You probably know that fish is part of a healthy diet. Fish — and its healthy fats — are well recognized for their heart health benefits. But research on the role that fish may play in cancer protection is less clear. And if you’re one of the many Americans who enjoys fish, there’s a good chance you also have concerns about its possible contaminants.
When it comes to cancer risk and overall health, here are the fish basics.
1. Nutrition Treasure
Any given serving of fish is packed with protein and contains B vitamins and minerals including potassium and selenium. One serving (3-ounces) contains from 80 (lean fish like cod) to 150 calories (fattier fish, like salmon).
Higher fat fishes with their omega-3 fatty acids are the ones most linked to heart health benefits. Omega-3 fats are found in fish like salmon, mackerel, herring, lake and rainbow trout, sardines and albacore tuna.
2. Fish and Cancer Risk
AICR’s report on liver cancer reveals hints that eating fish may protect against this cancer, although the evidence was not strong enough to form a conclusion. Some population studies have also linked higher fish consumption with reduced risk of other cancers, including colon and breast.
In lab studies, the omega 3-fats of fish are well researched. The major omega-3 fats in fish oil are called DHA(docosahexaenoic acid) and EPA(eicosapentaenoic acid). Lab studies have suggested these fats alter colon cell function and may cut down on inflammation.
Although fish oil is a popular dietary supplement, for people with no heart disease, the American Heart Association says getting omega-3 fatty acids through foods is best. For cancer protection, AICR recommends that people do not rely on supplements.
The Dietary Guidelines for Americans recommends eating 8 ounces of fish per week.
3. Health Trumps Contaminants (with caveats)
Almost all fish and shellfish come with at least some contaminants, accumulated in waters with pollutants and pesticides. For most people eating a variety of fish, either farmed or wild-caught, the levels of contaminants are too small to cause harm, according to government guidelines. The 2020 US Dietary Guidelines general recommendation for American adults is to eat at least 2 servings (approximately 8 ounces cooked) of a variety of fish and seafood per week.
Some people, including children, breastfeeding women and women who are or who could become pregnant, should steer away from certain types of fish. One toxin of concern is mercury, a heavy metal that can harm an unborn baby or young child’s developing nervous system if enough is consumed. Large fish that live the longest, such as sharks and swordfish, contain the highest amounts. For the specific recommendations visit the EPA’s What You Need to Know about Mercury in Fish and Shellfish. Another good resource on fish selection is the Monterey Bay Aquarium Seafood Watch.
4. Fish – One Part of the Whole
Again and again, research shows that people eating diets with a moderate amount of seafood have lower risk of cancer and other chronic diseases and longer lives.
This could be due to other parts of the diet. For example, if you’re eating more fish for dinner, you may be eating less red and processed meats, which increase colorectal cancer risk. Fish is a staple of several dietary patterns also linked to lower cancer risk, such as the Mediterranean diet. People eating a Mediterranean diet are also eating plenty of beans, whole grains, vegetables and other plant foods, which all play a role in reducing cancer risk.
These healthy fish-containing dietary patterns are also low on sugary foods and drinks and refined grains. Taken together, these diets high in plant foods, moderate in fish and seafood and low in sugar can help people stay a healthy weight. Overweight and obesity is now linked to increased risk of 10 cancers, including postmenopausal breast, liver and colorectal.