A second important aspect of the study is there were no untoward side effects from the dietary nitrate.
Beetroot juice supplements may help enhance exercise capacity in patients with heart failure, a study has found.
Exercise capacity is a key factor linked to these patients' quality of life and even survival, said researchers from Indiana University in the US.
The study, published in the Journal of Cardiac Failure, examined the impact of dietary nitrate in the form of beetroot juice supplements on the exercise capacity of eight heart failure patients with reduced ejection fraction.
It is a condition in which the heart muscle does not contract effectively and cannot get enough oxygen-rich blood to the body.
Tens of millions of people suffer from heart failure. In about half of all such people, the ejection fraction of the heart is reduced, the researchers said.
Because of their condition, these patients exhibit laboured breathing, have diminished peak oxygen uptake and use more energy while exercising than would otherwise be the case.
The researchers found that the beetroot supplement resulted in significant increases in exercise duration, peak power and peak oxygen uptake while exercising.
Those improvements were not accompanied by any changes in the breathing responses of the patients, and there was no change in their exercise efficiency, a measure of how much external work a person gets for a certain input of energy.
"Abnormalities in aerobic exercise responses play a major role in the disability, loss of independence and reduced quality of life that accompany heart failure," said Andrew Coggan from Indiana University.
"Perhaps more importantly, elevations in ventilatory demand and decreases in peak oxygen uptake are highly predictive of mortality in patients with heart failure," Coggan said.
A second important aspect of the study is there were no untoward side effects from the dietary nitrate, Coggan said.
"In this case, lack of any significant changes is good news," he said.
The data suggests that dietary supplementation may be a valuable addition to treatment for exercise intolerance among heart failure patients with reduced ejection fraction, he added.