by Craig Weatherby
Because of concerns about processed beef and pork products, it’s become common to associate dietary nitrates with cancer.
Actually, the cancer risks associated with nitrate-preserved processed meats probably have more to do with the meat than the nitrates.
And to remove any risk from the nitrates, lunch-meat makers have long been required to add vitamin C (ascorbic acid), which blocks creation of nitrate-based carcinogens.
Nitrates aren’t inherently carcinogenic, and they’re pretty abundant in common vegetables.
In fact, it’s looking more and more as though some of vegetables’ apparent health benefits stem from their nitrate content.
For example, last November we reported on a study in older adults, which showed that drinking juice from a nitrate-rich vegetable increased blood flow to key areas of the brain.
For more on that, see “Can Beets & Co. Boost Aging Brains?”
Now, research suggests that beet juice may also aid exercise capacity and efficiency.
And the findings likely extend to whole beets, borscht, and all nitrate-rich veggies.
Nitrates singled out as source of beet juice’s exercise benefits
Prior research from Britain’s University of Exeter showed that beet juice enabled people to exercise up to 16 percent longer and produced other substantial performance and health benefits (Bailey SJ et al. 2009; Bailey SJ et al. 2010; Vanhatalo A et al. 2010).
Amazingly, the humble vegetable’s deep red juice reduced oxygen needs to an extent never achieved in any other way.
The University of Exeter team wanted to confirm that the benefits of beet juice derived from its nitrates, as they supposed.
They enrolled nine healthy, physically active males for a randomized, double-blind, cross-over trial.
Some were assigned to drink regular beet juice, while others drank a nitrate-free beet juice.
The scientists compared the two groups on a range of measures such as blood pressure and mitochondrial oxidative capacity (Qmax)… a measure of how efficiently the muscles use oxygen.
The study began by recording all the participants’ scores on treadmill tests, maximal oxygen intake, blood pressure, heart rate, lung function and blood nitrite concentration. (Dietary nitrates largely convert to nitrites in the body.)
The participants were then randomized to receive 0.5 liters (16 ounces) per day of either regular beet juice (containing 6.2 mmol of nitrate) or deliberately nitrate-depleted beet juice (containing 0.003 mmol of nitrate) for six days.
The volunteers took part in treadmill exercise tests on days four and five. On day six, the men were asked to perform knee extension tests.
The knee extensions were designed to lower participants’ muscle phosphocreatinine levels, and also to allow the researchers to estimate the participants’ Qmax.
(Phosphocreatinine acts as a rapidly available reserve of high-energy phosphates in skeletal muscle and the brain.)
All of the tests were repeated during a second, “cross-over” period when the men in the two groups switched drinks for another six days.
Compared with drinking nitrate-depleted beet juice, drinking regular beet juice raised the men’s blood nitrite levels and reduced their systolic blood pressure.
Drinking regular beet juice also reduced the participants’ oxygen requirements during treadmill walking, moderate- or high-intensity running.
And drinking regular beet juice lengthened so-called “time-to-exhaustion” during severe-intensity running by 15 percent.
There was no difference in Qmax between drinking nitrate-free and regular beet juice.
Drawing the obvious conclusion, the Exeter team wrote, “These results indicate that the positive effects of six days of BR supplementation on the physiological responses to exercise can be ascribed to the high nitrate content” (Lansley KE et al. 2010).
Bailey SJ, Winyard P, Vanhatalo A, Blackwell JR, Dimenna FJ, Wilkerson DP, Tarr J, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. J Appl Physiol. 2009 Oct;107(4):1144-55. Epub 2009 Aug 6.
Bailey SJ, Fulford J, Vanhatalo A, Winyard PG, Blackwell JR, DiMenna FJ, Wilkerson DP, Benjamin N, Jones AM. Dietary nitrate supplementation enhances muscle contractile efficiency during knee-extensor exercise in humans. J Appl Physiol. 2010 Jul;109(1):135-48. Epub 2010 May 13. Erratum in: J Appl Physiol. 2010 Sep;109(3):943.
Lansley KE, Winyard PG, Fulford J, Vanhatalo A, Bailey SJ, Blackwell JR, Dimenna FJ, Gilchrist M, Benjamin N, Jones AM. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol. 2010 Nov 11. [Epub ahead of print]
Vanhatalo A, Bailey SJ, Blackwell JR, DiMenna FJ, Pavey TG, Wilkerson DP, Benjamin N, Winyard PG, Jones AM. Acute and chronic effects of dietary nitrate supplementation on blood pressure and the physiological responses to moderate-intensity and incremental exercise. Am J Physiol Regul Integr Comp Physiol. 2010 Oct;299(4):R1121-31. Epub 2010 Aug 11.