Once touted as beneficial for heart disease, omega-3 fatty acids from fish oils have proven to be mostly ineffective for those at risk of cardiovascular disease.
Researchers in Italy found in a massive study that the fish pills did little for those with risk factors like high blood pressure, high cholesterol, smoking or narrow arteries.
The study was considered gold-standard, randomized and controlled, meaning that it was exceptionally comprehensive and lasted over many years.
Researchers gave one group of elderly people one gram of fish oil per day while another group got olive oil.
The 6,224 patients were all over 64, were at risk of heart disease but had never had a heart attack.
After five years 11.7 percent of the 6,244 patients taking a capsule containing the fish oil had died or been hospitalized for heart problems.
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Those who took the olive oil were at 11.9 percent.
The initial research was to look at the death rates but few people died during the study.
Thus, they began looking at hospitalization and illness, which turned out to be the same for both groups.
Doctors said the amount of olive oil used was too small to make any remarkable difference.
The study was partially funded by fish oil supplement makers.
The findings were published in the New England Journal of Medicine.