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Fish and shellfish have been important in human nutrition since prehistoric times. Throughout history, fish and shellfish have been a source of economic power. The Vikings traded large amounts of stockfish (salted, dried cod) and Britain's empire was based largely on its control of the oceans as a result of its fishing industry. At one time, the English Parliament even forbade the nation's citizens to eat meat three days a week: Wednesday, Fridays and Saturdays. This decree increased the demand for fish and as a result, the demand for fisherman. Many of the fishermen became skilled seamen and a resource for the English Navy.


Why should I be aware of this?

  • Fish is good for heart, skin and even in cases of asthma.
  • Most fish are low in saturated fat, low in calories, and a great source of protein. They also contain omega-3 fatty acids.
  • All types of fish contain high levels of chemical residues from the water that they live in.
  • Some species of fish are also endangered.

Fish and health

For health purposes, fish can be divided into two categories -- oily fish and white fish. Oily fish includes mackerel, salmon, pilchards, herring, trout, sardines and fresh (but not tinned) tuna, while white fish includes cod, haddock, monkfish. Though both fish are excellent sources of protein, vitamins and minerals, oily fish is particularly nutritious as it has a fatty acid called omega-3, which lowers incidence of heart disease and boosts healthy cell function. (CHS International Research Limited Essential Fatty Acids). White fish on the other hand primarily comprises water and protein.

Fish have been found to reduce risk to Alzheimer's. Some fish are also used as medicine for curing asthma, though there is some controversy attached to it.

Oily Fish are usually cold water fish and white fish are most often warm water fish.

Fish and your skin

The Omega-3 in the fish also bolsters the skin barrier - that is, the layer of lipids that holds onto moisture and keeps irritants out.

There is even evidence that the skin-strengthening effects of omega-3s can improve chronic skin conditions like rosacea and atopic dermatitis, but more research is necessary to confirm that link.

Furthermore, many types of fish (like, once again, salmon and cod) are rich in vitamin D - as dermatologists increasingly emphasize sun avoidance, we also need to emphasize the importance of finding other sources of this vitamin, which is produced during sun exposure.

The Fish Debate

We have known that eating fish is good for us for some time. Most fish are low in saturated fat, low in calories, and a great source of protein. They also contain omega-3 fatty acid that keeps the heart healthy. It also contains healthy fats that reduce cholesterol and improve general health and longevity. But off late, fish-eaters across the world are facing a dilemma. Fish, which would otherwise have been one of the healthiest meats on the planet, accumulate high levels of chemical residues from the water that they live in. Residues in fish can be as much as 9 million times the amount found in the water!

Contaminants found in fish flesh include

  • Mercury
  • PCBs
  • Radioactive substances such as strontium
  • Toxic metals such as cadmium, lead, chromium and arsenic

Exposure to mercury increases the risk of

  • Attention and language deficits
  • Impaired memory
  • Inability to process and recall information
  • Decreased concentration
  • Impaired visual and motor function

Pesticides in fish, such as DDT, PCBs, and dioxin, are also dangerous. They have been linked to cancers, nervous system disorders, fetal damage and many other health problems.

The dilemma before fish consumers is – should they eat more fish because of the heart-healthy benefits of omega-3 fatty acids, or should they limit their consumption of fish because of the risk of toxins.

Farmed Fish

There has been a rise in the production of farmed fish over the years. Over 45% of all fish consumed by humans -- 48 million tonnes in all -- is raised on farms. Almost 50 percent of the salmon, 40 percent of the mollusks, and 65 percent of the freshwater fish consumed today are raised on fish farms.

Contrary to popular belief, farmed fish are not free of toxins. As fish farms raise large quantities of fish in confined areas, the overcrowding leads to disease and injuries. Farm fish are given antibiotics and chemicals for the parasites like sea lice, skin and gill infections and other diseases that commonly affect them.

They are also given drugs and hormones, and sometimes are genetically modified, to accelerate growth and change reproductive behaviors.

Farmed salmon, which would ordinarily have been grey because of their diet, are given chemicals additives to turn their flesh pink in order to make them more marketable. (Wild salmon eat a diet of shrimp and krill, which contain natural chemicals that make the salmon pink.)

According to the British Medical Journal, fish farming does not provide a solution as farmed fish contains fewer omega 3 fatty acids, this being dependent on what they are fed, usually wild caught fish products. The original source of the long chain omega 3 fatty acids found in fish is, however, the chloroplasts of marine algae and phytoplankton at the bottom of the food chain.

Some facts about mercury toxicity in fish

  • Nearly all fish and shellfish contain traces of mercury.
  • For most people, the risk from mercury by eating fish and shellfish will not pose a health concern but it may harm an unborn baby or a young child's developing nervous system. The risks from mercury in fish and shellfish depend on the amount of fish and shellfish eaten and the levels of mercury in the fish and shellfish.
  • Contrary to the popular belief, freshwater fish are more likely to be contaminated than ocean fish. A recent report released by the Environmental Protection Agency (EPA) showed that virtually every freshwater fish sample tested from lakes across the United States was contaminated with mercury.
  • Long-living larger fish living in the ocean have the highest mercury content. During their long life-span, large fish consume more toxins and being carnivorous, they consume toxins present in the small fish they eat. Some long living large ocean fish are salmon, tuna, swordfish, and sharks.


