Sweat Science

Andrew Jones, the man behind the beet juice fad of 2009, has more performance-enhancing revelations in a study just released online in the Journal of Applied Physiology. He found that taking the supplement L-arginine produced very similar effects to beet juice: by reducing the “oxygen cost of exercise,” it allowed subjects to last 20% longer in a ~10-minute cycle to exhaustion (11:47 versus 9:22 for controls) in a placebo-controlled double-blind trial. They estimate that’s equivalent to a boost of 1-2% in a fixed-distance race. (Abstract here, press release here.)

What’s significant here is that L-arginine acts in basically the same way as beet juice. Beet juice contains nitrate, which the body converts to nitric oxide, which has a number of effects such as dilating blood vessels and lowering blood pressure, ultimately allowing the body to perform more work from the same amount of oxygen. L-arginine is also converted by an enzyme to nitric oxide, producing the same cascade of effects — and, as the researchers note, the performance boosts observed in the two studies are very similar, giving them confidence that they really do understand what’s happening inside the body.

This is by no means the first L-arginine study — there have been a number of attempts to use it for performance enhancement, with conflicting results. Previous studies have generally given the supplement on a chronic basis — a little bit each day, or even several times a day. In this case, the researchers opted for one big dose, taken an hour before exercise, to make sure that nitric oxide availability really was elevated during the exercise bout. (They used 500mL of a drink called Ark 1, containing 6 g of L-arginine. There are no disclosures in the paper about who paid for the study.) This change may explain why they saw such a clear result compared to earlier studies.

So what’s next? According to the press release, “the researchers are hoping to find out whether combining the two methods could bring an even greater improvement in athletic performance.” In the meantime, perhaps L-arginine will prove to be a more user-friendly option than beet juice. Here’s what Amby Burfoot reported about one world-record-holder’s abortive try:

Two days before the ING New York City Marathon, I asked Paula Radcliffe if she actually drank beet juice. This moved her to stage one: silly giggles. And an embarrassing response. “I tried it once,” she said, “but most of it came out the other end.

supplements

The more we study antioxidants, the more it looks like — despite the hype — popping big doses of vitamin C and so on doesn’t do much to help your muscles recover from strenuous exercise. In fact, some researchers now suggest popping antioxidants might actually hurt your recovery.

On the other hand, no one doubts that eating lots of fruit and vegetables is just about the best thing you can do, nutritionally speaking. So how about taking a supplement that is, essentially, concentrated fruit and vegetable, like Juice Plus+, which is “whole food based nutrition, including juice powder concentrates from 17 different fruits, vegetables and grains“? That’s what researchers from the University of North Carolina Greensboro decided to test, in a study now appearing online in Medicine & Science in Sports & Exercise (funded, needless to say, by the makers of Juice Plus+).

The 41 volunteers in the study took Juice Plus+ (or a placebo) for four weeks  prior to an intense, muscle-damaging workout. They continued taking it for another four days after, while various measures of antioxidant status, muscle soreness, strength, and range of motion were recorded at intervals. The conclusion:

This study reports that 4 weeks of pretreatment with [Juice Plus+] can attenuate blood oxidative stress markers induced by [eccentric exercise] but had no significant impact on the functional changes related to pain and muscle damage.

So what does this tell us? Yes, fruit and vegetable concentrates supply antioxidants (along with, presumably, other interesting ingredients). These substances may have some health benefits — though whether the benefits are greater or less than taking pure vitamins, we don’t know. But, as far as exercise and recovery goes, antioxidants don’t seem to have anything to do with it.

