcast by industrial processes such as burning coal finds its way into our waterways where microbes break it down methylmercury

This is taken up by plankton and eventually accumulates in the tissues of the shrimp that eat that plankton, then the fish that eat the shrimp, and so on, becoming more concentrated the higher up the food chain. This is known as biomagnification

“We speculate that our findings may be attributable to contaminants in fish, such as polychlorinated biphenylsdioxins, arsenic and mercurysay Cho.

Previous research has found that higher fish intake is associated with higher levels of these contaminants in the body and has identified associations between these contaminants and a higher risk of skin cancer.”

The researchers, led by Brown University epidemiologist Yufei Li, used data from the USA NIH AARP Diet and Health Studyof participants recruited between 1995 and 1996. They collected this with the National Death Index and the state cancer registries and found that the risk of melanoma was 22 percent higher in those who ate about 43 ounces of fish per day compared to those who ate the median amount (about 3 ounces per day). ).

This link was linear, meaning the amount of tuna consumed increased the incidence of cancer, and it was consistent across several demographic and lifestyle factors, after considering other risks, such as mole count, hair color, history of severe sunburn, and exposure to the sun. related behavior.

However, fish intake was not calculated until the beginning of the study, so this may have changed over the participants’ lifetimes.

These findings do not in any way diminish other well-established causes of skin cancer.

“It’s critical that we don’t confuse or cloud the prevention message,” Melanoma Institute Australia CEO Matthew Browne warned in a statement. remark about the study. “The scientific evidence is clear – sun exposure is the single greatest risk factor for developing melanoma.”

But if levels of this contaminants increase thanks to intensification of land use and even climate change (mercury concentrations in some waterways are increases as rainfall increases) this possible cause of skin cancer should not be neglected. Li and colleagues are calling for further investigation.

This study was published in Cancer Causes & Control

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