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Omega 3 fatty acids: what they are, why you need them, and where to find them

Jan. 30, 2012

By Patricia Nicholson

We’re advised to eat fish to ensure we get enough omega 3s, and supermarkets are filled with products fortified with omega 3s. But what are they, and why are they so important?

Omega 3s are fatty acids, which are a type of polyunsaturated fat. An essential fatty acid is one that the body needs, but cannot make itself (that’s what ‘essential’ nutrient means). Essential fatty acids include omega 3, omega 6 and omega 9, but the omega 3 varieties get most of the press because of their health benefits.

Omega 3 fatty acids are ‘good’ fats, says Helen Emanoilidis, a registered dietitian with Women’s College Hospital.

“We kind of assume that fat is a bad thing, but this is a good fat,” she explains.

Omega 3s have many health benefits because of the roles they play in the body:

  • their cardiovascular benefits may include helping to lower triglyceride levels, cholesterol and blood pressure, and reducing risk of blood clots and stroke
  • they are important to the maintenance and functioning of the brain, eyes and nerves
  • they help develop cell membranes
  • they may also have benefits for people with conditions ranging from rheumatoid arthritis to depression to kidney disease

Types of Omega 3

There are three types of omega 3 fatty acids:

  • ALA (alpha linolenic acid), which comes mostly from plant sources
  • DHA (docosahexaenoic acid), which is found mostly in marine sources
  • EPA (eicosapentaenoic acid), also found mostly in marine sources

ALA is considered essential because the body can’t make it, but most of the health benefits associated with omega 3 are associated with DHA and EPA. The body can convert ALA into DHA and EPA (so DHA and EPA are not officially ‘essential’), but the conversion rate is not very high.

“So you can have a lot of ALA, but that doesn’t necessarily mean that that translates into a lot of EPA and DHA being produced in the body,” Emanoilidis says. “So generally we do recommend a diet that has a certain amount of EPA and DHA.”

Omega 3-rich foods

EPA and DHA omega 3s are primarily found in fatty fish such as salmon, trout, herring, sardines and anchovies.

ALA is found in flax oil, flax seed, natural soy products, walnuts and canola oil.

Algae and algae oil are also rich in omega 3. In fact, that’s where the fish get it.

“The fish eat the algae and that’s how they get their omega 3s,” Emanoilidis says. “You can buy algae and algae oil, so that works for vegetarians and vegans who can’t get the fish into their diet.”

However, Emanoilidis stresses the importance of letting your doctor know that you’re taking omega 3 supplements.

“There are risks involved in taking too much omega 3,” she says. “It’s really important that people make their health-care provider aware if they’re taking this type of supplement.”

Omega-3 fortified foods

The other option for incorporating more omega 3 into your diet is to choose foods that are fortified with omega 3. But Emanoilidis advises making careful selections and reading labels. Make sure the amount of omega 3 is worthwhile (see list below), and look for products enriched with DHA and EPA, rather than ALA.

“You’re paying a lot of money for these foods and you may not be getting as much omega 3 as you think,” she says.

Some fortified eggs, milk and cheese are enriched with ALA, by fortifying the chicken or cattle feed with flax seed or canola. EPA and DHA fortified foods are often enriched with algae, so they can be eaten by people with fish allergies.

How much omega 3 do people need?

Because AHA is the official essential fatty acid, there is a formally recommended daily intake amount: 1.1 grams per day for women, 1.6 grams per day for men.

There is no formal recommendation for EPA and DHA intake, but Emanoilidis notes that for general cardiovascular health, 500 milligrams per day is a good guideline for combined EPA and DHA. People undergoing cardiovascular treatment, such as trying to lower triglyceride levels, may be advised to get between one and four milligrams per day, under medical supervision.  

The right balance of fatty acids

Getting enough omega 3 fatty acids is important, but it’s also important to look at other fatty acids and other fats, Emanoilidis says. North American diets tend to have a high proportion of omega 6 fatty acids to omega 3s, which may influence the conversion of ALA omega 3s into EPA and DHA omega 3s, which have greater health benefits.

“They’re not bad fats – they’re healthy fats,” she says of omega 6s. “It’s just that we consume so much of them that it may affect how much ALA gets converted to EPA and DHA.”

Too many trans fats (which are bad fats) may also affect this process. Emanoilidis offers some recommendations to optimize conversion of ALA to EPA and DHA:

  • avoid foods high in trans fats and saturated fats,
  • consume a moderate amount of oils that are high in linoleic acid, such as sunflower, safflower and corn oils
  • obtain omega 3 fatty acids from good food sources of ALA such as flaxseed, flaxseed oil, hempseed products and walnuts

Sources, types and amounts of omega 3

ALA sources:

  • walnuts: 14 halves = 2.6 grams ALA
  • ground flax seed: 1 tablespoon = 1.2 grams ALA
  • omega 3 eggs = 0.3 grams ALA per egg (but check label because they vary)

DHA and EPA sources:

  • Salmon: 3 ounces or 90 grams = 1.8 grams DHA/EPA (recommended 2-3 servings per week)
  • Herring: 3 ounces or 90 grams = 1.8 grams DHA/EPA
  • Trout: 3 ounces or 90 grams = 1.0 grams DHA/EPA
  • Sardines: 3 ounces or 90 grams = 0.9 grams DHA/EPA
  • Omega 3 eggs = 0.1 grams DHA/EPA per egg (but check label because they vary)
  • Omega 3-fortified milk: 1 cup = 0.01 grams DHA/EPA


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  • A publication of:
  • Women's College Hospital