So for now, my feeling is: why take a powder that might have some benefits when you can take the actual fruits and vegetables that definitely have benefits, and taste better anyway? That being said, I’ll give some credit to Juice Plus+. I’m sure they didn’t get the results they were hoping for, but at least they’re making the effort to fund independent studies — which is a lot more than can be said for most of the products on health-food store shelves!

supplements

Jane Brody has a piece in today’s New York Times on vitamin D needs — nothing particularly new, but summing up the trend of the last few years to believe that insufficient vitamin D in modern sun-phobic societies is behind a whole range of chronic diseases, and noting that current recommended intakes are far below the levels some experts believe are necessary:

The current recommended intake of vitamin D, established by the Institute of Medicine, is 200 I.U. a day from birth to age 50 (including pregnant women); 400 for adults aged 50 to 70; and 600 for those older than 70. While a revision upward of these amounts is in the works, most experts expect it will err on the low side. Dr. Holick, among others, recommends a daily supplement of 1,000 to 2,000 units for all sun-deprived individuals, pregnant and lactating women, and adults older than 50.

With that in mind, it’s worth pointing out the press release from Osteoporosis Canada that I noticed last week, announcing a revision of their recommended vitamin D intake:

The new guidelines recommend daily supplements of 400 to 1000 IU for adults under age 50 without osteoporosis or conditions affecting vitamin D absorption. For adults over 50, supplements of between 800 and 2000 IU are recommended. For people who need added supplementation to reach optimal vitamin D levels, doses up to the current “tolerable upper intake level” (2000 IU) are safely taken without medical supervision.

I’m still a little gun-shy about the very broad claims made by vitamin D advocates, but the evidence is strong enough that D is the only supplement I’ve taken (albeit sporadically) over the past few years. The bottle I have right now is 400 IU per pill — maybe I need to ramp that up, or at least take it every day during the winter.

supplements

Reuters is reporting on a newly published article in Neuropsychopharmacology (a pretty cool journal name, I must say) about habitual caffeine use:

Bristol University researchers found that drinkers develop a tolerance to both the anxiety-producing and the stimulating effects of caffeine, meaning that it only brings them back to baseline levels of alertness, not above them.

“Although frequent consumers feel alerted by caffeine, especially by their morning tea, coffee, or other caffeine-containing drink, evidence suggests that this is actually merely the reversal of the fatiguing effects of acute caffeine withdrawal,” wrote the scientists, led by Peter Rogers of Bristol’s department of experimental psychology. [The study is described in more detail here.]

This caught my attention (a) because I don’t drink coffee and I enjoy making fun of my wife’s addiction, and (b) because I’ve seen conflicting information about whether habitual coffee drinkers get less of a boost from each cup. I spoke to Terry Graham from the University of Guelph, one of the world’s top experts on the effects of caffeine, for this article back in 2008. He said that, as far as sports performance goes, habituation isn’t a problem:

Surprisingly, the same performance boost from caffeine is seen in regular coffee drinkers and in complete abstainers. We do habituate to some of caffeine’s effects, such as elevated pulse and blood pressure, but apparently not to its performance-enhancing effects.

That finding was backed up by another study last year on the effect of caffeine on pain perception during intense 30-minute cycling sessions, by Robert Motl of the University of Illinois:

“What’s interesting,” Motl said, “is that when we found that caffeine tolerance doesn’t matter, we were perplexed at first. Then we looked at reviews of the literature relative to caffeine and tolerance effects across a variety of other stimuli. Sometimes you see them, sometimes you don’t. That is, sometimes regular caffeine use is associated with a smaller response, whereas, other times, it’s not.”

No one’s been able to figure out the reason for the inconsistency, Motl said.

“Clearly, if you regularly consume caffeine, you have to have more to have that bigger, mental-energy effect. But the tolerance effect is not ubiquitous across all stimuli. Even brain metabolism doesn’t show this tolerance-type effect. That is, with individuals who are habitual users versus non-habitual users, if you give them caffeine and do brain imaging, the activation is identical. It’s really interesting why some processes show tolerance and others don’t.”

Regarding the outcome of the current research, he said, “it may just be that pain during exercise doesn’t show tolerance effects to caffeine.”

So it seems that for enhancing sport performance, it doesn’t really matter whether you use caffeine regularly. But that boost you get every morning — well, that’s not really a boost, it’s just a return to normal.

supplements

I’ve spent quite a bit of time reading the research on supplements over the past few years — and frankly, the more I read, the less inclined I am to use any. But there is one supplement I’m taking right now (having started a few months ago), and that’s vitamin D. I’ve heard enough enthusiasm from researchers I trust, and seen enough suggestive results, to decide that it’s worth a try — especially during the depths of a Canadian winter.

