Previous studies have indicated a protective effect of long-chain n-3 polyunsaturated fatty acids (LCn3FAs) against cardiovascular disease; however, women are underrepresented in cardiovascular research.

The aim of this study was to explore the association between intake of LCn3FAs and the risk of cardiovascular disease in a large prospective cohort of young women (mean age at baseline: 29.9 years [range: 15.7-46.9]). Exposure information on 48 627 women from the Danish National Birth Cohort was linked to the Danish National Patients Registry for information on events of hypertensive, cerebrovascular, and ischemic heart disease used to define a combined measure of cardiovascular diseases. Intake of fish and LCn3FAs was assessed by a food-frequency questionnaire and telephone interviews.

During follow-up (1996-2008; median: 8 years), 577 events of cardiovascular disease were identified. Low LCn3FA intake was associated with an increased risk of cardiovascular disease (adjusted hazard ratio for women in lowest versus highest LCn3FA intake group: 1.91 [95% CI: 1.26-2.90]). Restricting the sample to women who had consistently reported similar frequencies of fish intake across 3 different dietary assessment occasions tended to strengthen the relationship (hazard ratio for lowest versus highest intake: 2.91 [95% CI: 1.45-5.85]). Furthermore, the observed associations were consistent in supplementary analyses where LCn3FA intake was averaged across the 3 dietary assessment occasions, and the associations were persistent for all 3 of the individual outcomes.

Our findings based on a large prospective cohort of relatively young and initially healthy women indicated that little or no intake of fish and LCn3FAs was associated with an increased risk of cardiovascular disease.