Health Discoveries Winter 2023 Health Discoveries Winter 2023 | Page 5

Of Mercury and Melanoma

A new analysis links fish consumption with skin cancer , possibly due to pollution .
Put on sunscreen . Wear a hat . And … don ’ t eat too much fish ?
A recent paper suggests that eating more fish may be associated with a greater risk of malignant melanoma . But the large , observational study comes with a lot of caveats , and the senior author notes that previous research has linked higher mercury levels and skin cancer .
“ Mercury consumption in the US is mostly from fish ,” says Eunyoung Cho , ScD , an associate professor of dermatology and of epidemiology at Brown . “ So if mercury is related to skin cancer , then it stands to reason that fish intake may be related , too .”
Nonetheless , Cho says this new study is important due to its large size and prospective design , as participants ’ fish consumption was assessed before they got cancer . “ The results of previous studies investigating associations between fish intake and melanoma risk have been inconsistent ,” she says . “ Our findings have identified an association that requires further investigation .”
The researchers analyzed data collected from nearly half a million US adults who were recruited to the National Cancer Institute ’ s NIH-AARP Diet and Health Study . Participants reported how frequently they ate fish as well as their portion sizes . Their average age was 62 .
The analysis , published in the journal Cancer Causes and Control , reports that compared to those whose median daily fish intake was 0.11 ounces , those who ate 1.5 ounces per day had a 22 percent higher risk of malignant melanoma and a 28 percent increased risk of melanoma in situ , the earliest form of the disease . ( A typical serving size for most fish is 5 to 6 ounces .)
The study accounts for sociodemographic and physiological factors as well as medical history and the average ultraviolet radiation levels in each participant ’ s local area .
However , it didn ’ t adjust for some risk factors for melanoma such as mole count , hair color , or history of severe sunburn and sun-related behaviors . And because average daily fish intake was calculated at the beginning of the study , it may not represent participants ’ lifetime diets .
Furthermore , as an observational study , it couldn ’ t point to a causal relationship between fish intake and melanoma risk . Cho , who studies the connection between diet and skin cancer , says that bio-contaminants in fish — like mercury , PCBs , dioxins , and arsenic — likely play a role in the cancer association , rather than the fish itself .
“ 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 ,” she says . But this study didn ’ t examine the concentrations of these pollutants in participants ’ bodies , Cho adds , so researchers will need to keep fishing around before they can draw stronger conclusions .