Factory Farming - A View from New Zealand

Much of the emphasis in food safety in the Western World has focussed on the dangers of genetically modified crops, or the addition of hormones and antibiotics to animal feed. Consumers everywhere want organic food if they can afford it. Although these issues are very important, public focus on them has tended to obscure some of the more basic questions. Is the current factory food production system capable of supplying us with healthy wholesome food?

The latest food to attract attention is salmon. A substantial portion of salmon sold today is from fish farms. An extensive study of chemical contaminants in salmon from many countries (Stokstad, TOXICOLOGY: Salmon Survey Stokes Debate About Farmed Fish, Science 2004 303: 154-155) has identified significantly higher levels of 13 toxins in farmed salmon, in comparison with wild salmon in many parts of the world. The undesirable toxic chemicals included PCBs, dioxins and pesticides.

The study found: The average dioxin level in farm-raised salmon was 11 times higher than that in wild salmon - 1.88 parts per billion compared with 0.17 ppb. For PCBs, the average was 36.6 ppb in farm- raised salmon and 4.75 in wild salmon. Salmon from Europe, Scotland in particular, was identified as worst. US and Canadian fish were next with Chilean salmon at the bottom of the danger list. Over half the world's salmon is now farmed. Most US supermarket salmon comes from Chilean fish farms.

It appears that Southern Hemisphere fish farms produce fish with contaminant levels that are generally only one eighth that of their Northern Hemisphere counterparts. This probably reflects the lower levels of pollutants in the Southern Hemisphere. It has to be remembered that 95% of the people in the world live in the Northern Hemisphere. People produce pollution!

It appears that the fundamental problem is that by feeding any species of carnivorous fish with food composed mainly of other fish, largely from polluted waters, environmental toxins are magnified. The debate is now focusing on just how dangerous are the levels of these toxins. Environmental and health agencies have very differing views on safety levels for the substances concerned. This is a concern in itself. If we can't agree what levels of toxins are acceptable (not too dangerous), it makes regulation difficult. It has been claimed that many fish farmers in the United States, Canada and Chile are slowly replacing some of the fish oil in salmon feed - the main source of toxins - with soybean and canola oil to address the pollutant problem. It is clear that salmon fed a different diet will as a result have a different tissue composition than their wild counterparts.

Here in New Zealand it has recently been revealed that two large salmon farms have been feeding their fish with chicken feathers: more precisely chicken feather meal provided by an Australian supplier. The farms involved say that the meal is a high quality safe source of protein. The feather meal is apparently heat treated to destroy any bacteria and claimed to be devoid of chicken faeces. Clearly the consumption of the feather protein is going to alter the chemistry of the salmon flesh. This practice may be unique to New Zealand. (Feeding of feather meal to cattle is permitted in the US.) One local expert here says that he has never heard of the practice in fish farming overseas. Unfortunately we all seem to have to rely on the press to ferret out information in our respective countries. Consumer groups here in New Zealand are concerned that bacteria, which may have developed resistance to antibiotics fed to chickens, could potentially infect farmed and ultimately wild fish. (Some farmed salmon do escape from their cages). Many also believe that it is wrong in principle to feed any chicken parts to fish. It is clear that this is the sort of farming practice which probably gave rise to mad cow disease in the UK, where cows were in reality turned into cannibals, eating feed which contained the remnants of other cattle and also sheep. Even today it seems that in the US it is still permissible to feed calves with cow's blood. Though the United States banned the use of cow parts in cattle feed in the 1990's, it still permits rendered matter from cows to be fed to pigs and chickens, and rendered pigs and chickens to be fed back to cows. Advantageous commercial practices are not easily changed.

A recent article in The New York Times explained - "Rendering yields fats, including tallows and greases, as well as meat and bone meal. The fats can be made into soaps and lubricants, and also added to some animal feeds. Most of the meat and bone meal is used in feed supplements for animals; 43 percent goes to poultry, 23 percent to pet food, 13 percent to swine, 10 percent to cattle and 11 percent to other uses, among them the production of feed for farmed fish." It is clear that the entire animal feed industry in the North America is highly integrated. That interdependence could provide opportunities for the spread of disease. The European Union does not permit any animal parts to be fed back as feed supplements to cattle.

Contaminated or inappropriate feed is not the only problem. It has just been revealed that some UK salmon have also been found to contain a dye called malachite green formerly used routinely as a fungicide in fish farms. The chemical which has traditionally been used as a fungicide to "disinfect" fish eggs, was banned from use on fish farms by the UK Government more than two years ago. (In New Zealand it was banned last year). Malachite green is a substance known to cause cancer and mutations. A major international battle over its use, or possible permitted levels, now seems inevitable. The reason for its continuing presence in salmon is not immediately clear.

Salmon farming is expanding rapidly. The main producers are Norway, Chile and Scotland. Worldwide production now exceeds one million tonnes a year. In salmon farming between 5,000 and 50,000 fish are held in sea cages. Farm fish are treated with antibiotics and injected with vaccines. The colourings astaxanthin and canthaxanthin are added to their feed to produce a pink-fleshed product. This is not all bad news, as both substances are powerful antioxidants which are now available as human supplements; without them farmed salmon flesh would look an unattractive muddy grey colour. Wild salmon naturally eat crustaceans containing such pigments. Other similar antioxidants are now being given to pigs and horses for health reasons.

Consumers have, in theory, got choices. If they want to eat wild salmon or any wild fish species, they will probably have to be prepared to pay up to three times as much. (Often it may not be clear where fish originated and whether they are from a natural environment.) Consumers have the power to vote with their teeth.

