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Posts Tagged ‘supplements’

Does caffeine REALLY help exercise performance?

December 16th, 2011

We all know caffeine helps exercise performance. Long, short, power, endurance, whatever. I wrote a Jockology column on it for the Globe back in 2008; Gretchen Reynolds had a round-up of the latest research in the New York Times a couple of days ago. So what more is there to say?

Well, if you want to get into the nitty-gritty, there’s a really interesting round-table discussion in the current issue of (wait for it) the Journal of Caffeine Research. It’s freely available online, and it’s not a research paper or a study — it just brings together a bunch of the leading researchers and practitioners in this area from around the world (like Terry Graham from the University of Guelph and Greg Cox from the Australian Institute of Sport) and gets them to air their opinions, thoughts, suspicions and doubts about how and in what contexts caffeine really works.

It turns out things are quite a bit more complicated than you might think. For example, Reynolds in the Times writes:

Caffeine has been proven to increase the number of fatty acids circulating in the bloodstream, which enables people to run or pedal longer (since their muscles can absorb and burn that fat for fuel and save the body’s limited stores of carbohydrates until later in the workout).

However, in the roundtable discussion, Graham disagrees with that statement. In fact, he makes a very broad argument:

I would take the controversial position that the ergogenic effect is not because of an alteration in either blood flow or alteration in delivery of blood-borne metabolites (fuels).

Instead, he believes the evidence points to effects in the muscle itself enhancing contractions, which would explain why it seems to work for virtually every sport. And the others appear to agree.

Interestingly, the editor-in-chief of the journal, Jack James of the National University of Ireland, proposes a totally contrary position. What if the supposed “ergogenic” effects of caffeine are really just due to the fact that, in virtually every study of caffeine, the subjects come to the lab in a state of withdrawal from not having had their usual morning dose? That, apparently, is what the evidence now suggests in studies of caffeine’s mental effects:

What we are talking about here arises from the fact that almost the entire population is exposed to caffeine on a regular basis, and studies show that decrements in psychomotor performance and mood are detectable after as little as 6–8 hours after caffeine was last ingested. Standard double-blind trials involve a brief pre-test period of caffeine abstinence, typically involving overnight abstinence to coincide with usual caffeine consumption patterns. By morning, participants are in the early stages of withdrawal and are experiencing negative withdrawal effects on cognitive performance and mood. When caffeine is then re-ingested under laboratory conditions, participants typically show improvements in performance and mood. However, studies that have controlled for withdrawal effects have repeatedly shown that the observed improvements are due to the reversal of withdrawal effects. That is, for cognitive performance, there is  little or no genuine net effect of caffeine over and above reversal of the negative effects caused by caffeine withdrawal. As such, can we be satisfied that this source of confounding has been adequately controlled in studies of physical performance?

It’s an interesting question. There are lots of other interesting nuggets in the discussion, on topics like dosage, responders vs. non-responders, whether habitually consuming caffeine reduces its ergogenic effects (Graham says no), and so on. In all cases, what you realize is that the literature is far less clear than we might have thought. The book on caffeine isn’t quite closed yet after all.

Antioxidants are more complicated than we thought

December 10th, 2011

I wrote last month about emerging evidence that taking antioxidant supplements may actually be counterproductive, especially for athletes. There’s an interesting paper coming up in Cell Metabolism that casts further doubt on the whole basis of our belief that (a) oxidative stress is what causes aging and other cellular damage, and (b) antioxidants can counteract these effects (press release here; abstract here).

What’s new about the study is that they didn’t use the typical indirect methods to guess about levels of reactive oxygen species (ROS – the bad guys) and antioxidants, averaged over the entire body. Using transgenic fruit flies, they were able to measure ROS activity directly and in real time, in different parts of the body. There are a whole bunch of surprising results in this study that fly in the face of the conventional antioxidant theory. A few of the key ones:

  • If oxidation is linked to aging, we’d expect to see more ROS as the flies get older. In fact, ROS levels stay constant throughout the aging process except in the intestine. Only the intestine shows gradually increasing levels of oxidation.
  • Even in the intestine, the flies who lived longest had ROS levels that increased more quickly than the flies who died earliest — exactly the opposite of what we’d expect if oxidative stress is linked to aging and eventual death.
  • When the flies were fed an antioxidant, their production of ROS increased in response.

This last point, of course, is most interesting from the perspective of supplementation. It suggests that there’s a homeostatic response that attempts to preserve the balance between oxidants and antioxidants at a roughly constant level. So if you take a lot of antioxidants, your body simply ramps up its level of oxidants in response — with who knows what effect!

Let me emphasize: this is a study of fruit flies. Fruit flies are not humans. Still, the results suggest that our basic understanding of the real-time dynamics of oxidant-antioxidant interactions is far from complete. Now, I’d happily ignore all this cell biology stuff if there were lots of controlled trials showing increased health or performance from antioxidants. If it works, who cares about the mechanism? But since (a) we have no consistent evidence that antioxidants work, and (b) it’s increasingly clear that we don’t even understand how or why they should work, or what supposed problem they’re supposed to fix, I still think a balanced diet with lots of brightly coloured fruits and veggies in the way to go. Not powders, and not pills.

The case against antioxidant vitamin supplements

November 17th, 2011

The December issue of Sports Medicine has an enormous, detailed review of research on the effect of antioxidant (i.e. vitamin C, vitamin E, coenzymeQ10, etc.) supplements on training. To most people, this seems like a no-brainer: what could be smarter than popping a multivitamin as “insurance” in case your diet isn’t giving you all the vitamins you need? But (as I’ve blogged about before) there’s an emerging school of thought arguing that taking antioxidants can actually block some of the gains you’d otherwise get from training. Here’s how I explained the debate back in April:

The traditional theory goes like this: strenuous exercise produces “reactive oxygen species” (ROS), which cause damage to cells and DNA in the body. Taking antioxidant supplements like vitamins C and E helps to neutralize the ROS, allowing the body to recover more quickly from workouts.

