The Nutritional Benefits of Fish

What are the nutritional benefits of fish?

Fish stocks are increasingly a cause of concern and fish from the oceans is often polluted with heavy metals.

Yet fish is touted as being healthy, low in fat and brimming with vitamins. So what's the truth? Should fish form part of a healthy and eco-friendly diet? Just how green is it to be eating fish regularly? And is it really so beneficial for our health?

This page explores some of the benefits of fish for our health and the environmental effects of the fishing industry.


The nutritional benefits of fish: some key facts

Fish typically contains good amounts of proteins and fats.

Oily fish such as mackerel and sardines contain Omega 3 fatty acids which are particularly beneficial and may have a role in preventing heart and artery diseases.

These oils also help prevent arthritis and help older people to maintain flexible joints and healthy muscles.

Fish also helps the memory and keeps our immune systems and eyesight in peak condition as it is a good source of vitamins A and D.

See here for more on the benefits of fish oil

That's the good news...

So what are the problems?

Overfishing is one of the main problems. Pollution is another.

We have just got too good at fishing. The technology has overwhelmed the natural supply. Factory ships now ransack the oceans for fish, hoovering up shoals and there are few areas left which do not come in for heavy fishing.

Here in the EU limits and quotas have been set for fishing fleets but still the problem remains; fish in the North Sea around Britain are getting scarcer and smaller. Cod caught in the North Sea are rarely more than two years old - not old enough to breed.

Fishermen themselves are likewise becoming an endangered species; they have declined in the UK by more than 60% in just ten years.

20% of the world's population is dependent on fish as the major source of protein, so over-fishing is a huge issue. Unfortunately, when peoples' immediate livelihood is involved it is easy to take refuge in denial! Many fishermen continue to believe that the problem is being over stated and that fish stocks will recover.

In the 1990s the fishing industry in Newfoundland collapsed, owing to over-fishing. It has not yet fully recovered.

Over-fishing is rife in the Mediterranean too.

The International Commission for the Conservation of Atlantic Tunas (ICCAT) has claimed that bluefin tuna will soon be lost forever from the Mediterranean if no action is taken. Nearly one bluefin tuna in three is caught illegally in the Mediterranean. French fishing fleets recently admitted to having caught more than half again of their allotted quota. And there are plenty more instances of illegal fishing.

The nutritional benefits of fish:



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How over-fishing works in the Mediterranean

In May Atlantic Bluefin tuna go to the warmer waters of the Mediterranean to breed.

Spotter planes and helicopters are waiting for the tuna as they enter the Mediterranean. Since 2001, the use of spotter aircraft during June has been illegal - this is to protect the spawning fish.


yellow fin tuna

However, illegal flights have been recorded inside Libyan airspace and operating from Malta and Lampedusa Island, Italy. Illegal driftnets have also been seen in some areas. Most of the fish are caught by high-tech purse seine and longline fleets.

In 2004 an incredible 25,000 tonnes of bluefin tuna was caught in just 2 months. That's nearly 80% of the total quota for the entire Mediterranean and Eastern Atlantic. Clearly these levels of fishing - legal and illegal - are not sustainable.

(Picture: yellow fin tuna courtesy of Greenpeace)

Most of the fish is put into cages and towed to Japan where it is fattened and grown on for the sushi industry.

There are similar problems in other parts of the world, with unsustainable fishing practices being used and fish stocks collapsing. Stocks of fish such as marlin and swordfish, for example, are also at an all-time low.

Some fish, notably pollack and haddock are recovering from over-fishing or are less badly affected and quotas have been raised.

Unfortunately these are regarded as some of the least popular fish! With imaginative recipes and innovative approaches to cooking, these fish can be delicious.

The nutritional benefits of fish:


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Is fish farming the answer?

Fish farming was regarded for a long time as a way to protect wild fish stocks and supply large quantities of fresh fish to the public. Unfortunately a number of problems has emerged.

Pollution from fish farms

Most fish farms are located in relatively small areas of water - in estuaries for example - where the supply of fresh, clean water is limited. Although in theory the water in an estuary is changed twice a day with the tides, in practice it is pretty much the same water sluicing in and out over again, with only a small amount of new water coming in each time.

As with any living animal fish have excreta which need to be cleansed and broken down by the environment. In conditions of crowding and limited fresh water, this does not happen effectively. The effect of all the concentrated effluent from the fish can be similar to that from a land-based factory farm, i.e. pollution of local water sources.

Fish food for fish farms also causes problems.

It is difficult to feed exactly the right quantities so that all the fish are fed. Inevitably some food drops to the floor or sea bed where it becomes another cause of algal blooms. There is too much nitrogen in a small area and algae feed on the nitrogen and grow out of control. Then the oxygen present in the water is depleted, causing other life forms to die.

Fish in fish farms are densely packed and crowded. Just as with battery farms for chickens and pigs, this leads to health problems.

The over-crowding in fish farms is also a welfare issue. Fish become stressed from the cramped conditions and fights break out.

Here's a very short video (from Youtube) showing just how crowded fish farms can be. The fish farm shown here is in the Mekong Delta, Vietnam.




Crowding can cause skin problems such as infestation by sea lice. These problems are often "solved" by liberal use of chemicals.

For example an extremely toxic anti-parasitic chemical, malachite green was used for some years in the EU until it was banned in 2002. Residues of this chemical were found in farmed trout and salmon.

