| Subject: Brain Food: Omega-3 fatty acids (dark fatty fish) |
Author:
Betty
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Date Posted: 10:10:55 03/13/04 Sat
In reply to:
Betty
's message, "Brain Food: Choline (eggs, liver, & meat)" on 08:56:04 03/13/04 Sat
Fish, and in particular dark fatty fish such as salmon, are the principal source of omega-3 fatty acids, key nutrients for healthy hearts and eyes, and essential building blocks for the neurological system of fetuses.
"Fish-oil fats are really important in reducing the risks of diseases that include certain forms of cancer, diabetes, arthritis, and other autoimmune diseases like lupus, as well as heart disease," said Peter Jones, director of the School of Dietetics and Human Nutrition at McGill University in Montreal.
While fish has long been viewed as "brain food," it is only in recent years that scientists have truly begun to understand the importance of the "good fats" in fish.
The crucial omega-3s are called docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA): DHA is what portions of our brains and eyes are made of, and DHA and EPA are essential to keep our heart beating well and to keep cells healthy.
As they learn more about how fish oils work, researchers have also discovered just how deficient the Canadian diet is in omega-3s. They fear that the recent furor over toxic fish could worsen the situation.
Health Canada recommends that 0.5 per cent of total daily calories be consumed in the form of omega-3 fats. For a person consuming 2,500 calories daily, that works out to 12.5 calories, or 1.4 grams.
Ms. Pye, a college professor in Toronto, was the exception. As someone eating salmon or trout twice a week, she was easily meeting the target. She also uses flaxseed on food, and eats a lot of soy.
"But now that I've given up the fresh fish, I'm taking supplements," she said. Ms. Pye also eats canned sardines and canned salmon, both rich sources of omega-3s containing few contaminants.
Even when other nutrients rich in omega-3s are factored in, less than half the population gets an adequate supply of the fatty acids. That places them in a medium- to high-risk category for heart disease, even without considering other factors such as obesity.
This is largely a reflection of the fact that Canadians are not big fish eaters, purchasing only about six kilograms of fish per capita, or about 30 servings per year.
Bruce Holub, a professor of nutritional sciences at the University of Guelph in Guelph, Ont., said those statistics don't tell the whole story. When it comes to omega-3s, the type of fish matters.
Canadians have a penchant for white fish, such as sole and haddock, and much of the time they eat it breaded and deep-fried. That breaded and deep-fried fish contains little omega-3 and is loaded with saturated fats and trans fats, which negate the beneficial effects of fish oils. "People are getting the message that fish is good," Dr. Holub said. "Unfortunately, the fish they're eating, the popular fish . . . has 10 parts of trans [fats] for every part of omega-3."
Research shows that eating an adequate amount of omega-3s can reduce the risk of sudden heart attack by about 70 per cent and lower a person's risk of heart disease by 32 per cent. Eating as little as one gram of trans fats daily, on the other hand, can increase the risk of heart disease by 20 per cent.
New research is also showing that the amount of omega-3s in the blood is a much better indicator of heart-disease risk than cholesterol.
"I think within five years everyone is going to get an omega-3 test when they go for their annual checkup," Dr. Jones said.
As knowledge about omega-3s increases, recommendations are becoming more precise. The American Heart Association recommends that adults consume a minimum of 650 milligrams of EPA/DHA combined daily, and that people who have cardiovascular disease get at least 900 milligrams.
Yet, the average intake of omega-3s in Canada is only 130 milligrams of EPA/DHA. According to research conducted by Dr. Holub, to meet the heart association's targets, a person would need to eat 2.5 servings a week of mackerel, or four servings of herring, or five servings of salmon, or 21 servings of cod.
At those levels, the toxic substances consumed are not insignificant, but are not considered dangerous, except perhaps to pregnant women. In fact, mothers-to-be are in a particularly difficult position when it comes to omega-3s. The fish oils are essential to the neurological development of the fetus, but the contaminants found in fatty fish, mercury in particular, attack that same neurological system.
As a result, there is now talk of fortifying foods with omega-3s, as has been done with calcium, iodine and folic acid. Many consumers are also resolving that quandary by turning to fish-oil capsules.
When the news arose about contaminants in fish, there were immediate worries about the capsules. But those who have been studying omega-3s have no doubt that fish oil, from fillets or capsules, is essential to good health and that consumers should not be overly concerned by contamination reports.
"I believe the huge effects of omega-3 acids outweigh the risk of mercury and PCBs," said Eric Dewailly, a professor of environmental health at the department of social and preventive medicine at Laval University in Quebec City who has been examining the health of fish-eating populations for years.
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