What Kind of Cold Water Fish Are Healthy to Eat?

Fish consumption has been linked to weight loss, improved blood lipids and reduced inflammation. Cold water fish, such as tuna, sardines and salmon, are loaded with protein and omega-3s. Their safety is subject to debate, though.

On one hand, health experts say that cold water fish protects your heart and lowers bad cholesterol. Some even claim that it may help prevent obesity and its complications. Others, on the other hand, warn about its mercury levels, which pose significant health risks.

Loaded with heart-healthy fats, fish is considered one of the most nutritious foods on the earth. The 2015-2020 Dietary Guidelines for Americans and health organizations worldwide recommend eating at least 8 ounces of seafood per week, including fish and shellfish. When consumed as part of a balanced diet, this food may protect against heart disease and obesity, among other illnesses.

The American Heart Association (AHA) points out that fatty fish is rich in omega-3s and should be consumed at least twice a week. One serving is about 3.5 ounces of cooked fish or three-quarters cup of flaked fish. The fats in sardines, mackerel, albacore tuna and other fish species may help reduce blood pressure, triglycerides and plaque buildup, leading to a lower risk of cardiac events.

There's a catch, though. Cold water fish may contain high levels of mercury, dioxins or polychlorinated biphenyls (PCBs), a class of organic chemicals. The latter have been linked to cancer, impaired immune function and elevated cholesterol.

Cold water fish include salmon, tuna, mackerel, herring, trout, anchovies and other species. King mackerel, tilefish, swordfish, bigeye tuna and shark are the highest in mercury, warns the FDA.

Read more: 13 Types of Fish to Avoid Eating

Some types of fish, such as white tuna, yellowfin tuna, Spanish mackerel and halibut, have moderate mercury levels and should be consumed no more than once a week (especially if you're pregnant or breastfeeding). The good news is that you may consume up to three weekly servings of:

• Salmon
• Sardines
• Cod
• Haddock
• Canned light tuna
• Atlantic mackerel
• Tilapia
• Whitefish
• Flounder

A fish a day keeps the doctor away, according to May 2013 review featured in the Indian Journal of Endocrinology and Metabolism. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), the healthy fats in cold water fish, may help reduce triglycerides and bad cholesterol, raise good cholesterol levels and improve cardiovascular function.

In the long run, these fatty acids may lower your risk of cardiac death. Furthermore, they may help in the prevention and treatment of heart failure, as the researchers note. But their health benefits don't end there.

Due to their anti-inflammatory properties, omega-3s may benefit people with lupus, inflammatory bowel diseases, arthritis and even cancer. However, more studies are needed to confirm these findings.

Rich in protein, fish is a good alternative to meat and dairy. In fact, most types of fish contain just as much protein as beef, chicken and pork, but without the extra fats and calories.

As you probably know, not all fats are created equal. Cold water fish is rich in omega-3s, a class of polyunsaturated fatty acids (PUFAs). Meat and dairy, on the other hand, contain mostly saturated fats, which may raise your bad cholesterol and lead to heart disease in the long run.

According to AHA, saturated fat should account for no more than 5 to 6 percent of your calorie intake. On top of that, red and processed meats may cause colorectal cancer over time, as reported by the World Health Organization.

Cold water fish has none of these side effects. Just make sure you choose low-mercury varieties and eat them in moderation. Here's a quick breakdown of the nutrients in fish, given the standard 3.5-ounce serving:

• Cooked sockeye salmon: 156 calories, 26.5 grams of protein and 5.6 grams of fat, including 1,016 mg of omega-3s per serving (3.5 ounces)
• Canned salmon: 167 calories, 23.6 grams of protein and 7.4 grams of fat, including 1,581 mg of omega-3s per serving
• Canned sardines: 208 calories, 24.6 grams of protein and 11.5 grams of fat, including 1,107 mg of omega-3s per serving
• Bluefin tuna (cooked): 184 calories, 29.9 grams of protein and 6.3 grams of fat, including 1,714 mg of omega-3s per serving
• Canned white tuna (in water): 128 calories, 23.6 grams of protein and 3 grams of fat, including 931 mg of omega-3s per serving
• Canned light tuna (in water): 86 calories, 19.4 grams of protein and 1 gram of fat, including 232 mg of omega-3s per serving
• Atlantic mackerel (cooked): 262 calories, 23.9 grams of protein and 17.8 grams of fat, including 1,309 mg of omega-3s per serving
• Cod (cooked): 84 calories, 20.4 grams of protein and 0.3 grams of fat, including 82 mg of omega-3s per serving
• Whitefish (cooked): 172 calories, 24.5 grams of protein and 7.5 grams of fat, including 1,885 mg of omega-3s per serving

As you see, most types of fish boast 20 or more grams of protein per serving. In general, low-calorie varieties, such as cod and canned light tuna, contain smaller amounts of omega-3s.

If you're trying to lose weight, go for low-calorie varieties. Whitefish, cod, cooked salmon and canned light tuna are all a great choice. They're also some of the best fish to eat for protein.

Cooked chicken breast, by comparison, provides 142 calories, 26.7 grams of protein and 3.1 grams of fat. At first glance, it has a similar nutritional value to cold water fish. However, if you take a closer look, you'll see that it's much lower in omega-3s. One serving (3 ounces) has only 34 milligrams of heart-healthy fats.

Read more: 9 Excuses to Eat More Seafood (Hint: It Can Make You Happy!)

In addition to protein and omega-3s, fish boasts high doses of zinc, magnesium, vitamin A, vitamin D, vitamin B12 and selenium.

Cooked bluefin tuna, for example, delivers 454 percent of the daily recommended vitamin B12 intake per serving. This nutrient supports nerve function and DNA synthesis. Low vitamin B12 levels can lead to anemia, constipation, fatigue and memory problems.

Cold water fish, whether it's salmon, tuna or sardines, can help you lose weight and keep it off. This delicious food is relatively low in calories and high in protein.

The British Journal of Nutrition wrote about the role of protein in weight loss and health back in August 2012. Researchers state that dietary protein increases metabolism and promotes fat loss while preserving lean mass. It also suppresses hunger, making it easier to manage your food intake. Furthermore, the consumption of 1 to 2 grams of protein per kilogram of body weight may help improve blood pressure and muscle-to-fat ratio.

A diet rich in fish may also help prevent weight gain, as reported in another review featured in the British Journal of Nutrition in January 2013. Scientists point out that fish consumption is unlikely to cause you to pack on pounds.

In fact, higher fish intakes have been linked to fat loss in a June 2019 article in Nutrition Research Reviews. Both lean and fatty seafood may help reduce body fat and improve insulin response when consumed as part of a calorie-restricted diet. In clinical trials, lean seafood has been shown to decrease energy intake by 4 to 9 percent compared to meat, leading to faster weight loss.

Read more: The 9 Safest Seafood Options

If your goal is to slim down, go ahead and fill up on cold water fish. Aim for up to three weekly servings and watch your overall calorie intake. Ideally, choose low-mercury varieties like cod, salmon, canned light tuna and whitefish.