Flaxseed and other plant-based foods including walnuts, canola oil, and soybeans are rich in an omega-3 fatty acid called ALA.
But flaxseed lacks the omega-3 fatty acids EPA and DHA, which have shown cardiovascular benefits in past studies. EPA and DHA are found in fatty fish such as salmon and mackerel, fish oilsupplements, and some fortified foods.
Does ALA deliver the same benefits as EPA and DHA? The jury's still out on that, note the researchers, who included James Friel, PhD, of Canada's University of Manitoba. The optimal dose of ALA is also not known.
Flaxseed and Firefighters
Friel's team studied 62 male firefighters in the Canadian city of Winnipeg.
Why firefighters? The researchers explain that firefighters tend to have risk factors for coronary heart disease, including high stress levels, high-fat diets, little exercise while in the fire hall, and being older than 40.
As expected, blood levels of EPA and DHA rose in the fish oil group, and ALA rose in the flaxseed oil group. EPA levels also rose in the flaxseed oil group, but only at the higher doses (2.4 to 3.6 grams per day). The researchers write that it's "quite attainable" to get that much ALA from foods without taking supplements.
Since flaxseed oil doesn't contain EPA, the firefighters' bodies must have converted some of the ALA into EPA. That didn't seem to happen at the lower doses of flaxseed oil.
DHA was a different story. The flaxseed oil group didn't get any increase in DHA levels; DHA only rose in the fish oil group.
None of the groups gained any advantage in terms of lowering total or LDL ("bad") cholesterol, raising HDL ("good") cholesterol, or reducing blood levels of inflammatory chemicals. The experiment was too short to track long-term health benefits.
The study was funded, in part, by the Canadian Flax Council and Flax Canada.