So why should I expect vitamin D to turn out any differently from all the other “miracle vitamins” that have preceded it and then been debunked? That’s the question that Tara Parker-Pope tackles in this entry on her Well blog. Her main point:

Although numerous studies have been promising, there are scant data from randomized clinical trials. Little is known about what the ideal level of vitamin D really is, whether raising it can improve health, and what potential side effects are caused by high doses.

And since most of the data on vitamin D comes from observational research, it may be that high doses of the nutrient don’t really make people healthier, but that healthy people simply do the sorts of things that happen to raise vitamin D.

Obviously, we need to figure these things out — which is where a new study comes in. The VITAL study is currently enrolling 20,000 older adults to take part in a five-year, placebo-controlled trial of vitamin D and omega-3 fatty acids. They’re looking for people all over the U.S. (no clinic visits are required, and all the pills will be mailed). If you’re interested, the details are here.

For now, I’ll keep taking vitamin D. But it’s worth remembering where the current research stands — and that many previous “miracle vitamins” have failed to pass the hurdle represented by the VITAL study.

supplements

To the scientist in me, this is a really interesting study. But to the athlete and fan in me, it seems like bad news. British researchers fed highly trained cyclists acetominophen (Tylenol, as it’s known around here) before a 10-mile time trial. It was a double-blind, placebo-controlled trial. The riders who were fed Tylenol cycled about 2% faster, and had higher heart rate and lactate production (i.e. they were working harder) — but their perceived exertion was identical to the placebo group’s.

To read more about the study and its implications, read this entry in Amby Burfoot’s Peak Performance blog, which includes a Q&A with one of the researchers. The basic interpretation is simple: Tylenol blocks pain, and pain is what makes us slow down during long races. This is an important scientific result, because it sheds light on a red-hot debate about the nature and origins of fatigue. The authors of the study view their results as supporting the “central governor” theory, which argues that our brain subconsciously makes sure that we never let our body get too close to its absolute limits.

This, of course, is not the main message that many athletes will take from the study. A 2% performance boost is nothing to sneeze at for the well-trained athlete, so I expect that many athletes will start experimenting with Tylenol in training and racing. Is this dangerous? I don’t really know. (Gretchen Reynolds wrote an interesting article last summer about the risks athletes incur by overuse of NSAIDs like ibuprofen; Tylenol is a different class of drug.) But I have to admit: whenever I see a study of a potentially performance-enhancing pill, I cheer when the results come up negative, because (in my view) it keeps the sport a little simpler.

cycling, supplements

Last fall, an excellent University of Georgia study failed to confirm the endurance-boosting effects of the supplement quercetin that earlier mouse studies had suggested. Now there’s a new study on quercetin from David Nieman’s highly respected lab at Appalachian State University, in the February issue of Medicine & Science in Sports & Exercise — and the news is mixed.

Reading the abstract, you might conclude the double-blinded crossover study was a success: they found “a small but significant improvement in 12-minute treadmill time trial performance” after two weeks of 1,000 mg of quercetin a day. Quercetin is a flavonoid that is thought to enhance the growth of new mitochondria, which is the most significant adaptation resulting from endurance training. So they also performed muscle biopsies, but these didn’t show a significant effect (though there were “insignificant increases”).

When you read the study closely, even the treadmill improvement is a disappointing result. An earlier study from the same lab had failed to find any improvement for well-trained cyclists in 5-, 10-, and 20-km time trials. So they hypothesized that the benefits of quercetin wouldn’t show up for well-trained athletes, who already have a high density of mitochondria. This study specifically enrolled sedentary young adults: the maximal exercise level permitted was 20 minutes, twice a week.

