Researchers at King’s BHF Centre of Excellence have challenged previous understanding of the impact of inorganic nitrite, commonly found in foods including beetroot and green leafy vegetables, and its potential cardiovascular benefits.
Previously it was thought that inorganic nitrite, which is produced by the body when nitrate-rich foods such as beetroot are consumed, widened small arteries to allow increased blood flow and reduce blood pressure.
However, new King’s research has shown that inorganic nitrite actually affects the large arteries, a discovery that could have major implications for the treatment of heart disease.
Our findings challenge previous understanding of their effect on arteries, which could have important implications for the treatment of heart disease and blood pressure – Dr Andrew Webb, Senior Lecturer in Cardiovascular Clinical Pharmacology, Honorary Consultant Physician.
By injecting nitrite into the coronary arteries of patients undergoing an x-ray of their heart and blood vessels, researchers found that it significantly dilated the larger coronary arteries, without increasing flow in the small vessels. This happened even when the heart continued beating normally – conditions which had been thought to enhance nitrite’s effects on small vessels.
Currently, a different type of nitrate (known as glyceryl trinitrate) is used to treat heart conditions such as angina, as it has been proven to dilate the larger arteries, such as those supplying the heart.
A major problem with this medicine, however, is that it can lose effect over time, as patients become more tolerant of its effects after repeated use.
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Researchers found inorganic nitrite was at least as effective at dilating larger arteries as current treatments, but importantly patients did not become tolerant to it.
Previous studies have shown that dilation of larger arteries was associated with a reduction in blood pressure near the heart (central blood pressure), and the new findings may be particularly relevant to the prevention or treatment of patients with forms of heart failure linked to high blood pressure.
The team (with the Department of Nutritional Sciences) also confirmed the effects of dietary nitrate on blood pressure by undertaking the largest and longest study of beetroot juice (the dietary nitrate) to date. 126 patients who had, or were at risk of type 2 diabetes, drank beetroot juice every day for six months. The study found that beetroot juice lowered central blood pressure over the six months, confirming that dietary nitrate does not lose effect due to tolerance.
‘It’s a significant development to be able to demonstrate these cardiovascular effects of dietary nitrate and nitrite. Our findings challenge previous understanding of their effect on arteries, which could have important implications for the treatment of heart disease and blood pressure. It is also promising that patients do not become tolerant to the effects of beetroot juice,’ adds Dr Webb.