“This study is important because it’s very large and it’s prospective by design, meaning that fish intake was assessed before the development of cancer,” said author Eunyoung Cho, ScD, associate professor of dermatology and epidemiology at Brown University in Providence, Rhode Island, in a release. Melanoma is the fifth most common cancer in the United States, and the risk of developing it over a lifetime is 1 in 38 for white people, 1 in 1,000 for Black people, and 1 in 167 for Hispanic people, according to the American Cancer Society (ACS). Almost all deaths due to skin cancer are from melanoma — it’s estimated that 7,650 Americans will die of skin cancer in 2022, according to the American Academy of Dermatology Association (AAD). It’s important to note that the study’s authors do not view the findings as a reason to avoid eating fish, and both the ACS and AAD agree that the most important way to reducing your risk of skin cancer is to limit your sun exposure and avoid tanning beds.
Tuna and Fish Consumption Was Linked to Increased Melanoma Risk — But Fried Fish Wasn’t
To examine the relationship between fish intake and melanoma risk, the authors analyzed data collected from 491,367 adults from across the United States who enrolled in the National Cancer Institute’s NIH–AARP Diet and Health Study between 1995 and 1996. The participants were an average of 62 years old, and over 90 percent were white. Participants reported how frequently they ate fried fish, non-fried fish, and tuna during the previous year, as well as their portion sizes. According to the U.S. Food and Drug Administration (FDA) (PDF), a serving size of fish is 4 ounces (oz), or 112 grams (g) — about the size of the palm of your hand. Cancer registries were used to calculate the incidence of new melanomas that developed over a median period of 15 years. Researchers accounted for several factors that could influence the results, such as income and education level, BMI (body mass index), physical activity levels, smoking history, family history of cancer, daily intake of alcohol, caffeine and calories, and the average ultraviolet radiation levels in each participant’s local area. During the study period, 5,034 participants (about 1 percent) developed malignant melanoma and 3,284 (0.7 percent) developed stage 0 melanoma. Stage 0 melanoma (also called melanoma in situ) has not grown deeper than the top layer of the skin, according to the American Cancer Society. The researchers found that higher intake of non-fried fish and tuna was associated with increased risks of malignant melanoma and stage 0 melanoma. An association is a statistical link; the findings don’t prove that eating fish caused the increased risk. The group that ate the most fish — nearly 3 servings per week — had 22 percent more cases of malignant melanoma. Researchers then looked at specific types of fish consumption and melanoma risk.
Compared with those whose median daily tuna intake was almost nothing — 0.3 g (0.01 oz), those whose median daily tuna intake was 14.2 g (0.5 oz) had a 20 percent higher risk of malignant melanoma and a 17 percent higher risk of stage 0 melanoma.Compared with a median intake of 0.3 g of non-fried fish per day, a median intake of 17.8 grams (0.62 ounces) of non-fried fish per day was associated with an 18 percent higher risk of malignant melanoma and a 25 percent higher risk of stage 0 melanoma.The researchers did not identify significant associations between consumption of fried fish and the risk of malignant melanoma or stage 0 melanoma.
“This is an intriguing study; one strength of this research is that it looked at a large number of patients, although it’s important to note that this data wasn’t gathered from a study designed to look at melanoma risk; it was primarily a nutrition study,” says Jeffrey Weber, MD, PhD, an oncology physician and co-director of the Melanoma Research Program at NYU Langone Health in New York City. Dr. Weber was not a part of the study. That means that was no information collected about the many known risk factors for developing melanoma, such as past sunburns or sun exposure, eye color, number of moles or freckles, and hair color, he says.
Experts Say There’s No Reason to Avoid Fish
“The relative risk increase found here was pretty low — a 20 percent difference between low fish and high fish consumption,” says Weber. A 20 percent increase in relative risk means that if the incidence in melanoma is usually 1 in 50 people, it would instead be 1 in 42 people, he says. Weber also points out that there are also some findings in the study that seem inconsistent. “For example, why would there be an increase in risk observed for tuna and fish intake but not for fried fish? I like fish, especially a good fish taco, and I’m not going to change my fish-eating habits on the basis of these findings, and I wouldn’t recommend that anyone else do so either,” he says.
Could Contaminants in Fish Such as Mercury Be Contributing to Increased Melanoma Risk?
These findings show an association that should be investigated further, said Dr. Cho. Researchers believe the increased risk may be related to biocontaminants in the fish, such as arsenic and mercury, 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. However, we note that our study did not investigate the concentrations of these contaminants in participants’ bodies and so further research is needed to confirm this relationship,” said Cho In a 2020 study of 29,000 adults (PDF), Cho and colleagues found an association between mercury and nonmelanoma skin cancer. Participants with the highest mercury levels in their blood were 79 percent more likely to report having had a nonmelanoma skin cancer compared to people with the lowest levels. Although this study doesn’t show that fish or the contaminants were the cause of the increased risk, there is evidence that exposure to toxins may be related to increased melanoma risk, says Weber. “We have found that 9/11 survivors have a very high risk of melanoma. This risk isn’t due to sun exposure, but rather a toxin or material that people were exposed to after the explosion that has possibly impacted the skin’s ability to repair damage,” he says. In terms of this current study on fish consumption, there’s no known connection between the contaminants that may be found in some fish and melanoma risk, says Weber.
Limiting Sun Exposure Is the Best Way to Reduce Melanoma Risk
The best way to reduce your risk of melanoma is to limit your exposure to UV rays, says Weber. That means when you’re enjoying the outdoors, seek shade, use sunscreen or clothing that blocks UV rays, wear a hat, and avoid the sun during the middle of the day when its rays are the strongest.
