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Nutrition Section

Fish - the good, bad and the toxic!

Fish is being touted as a wonder food today. The Omega oils are widely proclaimed as a miracle cure for cholestrol, ageing and almost everything from skin rejuvenation to increased chances of conception!

Most of the fish we eat are fairly high up in the food chain, often feeding off filter feeders or smaller fish, who collect and concentrate contaminants in their environment. It's important to know what type of fish you are buying and where it came from.

Infant in Chinese hospital
Fish oil - the latest "wonder food" fad.

Fish quickly deteriorates, so be fussy when buying fish. Fortunately there is an easy way to gauge its freshness. The eyes are the best indicator , they rapidly lose moisture and pressure, so fish with sunken eyes is stale - don't buy it.

It is difficult to assess the freshness of processed fish products like fish fingers, crumbed fillets and fish cakes. Even worse, it is difficult to see where the fish came from before the processors worked with it. The labelling laws only require them to say where the food was processed, not where it's ingredients came from. Often the processors get away with a phrase like "Made from local and imported product"

Not all countries have the same standards when it comes to food production and environmental testing. Food labelling laws allow manufacturers to avoid divulging where their constituents came from.

Fish are a good example to demonstrate the importance of product labelling and quality controls. We tend to believe the advertising hype when it comes to fish. We believe our salmon was snatched out of a pristine mountain stream in Canada by some fisherman who goes out daily, braving big brown bears as he selects only the right breed of fish for the canneries. In actual fact much of it comes from fish farms and has never seen a mountain stream. Fish used in products like fish patties, crumbed fillets, fish fingers and marinara topping for pizzas, can be sourced anywhere, most likely a fish farm.

Bear snatching salmon from waterfall
Manufacturers would like us to believe our salmon was snatched from some mountain stream in Canada but it most likely came from a fish farm

Manufacturers strive to keep us totally ignorant where the fish content of their product came from or what type of fish they use. Do you honestly believe that a processing plant, mincing fish up into a paste, is using prime fish?

If not then what type of fish are they using?
Then how "Sub" is their sub-prime fish?

On a popular brand of fish patties in our local supermarket, I read the line, "Made from local and imported fish for . . " and it continued to say it was produced here in Australia. The packaging stated it was Australian product and it even had the Ausbuy logo. How much more patriotic could you get?

However, the fish patty factory used imported fish and only when there was a drop in market prices did it use any local fish. The imported fish came from Asia, they told me. They even gave the name of the agent who handled the importing for them. I discovered that the "agent" imported the fish for animal feed, meal and fertiliser processing as well, from Vietnam. The fish was graded in Vietnam, not here.

Now I was alarmed. In Vietnam many fish farms are on the Mekong River. So are many cities and the two are often very close neighbours. On one trip there I recall driving over the bridge to My Tho, a fairly large city, and to my surprise, seeing the pens of a group of fish farms below, downstrean and opposite the city itself. I couldn't imagine obtaining a licence to place a fish farm in any river opposite a city, here in Australia, Canada, the UK or the USA. Even with strict environmental controls, the risk of accidental contamination is too high. Daily run off from busy roads contains high quantities of heavy metal pollutants. This runs into storm water drains and into waterways, not through sewage treatment plants like household and industrial waste

Fish farm near the city of My Tho in Vietnam
The bridge into My Tho, with the fish farms under the bridge (right hand side) opposite the city.

Given the effects of the defoliant spraying (Agent Orange) during the Vietnam war, where over 20,000,000 gallons of defoliant much of it containing Dioxin, was sprayed over the country and the fact that this is still leaching into the rivers, I would have reservations about using these fish for anything except fertiliser and even then only in small quantities. Dioxin is the most toxic man made poison ever created (see our article on Food Labelling).


While fish is low in fats and the few it does contain are high in good cholesterol, it can also contain a high level of contaminants and this can vary, depending on it's origin.

As the world's fish stocks decrease (and fisheries data worldwide indicates all stocks have dropped during the last century) we are turning to fish farming. As the world population increases, so does the level of pollution, especially in waterways - the most convenient sites for fish farms.

