SCIENTISTS have evidence that Popeye was right: spinach makes you stronger - but it's not the iron in the leafy greens that creates the effect, it's the nitrate.
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And it's not just spinach - concentrated juice from the humble beetroot has been shown to increase muscle power in patients with heart failure.
Based on research in elite athletes, especially cyclists who use beet juice to boost performance, researchers at Washington University School of Medicine in St. Louis suggested trying the same strategy in patients with heart failure.
In the September issue of the journal Circulation: Heart Failure, the scientists reported data from nine patients with heart failure.
Two hours after the treatment, patients demonstrated a 13 per cent increase in power in muscles that extend the knee.
The researchers observed the most benefit when the muscles moved at the fastest. The increase in muscle performance was significant in quick, power-based actions, but researchers saw no improvements in performance during longer tests that measure muscle fatigue.
“It’s a small study, but we see robust changes in muscle power about two hours after patients drink the beet juice,” said senior author associate professor of medicine Linda R. Peterson.
“A lot of the activities of daily living are power-based — getting out of a chair, lifting groceries, climbing stairs. And they have a major impact on quality of life.
"We want to help make people more powerful because power is such an important predictor of how well people do, whether they have heart failure, cancer or other conditions. In general, physically more powerful people live longer.”
The patients in the study each received the beet juice treatment and an identical beet juice placebo that had only the nitrate content removed. There was a one to two-week period between trial sessions to be sure any effects of the first treatment did not carry over to the second.
Neither the trial participants nor the investigators knew the order in which patients received the treatment and placebo beet juice.
The researchers also pointed out that participants experienced no major side effects from the beet juice, including no increase in heart rates or drops in blood pressure, which is important in patients with heart failure.
Heart failure can have various triggers, from heart valve problems to viral infections, but the result is the heart’s gradual loss of pumping capacity.
“The heart can’t pump enough in these patients, but that’s just where the problems start,” said Peterson, a cardiologist and director of Cardiac Rehabilitation at Washington University and Barnes-Jewish Hospital.
“Heart failure becomes a whole-body problem because of the metabolic changes that happen, increasing the risk of conditions such as insulin resistance and diabetes and generally leading to weaker muscles overall.”
While the trial was not designed to find out whether patients noticed an improved ability to function in daily life, the researchers estimated the size of the benefit by comparing the improvement in muscle power with what is seen from an exercise program.
The study’s corresponding author, Andrew R. Coggan, assistant professor of radiology compares the beet juice to Popeye eating his spinach.
“The magnitude of this improvement is comparable to that seen in heart failure patients who have done two to three months of resistance training.”
The nitrates in beet juice, spinach and other leafy green vegetables such as rocket and celery are processed by the body into nitric oxide, which is known to relax blood vessels and have other beneficial effects on metabolism.
“One problem in aging is the muscles get weaker, slower and less powerful,” Coggan said.
“Beyond a certain age, people lose about one percent per year of their muscle function. If we can boost muscle power like we did in this study, that could provide a significant benefit to older individuals.”
