Wild fatty fish such as salmon, tuna, mackerel, and sardines are rich in omega-3 fatty acids, the healthy fat that scientists believe raises the good HDL cholesterol, lowers unhealthy tryglicerides, and slows the growth of plaque, protecting the heart from disease.
In modern fish farming, the fish are usually fed pellets that contain a mixture of natural fish oil and vegetable oil. After a US study released this year showed far higher levels of dioxins and other potentially cancer-causing pollutants in farm-raised salmon, some vowed to move more toward pellets with vegetable oil.
The latest study challenges that. A the annual meeting of the European Society of Cardiology in Munich this week, Norwegian scientists showed that people who ate salmon fed on pure vegetable oil or on 50 percent fish oil and 50 percent vegetable oil did not get any meaningful improvement in the relevant blood tests.
The study involved 58 people with heart disease in Oslo, Norway, who were taking heavy medication for their illness. The fish were color-coded according to the pellets they were fed, and served to heart patients. One-third were fed salmon given pellets of fish oil, another third got fish fed on a 50/50 mix of fish oil and vegetable oil, and the last group got salmon raised on pure rapeseed oil pellets. Each volunteer ate one fish meal per day, for six weeks.
The scientists, led by Dr. Harold Arnesen of Ulleval University Hospital in Norway, tested blood from the volunteers for concentrations of omega-3 fatty acids and changes in blood chemicals linked to heart disease. Omega-3 levels increased substantially in the patients who ate salmon fed on fish oil, but not in the patients who ate salmon fed on mixed pellets or vegetable oil pellets.
