Eating an antioxidant–rich diet reduces the risk of stroke in women regardless of whether they have a previous history of cardiovascular disease, a new study has claimed.

Oxidative stress is an imbalance between the production of cell–damaging free radicals and the body's ability to neutralise them. It leads to inflammation, blood vessel damage and stiffening.

Antioxidants such as vitamins C and E, carotenoids and flavonoids can inhibit oxidative stress and inflammation by scavenging the free radicals. Antioxidants, especially flavonoids, may also help improve endothelial function and reduce blood clotting, blood pressure and inflammation.

"Eating antioxidant–rich foods may reduce your risk of stroke by inhibiting oxidative stress and inflammation," Susanne Rautiainen, first author of the study, said.

"This means people should eat more foods such as fruits and vegetables that contribute to total antioxidant capacity," she said.

For the study, the researchers used the Swedish Mammography Cohort to identify 31,035 heart disease–free women and 5,680 women with a history of heart disease in two counties. The women were 49–83 years old.

They tracked the cardiovascular disease–free women an average 11.5 years and the women with cardiovascular disease 9.6 years, from September 1997 through the date of first stroke, death or December 31, 2009, whichever came first.

Researchers identified 1,322 strokes among cardiovascular disease–free women and 1,007 strokes among women with a history of cardiovascular disease from the Swedish Hospital Discharge Registry.

The researchers collected dietary data through a food–frequency questionnaire. They used a standard database to determine participants' total antioxidant capacity (TAC), which measures the free radical reducing capacity of all antioxidants in the diet and considers synergistic effects between substances.

"In this study, we took into account all the antioxidants present in the diet, including thousands of compounds, in doses obtained from a usual diet," Rautiainen said.

They found that higher TAC was related to lower stroke rates in women without cardiovascular disease, and women without cardiovascular disease with the highest levels of dietary TAC had a statistically significant 17% lower risk of total stroke compared to those in the lowest quintile.

The study also found that women with history of cardiovascular disease in the highest three quartiles of dietary TAC had a statistically significant 46% to 57% lower risk of hemorrhagic stroke compared with those in the lowest quartile.

"Women with a high antioxidant intake may be more health conscious and have the sort of healthy behaviours that may have influenced our results.

"However, the observed inverse association between dietary TAC and stroke persisted after adjustments for potential confounders related to healthy behaviour such as smoking, physical activity and education," she added.

The study has been published in Journal of the American Heart Association.