Nitrate is a compound naturally present in the environment, and is essential for plant growth.
Researchers from the Edith Cowan University's School of Medical and Health Sciences studied the diets of more than 1,000 Western Australian women, focusing on nitrate intake derived from vegetables.
They found that over a 15-year period, the women who had the highest intake of nitrate from vegetables had up to a 40% lower risk of dying from heart disease or stroke.
PhD student Lauren Blekkenhorst said the research was built on her previous study that had collated data from around the world on the measured nitrate concentration in commonly eaten vegetables.
"We found that leafy green vegetables, such as spinach, lettuce and kale, had the highest amounts of nitrate, followed by radish, beetroot and celery," she said.
"People get roughly 80% of their average nitrate intake from vegetables, so they are the primary source."
One cup is enough
Blekkenhorst said about 75g per day (1 serving) of green leafy vegetables would provide enough nitrate to achieve these health benefits.
"This is about one cup of raw vegetables, which shouldn't be too hard for all of us to eat daily."
Lead researcher Dr Catherine Bondonno added that the bacteria living in our mouths were critical for the cardiovascular health benefits observed.
"The bacteria living on our tongue break down the nitrate that we eat into another compound called nitrite. Nitrite and other breakdown products play a key role in regulating our blood pressure," she revealed.
"This is the underlying mechanism that is resulting in the long-term improvements in heart health."
The study entitled Association of dietary nitrate with atherosclerotic vascular disease mortality: a prospective cohort study of older adult women was recently published in the American Journal of Clinical Nutrition, while Association of vegetable nitrate intake with carotid atherosclerosis and ischemic cerebrovascular disease in older women was recently published in the journal Stroke.