Overfishing in oceans has become a serious concern with several species of fish such as cod and haddock being in danger of becoming extinct. A report released by the FAO states that of the world’s commercially important marine fish stocks, ten per cent are depleted or slowly recovering, 15% are overexploited, 47% are fully fished, and 25% are underexploited.

What can I do?

  • While selecting and eating fish or shellfish, women and small children should avoid shark, swordfish, king mackerel, or tilefish as the mercury content in these fish is very high.
  • Since fish is so beneficial, at least two portions or 12 ounce of fish (fresh, frozen or canned) should be eaten in a week and at least one should be an oily fish.
  • Commonly eaten fish such as shrimp, canned light tuna, salmon, pollock, and catfish are low in mercury.
  • Though as popular as canned light tuna, albacore or white tuna has more mercury. It is advisable to consume only one portion of albacore tuna per week.
  • While eating locally caught fish, find out if any local advisories have been issued about the safety of fish. In the absence of such information, do not eat more than one portion of such fish in a week.
  • Though Tuna and salmon are very beneficial to health as they are rich in lean protein and omega-3 fatty acids, they have high mercury content.
  • Alternatives such as anchovies, herring, mackerel, sardines and trout are also rich in lean proteins and omega-3 fatty acids but have lower mercury content. In their short life spans, they don’t accumulate as many toxins as the bigger cold-water fish. They do not feature among the endangered species, breed faster, and eat much lower on the marine food chain.
  • Shellfish such as prawns are known to raise LDL cholesterol levels. These should be consumed in moderation by healthy people and avoided by people with raised blood lipid levels.

Measures to ensure safe eating

  • Try finding out if the fish have been lab tested for mercury and PCBs.
  • Avoid raw sea food, especially raw shellfish.
  • Store fresh fish in a refrigerator in a moisture proof wrap and consume it within two days of purchase.
  • Frozen seafood should not be kept for more than six months.
  • Do not refreeze fish after thawing it.
  • Wash your hands and utensils with soap and water both before and after cooking fish.

To help save fish

  • Go for those fish whose labels state that they are responsibly fished and from a sustainable source.
  • Avoid vulnerable and endangered species.
  • Eat less well-known fish such as saithe and pollack.
  • Bring variance in your fish menu instead of eating a select few.
  • Avoid eating fish sold as ‘baby fish’.
  • Buy your fish from responsible fish mongers.
  • Buy locally caught fish. You are also contributing to reducing greenhouse gas emissions.
  • While buying farmed fish, opt for those that have been farmed in open sea conditions.

'Avoid Eating these Endangered Fish

  • Atlantic and North Sea cod
  • Atlantic halibut
  • Dogfish
  • European hake
  • Porbeagle
  • Plaice
  • Seabass
  • Skate
  • Sole
  • Whitebait


  • Input in the form of other lesser fish or "trash" fish is required to produce the kind of fish we prefer to eat directly. To create 1 kg (2.2 lbs.) of high-protein fishmeal, which is fed to farmed fish (along with fish oil, which also comes from other fish), it takes 4.5 kg (10 lbs.) of smaller pelagic, or open-ocean, fish.
  • In 2006, 37% of all global seafood was ground into feed, up from 7.7% in 1948.
  • It takes about 20 kg (44 lbs.) feed comprising live pelagic fish such as anchovies, sardines and mackerel to get 1 kg of tuna ready for a sushi bar.
  • About 90% of all fish and fish products are traded in some processed form. Only ten percent is sold in a live, fresh, or frozen state. Although in recent years, due to improvements in refrigeration and transportation technology, live fish are a growing percentage of the market.
  • Fugu (blow fish) is a fish which contains deadly poison in the organs. Despite the risk, fugu dishes remain as special feasts in Japan
  • China's per capita domestic consumption of fish and fishery products has risen from less than 5 kg in the 1970s to 26 kg in 2007. Developing countries account for 91.4% of aquaculture production.
  • Though more than 1 billion people across the world eat fish, there are marked differences in regional consumption. Africa accounts for only 6.5% of global fish consumption. China is the largest producer of fish in the world. Japan which has been the largest importer of fish is set to be overtaken by the US as the largest importer in 2007.
  • By 2030, the addition of 2 billion more people to the world population will mean that aquaculture will need to produce nearly 85 million tonnes of fish per year, just to maintain current per capita consumption levels.


  • Traditional Indian remedy for asthma challenged in court
  • Mission 2001 - Saving The Ocean
  • Fugu - Blow Fish
  • What You Need to Know about Mercury in Fish and Shellfish
  • Nearly half of all fish eaten today farmed, not caught
  • Too Much Mercury in Freshwater Fish?
  • Food Outlook Global Market Analysis - Fish and Fishery Products
  • What You Must Know Before You Eat Fish
  • Fish Farming's Growing Dangers
  • Fish to avoid

Additional Information

  • Traditional Indian remedy for asthma challenged in court

See Also