Give up seafood, save the planet?
MARTIN MITTELSTAEDT
Globe and Mail Update
March 16, 2009 at 4:38 PM EDT
Eating fish has always been touted as an excellent dietary source of protein, with Health Canada's food guide recommending everyone eat two servings a week. The recent craze over the omega-3 fatty acids found in fish has only added to the allure.
But is eating fish the best choice for health and the planet?
Although negative views about fish consumption are almost never expressed, a group of medical and fisheries experts is making an argument against eating the seafood in the Canadian Medical Association Journal.
In an analysis being released Tuesday, they say that the purported benefits of fish for such things as cardiovascular health have been overstated, while the growing demand among health aficionados for the food is destroying global fish stocks.
"The public view is that fish are good for you. There is plenty of it and let's go for it," said David Jenkins, a nutrition professor at the University of Toronto and lead author of the journal article. "I don't think either of those views should be as strongly held as they are."
The pitch against fish consumption because it is environmentally tainted had one unusual author, for a medical journal. The well known Canadian nature writer Farley Mowat reviewed the analysis and decided to lend his imprimatur to the call against seafood.
"I'm just desperately worried about what's happening to the life in the ocean, as everybody should be who thinks about it at all," Mr. Mowat said in an interview.
While Mr. Mowat personally loves to eat fish, he takes the problem seriously and seldom has it on his dinner plate now.
"The fish population is declining so rapidly that I try not to lean on it any harder than I have to," he said.
The big health reason for eating fish is that they contain omega-3 fatty acids, or fish oils as they are also known, a nutrient linked to the prevention of coronary artery disease. There is also widespread interest in the oils as an elixir for a long list of conditions, including cancer, dementia, Crohn's disease, and multiple sclerosis.
Dr. Jenkins said the view that fish are among the best foods is strongly held by the public, but the claim is open to question.
One problem is that studies showing better coronary health among those who eat fish regularly could be skewed by so called confounding factors, or alternative causes. Fish eaters generally have better lifestyles than other people, exercising more and smoking less, another possible explanation for the results of health surveys.
Vegetarians get along just fine and do not appear to be at increased risk of heart disease, even though they eschew animal proteins, suggesting there may be other ways of achieving the benefits of fish, without actually having to eat them.
That is why Dr. Jenkins said a way to settle the question over the nutritional benefits would be to conduct studies to see "whether just by going for a walk and eating less saturated fat" would lead to the same improvements in health outcomes as fish eating.
Although many studies have found benefits from the oils, there are occasional examples of harm, including one that examined men with angina. This study unexpectedly showed an increased risk of cardiac death, according to the journal article While there are claims and counter claims about the benefits of fish, there is no dispute over the world's dwindling supply of the creatures.
"The demand for fish is higher than what oceans can supply, said Rashid Sumaila, acting director of the University of British Columbia's Fisheries Centre, who predicted that many of the world's most important fisheries are going the way of Newfoundland's exhausted cod stocks.
Aquaculture involving carnivorous fish isn't the answer either, according to Prof. Sumaila, a co-author of the journal article. It takes anywhere from two to five kilogram of edible smaller fish, such as anchovies, to make a kilogram of farmed salmon. Raising big fish this way only leads to the depletion of other species.
One possibility would be to farm plant-eating fish, such as carp, but Canadians typically turn their noses up at these species.
For those who want to have the benefits of fish oil and avoid the environmental harm, Dr. Jenkins suggests some alternatives. He said the DHA omega-3 found in fish can instead be extracted from algae (where fish ultimately get it). Infant formula has this type of DHA added for proper eye and brain development.
Research is also underway to see if a second type, EPA omega-3, can be extracted from modified yeast cells or plants instead of fish. In the meantime, he said some oils, such as the one from flax seed, also contain omega-3 and could be used as a substitute.