Unlike land farming, where we grow herbivores for meat, fish farming favours the predatory species and this creates another problem - concentration of toxins, as contaminants work through the food chain. For the purposes of this illustration, let's compare land produce to fish and assume that at each level of the food chain concentrates the toxins to double the previous concentration (actually it's usually much more).

On Land

1. The contamination on land appears in grasses , in low concentrations over a wide area of pasture.

2. Grazing animals eat the grass and the small intakes of contamination are added together and build up, concentrated in the meat by at least 100%. Because milk and eggs are 'short time' products, the contaminants don't have long periods to concentrate as much toxicity as the meat. Yearling lamb can contain 75% of the contaminants of hogget, the meat from older sheep.

3. Humans consume the produce and concentrate the contaminants, now at 1000% of what they were in the pasture. They are now in sufficient concentrations to be toxic.

Grazing Animals concentrate the contiminants in pasture

In the sea

1.Contaminants in the water are filtered out by algae and filter feeders and concentrated 100%. Each organism contains at least twice the level of the water's toxin.

2.These tiny creatures are eaten in their thousands by smaller fish. The toxins are now concentrated by a further 100%. In other words the level of toxicity is now 4 times the original water concentration.

3.The larger fish like tuna, trevally, salmon and many of the fish species we eat, are carnivorous and feed on the smaller fish. This concentrates the toxins a further 100% to 8 times the concentration of the original toxins.

4.Humans eat these fish, further concentrating the toxins by 100%. The level of toxins are now 16 times what they were at the start.

This is a much simplfied model. The filter feeders can concentrate the toxins much more than 100%. Tests on oysters have shown concentrations can exceed 5000%. Generally the problem is much worse in larger fish (which we prefer to eat) because they have been exposed to the toxins longer and have eaten more contaminated smaller fish. For this reason, only small shark is allowed to be served for eating in Australia because of the high concentrations of heavy metals like mercury in the older, larger species.

Diagranm of the marine food chain
Contaminants are concentrated much more in the ocean food chain because there are more stages.

Toxins are concentrated more in marine food chains than land food chains because there are more stages in the food chain. In the oceans, the initial contaminations are more diluted than land. Fish are caught in the ocean are lower in contaminants but the reverse is true when the fish are farmed. Fish farms are ideally placed close to land in river estuaries, lakes and harbours, closer to human pollution sources. Here in Australia and New Zealand these farms undergo rigorous and frequent testing, both of the water and their produce but the same cannot be said for other countries where testing is lax and corruption is rife.

It's important to note that most farm animals are only a few years old, at the most, when they are slaughtered. Fish, especially deep sea and cold water varieties can be 40 years old or more before they are caught. That's a lot of extra time to soak up any contaminants.


Noble Crustaceans

When we say someone is a "blue-blood", we're implying they are of noble birth. Crayfish and other sea crustaceans are one of the few creatures that really do have blue blood. Is the comparison intentional?


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Bar - Gold bar with Granny Smith Apple


Shellfish are a valuable source of Zinc and the body needs approximately 100mgs a day. 200 grams of shellfish (which includes crab and lobster meat) yields 7mgs of Zinc and is one of the richest natural sources of Zinc.

An assortment of shellfish at the markets

Shellfish are a valuable source of zinc.

Unfortunately shellfish has a very short shelf life. When not refrigerated, the shelf life can be measured hours. Bacteria rapidly reproduce, rendering the shellfish highly toxic. Shellfish should only be purchased chilled or frozen and if they don't look fresh - don't buy it!.

Because shellfish are filter feeders, it is vital to know that it was harvested in clean water. Contaminants like heavy metals are rapidly concentrated in shellfish so it is important to know where they came from.

In cases of shellfish poisoning, the poisonous ingredients are toxins made by algae-like organisms called dinoflagellates, which the shellfish have consumed. Poisoning can range from vomiting to paralysis and death, depending on the toxins in the shellfish. Shellfish poisoning (which covers several different types of poisons) only will occur if the shellfish comes from contaminated waters, is taken from above high tide (where it has become warm) or is not kept chilled. If dead and it is kept to long, it can rapidly become a breeding ground for toxic bacteria.

Bar - Gold bar with Granny Smith Apple

Basket of Fresh herbs

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