Beet juice vs. nitrate supplements

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

The story so far: beet juice improves endurance performance. We’re pretty sure it’s because of the nitrate in beets. But we’re not sure whether you can get the same effects by simply taking nitrate supplements directly.

Enter a study in this month’s Medicine & Science in Sports & Exercise, from researchers  in Spain. They administered either a placebo or a dose of sodium nitrate (10 mg per kg of body weight) to 11 well-trained cyclists and triathletes. Then, three hours later, the athletes did a series of sub-maximal cycling bouts and a progressive VO2max test to exhaustion. The results: well, this is where it gets confusing:

[W]e found that the VO2peak was significantly reduced when athletes ingested nitrate. These in vivo data were found without any changes in cardiorespiratory and performance parameters, which suggests that nitrate and its reaction products could play an important role in oxygen consumption at maximal intensity of exercise in well-trained athletes.

So basically, in the progressive test to exhaustion, the athletes lasted the same amount of time with or without nitrate (416 seconds with nitrate, 409 seconds with placebo, a nonsignificant difference) — but they reached failure while using less oxygen. So the good news is that nitrate did somehow make the cyclists more efficient at converting oxygen into power. But the bad news is that this didn’t improve their performance — they just used less oxygen.

What to make of this? I’m not sure. That’s partly because the paper is fairly confusing, but I think it’s also because researchers simply don’t know what exactly is going on yet! For practical purposes, my conclusion would be that if you’re looking for a boost, stick with real beet juice rather than sodium nitrate for now. There may be other differences between this study and previous successful performance-boosting studies (e.g. in the training of the subjects, their typical dietary habits and usual nitrate levels, etc.) — but until further studies sort this out, the only thing we know for sure is that beet juice, in some circumstances, works.

Asker Jeukendrup on beets, hydration, train low, etc.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Amby Burfoot has an interesting interview with Asker Jeukendrup on his Peak Performance blog. Jeukendrup has long been associated with PowerBar, but apparently moved over to the Gatorade Sports Science Institute as “global senior director” a few months ago.

I’ll be interested to see whether this signals a shift in direction for Gatorade: a couple of years ago, Gatorade relaunched its product line to feature a lot of mumbo-jumbo like “theanine to improve focus” and “B vitamins to help you metabolize energy” and so on. At the same time, it also disbanded its U.S. scientific advisory panel, which was composed of external scientists. One of the advisory scientists I spoke to at the time felt that it signalled an unfortunate change in direction away from high-quality, science-based product claims. Hopefully Jeukendrup’s hiring indicates a renewed commitment to science over marketing.

Anyway, the real point of this post is to recommend that you read the interview. Burfoot takes Jeukendrup through half-a-dozen topics of interest to readers of this blog, from beet juice to training on an empty stomach to whether thirst is a reliable mechanism to determine how much to drink. Somewhat surprising to me was Jeukendrup’s response when Burfoot asked if he could explain why beet juice seems to offer such a boost to endurance:

No I can’t explain them. I don’t know the mechanism that would cause them, and that bothers me. It also bothers the scientist who has done much of the work, Andy Jones, who is very good as you say. But he also can’t figure out why the beet juice is enhancing endurance.

I had thought some of the results from the Karolinska Institute in Sweden were shedding some light on how beet juice works — but then again, the explanation was complicated enough that I had trouble following it. So maybe it’s not as clear-cut as I thought. Still, the results have been repeated multiple times under different conditions, so in a sense the “why” is not essential.

Timing of baking soda loading, and the future of fatigue research

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

I spent three days last week at a conference called “The Future of Fatigue in Exercise,” hosted by Frank Marino and Rob Duffield at Charles Sturt University in Bathurst, Australia. Lots of interesting presentations and discussions, which I’ll be writing about in various forms over the next few months. To start, I thought I’d share a couple of short “practical” tidbits of research-in-progress that were presented at the conference. First: the timing of baking soda loading.

The practice of taking baking soda to buffer acid-base balance in the blood for short-duration exercise has been around for at least 30 years. It’s commonly used by athletes in events lasting around 2:00 (like 800-metre running), and may also help with repeated-sprint ability. Does it work? The research isn’t clear-cut, but most sports scientists believe that it works to some degree. The problem is that it also messes with your stomach, causing diarrhea and other lovely effects that aren’t conducive to great performance. (Random aside: I actually got my “big break” in university when one of my teammates had to bail out of the 4x800m relay team at the conference championships because he’d taken too much baking soda. I was inserted as a last-minute sub and ran a breakthrough race, earning a spot on the team at nationals. But I digress…)

Anyway, Jason Siegler of the University of Western Sydney presented some data looking at the timing of soda loading. Usually athletes take soda about an hour before competition, so that levels of of bicarbonate in the blood peak roughly when you’re competing. This also happens to be when gastrointestinal symptoms peak. What Siegler and his colleagues had noted in previous experiments was that bicarbonate levels actually stay high for several hours, while stomach problems tend to subside after a few hours.

So they ran a test of repeated sprint ability where the subjects took baking soda either 60, 120 or 180 minutes prior. As expected, the levels of bicarbonate in the volunteers’ blood before exercise were essentially identical no matter when they took the baking soda. The incidence and severity of gastrointestinal symptoms peaked about 90 minutes after taking the soda, and returned to normal after 180 minutes. All three groups performed essentially the same in the sprint test.

