According to the research, published in the Journal of Cardiac Failure, around half of all heart failure cases suffer reduced ejection fraction (rEF), a condition in which heart muscle contraction is ineffective, preventing enough oxygen-rich blood from reaching the body.
Patients in this small proof-of-concept study who were given dietary nitrate in the form of beetroot juice saw significant increases in exercise duration, peak power and also peak oxygen intake (VO2 peak), compared with placebo.
No accompanying changes in breathing response (ventilatory demand) or exercise efficiency occurred, noted the research team, a collaboration between Washington University School of Medicine, St. Louis, Missouri and Indiana University Purdue University Indianapolis (IUPUI).
“The results of this proof-of-concept study demonstrate that acute ingestion of nitrate (in the form of a concentrated beetroot juice supplement) increases aerobic exercise performance and VO2peak, but does not alter ventilatory responses or gross or delta efficiency during exercise, in patients with mild-to-moderate HFrEF,” commented first author Professor Andrew Coggan at IUPUI.
"Abnormalities in aerobic exercise responses play a major role in the disability, loss of independence and reduced quality of life that accompany heart failure," explained Coggan.
"Perhaps more importantly, elevations in ventilatory demand and decreases in peak oxygen uptake are highly predictive of mortality in patients with heart failure."
If findings are replicated in larger trials, beetroot juice might be used in interventions to improve quality of life, and possibly lengthen the lives of patients with HErEF, the researchers suggested.
“Larger (i.e. multicentre) trials are needed to confirm the present findings and to determine whether longer term dietary NO3 − treatment improves physical activity levels, quality of life, and perhaps even survival in patients with HFrEF,” said Coggan.
No side effects
Another important outcome from the trial was the lack of harmful side effects from the beetroot juice.
"In this case, lack of any significant changes is good news," Said Coggan.
However, the effectiveness of the treatment may depend on the ability to convert nitrate (and nitrite) to the active metabolite nitric oxide. Therefore, the researchers excluded patients taking proton pump inhibitor and other ant-acid medications, as low stomach-acid conditions are known to impair this conversion capability.
The study was a randomised placebo-controlled, crossover type with a one-week washout period. Ten people were enrolled originally, although only eight completed the trial.
The subjects were given either 140 millilitres of beetroot juice (Beet It, manufactured by James White Drinks, UK) or placebo. Interestingly, the placebo was specially produced by the same manufacturer, who extracted the nitrate from the beetroot juice using an ion exchange resin. The placebo was therefore indistinguishable from the active product in packaging, taste, smell, colour and texture.
Scientists measured blood nitrate and nitrite and also breath nitric oxide levels at baseline and two hours after consuming the beetroot juice or placebo. Heart rate and blood pressure measurements weretaken before, during and after exercise. The researchers also measured perceived exertion just prior to the end of each stage.
The exercise consisted of steady state pedalling on a cycle ergometer below peak exertion, after which intensity was gradually increased until the participants no longer wished to continue.
Source: Journal of Cardiac Failure
Volume 24, Issue 2, pages 65-73, doi: 10.1016/j.cardfail.2017.09.004
“Dietary Nitrate Increases VO2peak and Performance but Does Not Alter Ventilation or Efficiency in Patients With Heart Failure With Reduced Ejection Fraction”
Authors: Andrew R. Coggan et al