Choosing healthy fish or other seafood is however not a simple matter. Everyone now believes that fish have many nutritional benefits. Clearly seafood other than salmon can be chosen, but wild tuna and other big fish like king mackerel and shark contain significant mercury levels that are dangerous for pregnant women. The ongoing controversy over acceptable mercury levels in fish has been re-ignited with the recent release of new data from the Faeroe Islands study on the effects of mercury on children whose mothers have been exposed to mercury during pregnancy. The new information, derived from tests on 14-year-olds, suggests that such children suffer long-term, probably permanent neurological damage. The US EPA (Environmental Protection Agency) now believes that one in eight US newborns have potentially unsafe levels of mercury in their blood. For detailed information on the mercury controversy see http://www.ewg.org/

Unfortunately food regulatory authorities provide advice which varies significantly from country to country. For example - Health Canada advises Canadians to limit consumption of shark, swordfish and fresh and frozen tuna, to one meal per week. Pregnant women, those of child-bearing age and young children are advised that they should eat no more than one meal of the fish concerned, per month. Currently Food Standards Australia / NZ recommends only four portions of high mercury fish per week for pregnant women. They also advise that canned tuna has very low levels of mercury and can be eaten without restriction. Mercury levels vary according to tuna species. Albacore tuna has approximately three times the amount of other tuna species. The FDA in the US now advise women of childbearing age to eliminate swordfish, king mackerel, shark and tilefish from their diet. The US researchers, who have just completed the extensive salmon survey mentioned above, recommend that Scottish salmon should only be eaten three times a year to minimise toxin exposure. (Note: Salmon does not contain high mercury levels.) Scottish fish farmers are understandably unhappy!

Concerned consumers may opt for chicken, which is widely praised by nutritionists as a healthier food than red meat. Unfortunately the news from the chicken farm is not reassuring. The latest research by the US Department of Agriculture paints a depressing picture. (Environ Health Perspect 112:18-21 2004.) [Online 1 October 2003]

Concern about chicken meat has in the past been focused on high levels of bacterial infection, the presence of growth hormones and antibiotic residues. The reality may be much worse however. USDA researchers have now found that chicken is the primary source of arsenic in the US diet. Readers old enough to have read a Victorian melodrama will realise that arsenic is a deadly poison. In fact it is now a well recognised cancer- causing substance linked to a variety of important human cancers. Its presence in water in many regions of the world is a major health problem. It is arsenic in the inorganic form which is considered most dangerous. Organic arsenic is readily excreted from the body and in tiny quantities may even be a necessary dietary element. The research has found that:

The mean concentration of total arsenic in young chickens was 0.39 ppm, 3- to 4-fold higher than in other poultry and meat. At mean levels of chicken consumption (60 g/person/day), people may ingest 1.38-5.24 g/day of inorganic arsenic from chicken alone. In people who consume the most chicken their daily intake could be 21.13-30.59 g inorganic arsenic/day and 32.50-47.07 g total arsenic/day from chicken.

Many readers will wonder how chickens can possibly contain arsenic. The reason, surprising to most of us, is that chicken farmers are allowed to feed it to them (in the US at least), to kill intestinal parasites. To be fair, it has to be pointed out that those who pass judgment on risks to our health do not regard the levels of these substances as specifically hazardous. The US researchers have however carried out a very detailed analysis of just how much arsenic various chicken eaters might be exposed to. Those who eat chicken frequently could be getting significant amounts of the substance. Young children could be at greater risk than adults. They also noted that chicken livers contain substantially elevated amounts. It seems prudent to avoid chicken livers.

There is no doubt however that many toxic substances from food and other environmental sources do get into our bodies. It is the ultimate long-term effects that are uncertain. Last year 270,000 people were diagnosed with cancer in the UK - an all time high. A UK newspaper reported last November the results of a study done by the Worldwide Fund for Nature. They took blood samples from 155 people in 13 UK cities. They found that dangerous man-made chemicals were present in the blood of all the participants. The average number of the various chemicals in an individual's blood was twenty-seven! Seventy different banned chemicals were found overall. Some like DDT have been banned in the UK for over 30 years; but clearly still linger in the environment. The newspaper reported that PCBs - another banned chemical group, were found in the blood of 99% of the participants.

It seems inevitable that modern factory-style food must contain various contaminants in greater amounts than most naturally produced foods. There may however be other problems to address such as methods of food handling and processing. A good example is the recent revelations that some processed carbohydrate foods contain significant amounts of acrylamides; substances thought to be mild human carcinogens. The discovery of acrylamides in people is a timely warning on complacency in human nutrition. A tunnel fire in Sweden exposed workers to a cocktail of toxic chemicals, one of which was suspected to be acrylamides. Diligent investigators compared levels of the chemical in the victims' blood with a control group of unexposed citizens. It soon became clear that the control group had high levels of acrylamides in their blood. That was the beginning of the search for acrylamides in the human diet, substances previously unknown to be present. Research has now determined the origin of acrylamide and the mechanism of its formation. Manufacturers of a variety of bread and potato foods which contain the highest levels, are racing to develop safer products containing lower acrylamide levels.

Dairy products from grass fed animals contain similar beneficial advantages. The more grass and fodder consumed by an animal the higher the level of CLA in their milk. CLA may be beneficial for weight control and the management of diabetes. It is now the focus of growing interest in agricultural and human nutritional research. Current CLA intake in the US has been estimated to be approximately one fifteenth that required for health and weight control benefits. For information about European CLA research see http://www.flair-/ Note: Strict vegetarians can use CLA supplements derived from vegetable oils. It appears that grass fed everything ought to be the future goal for every country where environment permits. Hopefully extra costs could eventually be recouped in reduced health care bills.