Can You Eat Raw Tuna Fresh From the Water?

As a lean protein filled with omega-3 fatty acids, tuna can help you build muscle and lose weight. But choosing the form in which you eat it, whether raw tuna, canned or cooked — as well as how you prepare it — can have an effect on your health.

Tuna, a saltwater fish that's often touted for its health benefits, is high in protein and low in fat and carbs. You've likely eaten your share of tuna salad sandwiches or raw tuna in sushi, but may have overlooked the health benefits of this fish, whether it's raw, canned or cooked.

Fish, particularly salmon and tuna, are high in protein, making them ideal for bodybuilders and athletes. One ounce of raw yellowfin tuna, for example, contains nearly 7 grams of protein, no carbs and a small amount of healthy fat.

Tuna, like salmon, contains healthy fats in the form of omega-3 fatty acids, which have been shown to have a variety of health benefits. These unsaturated fatty acids are different from the saturated fats found in meats like beef, which are less healthy.

Omega-3 fatty acids in fish have been linked to improved heart health. Eating one to two servings of fish per week could potentially lower your risk of heart attacks, Mayo Clinic states. Omega-3 fatty acids have also been shown to reduce inflammation in the body, lower triglycerides and improve blood pressure.

Eating fish in its whole form, rather than getting fish oil supplements, may provide the most benefits. A study published in September 2014 in Food and Chemical Toxicology found that eating canned bluefin tuna was safer and more beneficial to heart health than commercial fish oil supplements.

Albacore tuna also contains a decent amount of other vitamins, such as folate, vitamin K, vitamin B-12, vitamin D and niacin. It also contains zinc and magnesium.

Read more: The Healthiest Way to Enjoy a Fish and Vegetables Diet

While you may not be hand-catching and eating fresh tuna from a river, you may come across raw fish in a variety of forms in restaurants and meals. For example, raw tuna for sushi or sashimi is common in Japanese dishes.

Typically, poke bowls, or Hawaiian salads, contain raw fish mixed with vegetables. Then there's ceviche, marinated raw fish mixed with lemon or lime. You may also come across raw fish in the Italian dish carpaccio, which typically also contains raw meat.

How do you decide whether raw fish is better for you than cooked fish, or the other way around? In short, whether you're eating tuna for sushi or tuna in a can, both raw and cooked tuna should contain the same nutrients, vitamins and omega-3 fatty acids. What makes the difference is how the tuna is prepared, and whether the raw fish has a risk of parasites or bacteria.

Generally, eating raw fish means you're eating fish in a cleaner state, with fewer cooking oils, butters or sauces than you might come across in cooked fish dishes. In addition, pure raw fish doesn't contain any added salts, fats or calories. Some canned tunas can be high in sodium or oil, but raw tuna, when prepared cleanly, is the fish in its simplest form: pure protein and healthy fats.

While eating raw fish can be a tasty experience, it also comes with a slew of health risks. Some of these health dangers are potentially bad enough to steer many people away from consuming raw fish unless it's been expertly regulated and prepared at restaurants.

One of the biggest risks is foodborne illness caused by parasites or bacteria that thrive in raw fish, according to the Academy of Nutrition and Dietetics. All meats and seafood pose this risk before they're cooked, which is why it's recommended to cook food to the temperature high enough to kill the bacteria.

Raw tuna, in particular, can run the risk of Salmonella and Listeria monocytogenes, a study published in March 2016 in Foods found. Raw yellowfin tuna showed signs of Listeria monocytogenes even after being stored in a refrigerator, prompting the researchers to note that it's important to handle raw fish properly from farm to table.

The same issue exists with nearly all types of raw fish, as a study published in January 2017 in Letters to Applied Microbiology reports. Raw seafood, from tuna to oyster and squid, all have a risk of spreading foodborne illness if they're not cooked properly.

Finally, a common concern in eating any type of fish is the level of contaminants they contain, particularly mercury. The Food & Drug Administration (FDA) states you should avoid fish that are higher in mercury, like king mackerel, shark and swordfish.

The safest fish, which are recommended to be eaten two to three times a week, include butterfish, cod and salmon, among others. Canned light tuna is generally considered one of the best choices as well. But certain other types of tuna, like albacore and yellowfin (either fresh, canned or frozen) fall under the "good choices" category, to be eaten only once a week, due to the higher mercury levels.

Read more: Fishing for Answers: Wild-Caught or Farm-Raised Fish — Which Is Better?

Despite the risk of these contaminants, many experts argue that the benefits of eating fish outweigh the potential risks — assuming the fish is prepared properly. The FDA notes that fish are part of a healthy diet.

Because of the encompassing nature of pollution in oceans and freshwater, nearly all fish and shellfish will contain some level of mercury and contaminants, according to the American Institute for Cancer Research. And while these chemicals can certainly build up if eaten too much, the majority of fish contain levels low enough to not be cause for concern.

Thus, the best way to get the health benefits of tuna and other types of fish is to simply choose the safest types. Unless you're an expert fisher, you may want to avoid catching and eating your own raw fish. However, if you do come across raw fish you'd like to eat, you can try to freeze it to kill parasites.

In order for freezing to be completely safe and effective, it all depends on the type of fish, the parasites in the fish, the temperature at which you freeze it and the length of time it's frozen, according to Public Health Ontario. And even in some cases, freezing frozen fish may not work: The Centers for Disease Control & Prevention have reported Salmonella outbreaks in the past even with frozen tuna.

If you're buying your fish rather than catching it, check to make sure you're purchasing it from the most reliable sources. Restaurants and fish suppliers will typically be regulated to make sure they're following the protocol for keeping fish clean and safe. Most raw tuna for sushi, for example, is well prepared and has a lower risk of getting you sick.

Once you've brought your raw tuna or other type of fish home, you can freeze it, or store it in your fridge and cook it immediately within a day or two. If fish smells overly fishy, that's a sign it may be going sour; fresh fish shouldn't have much of a smell.

Finally, disinfect all areas in your home or kitchen where you've been preparing raw fish. Following these protocols will help ensure you can get the best benefits of tuna and other types of fish, without the potential health risks.