Farmed salmon may not be as nutritious as it once was, new research suggests

New research led by USDA scientists suggests farmed salmon may no longer provide as much omega-3 as previously thought, raising questions about the accuracy of dietary guidance. The study reports that omega-3 levels in farmed salmon have dropped considerably, potentially making recommendations—including advice in the U.S. Dietary Guidelines and similar guidance from the American Heart Association—outdated. The USDA said the sample size examined wasn’t large enough to justify changing official advice, and the authors called for broader, more representative research. The study links the decline to a shift in feed: salmon have moved from diets based on smaller fish to mixtures that include land-based oils and crops such as soy and canola.