Eating Oily Fish May Help Protect Against Stroke

Megan Brooks

November 01, 2012

Eating at least 2 servings of oily fish a week is moderately but significantly associated with a reduced risk for stroke, but taking fish oil supplements does not seem to have the same effect, suggest results of a large meta-analysis of relevant research.

"Consumption of fish and long-chain omega 3 fatty acids has been associated with a reduced risk of coronary heart disease [CHD] and sudden cardiac death," Oscar H. Franco, MD, PhD, professor of preventive medicine, Erasmus MC, University Medical Center, Rotterdam, the Netherlands, told Medscape Medical News. "However, observational and experimental evidence supporting a similar benefit for cerebrovascular disease remain conflicting," he said.

To help clarify the value of fish intake on stroke risk, Dr. Franco and colleagues performed a systematic review and meta-analysis of 26 prospective cohort studies and 12 randomized controlled trials involving a total of 794,000 participants and 34,817 cerebrovascular outcomes.

"Observational findings in this meta-analysis show that consumption of both fish and long chain omega 3 fatty acids may modestly reduce the risk of stroke, whereas results were significant only for fish intake," he concluded.

They report their findings in an article published online October 30 in BMJ.

Fish Beats Fish Oil Pills

After adjusting for several risk factors, participants consuming 2 to 4 fish servings a week had a moderate but significant 6% lower risk for cerebrovascular disease compared with those having 1 or fewer fish servings a week (relative risk [RR], 0.94; 95% confidence interval [CI], 0.90 - 0.98).

Participants eating 5 or more fish servings a week had a 12% lower risk (RR, 0.88; 95% CI, 0.81 - 0.96). In a dose-response meta-analysis, an increment of 2 servings per week of any fish was associated with a 4% reduced risk for cerebrovascular disease.

In contrast, there was no evidence for similar inverse associations with cerebrovascular disease for long-chain omega 3 fatty acids measured as circulating biomarkers in observational studies or fish oil supplements in primary and secondary prevention trials.

"We expected to find significant associations for fish intake and long-chain omega 3 fatty acids (both biomarkers and intake)," Dr. Franco said. "The beneficial effect of fish intake on cerebrovascular risk is likely to be mediated through the interplay of a wide range of nutrients abundant in fish," he added.

It is possible, the researchers say, that eating more fish curbs the intake of other foods, such as red meat, that are detrimental to vascular health; or higher fish intake may simply be an indicator of a generally healthier diet or higher socioeconomic status, both associated with better vascular health.

Having 1 or 2 Weekly Servings "Reasonable" Advice

The current findings are "in line with disappointing results" from controlled trials of supplementation with long-chain omega 3 fatty acids for the prevention of CHD, say the coauthors of a commentary published with the study.

"It seems that the additional benefit of supplementation in patients who are optimally managed may be small," write Janette de Goede and Johanna M Geleijnse, PhD, of the Division of Human Nutrition, Wageningen University, the Netherlands.

On the basis of available evidence, it is "reasonable to advise people that eating one or two portions of fish a week could reduce the risk of CHD and stroke," they write.

"Any benefit of long chain omega 3 fatty acid supplementation for the secondary prevention of CHD and stroke is likely to be small," they conclude. "However, it is possible that patients who are less than optimally medically treated or who have additional risk factors (for example, as a result of comorbidities such as diabetes) may benefit."

The study had no specific funding. The authors and editorial writers have disclosed no relevant financial relationships.

BMJ. Published online October 30, 2012. Abstract, Commentary