The facts about omega-3s

Source: Best Health Magazine, Spring 2008; Photo: Michael Alberstat

Finally, everything you need to know about omega-3 fatty acids: what they do for you, how much is enough and the best ways to get them into your diet.

The benefit of eating fish isn’t an entirely new discovery. Scientists have known for decades that fish oils have positive health effects. Studies in the 1970s showed that the Inuit had a much lower incidence of cardiovascular disease than most Europeans, as did people who ate a Mediterranean diet. The Japanese, meanwhile, have one of the highest life expectancies. All these diets are particularly rich in omega-3 fatty acids’found in large amounts in most fish. Mounting scientific evidence shows that as well as helping our hearts, a diet rich in omega-3s is beneficial in reducing diabetes, depression, attention-deficit hyperactivity disorder (ADHD), cancer and Alzheimer’s disease. And there’s also strong evidence that omega-3s counter inflammatory diseases such as rheumatoid arthritis and Crohn’s disease.

Omegas are types of polyunsaturated fatty acids. They are called ‘essential’ fatty acids because the body needs them but can’t manufacture them, so we have to get them from our diet. The ones getting all the attention right now are omega-3s; others include omega-6s and -9s. Researchers believe our contemporary Western diet is unbalanced, because it contains high amounts of omega-6 fatty acids (which come from grains) and not enough omega-3s.

Scientists believe omega-9s, found in fats such as olive oil, are neutral (meaning they are not necessarily good for you, but are better to consume than unhealthy saturated fats). However, most of us don’t consume nearly enough omega-3s. And that imbalance could lie at the root of many modern health problems.

The name omega-3 covers a range of fatty acids, three of which are particularly important for our health: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)’both found in oily fish’and alpha-linolenic acid (ALA), found in plant sources. These fatty acids form part of the membrane around every cell in our bodies. They control what substances pass in and out of the cells, as well as how cells communicate with each other. Cells with high levels of omega-3s in their membranes are more fluid and work more effectively. Get lots of omega-3 in your diet and you’ll be a well-oiled machine.

Omega fatty acids also modulate the production of powerful hormone-like substances known as eicosanoids. Those produced by omega-3s are anti-inflammatory and reduce blood clotting, and scientists are now certain that omega-3 fats lower the risk of heart attacks for that reason. If an attack does occur, it’s less likely to be fatal. One study of heart attack survivors showed that if they took one gram of omega-3s daily in a capsule, they lowered their risk of dying from heart disease by 25 percent. Omega-3 fats also lower blood triglycerides (a type of stored fat that is associated with increased blood clots), reduce abnormal heart rhythms and the incidence of stroke, slow the buildup of artery-hardening plaques and lower blood pressure.

Other promising research indicates that omega-3s might help to counter depression. But it’s still too early to tell if they can be used to treat clinical depression or bipolar disorder. One study being funded by the National Institutes of Health in the U.S. is looking at whether DHA can slow the progression of Alzheimer’s disease. And a preliminary Canadian study on mice may hold important clues for the prevention of Parkinson’s disease.

Other preliminary research has shown that increasing omega-3 intake in the diet or through supplements can help organ transplant patients, and reduce the risk of developing breast, colon and prostate cancer. Other studies are under way on the effect of omega-3s on asthma, dysmenorrhea, eczema, lupus, preeclampsia, nephrotic syndrome, schizophrenia, stroke prevention and ulcerative colitis. It’s not yet known, however, how effective omega-3s may be in these areas.

How much omega-3 is right?

It’s virtually impossible to get too much omega-3 from your diet. Oily fish is by far the most significant source of omega-3s (and the general principle is the colder the water, the more omega-3 in the fish). The EPA and DHA’or ‘long-chain’ fatty acids’we need for good health are produced by algae, which in turn are eaten by fish such as mackerel, sardines and salmon. Other fish and seafood, including halibut, scallops and shrimp, also contain EPA and DHA. The other form of omega-3, ALA’a ‘short-chain’ fatty acid’comes from nuts and vegetable oils. Our bodies have to convert the short chains into long ones. But because all the fatty acids are competing for the same enzymes, if we have too much omega-6 in our diet (which nearly all of us do), then not much of the ALA gets converted. So if you and your family are not eating enough fish, cut down on sources of omega-6s, such as sunflower margarine and corn oil.

While Health Canada has not established recommended daily intake levels for omega-3s, Canada’s Food Guide suggests eating at least two 75-gram servings of fish per week. ‘Based on this amount, we’re looking at about 500 mg of EPA plus DHA daily,’ explains Karen Graham, a registered dietitian in Portage la Prairie, Man., and author of Meals for Good Health. ‘The bottom line is that most of us probably aren’t getting enough omega-3s from our diets.’ Along with fish, Graham recommends eating other good sources of omega-3s, such as ground flaxseed (whole flax simply passes through our bodies), pumpkin seeds, walnuts and soy nuts, as well as omega-3-fortified eggs and yogurts.

As for recent concerns that some fish are contaminated with mercury, doctors think the health benefits of eating fish far outweigh the potential for harm if you’re eating it only twice a week. If you’re worried, go easy on the swordfish, tuna and catfish. Pregnant women, nursing mothers and young children should especially avoid these fish.

That leaves supplements of fish oil, which come in capsule form. There’s virtually no mercury in these supplements, because the purification process removes heavy metals. Supplements are no substitute for eating right, but are especially good for those who don’t like fish. To avoid a fishy aftertaste, take the capsules with meals.

People with diabetes and those at risk of bleeding should seek medical advice before taking supplements, as omega-3s may increase blood sugar and reduce blood clotting. In theory, omega-3 products may interact with drugs that also have a ‘blood-thinning’ effect, such as ASA and anticoagulants (warfarin, heparin), and non-steroidal anti-inflammatories such as ibuprofen. So if you are taking any medicines, ask your doctor before increasing your omega-3 intake.

Get your omega-3s

MARINE SOURCES
LEVEL OF OMEGA-3s (MG PER 100 G)*

Atlantic salmon, farmed 2,153
Sardines, canned 2,000
Chinook salmon, wild 1,741
Halibut 1,176
Tuna, white, canned in water 859
Shrimp 317
Haddock 235
Tilapia 100

*NOTE: Levels are approximate, as they can differ due to seasonal and feeding variations.

PLANT SOURCES
LEVEL OF OMEGA-3s (MG)

Canola oil, 1 tbsp (15 mL) 2,000
Ground flaxseeds,
1 tbsp (15 mL) 900
Walnuts, 1 tbsp (15 mL) 750
Soybeans, 1/4 cup (50 mL) 500
Canola spread, 2 tsp (10 mL) 500
Baked beans, small tin 340
Omega-enriched egg, 1 250
Broccoli, 1/2 cup (125 mL) 100

Buying omega-3s at the grocery store

All sorts of grocery products’from eggs, milk and yogurt to orange juice and even chocolate’now contain added omega-3s. So how do you decide what to buy?
Keep in mind that you should be getting around 500 mg of EPA and DHA omega-3s a day. Many of the products that claim to be good sources contain less than one-tenth of that. ‘Consumers also need to look at what kinds of omega-3s have been added,’ says dietitian Karen Graham. ‘Many foods contain added ALA, which is not as effective as EPA and DHA.’

Check the nutrition label on fortified foods to ensure they contain EPA and DHA from marine sources and not just ALA from plants. While you’re reading the label, determine the overall nutritional value. Your choice may be high in calories or sodium, which may outweigh the benefits of the omega-3s.

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