Is fish healthy? How to make the best choice for your diet

Eating healthy means eating lean protein. If you don’t get enough protein, your body uses what you have and breaks down your muscle. You get tired easily and feel weak.

Enter fish. It’s one of your options for getting this essential food group without over-doing the bad stuff like animal fat.

But there are some important things to bear in mind when choosing what fish to eat, and how much.

We got the details from MD Anderson Senior Clinical Dietitian Karla Crawford.

Farmed fish versus wild fish

Wild fish is caught from rivers, lakes and oceans and eats only food it finds by itself. It is generally better for you because it is leaner and higher in healthy fats like omega 3 oils. Wild fish are also free of growth hormones and antibiotics.

Farmed fish is bred by farmers. Farmed fish usually has more fat and fewer omega 3 oils, and may have been given hormones or antibiotics. There is no evidence these drugs harm you if you eat the fish, but some people may want to choose the alternative. Pesticide run off also is a bigger problem for farmed fish. Farms usually have a higher concentration of these chemicals because they are used in other parts of the business like crops.  Pesticides can run off into ponds and be absorbed by fish.

If you do buy farmed fish, pay attention to where it was raised and processed. Rules on what fish are fed and how they are kept vary from country to country.

Fish in cans or jars versus fresh fish

Canned fish generally does not have quite as many nutrients as fresh fish, but you can get added benefits. If you eat the bones, canned or jarred fish can be an excellent source of calcium.

The main thing to remember is to look for something high quality that contains whole fish or steaks. Poor quality canned fish is sometimes a hodgepodge of ground up fish leftovers.

“I prefer jarred fish over canned fish,” says Crawford. “It has a bit better quality and the texture of the fish is firmer.”

If you buy canned fish, you may want to look for BPA free cans.

What about mercury?

Mercury is a toxin that exists naturally, but industrial pollution means the level in some water is high. The mercury collects in some larger fish and makes them unsafe to eat, especially for pregnant women.

Mercury cannot be cleaned from the fish so it’s best to avoid species most at risk. These include swordfish, shark, king mackerel and other large predatory fish.

Light canned tuna is listed as low in mercury by the Food and Drug Administration. Tuna steaks generally have higher levels of mercury. The FDA says you should only eat one portion – that's 6 ounces of tuna steaks – per week.

Omega oils

Omega oils are fats found in fish and come in a few types. Omega 3 oils are good because they reduce inflammation. Fish like salmon, mackerel, herring and sardines are high in omega 3 oils.

Omega 6 oils are bad because they do the opposite. They make inflammation worse. Talapia and catfish are high in omega 6 oils.

Processed fish

Any processed food puts you at higher risk of eating more fat and salt. This is true of processed fish like fish sticks because they are usually breaded and fried. Processed fish also may contain more filler ingredients like white flour.

It’s always better to buy a piece of fish and bread and bake it yourself.

Raw fish

If you want to eat sushi or another type of raw fish, the most important thing is to get it from a trusted source. Choose a well-known supplier or a store with a high turnover so you know your fish is as fresh as it can be.

If you live in rural areas where fishing is a popular sport, the stores near you may struggle to sell fish quickly. Talk to the staff at the fish counter or in the restaurant about when they got their fish.

How much should I eat?

Our dietitian recommends you eat fish twice a week to take advantage of this nutrient rich lean protein. The meals should add up to 8 ounces of fish in total for the week.

“It won’t hurt you if you eat more. I have some patients that eat fish every day,” Crawford says. “But it’s unclear whether eating more fish has any added benefit.”

You also may want to consider that eating too much fish can cause environmental problems. Overfishing can drastically reduce the number of fish available. To avoid this, look for fish that has been sustainably caught. This means that it has been caught or farmed in ways that consider long-term fish populations. This could be by staying within quotas, or not taking young fish, so there are enough fish left to breed.

What about if I am pregnant or trying to become pregnant?

If you are pregnant or trying to become pregnant, pay special attention to the advice about the mercury content of your fish. Do not eat large predatory species like swordfish, shark or king mackerel. If you eat tuna steaks, only have 6 ounces per week. This does not include canned light tuna.

To minimize the risk that you will take in toxins, do not eat more than the recommended amount of 8 ounces of fish per week.

Eat fish as part of a plant-based diet

If you follow the guidelines about eating fish, it can be a good start to improving your diet overall. But for the most benefit, you should eat a plant-based diet.

This means two-thirds of every meal is made up of vegetables, fruits and whole grains. Fish is one lean protein that can make up the remaining third.

This diet has been proven to lower your risk for cancer and other diseases, especially if you get enough exercise.

You should aim for at least 150 minutes of moderate or 75 minutes of vigorous exercise each week, and a full strength training routine twice a week.