The new theory, in contrast, goes like this: strenuous exercise produces ROS, which signal to the body that it needs to adapt to this new training stress by becoming stronger and more efficient. Taking antioxidant supplements neutralizes the ROS, which means the body doesn’t receive the same signals telling it to adapt, so you make smaller gains in strength and endurance from your training.

The new paper comes down firmly on the side of the latter view:

The aim of this review is to present and discuss 23 studies that have shown that antioxidant supplementation interferes with exercise training-induced adaptations. The main findings of these studies are that, in certain situations, loading the cell with high doses of antioxidants leads to a blunting of the positive effects of exercise training and interferes with important [reactive oxygen species]-mediated physiological processes, such as vasodilation and insulin signalling.

So is this definitive? Far from it. As the review notes, there have been a few studies that found beneficial effects of antioxidant supplements on exercise performance, tons that have found no effect, and a few (23, to be exact) that have found negative effects. What most of the studies have in common:

As commonly found in sports nutrition research, the vast majority do not adhere to all the accepted features of a high-quality trial (e.g. placebo-controlled, double-blind, randomized design with an intent-to-treat analysis). Indeed, most studies fail to provide sufficient detail regarding inclusion and exclusion criteria, justification of sample size, adverse events, data gathering and reporting, randomization, allocation and concealment methods, and an assessment of blinding success. The poor quality of the majority of studies in this field increases the possibility for bias and needs to be always considered when evaluating the findings.

This is a really important point to bear in mind, and not just when it comes to sports nutrition. Whatever the supplement, training method, or piece of equipment you’re talking about, there’s nearly always a crappy, poorly executed study that seems to “prove” that it works. So where does that leave us? On this topic, I’m in agreement with the authors:

We recommend that an adequate intake of vitamins and minerals through a varied and balanced diet remains the best approach to maintain the optimal antioxidant status in exercising individuals.

Beliefs vs. science for vitamin supplements

October 17th, 2011

Marion Nestle has an interesting blog post about the two most recent studies that fail to find benefits from taking vitamin supplements. (One study followed 38,772 women for 22 years, and found that those taking multivitamins or certain single vitamins were slightly more likely to die than those not taking any supplements; the other was a placebo-controlled trial of 35,533 men, which found that taking 400 IU per day of vitamin E increased the risk of prostate cancer during a 12-year follow-up.)

The reason I’m posting this isn’t that I think vitamins will kill you — the effects were small, and for the most part I think supplements tend to do nothing, rather than have big effects either way. Personally, I suspect that the most negative effect of vitamin supplements is the feeling of false healthiness they provide, which then allows you to justify making other, less healthy choices throughout the day.

Anyway, what I found most interesting in Nestle’s post was her explanation of two very different ways of looking at research into nutritional supplements — both of which rely on a collection of “true” statements, but reach opposite conclusions:

For example, on the need for supplements, a belief-based approach rests on:

  • Diets do not always follow dietary recommendations.
  • Foods grown on depleted soils lack essential nutrients.
  • Pollution and stressful living conditions increase nutrient requirements.
  • Cooking destroys essential nutrients.
  • Nutrient-related physiological functions decline with age.

A science-based approach considers:

  • Food is sufficient to meet nutrient needs.
  • Foods provide nutrients and other valuable substances not present in supplements.
  • People who take supplements are better educated and wealthier: they are healthier whether or not they take supplements.

I’m not sure I quite agree with her labels (“belief-based” and “science-based”), but I definitely see these patterns of thinking in discussions of pretty much all areas of health and exercise research. The first set of statements makes a strong case that it’s plausible that supplements could improve health — but it leaves out the final step, which is to show that they do improve health. Similarly, the second set of statements explains why we shouldn’t be surprised if supplements don’t improve health, but doesn’t prove it. So to me, neither of these two approaches is satisfying — because the debate should be settled empirically.

Of course, research is complicated, and in many health debates it’s difficult to agree on what constitutes empirical evidence. That’s less and less true in the case of vitamin supplements, though. Study after study fails to find any benefits, so the hypotheses of the “belief-based” approach seem emptier and emptier to me.

Beet juice: practical tips from elite marathoners

October 7th, 2011

Yesterday, I participated in a live chat previewing next weekend’s Scotiabank Toronto Waterfront Marathon. Among the participants were elite marathoners Reid Coolsaet, Dylan Wykes and Brandon Laan, who answered lots of questions about diet, warm-up, tapering and things like that. The most interesting nugget for me was some practical info about how to use beet juice: while I’ve blogged numerous times about the studies showing that beet juice provides a significant endurance boost, lab studies are very different from on-the-ground experience.

The most recent lab study used 500 mL of beet juice 2.5 hours before a time trial. But here’s what Reid had to say:

ReidCoolsaet: 500ml the day before. Anything the morning of upsets the stomach too much.
And Dylan followed up with:
DylanW: Trent Stellingwerf has a protocol for 500ml in the 3 days before and 250ml morning of.
Interestingly, Trent (who recently took a position as Senior Physiologist with the Canadian Sport Centre in Victoria) also works with Reid — which drives home the message that dosing is individual. You’ve got to figure out what your digestive system can handle. And it’s best to do that in practice, not races!

Beet juice vs. nitrate supplements

October 3rd, 2011

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.

September 26th, 2011

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

August 28th, 2011

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

August 20th, 2011

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

July 15th, 2011

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.