Beet juice: it’s the nitrates, stupid
More research from Andrew Jones’s group at the University of Exeter on the endurance-boosting effects of beet juice, which they previously reported can extend time-to-exhaustion by about 15% (equivalent to about a 1% improvement in a race over a specific distance), in a forthcoming paper in the Journal of Applied Physiology (press release here).
The most interesting new twist: they’ve developed a way of filtering the nitrates out of beet juice using an “ion-exchange resin,” allowing them to create a placebo form of beet juice that is identical to the real thing in every way except for the absence of nitrates. They’ve hypothesized that it’s the nitrate in beet juice that reduces the “oxygen cost” of running and other endurance exercise — i.e. you burn less energy to produce the muscular force needed to propel yourself forward, allowing you to last longer. But beet juice has a whole bunch of potentially beneficial ingredients, including big names like quercetin and resveratrol, so they needed some way to check which ingredient was actually making the difference. The new double-blinded study does that nicely: the nitrate-free beet juice had no effect on subjects, while the regular beet juice lowered blood pressure and improved performance in various endurance running tests.
One other new result is that they tested low-intensity exercise as well as high-intensity. Sure enough, they found that the oxygen cost of walking was significantly decreased after just four days of drinking 500 ml of beet juice per day.
For senescent populations or individuals with pulmonary, cardiovascular or metabolic disorders, [they write,] a reduction in the O2 cost of daily activities might significantly improve functional capacity.
Maybe, maybe not — I’m not convinced seniors will really care about shaving 1% from their evening walk time. But for competitive athletes, the body of evidence for beet juice is getting solid enough to make me reconsider my initial skepticism. I’d like to see similar results from other labs, though.