Can blood glucose levels influence the effect of omega-3 fatty acids on heart attack risks?

This study evaluated whether blood glucose (sugar) levels affect the relationship between n-3 (or omega-3) long-chain polyunsaturated fatty acids and risk of acute myocardial infarction (AMI) in patients with coronary artery disease (progressive narrowing of the arteries that supply blood and oxygen to the heart due to accumulation of fatty material on the inner lining of the blood vessels).

Most heart attacks, also referred to as acute myocardial infarctions (AMI), are caused by blood clots that block one of the coronary arteries (the arteries that supply blood and oxygen to the heart). Risk factors for AMI include high cholesterol levels, obesity, and lack of physical activity, high blood pressure and diabetes mellitus (high blood glucose levels) due to ineffective glucose metabolism (breakdown). Omega-3 (n-3) long-chain polyunsaturated fatty acids are fatty acids found in fish, other seafood including algae and krill, some plants, and nut oils. A diet made of omega-3 fatty acids, especially those found in fish and fish oil, were shown to help in reducing risk factors for AMI in patients with CAD. This study evaluated the association of omega-3 fatty acids intake with risk of AMI at varying blood glucose levels.

2,378 patients with CAD were included in this study. Out of these, 1012 patients had normal blood glucose levels, 1049 had pre-diabetes (blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes), while the other 317 had established diabetes mellitus. A questionnaire was used to evaluate the daily intake of omega-3 fatty acids and the main parameter evaluated was the risk of developing AMI. 

Results showed that among patients with diabetes who consumed an average of 2.38 g/day of omega-3 fatty acids had a 62% lower risk of an AMI. In patients with pre-diabetes, there was no association between omega-3 fatty acids consumption and risk of AMI. On the other hand, patients without diabetes taking the same amount of omega-3 fatty acids had a 45% higher risk of developing AMI. In addition, risks of fatal AMI (AMI that is likely to cause death) were significantly higher in patients without diabetes who consumed an average of 2.38 g/day of omega-3 fatty acids.

In summary, a high consumption of omega-3 fatty acids reduced the risks of AMI in diabetic patients with CAD, while increasing the risks among patients with normal glucose metabolism.