Dietary antioxidant capacity and risk for stroke in a prospective cohort study of Swedish men and women

Highlights

• Dietary nonenzymatic antioxidant capacity (NEAC) is a measure of the overall antioxidant capacity of diet.

• Dietary NEAC takes into account synergistic interactions among dietary antioxidants.

• The relationship between dietary NEAC and risk for stroke has not been extensively explored.

• High levels of dietary NEAC are associated with a decreased risk for ischemic stroke in women.

Abstract

Objective

Both observational studies and randomized trials have shown that a diet rich in antioxidants can reduce systemic inflammation and oxidative stress, two conditions that, together with obesity and smoking, are established risk factors for stroke. However, the association between antioxidant intake and risk for stroke is poorly understood, particularly when studying possible interaction with sex. We investigated the relationship of nonenzymatic antioxidant capacity (NEAC) on risk for stroke in a large Swedish prospective cohort.

Methods

The cohort study included 34 555 men and women from the Swedish National March Cohort. NEAC was assessed using a detailed food frequency questionnaire, collected at baseline. We achieved complete follow-up from enrollment in 1997 through 2010 by record linkage to nationwide registers. We identified 1186 incident cases of a first stroke, of which 860 were ischemic, 201 hemorrhagic, and 125 unspecified. We used multivariable Cox proportional hazards models to estimate adjusted hazard ratios (HR) with 95% confidence intervals (CIs).

Results

Compared with women in the lowest quartile of NEAC, women in the highest quartile had a 27% lower incidence of total stroke (HR, 0.73; 95% CI, 0.53–0.99; P_trend = 0.03) and 35% lower incidence of ischemic stroke (HR, 0.65; 95% CI, 0.43–0.99; P_trend = 0.01). Among men, the relationship between NEAC and risk for stroke was not statistically significant and all HRs were close to unity.

Conclusion

Findings from the present study suggest that dietary antioxidant capacity from different foods and beverages is inversely associated with risk for stroke, more specifically ischemic stroke, in women.

Introduction

Stroke is the second leading cause of death in the world [1]. Well-known modifiable risk factors for this neurovascular emergency include hypertension, obesity, physical inactivity, an unhealthy diet, and smoking [2]. Furthermore, oxidative and inflammatory stress promotes atherosclerosis [3] that ultimately can lead to stroke [2], [4]. A high consumption of flavonoids and phytochemicals with antioxidant properties contained in fruits and vegetables is associated with reduced oxidative stress [5] and reduced systemic inflammation [6], [7]. Antioxidants in fruits, vegetables, and other foods and beverages may therefore prevent stroke and other cardiovascular diseases by reducing excessive production of free radicals induced by oxidative and inflammatory stress [8], [9], [10], [11], [12], [13], [14], [15].

However, few observational studies have investigated the association between total antioxidant capacity from diet and risk for stroke [10], [11], [16]. Two studies found an inverse association between consumption of antioxidants and risk for stroke. A third study did not find any evidence of neither a positive nor a negative association [16]. Therefore, the association remains open for discussion. Moreover, to our knowledge, a possible interaction with sex has not been investigated. However, previous studies have suggested a possible sex difference in antioxidant status [17], which may in turn lead to a potential different effect of dietary antioxidants on the risk for stroke.

Nonenzymatic antioxidant capacity (NEAC), also known as total antioxidant capacity (TAC), is a measure proposed to assess the cumulative power offered by all antioxidant sources from diet [18], [19]. NEAC can be estimated through antioxidant capacity assays such as ferric-reducing antioxidant potential (FRAP) [20].

We investigated the relationship of NEAC, estimated using food item–specific antioxidant FRAP values, on risk for stroke in a large Swedish prospective cohort of women and men.