I’ve been ignoring cherry juice for well over a decade now. The studies keep popping up in my grid of potentially interesting research suggesting that tart cherries speed up post-workout recovery, mostly funded by the Cherry Marketing Institute. But other studies find no benefit. And more generally, with supplemental research, my assumption is that (a) nothing works, and (b) if something actually works in a meaningful way, you don’t need to look for evidence because everyone will be talking about it.
Cherry juice still hasn’t reached the stage where everyone is talking about it, at least in my circles, but studies are progressing, including some recent reviews and meta-analysis. Interestingly, the gist of some of this more recent work is less “Does cherry juice work?” and more “We know cherry juice works, so why aren’t more athletes using it?” With that in mind, I’ll try to summarize the current body of research and then some Share thoughts on why athletes might – and maybe should – hesitate.
The best place to start is a meta-analysis published in the last year International Journal of Sports Nutrition and Exercise Metabolism by Jessica Hill of St. Mary’s University and her colleagues. Hill’s team combined the results of 14 studies involving 303 subjects looking at recovery from strenuous exercise. They found evidence of a “small beneficial effect” on muscle soreness, a “moderate beneficial effect” on muscle strength recovery, and mixed effects on blood markers of muscle damage and inflammation.
That sounds pretty good. But if you look at the results from each study, you’ll find many results clustered around zero and a few outliers — generally those with the largest error bars — that are strongly positive. It doesn’t fill me with a ton of confidence.
Here is an illustration of what I mean. This is called a “forest plot,” with each individual study result represented by a horizontal line and the overall average represented by a diamond. Lines or diamonds to the left of the vertical line indicate that cherry juice aided in strength recovery after damaging exercise; Lines or diamonds on the right indicate the opposite. The wider the horizontal line, the larger the error bar. The studies at the forefront focus on “metabolism” exercises such as endurance cycling; The studies below focus on “mechanical” exercises like lifting heavy weights. I realize this sounds overly complicated, but it’s a great way to get an overall view of a whole range of research:
Again, this was the data on strength recovery, which had the most positive effect of all outcome variables in the meta-analysis. What strikes me are four strongly positive studies — which, if you look closely, turn out to be a single study by Connolly in 2006, with four results measured at 24, 48, 72, and 96 hours. Remove that study, and I suspect the overall “moderately beneficial” effects would largely fade away. (And yes, for the record, the Connolly study was funded by Cherrypharm, a tart cherry juice company, and the three authors of the study each had an equity interest in the company.)
In conclusion, this meta-analysis has not allayed my skepticism when it was published last year. What caught my eye instead was a recent review in the Scandinavian Journal of Medicine and Science in Sport by Malachy McHugh of the Nicholas Institute of Sports Medicine and Athletic Trauma in New York (and, it turns out, co-author of the 2006 Connolly study).
McHugh’s article provides a great overview of the arc of tart cherry research. For example, why is the focus on tart cherries rather than sweet ones? It’s simply a matter of cost and availability: both function similarly, but Montmorency’s Michigan tart cherry industry offers a convenient supply. There are juices, gels, and powders that all seem to work. A typical dose is about 100 fresh cherries per day. And there’s a key misconception that might explain some of the conflicting study results, says McHugh: Cherry juice is more of a “prep drink” than a recovery drink. It takes several days of supplementation to build up your defenses against exercise-induced muscle damage, so go for cherry juice according to Exercise probably won’t help.
This is the idea that caught my attention and eventually inspired me to delve into cherry juice literature. The main component of tart cherries is their anthocyanins, which are responsible for the red, blue, and purple color of cherries, blueberries, grapes, and various other foods. Anthocyanins have both antioxidant and anti-inflammatory properties, which is why they may help the body deal with the powerful oxidative and inflammatory effects of hard exercise.
According to a survey of athletes from 15 countries in 21 sports published last year, 22.6 percent of respondents had used or used cherry juice supplements. I’d be wary of taking that number too literally, because when a group of cherry juice researchers are recruiting subjects “through social media and posters,” you have to ask yourself if the people they reach are perhaps more than likely to have heard of cherry juice. The real reason I mention this study is because one of the 21 sports covered was weaseling, which to my disappointment appears to be more of a quintessentially British cross between bouldering and caving than literal hunting of live weasels.
As I said above, new studies keep coming out. Just this month, one was released by the University of Exeter showing a nice improvement in post-workout strength recovery after seven days of tart cherry concentrate loading. Other studies published this year look at mental fatigue and mood, blood pressure and glycemic control. It’s easy to get excited about the potential benefits, but the overall results remain stubbornly ambiguous. And there are also methodological issues: some studies, for example, require participants to limit their consumption of anthocyanin-rich foods in the days leading up to the experiment. Perhaps a normal balanced diet will provide you with all the anthocyanins you can use and the benefits will only materialize if you create an artificial deficiency.
While the evidence that cherry juice speeds recovery has been crystal clear, there’s a more fundamental question. Anthocyanins fit into a larger research group on antioxidants and exercise that remains highly controversial, a recent review explains. As with cherry juice, there is some suggestive but ambiguous evidence that antioxidants in general can aid in recovery. But there’s a parallel stream of research that suggests antioxidant supplements interfere with the gains you’d normally get from both aerobic and endurance training. The reactive oxygen species that cause oxidative damage also happen to be important signaling molecules that tell the body to adapt and get stronger in response to exercise. Neutralize them with antioxidants and you may feel better tomorrow but be less fit next week or next month.
To be clear, the practical relevance of this research is still debated. One school of thought argues that you should use antioxidants before a big event when recovery is your top priority, but avoid them during heavy training when fitness gains are the primary goal. In theory this sounds like a nice idea, but I don’t think anyone has shown that it leads to better performance in the real world.
The problem with cherry juice research, generously funded by the cherry industry, is that there is little incentive to study the potential for indirect adverse effects. I realize there’s a catch of sorts for supplement companies: if they don’t fund the research, they’re criticized for selling unscientific products; When they fund research, they are criticized for biasing the literature. So for the record, I think it’s great that cherry growers are funding good independent studies, even if the results didn’t convince me.
I’m also a big cherry fan. I always keep a bag in the freezer for granola toppings and smoothies, and I especially like the sour cherries from my neighbor’s tree. I also love and frequently consume other foods high in anthocyanins like blueberries and Saskatoon berries. I find both delicious and healthy. But for me, it’s a big step from consuming a food to consuming a processed extract or concentrate of that food with the goal of enhancing performance. To make that leap, I’d like to see clear and conclusive evidence that you’re winning more than you’re losing – and I’m still waiting for tart cherry juice.
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