Study Links Eating Fish to Increased Risk of Skin Cancer. Here’s Why

The Mediterranean diet and other mostly plant-based diets that replace meat with fish for the sake of health may be creating an unwanted side effect. The knowledge that meat is linked to heart disease has created a generation that eats fish regularly, which doctors and nutritionists alike have applauded as a healthy choice.

Now, however, because of contaminants such as mercury and other pollutants that have made their way into the oceans' eco-systems, fish carries its own risk and a new study has linked regular fish consumption to an increased risk of malignant melanoma, a potentially fatal form of skin cancer. The risk of developing melanoma is 22 percent greater for those who eat the most fish in their diets, the study found.

Published in the medical journal Cancer Causes, the review study looked at the potential connection between fish consumption and risk of melanoma, using data from nearly one half a million adults. The study subjects were originally part of the Nation Cancer Institute’s NI-AARP Diet and Health Study that recruited people between 1995 and 1996. At the time, the participants’ average age was 62. The original cancer research study recorded the frequency the participants ate fried fish, tuna, and non-fried fish and how often they developed cancer.

Using this data, the research team recorded the instances of melanoma over 15 years by syncing the data with cancer registries. To properly assess the data, the researchers noted that the study accounted for physical activity levels, smoking history, family history, alcohol consumption, caffeine levels, ultraviolet radiation specific to location, and body mass indexes.

The study concluded that people who consumed an average of 1.5 ounces of fish a day (or 3 ounces every other day, which would be about the amount in a tuna salad sandwich) experienced a 22 percent higher risk of malignant melanoma – and 28 percent higher risk of developing abnormal cells in the outer skin layers – than those who didn't consume nearly as much fish (about one tenth of an ounce daily on average). The findings have serious implications for consumers who, like pescatarians, regularly eat fish for their health,

The study also examined the differences between the three categories of fish products that people consumed. Most significantly, those consuming 14.2 grams (0.5 ounces) of tuna showed a 20 percent higher risk of malignant melanoma and 17 percent higher risk of stage 0 melanoma than those who consumed 0.3 grams (0.01 ounces) of tuna.

Researchers also found that non-fried fish consumption substantially increased the risk of skin cancer. The study group with a median intake of 17.8 grams (0.62 ounces) showed an 18 percent higher risk of malignant melanoma and a 25 percent higher risk of stage 0 cancer. Overall, 5,034 participants from the original data pool developed malignant melanoma and 3,284 were afflicted by stage 0 cancers.

The study noted that non-fried fish and tuna consumption were linked to higher spikes in skin cancer risks. Although this study did not examine the exact reason why skin cancer and fish consumption were linked, the study author Eunyoung Cho speculates that human-related bio-contaminants could cause the fish to carry more carcinogens, presenting a higher risk to humans.

“We speculate that our findings could possibly be attributed to contaminants in fish, such as polychlorinated biphenyls, dioxins, arsenic, and mercury,” Cho, an associate professor of dermatology and epidemiology at Brown University, said in a statement. “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.”

This study joins a growing body of research that links consumption of animal-based foods to higher risks of several types of cancers. This March, another study found that you can reduce your cancer risk by 14 percent by cutting meat out of your diet. The study found that even marginally lowering your meat consumption can significantly help curb your risk of cancer.

The World Health Organization has characterized red meat and processed meat as a class one carcinogen, which if consumed daily is as deadly to long-term health as smoking.

“This study adds to a growing body of research reinforcing the positive, protective effects of a vegetarian diet,” Chief Executive of the Vegetarian Society Richard McIlwain said at the time. “With cancer now affecting one in every two of us across the country, adopting a healthy vegetarian diet can clearly play a role in preventing this disease. Indeed, evidence from previous surveys suggests a balanced vegetarian diet can also reduce the risk of heart disease and diabetes, in addition to cancers.”

This new study links fish consumption with higher risks of developing skin cancers – malignant melanoma or stage 0 cancers. The study authors suggest that this correlation is likely due to the increase of bio-contaminants in the ocean. Luckily, the plant-based seafood market is expanding at unprecedented rates with some brands developing fully vegan salmon fillets. To start incorporating plant-based seafood, check out The Beet’s favorite vegan seafood products.

For more plant-based happenings, visit The Beet's News articles.

Here are the best foods to eat on repeat, to boost immunity and fight inflammation. And stay off the red meat.

Your body does not produce vitamin C, which means you need to get it daily to have enough to create healthy collagen (the building blocks for your skin and healing).The recommended daily amount to shoot for is 65 to 90 milligrams a day, which is the equivalent of one small glass of orange juice or eating a whole grapefruit. Almost all citrus fruits are high in vitamin C. With such a variety to choose from, it's easy to get your fill.

Want even more vitamin C, add red bell peppers to your salad or pasta sauce. One medium-sized red bell pepper contains 152 milligrams of vitamin C, or enough to fulfill your RDA. Peppers are also a great source of beta carotene, a precursor of vitamin A (retinol). How much beta carotene do you need a day: You should try to get 75 to 180 micrograms a day which is the equivalent of one medium bell pepper a day. But a red pepper has more than two and a half times your RDA for vitamin C so eat them all winter long.

Broccoli may be the most super of superfoods on the planet. It's rich in vitamins A and C as well as E. The phytochemicals in it are great for arming and strengthening your immune system.How much lutein should you eat in a day: There is no RDA for lutein, but experts say get at least 6 milligrams.

