Neglected Evidence About Beetroot

The International Olympic Committee recognized beetroot as a potent performance booster, among other nitrate supplements. Everybody else claims beetroot is “powerful” stuff to take before exercise. Is it? Zheln collected and appraised current research and found no ground for such optimism, even though there are data from dozens of trials that might come useful in specific contexts. Watch popular internet claims smash against evidence in this Zheln Thread.

A video report about the Making Of this post is available from Write in Stone, a research transparency platform. Also, be sure to check Publication Notes to learn more about the Zheln process.

How to Cite This Post?

Effects of Beetroot Supplements on Muscular Performance

Lots of Studies to Digest on Beetroot, (Not So) Surprisingly

So, a Zheln search located this systematic review on the effects of beetroot, first published online back in May 2023. It seemed fascinating that somebody conducted a scientific investigation centered on beetroot ingestion. However, that review only focused on muscular strength and endurance and only on healthy males, which seemed too restrictive, so I looked up more and broader reviews that focused on muscular and sports performance, exclusive of the effects beetroot has on blood pressure. Perhaps surprisingly, but whenever a new systematic review is published, it is usually the case that it is not the first one, so it is always good practice to lurk more.

I also wanted to focus only on those reviews that looked at randomized trials because the effects of beetroot ingestion is a pretty interventional research question, meaning that an experiment can be conducted where a group of people is divided randomly into two, with one group taking actual beetroot juice or supplements and the other one taking a placebo, and nobody knows what the heck they are taking, including any health care staff on-site. That’s a study design called a double-masked placebo-controlled randomized trial, and it’s basically the only study design that has a chance of looking remotely convincing to scientists about causality. And, it’s a commonly used study design in health research actually, so the odds of identifying such studies are pretty good.

Instead of looking up individual studies ourselves, Zheln’s strategy is to make use of systematic reviews of studies already available out there. A systematic review is a sophisticated version of your regular “top 5 smartphones” or “best 10 action movies” kind of study, with a research study of a particular type as their focus of interest and a streak of comprehensiveness in them, instead of selecting the “top” or “best,” but the quality of the included studies is also considered. I used Epistemonikos to look up systematic reviews on beetroot. And, as a pretty illustrative case, 25 reviews mentioning “beetroot” were found, in addition to the one from May 2023.

I reviewed all of these, and 2 additional systematic reviews were worthy of further discussion. One review looked at and did not find any effects of ingesting beetroot or nitrates (yeah, that’s what beetroot is rich in) on body weight, fat mass, and some other body indicators. Based on the quality of the included studies, the review authors had low to moderate certainty in this conclusion (i.e., no effects found), which means more and better research could potentially challenge it in the future. The authors of the other review found some evidence of a small positive impact of beetroot/ nitrate supplementation on muscle recovery 2 to 3 days post-exercise but were not very certain in this conclusion, due to multiple concerns about the quality of the research they examined. Finally, let’s look at that biased review that only considered young healthy males: here they found a small positive influence of beetroot on muscular strength and endurance, and also seemed pretty certain of this finding.

International Olympic Committee (Almost) Got It Right

In 2018, the International Olympic Committee listed beetroot under “Supplements with good to strong evidence of achieving benefits to performance when used in specific scenarios,” as a food rich in nitrates. Under “Performance impact,” they referenced 5 randomized trials and 1 additional systematic review. In summary, they did find some evidence of some small impacts on performance. Comparing their wording to what we saw above, I would say that their wording is close to accuracy, except that they trusted the evidence too much, not taking study quality issues into account (as also is clear from the “hierarchy of evidence” they presented), so their “good to strong evidence […] in specific scenarios” is in fact “good evidence […] in specific scenarios” at best.

It’s worth noting that the trials under consideration in all those papers spanned a huge variety of settings, such as different sports and performance metrics, and different timelines. They were usually very small, only a dozen participants or so, which makes them hardly generalizable to an average folk. Many of the trials also employed crossover between groups, which is a delicate technique that necessitates applying sophisticated analysis methods, which some researchers eventually fail to apply.

Examining Top Google Hits on Beetroot: Good Evidence Is Not There

Now that we are aware of the status quo of evidence about beetroot, let’s look at what the internet has to say about it. The fun start is that one of the top hits on Google’s “beetroot + gym” is actually a systematic review, but it did not limit inclusion to randomized trials and did not perform quality and certainty of evidence assessment, so shame on Google’s algorithms.

