The studies by Agricultural Research Service (ARS) nutritionist Susan Raatz and physiologist Matthew Picklo address concerns about whether farm-raised salmon have less available omega-3s than salmon caught in the wild. The scientists work at the ARS Grand Forks Human Nutrition Research Center in Grand Forks, N.D. ARS is USDA's principal intramural scientific research agency.
Two omega-3 fatty acids—EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)—are abundant in oily fish such as salmon, tuna, mackerel, and herring. Consuming 250 milligrams daily of EPA and DHA—the amount in a 3-ounce farmed salmon fillet—has been associated with reduced heart disease risk.
The scientists evaluated a group of 19 healthy human volunteers who were provided three different portion sizes of farm-raised Atlantic salmon. Each volunteer was assigned to consume two weekly servings of one of the three portion sizes of salmon for a four-week period. After a "blood-clearing" break of four to six weeks, a different portion size was served, followed by another break. Then the third portion size was served, so that each volunteer had tested all three portion sizes.
The raw weights of the salmon portions fed to the volunteers were 90 grams (about 3.2 ounces), 180 grams (about 6.3 ounces), and 270 grams (about 9.5 ounces). The Dietary Guidelines for Americans recommend consuming eight ounces of seafood weekly.
Blood was collected from each of the 19 subjects to mark fatty acid levels and other heart disease risk indicators at the beginning and end of each treatment.
The results showed that EPA blood levels doubled after the volunteers consumed the 6.3-ounce portions and increased nearly threefold after they consumed the 9.5-ounce portions. Also, based on the blood indicators, DHA levels were elevated by about 50 per cent, regardless of portion size.
This research was published in the Journal of the Academy of Nutrition and Dietetics.