A new post-hoc analysis from the STRENGTH study suggests that omega-3 fatty acids from prescription fish oil may not have an effect on reducing cardiovascular events.
These results were presented at the American College of Cardiology (ACC) annual scientific meeting.
Researchers from the double-blind, multi-stage STRENGTH study reported neutral results between patients who consumed a mixture of EPA and docosahexaenoic acid (DHA) and those who received a placebo.
On the other hand, the results of the REDUCE-IT study showed that patients who consumed omega-3 CA experienced a 25% reduction in events compared to patients who took a mineral oil placebo pill.
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Therefore, a team of investigators led by Dr. Steven Nissen, MACC, Cleveland Clinic, reconciled the conflicting evidence between studies.
First, they rated a subgroup of the 13,078 people from the STRENGTH study (n = 10,382). Of this subgroup, 5175 had received omega-3 carboxylic acid and 5,207 had received corn oil.
The mean age of the population was 62.5 years, a majority (2/3) were men, and a third of the patients had diabetes.
As such, they found that cardiosvascular events – such as cardiovascular death, heart attack, stroke, need to open blocked arteries, or chest pain that required hospitalization – occurred in 11.1% and 11% of omega-3 and placebo patients, respectively .
Nissen and his team then used available blood counts to divide the population into tertiles according to the EPA and DHA levels achieved. Patients were examined at baseline and 12 months after randomization.
Overall, the upper tertile achieved EPA values of 151 (132-181) μg / ml and DHA values of 118 (102-143) μg / ml – compared with mean EPA and DHA values of 89 (46-131) μg / ml and 91 (71-114) µ g / ml.
Similar to the overall results, there were no differences in cardiovascular event rate between top EPA and DHA tertiles and placebo cohorts.
“To be thorough, we examined the data in several ways – absolute EPA and DHA levels, changes in levels of these omega-3 fatty acids, levels of red blood cells, and by subgroups of primary and secondary prevention,” said Nissen in a press release. “None of these analyzes showed any advantages or disadvantages.”
He outlined several possible underlying factors, including the possibility that DHA might counteract any potential benefit from EPA – although he noted that their post-hoc analysis showed no benefit from EPA or harm to DHA.
One possible explanation for the REDUCE-IT results could be the use of mineral oil, which could have serious adverse effects and therefore lead to a false positive study.
Nissen’s team also looked at the possible harmful effects of fish oil. Although not significant, the increase in new atrial fibrillation in fish oil patients was 69%. The condition occurred in 2.2% of the patients in the fish oil group – compared to 1.3% in the corn oil group.
“Fish oils significantly increase the risk of atrial fibrillation, and there is no solid evidence that they help the heart anyway,” noted Nissen. “It’s a sad story for cardiology.”
The team indicated that research comparing mineral oil with corn oil, as well as purified EPA and other formulations of omega-3 fatty acids, is warranted.
The study “Relationship between Omega-3 Fatty Acid Levels and Serious Adverse Cardiovascular Outcomes in Patients at High Cardiovascular Risk” was presented at ACC 2021.