Several other top hits from Google are very interesting and controversial:

• A blog and shop Vivo Life from January 2023 advertised beetroot supplements as a “powerful supplement that can benefit athletes and fitness enthusiasts.” It goes on to mention one systematic review (without including a complete reference, though, so I had to guess), and it’s very cool because this is the first time I see this review, despite my efforts above (which just highlights how much there can be out there even on mere beetroot).

  Upon examination, this review has a pretty controversial methodology, but it’s still interesting that they found slightly improved peak muscle power after beetroot supplementation. However, “an average of 5%” power increase, as cited by Vivo Life, is not substantiated by the review authors: “an ES [effect size] of this magnitude [Hedge’s G of 0.3, see an explanation here]–which equates to a ~ 5% increase in maximal muscle power–is likely to be of considerable athletic and clinical significance, as previously discussed,” they write. However, this statement is purely speculative, and one of the papers they cite to support it presented a 4% increase in the setting of a large effect size anyway, not a small one that we have here, and for one particular muscle only, not for “muscle power” in general. Also, the review authors failed to account for the quality of the included studies appropriately, which led to unwarranted certainty in the conclusion.

  Vivo Life authors referenced just two other sources of evidence to support their claim, both subpar reviews (one; two). What I am trying to say is that Vivo Life’s vigorous enthusiasm about beetroot supplements is not supported by solid scientific evidence.

• A 2017 article on Delish, another top hit for “beetroot + gym” on Google, claims that beetroot will “dramatically boost your workout” (“True story: this food’s hard to beat,” goes the subtitle). They only reference that top-hit, subpar review we already looked at, as well as several non-academic sources, so the claims are, clearly, pretty far from okay.
• A 2015 article on the U.S. National Public Radio (NPR) website suggested “dramatic power boosts to be gained from beet juice,” drawing extensively on only 3 trials (one; two; three). We have already discussed at length why relying on three trials only is completely inappropriate in this case.
• “Verywell Fit articles are reviewed by board-certified physicians and nutrition and exercise healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates.” A Verywell Fit article, last updated in July 2023, covered a multitude of purported beetroot effects, so this largely falls outside of this post’s coverage, but the athletic performance section only referenced the aforementioned top-hit, subpar review and 1 trial – clearly, a poor selection of research.
• I was running out of time, so only had a brief look at Washington Post’s 2019 coverage of the beetroot problem, and the sources covered did not seem to coincide much with those that we covered above. But, this was 2019, so please let me know if you reviewed in more detail and think Washington Post did a great job there.

ChatGPT Is Optimistic About Beetroot, But Not Based on Evidence

Zheln:

is beetroot good before exercise?

ChatGPT:

Yes, beetroot can be a beneficial food to consume before exercise. Beetroot is rich in nitrates, which the body can convert into nitric oxide. Nitric oxide helps to relax blood vessels, improve blood flow, and increase oxygen delivery to muscles. This can potentially enhance exercise performance, especially during endurance activities.

Beetroot juice or whole beets are commonly used for this purpose. Some studies suggest that consuming beetroot about 2-3 hours before exercise may be optimal for maximizing the nitric oxide benefits. However, individual responses can vary, so it's a good idea to experiment with timing and amounts to see what works best for you.

It's essential to be aware that beetroot can also have a mild laxative effect in some individuals, so it's a good idea to try it in a controlled manner before a workout to see how your body responds.

Always consider your personal preferences, tolerances, and any potential interactions with other foods or medications you may be taking. If you have specific health concerns or conditions, it's advisable to consult with a healthcare professional or a nutritionist before making significant changes to your diet.

Written in Stone

Publication Notes

• The initial draft of this post was written by Claude 2 AI was completely rewritten before publication. In the interest of transparency, a full changelog is available.
• The opening summary was generated by prompting ChatGPT 3.5 to “write an engaging one-sentence description for this post,” then asking it for “less drama,” and tweaking the end result a bit.
• The image for this post was generated with DALL·E 3 via Microsoft Bing Image Creator Preview by copying and pasting the post description as a prompt. Four images will be generated, of which the most suitable was selected manually.
• Please refer to the video report for the methodology behind the research underpinning this post. The original Zheln methodology is available as a preprint.
• This publication is a piece of volunteer research and journalism. To express support, you can donate or reach out.

Citation

Zhelnov P. Neglected Evidence About Beetroot. Zheln. 2023 Dec 28;51(1):t4e3. URI: https://zheln.com/thread/2023/12/28/1/

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