Fish is a really healthy food. Eating it regularly may lower your risk of a number of health conditions, including heart disease, stroke and depression (, , , ).
Because of this, health professionals often recommend that people eat fish at least once or twice a week ().
However, the way you cook your fish can change its nutritional composition, so some cooking methods may be better for your health than others.
This article explores how different cooking methods may change the nutritional value of your fish, and examines which methods are healthiest.
There are many types of fish, all with different nutrition profiles. In general, they are divided into two categories: lean and fatty.
Both are considered nutritious and a great source of high-quality protein, but fatty fish are thought to be especially important for health. This is because they contain some important nutrients, including omega-3 fatty acids and vitamin D ().
Currently, around 40% of people have low levels of vitamin D. This has been linked to a higher risk heart disease, diabetes, cancer, dementia and some autoimmune diseases ().
The best way to get vitamin D is through sun exposure. However, fatty fish are one of the few food sources of vitamin D and can contribute a good amount (, ).
Your body and brain also need omega-3 fatty acids to function at their best. In fact, getting enough omega-3s has been linked with a number of health benefits, including a decreased risk of heart disease and some cancers (, , , ).
These special fats may also slow down the decline in brain function that people commonly experience as they age (, ).
Eating lean fish may also have health benefits. Some studies have linked it to a lower risk of metabolic syndrome and reduced risk factors for heart disease (, , , ).
These are some of the reasons why health experts recommend eating fish at least once or twice a week (, ).
Summary: Fish is a good source of high-quality protein, vitamin D and omega-3 fatty acids. Health experts recommend eating fish at least once or twice each week.
Grilling and broiling are very similar cooking methods. They both involve applying dry heat to your food at very high temperatures.
The main difference between the two methods is that grilling applies heat from below and broiling applies it from above.
Both methods are a fast way to cook really tasty fish without adding any fats.
Unfortunately, both grilling and broiling are known to cause the formation of some harmful compounds called heterocyclic amines (HAs) and polycyclic aromatic hydrocarbons (PAHs) (, ).
These two types of compounds form when muscle tissue from meat or fish is heated to very high temperatures, particularly over an open flame ().
However, the risks associated with these compounds have only been linked to high intakes of red or processed meat. Eating fish hasn't been associated with the same risks (, , , , , ).
Grilling and broiling may also result in the formation of compounds called advanced glycation end products (AGEs).
These compounds form naturally in your body as you age, but can also form in muscle-containing foods like meat and fish when they are cooked at high temperatures (, , ).
High levels of AGEs have been linked to a range of diseases, including heart disease, diabetes and Alzheimer's (, , ).
To reduce your exposure to these compounds, avoid cooking with an open flame, try to keep your cooking times as short as possible and avoid charring meat ().
Additionally, applying a marinade to your fish before you grill it may help reduce the formation of HAs and PAHs ().
Summary: Grilling and broiling fish can produce some harmful compounds. To minimize them, cook fish for the shortest time possible, avoid charring the flesh and add a marinade.
Pan-frying and deep-frying are high-temperature cooking methods that use hot fat.
Deep-frying involves submerging food in a large amount of fat, while pan-frying uses a much smaller amount of fat in a skillet, wok or pot.
During frying, fish will absorb some of the fat, increasing its calorie content and changing the types of fat it contains (, ).
Cooking your fish in an oil, such as vegetable oil, that contains high amounts of omega-6 fatty acids can increase its content of inflammatory omega-6s (, ).
This has been shown to happen to a greater degree in fish that has been deep-fried rather than pan-fried, due to the larger amounts of oil used. In general, lean fish also tends to absorb more oil than fatty fish (, ).
The high temperatures during frying also damage the healthy omega-3 fatty acids in fish more than other cooking methods do (, ).
In fact, one study found that frying tuna decreased the amount of beneficial omega-3 fatty acids by 70–85% ().
However, it seems that these effects can vary depending on which species of fish you cook. Other studies have found that some fish, such as herring, may still contain beneficial amounts of omega-3s after they're fried (, , , ).
Other nutrients may be at risk too, as one study found that frying salmon reduced the amount of vitamin D it contained by half ().
