Dietary Fish, Omega-3 PUFAs Don't Cut CV Risk: Women's Health Study

Patrice Wendling

October 04, 2016

BOSTON, MA — Consumption of fish and long-chain omega-3 polyunsaturated fatty acids (PUFAs) did not reduce the risk of major CVD among healthy postmenopausal women in a Women's Health Study cohort analysis[1].

The study was published online September 16, 2016 in the American Journal of Preventive Medicine.

"There could be substantial heterogeneity in the way fish, omega-3 PUFAs, and fish oil can have an effect on cardiovascular risk," and their cardioprotective effects also "may be influenced by other clinical conditions and comorbidities," principal investigator Dr Jinnie J Rhee (Harvard School of Medicine, Boston, MA) told heartwire from Medscape.

She noted that previous studies have suggested increased fish intake as part of a healthy diet may lead to a decreased risk of CVD but that more recent cohort studies and meta-analyses have shown no significant benefits.

For example, an Iowa Women's Health Study analysis found no significant association between fish and marine omega-3 fatty-acid intake and CHD or stroke mortality in postmenopausal women[2], while a recent meta-analysis of eight prospective studies showed no overall association between PUFA intake and stroke[3].

For the present analysis, the investigators examined prospective data from 39,876 healthy women aged >45 years who participated in the Women's Health Study from 1993 to 2014 and completed a 131-item validated semiquantitative food frequency questionnaire (SFFQ) at baseline.

During 713,559 person years of follow-up, 1941 incident major CVD cases were documented.

Women who consumed tuna and dark fish (mackerel, salmon, sardines, bluefish, and swordfish) less than once a month had the same major CVD risk as those who did so one to three times per month (hazard ratio [HR] 1.04, 95% CI 0.91–1.19), once per week (HR 1.00; 95% CI 0.87–1.15), or more than once per week (HR 1.00; 95% CI 0.86–1.16) after full multivariate adjustment (P for trend=0.78).

No statistically significant associations between intake of energy-adjusted α-linolenic acid (P for trend=0.64) or marine omega-3 fatty acids (P for trend=0.87) and risk of major CVD were identified across quintiles of intake in multivariable models.

"We looked at MI, ischemic stroke, total stroke, and cardiovascular mortality as four different end points, and even so we didn't find any significant associations across the board," Rhee said.

She noted that the dietary questionnaire has been validated but that the single baseline dietary assessment did not allow them to capture cumulative intake or dietary changes during long-term follow-up, making the data subject to random error of self-report or underestimation of the true associations. "It could be a substantial bias," Rhee said.

"Going forward, I think it would be important to see how and to what extent these biological effects of omega-3s are influenced by various clinical factors and what impact this would have on implementation of intervention in healthy women," she added.

The research and the Women's Health Study were supported by grants from the National Institutes of Health. The authors reported no relevant financial relationships.

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