A study asks if people who eat a lot of fish have a higher risk of skin cancer melanoma.
If you’re trying to stick to a healthy diet, fish is a good choice, right? After all, fish is high in protein, low in saturated fat, and a good source of omega-3 fatty acids, vitamin D, and many other nutrients. Eating more fish may mean eating fewer foods with harmful fats and higher calorie counts. Indeed, nutritionists generally recommend more seafood (and fewer cheeseburgers) to improve your diet, and nutritional guidelines promote fish as part of a healthy diet.
So it seems surprising that a new study published in Cancer Causes and Control suggests a link between fish consumption and skin cancer, especially since the biggest known risk factor for melanoma is not food – it is exposure to the sun. Having five or more sunburns in your lifetime doubles your risk of developing melanoma.
Study links fish consumption to higher risk of melanoma
Melanoma, the most serious type of skin cancer, is responsible for more than 7,500 deaths in the United States each year. And the cases are multiplying.
In the new study, researchers found a higher risk of melanoma in people who ate the most fish. This study is among the largest and best designed to examine this link. Nearly 500,000 people in six US states completed a diet questionnaire in 1995 or 1996. The average age of participants was 61 and 60% were male. More than 90% were white, 4% were black, and 2% were Hispanic.
Over the next 15 years, researchers counted the number of people who developed melanoma and found that:
- Melanoma rates were 22% higher among people who reported eating the most fish (about 2.6 servings per week) compared to those who ate the least (0.2 servings per week, or about one serving every five weeks). Similar trends were noted for tuna consumption.
- The risk of precancerous skin changes (called melanoma in situ) similarly increased among people in the group who ate the most fish.
- Interestingly, the researchers found no increased risk of melanoma in those who ate the most fried fish. This is surprising because, if eating fish increases the risk of melanoma as the study suggests, it is unclear why frying the fish would eliminate the risk.
Does this mean that eating fish causes melanoma?
No, this is not the case. It is too early to draw firm conclusions about the relationship between fish in our diet and melanoma. The study had significant limitations, including
- Type of study. Observational studies like this can detect a possible link between diet and cancer but cannot prove it.
- Use of self-reported survey data. People self-reported how many servings of fish they ate each week, which may not be accurate. Additionally, the researchers assumed that the fish consumption reported in the original survey had persisted for 15 years, which may not have been the case.
- Consideration of other factors. Many factors influence the risk of melanoma, such as varied sun exposure depending on where the participants lived. The analysis took into account some key factors, but the study did not collect information on sun exposure, past sunburn or sunscreen use – all important in the risk of melanoma. The researchers also didn’t ask about skin type or number of moles; fair skin or a high number of moles increase the risk of melanoma.
- Contaminants. Mercury or arsenic in fish may be to blame for their link to melanoma. This study did not record any contaminants, but previous studies link mercury exposure to the risk of skin cancers, including melanoma.
- Lack of diversity. It’s unclear whether the findings apply broadly to people of different racial and ethnic groups, as nine out of 10 study participants were white.
Are some fish safer to eat than others?
The study did not explore this question. However, if contaminants like mercury in fish are responsible for increasing the risk of melanoma, the FDA offers guidance on the safest fish to eat, especially for children and pregnant or nursing women.
Yet, even though fish is confirmed to contribute to melanoma risk, other positive effects of fish consumption (such as cardiovascular benefits) may far outweigh this risk.
The bottom line
The researchers responsible for this study do not recommend changing the amount of fish people eat. Further studies are needed to confirm the findings, determine which types of fish affect melanoma risk, and determine whether certain contaminants in fish are responsible for any additional risk.
In the meantime, low-mercury fish (like salmon and clams) remain better food choices than the high-fat, highly processed foods typical of many Western diets.
If you plan to spend a lot of time outdoors this summer, limiting sun exposure and using sunscreen will likely have a greater impact on skin health and your overall health than avoiding seafood. .