When it comes to eating fish, there are 2 big things to be concerned about – methylmercury and PCBs. These aren’t the only issues, but they’re the most important ones. And as you’ll see below, you don’t have to worry about either of them when you’re eating wild salmon from Alaska.
Methylmercury levels are highest in large fish grown in more industrial areas.
Methylmercury levels are highest in large fish grown in more industrial areas.
Methylmercury
Methylmercury is a toxic substance that is dangerous for a developing fetus (especially during the early months of pregnancy), and it comes from industrial pollution. Coal-burning power plants emit large amounts of mercury into the air, it falls to the ground through rain, and then it ends up in our lakes, rivers, and oceans. When mercury gets into water, microorganisms convert it into methylmercury, which is easily absorbed by the human digestive tract.
Methylmercury is ingested by all fish grown in waters near industrial areas, and it accumulates in large, predatory fish as they eat lots and lots of small fish. Shark, swordfish, and albacore tuna tend to accumulate levels of methylmercury that are dangerous for pregnant woman, which is why women who are pregnant or might become pregnant are advised to limit their consumption of these types of fish.
Methylmercury levels tend not to be much of an issue for salmon because they’re not that high up on the fish food chain. They are carnivorous, but they eat mostly krill (tiny crustaceans) and very small fish.
That being said, higher levels of methylmercury will undoubtedly be found in salmon that are raised or live naturally in more polluted areas. And this is where the Alaskan thing comes in – Alaska is geographically isolated and therefore has much lower levels of industrial pollution. Therefore, its waters tend to be very low in methylmercury.
So this is why you don’t need to worry about methylmercury levels in wild Alaskan salmon.
Methylmercury is ingested by all fish grown in waters near industrial areas, and it accumulates in large, predatory fish as they eat lots and lots of small fish. Shark, swordfish, and albacore tuna tend to accumulate levels of methylmercury that are dangerous for pregnant woman, which is why women who are pregnant or might become pregnant are advised to limit their consumption of these types of fish.
Methylmercury levels tend not to be much of an issue for salmon because they’re not that high up on the fish food chain. They are carnivorous, but they eat mostly krill (tiny crustaceans) and very small fish.
That being said, higher levels of methylmercury will undoubtedly be found in salmon that are raised or live naturally in more polluted areas. And this is where the Alaskan thing comes in – Alaska is geographically isolated and therefore has much lower levels of industrial pollution. Therefore, its waters tend to be very low in methylmercury.
So this is why you don’t need to worry about methylmercury levels in wild Alaskan salmon.
PCBs
PCBs (polychlorinated biphenyls) are toxic chemicals that were once used in manufacturing (they were banned in 1979). Today, our rivers, lakes, and oceans are heavily polluted by these and many other chemicals (coming from industrial emissions and agricultural pesticide runoff), even though many of the most dangerous ones have been banned for years. Since PCBs pose the biggest risk to our health, it’s helpful to use the acronym “PCBs” as shorthand for all of the dangerous toxic chemicals that are found in our waters today. Suffice it to say, these are chemicals that you should do your best to consume in only very small amounts.
Unlike methylmercury, which is stored in the muscles of fish, PCBs accumulate in the fatty tissues of fish as they move up the food chain. Levels of PCBs therefore depend on four things: the fish species, where they grew, how fatty they are, and what they were fed. Because of the last 2 factors especially, farmed fish are most at risk, and farmed salmon is especially risky because it’s one of the most industrial fishing industries.
Farmed salmon are raised very much like cattle in feedlots – they’re confined in overcrowded pools filled with antibiotics, pesticides, chemicals, and waste. Also like cattle, they’re fed lots and lots of food to make them grow as quickly as possible, which makes them more fatty. Instead of live krill and small fish, their food comes in the form of pellets, which contain fish meal and oil because fish grow best when they’re fed proteins and fats from other fish.
Unlike methylmercury, which is stored in the muscles of fish, PCBs accumulate in the fatty tissues of fish as they move up the food chain. Levels of PCBs therefore depend on four things: the fish species, where they grew, how fatty they are, and what they were fed. Because of the last 2 factors especially, farmed fish are most at risk, and farmed salmon is especially risky because it’s one of the most industrial fishing industries.
