The question: What's the difference between omega-3 and omega-6 fatty acids? How much of each are we supposed to be eating?
The answer: First, let's tackle the science: Omega-3 and omega-6 fatty acids are polyunsaturated fats, which means, from a chemical standpoint, they have long carbon chains with many double bonds.
(If all the bonds between the carbons are single bonds, the fat would be a saturated fat – the type that raises blood cholesterol.)
Scientists use the Greek omega system to indicate where a double bond is located on a fatty acid. Omega-3s have their first double bond located three carbons away from the end; the first double bond of omega-6s is located six carbons away.
Both types of fatty acids help form cell membranes, keep our vision sharp and play a role in heart health. They also help make eicosanoids, potent chemical messengers that are instrumental in the body's immune and inflammatory responses.
But because our bodies can't make omega-3s and omega-6s, they are considered essential nutrients and must come from our diet.
That's why linoleic acid (LA) is an essential omega-6 fatty acid and, when consumed, is used to synthesize other omega-6s. Many studies have found that higher intakes of LA are linked with a lower risk of heart disease.
Men aged 19 to 50 need 17 grams of LA per day; women require 12 g. Older men should consume 14 g per day, while older women need 11 g.
Good sources of LA include nuts, seeds, sunflower oil, safflower oil and corn oil.
Alpha-linolenic acid (ALA) is the fatty acid used to make other omega-3s in the body. Studies suggest that higher intakes of ALA may protect you from heart disease, especially in people who don't eat much fish. ALA has also been shown to decrease C-reactive protein in the blood, a marker of inflammation that's strongly tied to heart attack and stroke.
Women require 1,100 mg of ALA each day; men need 1,600 mg. The best food sources include:
- ground flax seed (2 tbsp = 2,400 mg)
- flax oil (1 tsp = 2,400 mg)
- chia seeds (2 tbsp = 3,600 mg)
- walnuts (7 halves = 1,280 mg)
- walnut oil (1 tsp = 470 mg)
- soybeans, canola oil and foods fortified with ALA (e.g. milk, soy beverages, eggs) also provide ALA.
There are also two other important omega-3s, which are found in fatty fish such as salmon, trout, sardines and herring: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Both are strongly linked to cardiovascular protection, while DHA also plays a role in brain and eye function.
There's no official recommended intake for DHA and EPA. However, many experts advise consuming at least a combined total of 500 to 1,000 mg per day (that's on top of the daily recommended intake of ALA), which is easily achieved by eating six to 12 ounces of salmon each week.
You may have heard it's important to eat the right balance, or ratio, of omega-3s and omega-6s in your diet. Many experts believe it's actually more important to consume the recommended levels of each type of fat, rather than focus on ratios.
For most of us, that means increasing our omega-3 intake.
Leslie Beck, a registered dietitian, is the national director of nutrition at BodyScience Medical. She can be seen every Thursday at noon on CTV News Channel'sDirect (www.lesliebeck.com).
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Leslie Beck