Garlic isn't just a great flavor-enhancer, it's essential for your health. Garlic’s immune-boosting properties are tied to its sulfur-containing compounds, such as allicin. Allicin is thought to improve your immune cells' ability to fight off colds and flu, and viruses of all kinds. (Smelling more garlic on the subway? It could be smart coronavirus management.) Garlic also has anti-microbial and anti-viral properties thought to fight off infections. How much should you eat in a day: The optimal amount of garlic to eat is more than most of us can fathom: Two to three cloves a day. While that may not be doable, realistically, some people take garlic supplements to get 300-mg dried garlic in a powdered tablet.

Ginger is another ingredient that has super properties when it comes to fighting off illness. It has been shown to decrease inflammation, which can help if you get swollen glands or a sore throat or any inflammatory ailment. Gingerol, the main bioactive compound in ginger, is a relative of capsaicin, and is responsible for much of its medicinal properties. It has powerful anti-inflammatory and antioxidant benefits.How much should you eat a day: Most recommendations land on 3–4 grams of ginger extract a day, or up to four cups of ginger tea, but no more than 1 gram a day if you are pregnant. Some studies have linked high dosages to an increased risk of miscarriage.

Spinach is not only packed with vitamin C but also antioxidants and beta carotene, both of which give your immune system the healthy boost it needs to fight off invaders. Don't overcook your spinach, since the more it's cooked the less active the antioxidants will be. If you eat it raw or lightly steamed you'll keep more of the nutrients intact.How much should you eat a day: Aim for 1 cup fresh spinach or 1/2 cup cooked per day, but this is the right moment to try the raw or slightly wilted approach. Order warm or wilted spinach salad when you go out, or make it yourself with olive oil, pine nuts, and vegan parm.

Vitamin E in almonds will help ward off colds and flu and is key to your immune system humming along. It’s a fat-soluble molecule, meaning it requires the presence of fat to be absorbed, so nuts are the perfect package for E to make it into your system.How much should you eat in a day: A half-cup serving, or 46 whole, shelled almonds, provides almost 100 percent of your RDA of vitamin E. Almonds are great for you but they don't come with a "free" pass, since 1/4 cup is a serving and has 162 calories, so double that for your RDA and you're eating about 325 calories. Throw them into smoothies instead.

This highly pigmented spice is known for its anti-inflammatory qualities. How it helps immunity? It decreases exercise-induced muscle damage. Tumeric bolsters the immune system by stimulating antibody formation and people with auto-immune diseases are told by their doctors to take 500 mg of curcumin daily to reduce inflammation and stave off soreness.How much should you eat in a day: Try adding extra Tumeric to your diet during periods of stress or during flu season. Or take 500-2,000 mg of curcumin to help fight inflammation and power up your immune system.

Green tea has high levels of EGCG, (epigallocatechin gallate) a hard-working antioxidant that is known to boost immune function. Green tea is steamed so the EGCG is still active when you drink it.Green tea also contains L-theanine, an anti-oxidant which appears to help in the production of T-cells in your body, the killer  L-theanine may aid in the production of germ-fighting compounds in your T-cells.How much green tea should you drink in a day: The optimal amount is three to five cups in a day, but most people won't get to that level. Any amount is better than nothing. Swap out a usual beverage daily for green tea could improve your health.

Papaya delivers over twice your recommended daily amount of vitamin C in one fruit. It also contains an enzyme called papain that has anti-inflammatory effects -- and inflammation is one factor in most illnesses, so avoiding it can help your body fight off bacterial infections like sinusitis.Papayas contain potassium, vitamin B, and folate, which is a powerful cell rebuilder. Exactly how folic acid works to build immunity is linked to its role in protein synthesis, and researchers think that any mechanism in which cells proliferate can be affected (which is why it's critical for pregnant women). People who are folate-deficient have compromised immune systems.How much folate should you eat a day: Whether you are pregnant or not, folate (vitamin B9) is a great vitamin to keep your cells healthy and strong. The recommendation is 400 micrograms a day, or get it from legumes, spinach, papayas, and avocados.

Kiwis are full of folate, vitamin K, vitamin C, and potassium. These vitamins in combination work in the body to build healthy cells, fight infection and keep your immune system humming along. Vitamin K deficiency is rare but when people don't have enough they suffer from weak bones and compromised immune systems. The inflammation system in the body is also dependent on vitamin K, especially your killer T cells that mobilize and fight cancer and other diseases.How much should you eat in a day: Vitamin K is one of the unsung heroes of the body. Women should get 90 micrograms a day, and men should have 120 micrograms.

Sunflower seeds are especially healthy since they provide phosphorus, magnesium and vitamin B-6 as well as vitamin E. Your immune system needs vitamin E to function at full throttle. You can also get vitamin E from avocados and spinach and broccoli.How much should you eat in a day: Anywhere from 1 ounce (30 grams) per day to a healthy handful is considered healthy, but because they are high in sodium you might want to refrain from eating the entire bag. The raw seeds have 204 calories per quarter cup.

The nutrients in miso -- which is a soybean paste that has been fermented with salt and a koji starter -- boosts immune system function by delivering healthy probiotics to the gut, making your microbiome healthier. How does Miso benefit your immune system?  It is a "sirt" food, which are foods that contain high levels of ‘sirtuins’ or proteins that regulate cells and activate metabolism. A diet high in sirts is believed to lead to weight loss, increased wellness and longevity.How much should you eat in a day? Researchers believe that consuming one bowl of miso soup per day, as is the tradition in Japan, lowers the risks of breast cancer. Other than its high sodium content there is no reason to stay away from miso with all its varied health benefits. We say cheers to that.