Farmed salmon are raised very much like cattle in feedlots – they’re confined in overcrowded pools filled with antibiotics, pesticides, chemicals, and waste. Also like cattle, they’re fed lots and lots of food to make them grow as quickly as possible, which makes them more fatty. Instead of live krill and small fish, their food comes in the form of pellets, which contain fish meal and oil because fish grow best when they’re fed proteins and fats from other fish.
However, because of the way that these pellets are made from smaller farmed fish, they tend to have very high concentrations of PCBs. And because farmed salmon are fed massive amounts of these pellets in order to speed up their growth, they tend to have much higher levels of PCBs than wild fish.
Wild Alaskan salmon is therefore much safer than farmed salmon for three reasons:
1. They grow in Alaska where the waters are the least polluted.
2. They aren’t fed food pellets.
3. They tend to be less fatty because they grow at a natural pace.
Nutrient Differences
Wild Alaskan salmon is therefore much safer than farmed salmon for three reasons:
1. They grow in Alaska where the waters are the least polluted.
2. They aren’t fed food pellets.
3. They tend to be less fatty because they grow at a natural pace.
Nutrient Differences
From both a nutritional and environmental impact perspective, farmed fish are far inferior to their wild counterparts:
- Despite being much fattier, farmed fish provide less usable beneficial omega 3 fats than wild fish.
- Due to the feedlot conditions of aquafarming, farm-raised fish are doused with antibiotics and exposed to more concentrated pesticides than their wild kin. Farmed salmon, in addition, are given a salmon-colored dye in their feed, without which, their flesh would be an unappetizing grey color.
- Aquafarming also raises a number of environmental concerns, the most important of which may be its negative impact on wild salmon. It has now been established that sea lice from farms kill up to 95% of juvenile wild salmon that migrate past them.(Krkosek M, Lewis MA. Proc Natl Acad Sci U S A.)
Omega 3 Fat Content Differences
FDA statistics on the nutritional content (protein and fat-ratios) of farm versus wild salmon show that:
- The fat content of farmed salmon is excessively high--30-35% by weight.
- Wild salmon have a 20% higher protein content and a 20% lower fat content than farm-raised salmon.
- Farm-raised fish contain much higher amounts of pro-inflammatory omega 6 fats than wild fish.
These unfortunate statistics are confirmed in a recent (1988-1990) study conducted by the U.S. Department of Agriculture (USDA) to compare the nutrient profiles of the leading species of wild and cultivated fish and shellfish. Three species of fish that contain beneficial omega 3 fats were included: catfish, rainbow trout, and coho salmon.
Farm-raised Fish are Fattier
In all three species, the farm-raised fish were fattier. Not surprising since farm-raised fish do not spend their lives vigorously swimming through cold ocean waters or leaping up rocky streams. Marine couch potatoes, they circle lazily in crowded pens fattening up on pellets of fish chow.
In each of the species evaluated by the USDA, the farm-raised fish were found to contain more total fat than their wild counterparts. For rainbow trout, the difference in total fat (5.4g/100g in wild trout vs. 4.6 g/100g in cultivated trout) was the smallest, while cultivated catfish had nearly five times as much fat as wild (11.3g/100 g in cultivated vs. 2.3 g/100g in wild). Farm-raised coho salmon had approximately 2.7 times the total fat as wild samples.
Farm-raised Fish Provide Less Usable Omega-3 Fats
The reason for this apparent discrepancy is that both omega 3 and omega 6 fats use the same enzymes for conversion into the forms in which they are active in the body. The same elongase and desaturase enzymes that convert omega-3 fats into their beneficial anti-inflammatory forms (the series 3 prostaglandins and the less inflammatory thromboxanesand leukotriennes) also convert omega-6 fats into their pro-inflammatory forms (the series 2 prostaglandins and the pro-inflammatory thromboxanes and leukotrienes).
So, when a food is eaten that contains high amounts of omega 6s in proportion to its content of omega 3s, the omega-6 fats use up the available conversion enzymes to produce pro-inflammatory compounds while preventing the manufacture of anti-inflammatory substances from omega-3s, even when these beneficial fats are present.
Farm-raised Fish Contain More Pro-inflammatory Omega-6 Fats
In all three types of fish, the amount of omega 6 fats was substantially higher in farm-raised compared to wild fish. Cultivated trout, in particular, had much higher levels of one type of omega 6 fat called linoleic acid than wild trout (14% in farm-raised compared to 5% in wild samples). The total of all types of omega 6 fats found in cultivated fish was twice the level found in the wild samples (14% vs 7%, respectively).