The high temperatures of frying may also cause more of the harmful compounds HAs, PAHs and AGEs to form (, ).
Overall, pan-frying is considered healthier than deep-frying due to the smaller amounts of oil it uses. Additionally, it's best to choose an oil that's stable at high heat and will add healthier fats to your fish. Olive oil is one healthy option.
Summary: Frying can increase the amount of fat in your fish and negatively affect its ratio of omega-3 to omega-6 fatty acids. If you're frying, pan-fry rather than deep-fry your fish, and use a healthy oil like olive oil.
Poaching and steaming are cooking methods that use water or other liquids during the cooking process.
Poaching involves submerging your fish in a liquid such as water, milk, stock or wine while cooking in the oven.
Steaming is often carried out in a specially designed pot or appliance, and uses hot, vaporized water to cook your fish.
Neither poaching nor steaming add oil or fat to the fish, so using these methods won't add calories or change the fats in your fish ().
Poaching and steaming also cook fish at slightly lower temperatures than other methods, which helps preserve nutrients and is thought to minimize the formation of harmful chemicals like HAs and PAHs.
One study suggested that the longer cooking time required to steam fish may increase the number of cholesterol oxidation products. These are potentially harmful compounds formed when cholesterol is heated (, ).
However, both steaming and poaching are considered healthy, since their lower temperatures and lack of cooking fat help preserve the beneficial omega-3 fatty acids in fish better than other cooking methods ().
Summary: Poaching and steaming are low-temperature cooking methods that may preserve healthy omega-3 fatty acids better than other methods.
Baking is a dry heat method that involves cooking fish in an oven.
Some studies have shown that baking fish causes less loss of omega-3 fatty acids than both frying and microwaving (, , ).
Baking may also be a better way to retain the vitamin D content of fish.
One study found that baked salmon retained all its vitamin D, whereas fried salmon lost around 50% of this important vitamin ().
For these reasons, oven-baking is considered a healthy way to cook fish.
However, as with other cooking methods, covering your fish in oil during cooking can change its fatty acid profile ().
If you're baking fish, use minimal amounts of a heat-stable healthy oil, like olive oil.
Summary: By baking your fish, you'll likely lose less healthy omega-3 fats than if you fry or microwave it.
Microwave ovens cook food using waves of energy.
These waves interact with some of the molecules in food, causing them to vibrate, which heats the food.
This way of cooking may be controversial, since some people believe that cooking with a microwave can reduce the nutrients in food ().
However, microwaving is a fast and relatively low-temperature cooking method.
Because of this, it can actually preserve some nutrients better than some other cooking methods. In fact, many studies have found that microwaving fish can help prevent the loss of its healthy omega-3 fatty acids (, , ).
Additionally, the lower temperatures mean that harmful compounds like PAHs and HAs are less likely to form, compared to other cooking methods, like frying.
Summary: Microwaving fish can help prevent it from losing healthy omega-3 fatty acids, and may also cause fewer harmful compounds to form.
Sous vide is French for "under vacuum." In this cooking method, food is placed inside a sealed pouch and cooked in a temperature-controlled water bath.
It's a low-temperature cooking method in which food is cooked very slowly over a long period of time.
Although sous vide takes a long time, it's considered a very healthy way to cook, because it uses a tightly regulated, very low temperature that's thought to lock in moisture and retain nutrients.
One study found that fish cooked sous vide retained more omega-3 fatty acids than oven-baked fish ().
Additionally, like other low-temperature cooking methods, sous vide may result in fewer harmful HAs forming during the cooking process (, ).
Summary: Sous vide is a low-temperature cooking method. It may help preserve some of the healthy omega-3 fats in fish, as well as reduce the amounts of harmful compounds that can form during cooking.
Fish is a healthy food that's a great addition to any diet.
However, the type of fish, cooking method, length of cooking time and cooking oil you use can all affect the nutrition profile of your fish.
Overall, the healthiest cooking methods limit the loss of healthy omega-3 fats, retain the most nutrients and minimize the formation of harmful compounds.
In general, this means that sous vide, microwaving, baking, steaming and poaching your fish are your best bets.
On the other hand, deep-frying fish is the least healthy cooking method.