PITTSBURGH (KDKA) – Fish Oil and its Omega-3 Fatty Acids are so popular as a supplement it accounts for about $2 billion in sales globally each year.

But, a new study in the Journal of the American Medical Association could send shockwaves through fish oil believers.

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Dr. Steven Nissen a cardiologist from the Cleveland Clinic says the study used prescription-strength fish oil in 600 locations in 20 countries to determine its benefit in reducing heart issues.

“This is a drug that is like the fish oil people buy over the counter, but much much more effective,” Dr. Nissen explained. “It has a higher amount of what we call omega-three fatty acids.”

And the result?

“There was absolutely no reduction in cardiovascular events using this very active fish oil,” he said.

This result comes just a year after another study showed positive impacts of fish oil but Dr. Nissen says that study was flawed by using a placebo that was actually harmful.

“The earlier drug that was favorable and is being widely marketed got approved by the FDA, but we think it’s a mistake,” he said.

WATCH: Fish Oil Fears

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Dr. Nissen is emphatic about that because this new study used harmless corn oil as the placebo.

“In patients treated with the fish oil product, there was a 69% higher risk of atrial fibrillation,” Dr. Nissen said. “So that actually some harms associated with taking the fish oil, and that we think is also an important finding.”

Knowing people believe in the benefits in cognitive health, weight loss, better eyesight, and the list goes on but Dr. Nissen says the study results are crucial.

“It’s also important for the public,” he said. “Because people believe that fish oil is beneficial.”

The potential for harm he says is something people need to understand.

“It’s really kind of a wake-up call,” he explained. “When you see a study like this where the most potent prescription-grade fish oil didn’t have any favorable effects. It certainly doesn’t suggest that over the counter fish oil is something that shouldn’t be widely consumed.”

But when asked if people should dump their fish oil supply Dr. Nissen says it’s important to understand that the participants in the study received prescription-strength fish oil many times stronger than what anyone can purchase over the counter.

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Also, if fish oil is a regular part of your day a sudden stop could cause issues so you should talk to your doctor and decide your level of risk vs benefit.