Wild Fish Provide More Omega-3 Fats
In all three species evaluated, the wild fish were found to have a higher proportion of omega-3 fats in comparison to omega 6 fats than the cultivated fish. The wild coho were not only much lower in overall fat content, but also were found to have 33% more omega 3 fatty acids than their farm-raised counterparts. Omega 3s accounted for 29% of the fats in wild coho versus 19% of the fats in cultivated coho. Rainbow trout showed similar proportions in fatty acid content; wild trout contained approximately 33% more omega 3s than cultivated trout, however both cultivated and wild trout did have much lower amounts of omega 6 fats than the other types of fish.
Antibiotic and Pesticide Use
Disease and parasites, which would normally exist in relatively low levels in fish scattered around the oceans, can run rampant in densely packed oceanic feedlots. To survive, farmed fish are vaccinated as small fry. Later, they are given antibiotics or pesticides to ward off infection.
Sea lice, in particular, are a problem. In a recent L.A. Times story, Alexandra Morton, an independent biologist and critic of salmon farms, is quoted as beginning to see sea lice in 2001 when a fisherman brought her two baby pink salmon covered with them. Examining more than 700 baby pink salmon around farms, she found that 78 percent were covered with a fatal load of sea lice while juvenile salmon she netted farther from the farms were largely lice-free.
Scientists in the United States are far more concerned about two preliminary studies-one in British Columbia and one in Great Britain-both of which showed farmed salmon accumulate more cancer-causing PCBs and toxic dioxins than wild salmon.
The reason for this pesticide concentration is the salmon feed. Pesticides, including those now outlawed in the United States, have circulated into the ocean where they are absorbed by marine life and accumulate in their fat, which is distilled into the concentrated fish oil that is a major ingredient in salmon feed. Salmon feed contains higher concentrations of fish oil-extracted from sardines, anchovies and other ground-up fish-than wild salmon normally consume. Scientists in the U.S. are currently trying to determine the extent of the pesticide contamination in farmed salmon and what levels are safe for human consumption.
Research on this issue published July 30, 2003, by the Environmental Working Group, indicates that levels of carcinogenic chemicals called polychlorinated biphenyls (PCBs) found in farmed salmon purchased from U.S. grocery stores are so much higher than levels of PCBs found in wild salmon that they pose an increased risk for cancer. PCBs have been banned in the US for use in all but completely closed areas since 1979, but they persist in the environment and end up in animal fat.
When farmed salmon from U.S. grocery stores was tested, the farmed salmon, which contains up to twice the fat of wild salmon, was found to contain 16 times the PCBs found in wild salmon, 4 times the levels in beef, and 3.4 times the levels found in other seafood. Other studies done in Canada, Ireland and Britain have produced similar findings.(September 8, 2003)
Color of Wild Salmon vs. Farmed Salmon
With salmon, color is the key. Wild salmon flesh is a deep red color, while farmed fish flesh is orange. (Actually, farmed fish have gray flesh, but they are fed a product that adds color to their meat in the months just before they are harvested.)
The other distinguishing characteristic is price. Fresh farmed Atlantic salmon can sell for as little as one-quarter the price for wild Alaskan salmon. In truth, you are getting more for your money with the more expensive product. Ounce for ounce, wild salmon has much more flavor than the farmed variety, which is raised on pelleted fish chow, and wild salmon is much higher in the types of fatty acids that make fish a healthy diet choice.
When farmed salmon from U.S. grocery stores was tested, the farmed salmon, which contains up to twice the fat of wild salmon, was found to contain 16 times the PCBs found in wild salmon, 4 times the levels in beef, and 3.4 times the levels found in other seafood. Other studies done in Canada, Ireland and Britain have produced similar findings.(September 8, 2003)
Color of Wild Salmon vs. Farmed Salmon
With salmon, color is the key. Wild salmon flesh is a deep red color, while farmed fish flesh is orange. (Actually, farmed fish have gray flesh, but they are fed a product that adds color to their meat in the months just before they are harvested.)
The other distinguishing characteristic is price. Fresh farmed Atlantic salmon can sell for as little as one-quarter the price for wild Alaskan salmon. In truth, you are getting more for your money with the more expensive product. Ounce for ounce, wild salmon has much more flavor than the farmed variety, which is raised on pelleted fish chow, and wild salmon is much higher in the types of fatty acids that make fish a healthy diet choice.
No comments:
Post a Comment