In other words, these were subjects ripe for LARGE improvements. What they found was an improvement of 2.9% in treadmill distance, while the placebo group actually got 1.1% worse. It is statistically significant (barely: P=0.038), but it’s hard to argue that it’s practically significant. For people this sedentary, an occasional walk around the block would have done more. An improvement of a percent of two is only really significant for elite athletes — precisely who this study wasn’t aimed at.

The authors acknowledge that the effect is far smaller than that seen in mouse studies, and they conclude that further research is needed with higher doses and longer study periods. This sounds like a good idea — but until those studies come in, the logical assumption is that quercetin doesn’t offer any practical benefit for people of any fitness level.

supplements

The idea that popping antioxidant supplements doesn’t help — and may even counteract — some of the benefits of exercise and training is something I’ve written about several times, most recently here. So I’m duty-bound to point out the latest study, due in a future issue of Medicine & Science in Sports & Exercise (abstract available here).

The gist: 12 weeks of strenuous, supervised bicycle training, five days a week. Supplement with vitamins C and E or placebo, double-blinded. A whole bunch of physiological parameters were measured as outcomes (maximal oxygen consumption, maximal power output, workload at lactate threshold, glycogen concentration, citrate synthase, [beta]-hydroxyacyl-CoA dehydrogenase activity, if you’re interested in the details). The result:

[T]here were no differences between the two groups with regard to any of the physiological and metabolic variables measured… Our results suggest that administration of vitamins C and E to individuals with no prior vitamin deficiencies has no effect on physical adaptations to strenuous endurance training.

Of course, there are many other purported benefits to these vitamins, such as on immune function. But chalk this up as another data point in an ongoing story.

supplements

I’ve written a bunch about supplements recently, but bear with me for one more quick post. The American Dietetic Association just released its new position stand on “nutrient supplementation.” (The full text is available here.) A few interesting nuggets in there — for one, they note that supplement sales in the U.S. totalled an astounding $23.7 billion in 2007. About half of Americans take dietary supplements, and in particular about a third take a multivitamin/mineral (MVM). However you slice it, that’s a lot of money.

The basic gist of the position stand is as follows:

It is the position of the American Dietetic Association that the best nutrition-based strategy for promoting optimal health and reducing the risk of
chronic disease is to wisely choose a wide variety of nutrient-rich foods. Additional nutrients from supplements can help some people meet their nutrition needs as specified by science-based nutrition standards such as the Dietary Reference Intakes.

Pretty basic stuff. As you read further, it gets a little more forceful:

Although MVM supplementation can be effective in helping meet recommended levels of some nutrients, evidence has not proven them to be effective
in preventing chronic disease. A study published in 2009 from the Women’s Health Initiative found no association between MVM supplementation and cancer or cardiovascular disease risk or total mortality in postmenopausal women…

They then do a pretty good job of summing up the evidence for and against various health claims, like vitamin B-12 and cognitive function, vitamin D and bone health and so on. If you’re taking vitamins, it’s worth a look to see what they have to say about the benefits you’re looking for (though it’s a far from comprehensive list).

The bottom line for me (as I ranted in a recent comment) is that supplements offer many people a false sense of security with, in many cases, very little evidence to back them up. Eating enough fruits and vegetables is a real challenge — one that I certainly struggle with, especially at this time of year — but I’m not sure it’s helpful to convince ourselves that coming up short doesn’t matter because we’re taking some pills that will compensate.

nutrition, supplements

This week’s Jockology column delves into the highly controversial body of research on antioxidants and exercise:

The question

How do antioxidants affect my workout?

The answer

Sales of orange juice are soaring as people seek flu protection from vitamin C, The Globe and Mail reported last month.

Old habits die hard, and our faith in the power of antioxidants is deeply entrenched. Over the past few years, a vast series of studies involving hundreds of thousands of subjects have failed to find any health benefits from antioxidant supplements.

Now, a handful of studies suggest that popping these pills may even block some of the benefits of exercise, and even slow down post-workout muscle recovery. [read on...]

Not to spoil the ending, but to me this research is yet another reason to focus on meeting nutritional needs by eating good foods (in this case, fruits and vegetables) rather than by swallowing pills.

nutrition, recovery, supplements