PROVIDENCE, IR [Brown University] “Eating large amounts of fish, including tuna and unroasted fish, is associated with an increased risk of malignant melanoma, according to a large study by U.S. adults published in the Journal of Causes and Control of Cancer.
“This study is important because it is very large and promising in terms of design, i.e., fish nutrition has been evaluated prior to the development of cancer,” said author Yongyong Cho, an associate professor of dermatology and epidemiology at Brown University. “Although fish consumption has increased in the U.S. and Europe in recent decades, the results of previous studies examining the link between fishing and the risk of melanoma have been conflicting – our findings identify an association that requires further research.”
The researchers found that those who ate 42.8 grams (1.5 ounces) had a 22% higher risk of developing malignant melanoma and a 28% higher risk of developing abnormal diseases compared to those who averaged 3.2 grams (.11 ounces). Only the cells in the outer layer of the skin are called stage 0 cancer or melanoma in situ. The volume of cooked fish is approximately 140-170 grams (5-6 ounces); Canned tuna weighs 142 grams (5 ounces).
According to the American Cancer Society, melanoma is the fifth most common cancer in the United States, with a lifetime risk of 38 for whites, 1,000 for blacks, and 167 for Spaniards.
To study the link between fish exposure and the risk of melanoma, the authors analyzed data collected from 491,367 adults in the United States from the National Cancer Institute’s NIH-AARP Diet and Health Survey between 1995 and 1996. Participants aged 62 years. On average, they reported how much they ate fried fish, non-fried fish and tuna last year, as well as the size of their portions.
Using data from the cancer registry, the researchers estimated the incidence of new melanomas in an average of 15 years. They took into account socio-demographic factors, as well as the body mass index of the participants; level of physical activity; history of tuxedo; family history of cancer; daily consumption of alcohol, caffeine and calories; and the average ultraviolet radiation level in the local area of each participant.
During the study period, 5,034 participants (1%) developed malignant melanoma and 3,284 (0.7%) developed stage 0 melanoma. Researchers have found that eating more uncooked fish and tuna is associated with an increased risk of malignant melanoma and stage 0 melanoma:
- Those at 14.2 grams (0.5 ounces) had a 20% higher risk of developing malignant melanoma and a 17% higher risk of stage 0 melanoma compared to those with an average daily intake of 0.3 grams (0.01 ounces).
- The average consumption of 17.8 grams (0.62 ounces) of uncooked fish per day was 18% and 25% higher than the average consumption of 0.3 grams of non-fried fish per day, respectively. Stage 0 melanoma.
- Researchers have not found a significant association between the risk of malignant melanoma or stage 0 melanoma using fried fish.
The researchers revealed some limitations: The analysis did not take into account some risk factors for melanoma, such as the number of moles, hair color or history of severe sunburn and sun-related behavior. In addition, since the average daily fish consumption was calculated at the beginning of the study, it may not reflect the participants’ lifelong diet.
The researchers also warned that the observational nature of their research did not allow them to draw a causal link between fish intake and the risk of melanoma.
Cho, who studied the link between diet and skin cancer, has been involved in high-profile studies showing a link between mercury levels and skin cancer.
“Mercury consumption in the U.S. is mostly derived from fish,” Cho said. “So if mercury is linked to skin cancer, it could also be related to eating fish.”
Cho said that bio-pollutants such as mercury in fish, not the fish itself, would play a role in the cancer association.
“We suspect that our findings may be related to pollutants in fish such as polychlorinated biphenyls, dioxins, arsenic and mercury,” Cho said. “Previous research has shown that high consumption of fish is associated with high levels of these pollutants in the body, and has linked these pollutants to the risk of skin cancer. However, our study did not study the concentration of these pollutants in the participants’ bodies, so we note that additional research is needed to confirm this link.
The authors suggest that future research will contribute to the observed link between fish components, especially pollutants, fish intake and the risk of melanoma, as well as the need to understand the biological mechanisms of this association. At present, they do not recommend any changes in the use of fish.
Yufei Lee, who received a master’s degree in public health from Brown University in 2021, was the first author of the paper. Other Brown contributors included Abrar Qureshi, Terrence Vance and Tongjan Zheng.