Implications for practice and research

• A diet rich in natural antioxidants may reduce the risk of developing heart failure.

• Well-designed intervention studies are needed to investigate the effect of a diet rich in antioxidants on heart failure incidence.

Context

Heart failure is a syndrome comprising symptoms such as breathlessness alongside objective evidence of cardiac dysfunction. This is a common condition with a considerable economic impact on health services.1 Nutritional intake and status appear to be important in heart failure. Non-intentional weight loss in the setting of heart failure (cardiac cachexia) is an independent predictor of mortality.2 Heart failure is associated with increased levels of oxidative stress3 and observational studies suggest that affected patients have reduced intake and suboptimal status of a number of antioxidant dietary micronutrients, such as selenium, vitamin C and vitamin E.4 Rautiainen and colleagues investigated the relationship between dietary antioxidant intake and risk of incident heart failure.

Findings

During 11.3 years (394 059 person-years) of follow-up, there were 894 cases of incident heart failure (769 cases of hospitalisation and 125 deaths). The cohort was divided into quintiles based on total antioxidant capacity of the diet and there was an inverse association with incident heart failure (p<0.001). The crude incidence rate was 18/10 000 person-years in the highest quintile versus 34/10 000 person-years in the lowest quintile (RR=0.50, 95% CI 0.40 to 0.62). This association remained statistically significant after adjustment for educational level, smoking status, body mass index, physical activity, diabetes mellitus, family history of myocardial infarction, alcohol consumption, total energy intake, dietary supplement use and incident myocardial infarction.

Commentary

This observational study suggests that a diet rich in antioxidants may help prevent the development of heart failure. The strengths include the prospective design, the large number of patients, the long duration of follow-up and the use of robust clinical endpoints. Limitations include the observational design, which makes it impossible to exclude unmeasured confounders, such as concurrent medication use, as a cause for the observed results. The study population was limited to middle-aged to elderly women from a single country. The FFQ was administered only once during the course of the study. It is, therefore, not possible to exclude a change in dietary intake over the period of follow-up. No biochemical assessment of antioxidant status was performed to confirm the findings of the FFQ. Finally, the diagnosis of heart failure was based solely on the identification of a hospital discharge or cause of death code. Individuals managed only as outpatients were, therefore, excluded.

The results of this study are in keeping with previous observational studies, demonstrating an inverse association between risk of developing heart failure and blood concentration of antioxidant micronutrients,5 and support the case for undertaking well-designed, large-scale intervention studies to investigate the effect of a diet rich in antioxidants on heart failure incidence.