I should point out that there was no control group, so this study doesn’t tell us anything about whether the intervention works or not. Also, the stomach problems don’t appear to have hurt performance in the actual sprints, despite reaching an average of 5-6 out of 10 of the scales of incidence and severity. Apparently the volunteers managed to grit their teeth, clench their cheeks, and get the job done despite the discomfort. Still, if I was a middle-distance athlete inclined to try my luck with baking soda (and, for the record, I never did try it — in fact, when I was competing in the 1990s it was briefly listed as a “banned technique” by doping authorities, though they obviously couldn’t make baking soda a “banned substance”) — anyway, if I was using it, these results would certainly encourage me to take it ~3:00 before competition to hopefully give my stomach a chance to settle down.

For nitrate boost, stick to beet juice and avoid supplements

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

I’ve blogged a bunch of times this year about the incredible performance-boosting effects of juice; studies showing that it’s the nitrates in beet juice that are responsible; and further studies exploring how nitrate from beets is converted (by bacteria in your mouth) to nitrite, and then to nitric oxide, which is where all the magic happens. This has led to all sorts of questions, like (a) aren’t nitrates, as found in hot dogs and so on, really bad for you?, and (b) can I just take a nitrate supplement instead of drinking all that beet juice that turns the toilet a funny colour?

The answer to the first question is, well, I don’t know — but scientists are definitely rethinking the idea that nitrates are a big villain. Stephan Guyenet had a good blog post that explored some of this change in thinking.

As for the second question, there’s a series of letters to the editor in the current issue of the Journal of Applied Physiology that should make you think twice before considering supplementing. The first is from a group of Swedish researchers who have pioneered some of the research into the health benefits of nitrates. They basically suggest that direct supplementation of nitrate (in the form of nitrate salt) is probably okay (it’s “nontoxic even in higher doses”), because the body can only convert it slowly to nitrite through the help of friendly mouth bacteria. But taking nitrite supplements directly has a toxicity comparable to cyanide — and there’s great potential for confusion, according to the researchers:

A case of unintentional ingestion of nitrite by an athlete was recently reported on a runners’ internet forum. The subject had taken a nitrite salt before exercise in the belief that it was nitrate, and he developed symptoms suggestive of methemoglobinemia.

They also point out that “organic nitrates and nitrites, for example nitroglycerine and amyl nitrite” can be fatal at too high a dose. The bottom line, they say:

In summary, at this time we advise athletes to refrain from the uncontrolled use nitrate and nitrite salts as dietary supplements. While the acute toxicity of nitrate is very low or absent, any confusion leading to a large unintentional intake of nitrite or organic nitrates and nitrites is potentially life threatening. In contrast, with natural sources of nitrate such as whole vegetables or vegetable juices, we do not foresee any acute risks.

There are a couple of letters in response from beet juice researchers, and they’re basically in agreement. To paraphrase very roughly, they basically say “Yes, taking nitrites would be a really dumb thing to to do, so stick with whole fruits and vegetables as a nitrate source.”

Having read all of that, it’s still not entirely clear to me if there’s a problem with taking nitrate salt. However, my confusion on that point is precisely the point, I guess: if nitrites and organic nitrates are potentially very dangerous, it’s best not to mess around if you’re not absolutely sure you’ve got the right stuff. Stick with the beets.

Vitamin D and muscle injuries

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

I’m on the record as a bit of a vitamin D skeptic. Not a total skeptic, mind you — it’s actually the only supplement of any kind that I take on a regular basis these days. But the claims that vitamin D enhances athletic performance have seemed pretty weak to me so far. However, I’ll dutifully pass along this press release from the American Orthopaedic Society for Sports Medicine, which describes some new research linking vitamin D levels with muscle injuries in NFL football players.

The study: 89 players from one NFL team were tested for vitamin D levels in spring 2010, during pre-season. Not surprisingly, the levels were generally low compared to what’s considered desirable (which seems to be true for pretty much every population group in the developed world):

Twenty-seven players had deficient levels (< 20 ng/ML) and an additional 45 had levels consistent with insufficiency (20-31.9 ng/mL). Seventeen players had values within normal limits (>32 ng/mL).

The team then provided data on time missed due to injuries during the season. Sure enough, players who suffered muscle injuries has “significantly lower levels” of vitamin D. How much lower? It’s not clear: this is conference data, so not yet published in a journal, and unfortunately the press release release doesn’t do a very good job of presenting the data. The average level for players with a muscle injury was 19.9, but it doesn’t tell us what the average for uninjured players was.

First thing to wonder: is it this cause or correlation? Do the players with crappy diets also neglect their strength, flexbility and warm-up routine? Second thing: if it is causal, what’s the mechanism? Why does this work?

Leaving that aside, I’ll just reiterate my hair-splitting distinction between a “performance-enhancing” substance and one that hurts performance if you’re deficient in it. Water helps your performance if you’re dehydrated, but we don’t consider it an ergogenic aid. As far as I can tell, vitamin D falls into the same category: something that you shouldn’t be deficient in, whether you’re an athlete or not. But I’m still not convinced that more is better if you’re in a healthy range.