WESTON, Fla. -

Doctors worry that fish oil supplements many men take for heart health may increase their risk of developing prostate cancer.

Fish oil is supposed to lower bad cholesterol, which reduces the risk of heart attacks and other vascular diseases.

"There's a lot of industry-driven advertisement of those things and people start taking it and ultimately some people might get hurt with this," said Dr. Alok Shrivastava with the Cleveland Clinic Florida in Weston.

"I hear about the stories about fish oils and it's good for you, good for your metabolism, good for your fat," said Guiseppe Imbrenda, who seven years ago began taking fish oil supplements twice a day.

Earlier this year, Imbrenda was diagnosed with prostate cancer.

I said, 'Doc, I have prostate cancer on both sides of my family. Did this affect me?' and he said what it did is it increased your risk early on, that's why you developed cancer early on at an early age," recounted Imbrenda.

A study published in the Journal of the National Cancer Institute found an increased risk of prostate cancer among men who had a high intake of Omega-3 fatty acids from fish oil supplements.

"At this point in time, we really have not been pointed at a particular molecule or mechanism, so there's a lot of study going on and this is my worry," said Shrivastava. "I'd rather have a known enemy than an unknown friend."

Imbrenda recovered fully following his treatment.

"I feel perfect," he said.

Doctors recommend getting Omega 3 fatty acids from food instead of supplements.