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 can mean eating less of foods with harmful fats and higher calorie counts. Indeed, nutritionists commonly recommend more seafood (and fewer cheeseburgers) to improve your diet, and nutrition guidelines promote fish as part of a healthy diet.

So, it seems surprising that a new study in Cancer Causes and Control suggests a link between eating fish and skin cancer, particularly since the biggest known risk factor for melanoma is not dietary ­— it’s sun exposure. Having five or more sunburns in your life doubles your risk of developing melanoma.

A study links eating fish often with higher risk of melanoma

Melanoma, the most serious type of skin cancer, is responsible for more than 7,500 deaths in the U.S. each year. And cases are on the rise.

In the new study, researchers found a higher risk of melanoma among people who ate the most fish. This study is among the largest and most well-designed to examine this link. Nearly 500,000 people in six U.S. states completed a dietary questionnaire in 1995 or 1996. The average age of participants was 61 and 60 percent were male. More than 90 percent were white, 4 percent were Black, and 2 percent were Hispanic.

Over the following 15 years, the researchers tallied how many people developed melanoma, and found that:

• The rate of melanoma was 22 percent higher among people reporting eating the most fish (about 2.6 servings per week) compared with those who ate the least (0.2 servings a week, or about one serving every five weeks). Similar trends were noted for intake of tuna.
• The risk of precancerous skin changes (called melanoma in situ) rose similarly among those in the group that ate the most fish.
• Interestingly, researchers found no increased risk of melanoma among those eating the most fried fish. This is surprising because, if eating fish increases the risk of melanoma as the study suggests, it’s not clear why frying the fish would eliminate the risk.

This is an excerpt from an article that appears on the Harvard Health Publishing website.

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Robert H. Shmerling is the senior faculty editor for Harvard Health Publishing and a current member of the corresponding faculty in medicine at Harvard Medical School.