Recent studies (2007) have identified traces of malachite green in fish imported to the US from China. There are also other chemical boosters favoured by fish farmers. There has been interest in using hormones to promote growth. Clearly such practices can affect the nutritional value of fish produced.

The nutritional benefits of fish:


The effects of fish farming on wildlife

Sometimes captive bred fish escape and interbreed with wild stocks. Because of the impoverished health of the farmed stock, this can lead to a loss of adaptation to wild conditions. There is some evidence that wild salmon are now more prone to viruses than formerly.

Fish farmers often view wild creatures as competitors. There have been many instances of fish farmers in Scotland killing seals, cormorants and herons according to the RSPB. Farmed fish are often kept in cages which are vulnerable to attack from the air, in particular.

While fish farming may enable us to rear large numbers of fish for the mass market there are reasons to be concerned for the nutritional benefits of fish so produced and for the health of the environment and wildlife.

Taste and nutritional value of farmed fish

Fish from fish farms tastes nothing like as good as fresh caught wild fish, though organic farmed fish is better.

Salmon from non-organic fish farms is artificially coloured in order for it to have the expected healthy shade of pink of the wild caught salmon. Colourants are added to the fishes' food so that the desired shade of pink is reached. Chemical firms even supply farmers with a dye colour swatch so that the farmer can choose the hue!

The nutritional value is relatively poor. Yes, the famous Omega 3 fish oils are present. But there are chemical residues from pesticides present in some fish. There are also concerns about the antibiotics and other drugs which are often routinely used to control disease.

See below for more details of the nutritional benefits of fish and contamination of wild fish stocks by pollutants.


Contamination of fish stocks


Mercury and dioxins, both major pollutants, are found in some fish. PCBs are also a health hazard. These chemicals are used in industry and find their way into the seas. Both wild and farmed stocks can be affected.

Mercury occurs both naturally and as a result of human industrial activities. It tends to concentrate in the bodies of long-lived predatory species such as swordfish, marlin and shark. Tuna is also affected.

In Britain the Food Standards Agency still advises people to eat fish at least twice a week, one portion being of oily fish.

However, they also recommend that pregnant and breast-feeding women and young children avoid shark, marlin and swordfish altogether. Pregnant and breast-feeding women are also advised to limit their tuna intake to one or two tins a week.

Salmon from fish farms are also likely to store more toxins than wild fish, partly because they are fatter than wild fish and the toxic pollutants concentrate in the fishes' fat.

Fish from farms also come with a toxic load of deliberately added chemicals: disinfectants, anti-parasitic treatments, antibiotics andanti-microbial agents may all play a part.

In 2004 a study of Scottish farmed salmon found the level of cancer-causing chemicals to be so high that the authors (Scientists from Cornell University and others) recommended that it be eaten no more than once in 4 months.

Salmon is becoming almost as accessible as battery-farmed chicken - a cheap source of protein. However when the environmental costs are added up and the effects on human health are considered, the benefits are less clear.

Fish clearly has nutritional benefits but the best benefits are obtained from organic and sustainably farmed fish and wild fish from unpolluted waters.

If you are concerned about the nutritional benefits of fish for yourself or your family, it is perhaps wise to limit your intake and seek the same nutrients elsewhere. Clearly, the toxic load carried by some species may well negate some of the nutritional benefits of fish for many of us.


Some conclusions about eating fish

So, what conclusion can we come to about how much fish to include in our diets?

I believe that the health benefits of fish are clear and that it is wise to eat fish once or twice a week on average.

But, for the sake of our health, and for the sake of the wider environment, we should try to source all our fish from organic, legal, wild and sustainable sources.

How can we do this? Isn't that easier said than done?

On a personal level we can begin asking our fish suppliers - supermarkets, fishmongers and market stalls - a few searching questions! Most retailers should be able to reveal their sources, though whether they actually will may be another matter. Many whole food outlets and farmers markets are proud to advertise the sources of their foods and some include fishmongers amongst their retailers.

For those who do not live near such outlets, there are also some organisations and books to help...

Which fish to buy for a sustainable future

Fish Forever: The Definitive Guide to Understanding, Selecting, and Preparing Healthy, Delicious, and Environmentally Sustainable Seafood is a good guide to seafood for a sustainable diet. It is one of the best books available on the subject and contains lots of easy-to-follow recipes.

For advice on what fish to buy and which methods of fishing are most sustainable please see the excellent website FishOnline which has extensive details on all issues to do with marine fish. This is a British site but it appears to deal with fish world wide. It has lots of good information on 150 types of fish and their present status, information on buying from supermarkets and the different kinds of fishing with details of their environmental impact.

This site is run by the Marine Conservation Society.

The US site run by the Marine Stewardship Council is also well worth checking for information on sustainable fishing.
For more information about the issue of illegal fishing and about the fight to preserve the marine environment see Greenpeace's extensive coverage. You can also become an Ocean Defender and participate in a forum about conservation of the oceans and sea life.

Please see the links page for links to Greenpeace and Ocean Defenders.




Hugh's Fish Fight

Join the fish fight! Hugh Fearnley-Whittingstall has joined forces with other top British chefs to get the practice of dumping dead and dying "by-catch" back into the sea. This is an EU policy which fishermen have to abide by. For example, if the seamen are fishing for monkfish but have already fulfilled their quota of cod, then any cod caught in the nets have to be discarded. The practice is a part of the quota system designed to protect fish stocks but there is clearly a lot wrong with it! (This is not strictly to do with the nutritional benefits of fish - but an important wildlife and sustainability issue!)

Learn more here:


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