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Toolbox: Sports Drinks – Who Needs What?
One of the things that La Vuelta is known for, besides it’s red-hot racing, is the red-hot thermometer from the heat of summertime Spain. With that comes the need to hydrate. Or does it? Let’s try to bring some rationale perspective to the whole idea of proper fluid replacement.

It is about 40 years since Gatorade first came onto the scene. Since then, it and other sports drinks have become seen as essential by everyone from top athletes to Joe Q Public. We’ve seen this in every youth sport from youth soccer to my boys in gymnastics, not to mention folks exercising in the gym for 30 min and to the general public as an everyday drink. At the same time, walk down any supermarket and you’ll see a long aisle of dozens of choices in sports drinks.

Investigative Journalism
How much of this change is from sports drinks fulfilling an actual need, versus how much does this popularity stems from clever marketing and fulfilling a corporate need? This July, the very respected medical British Medical Journal published an investigative expose on the science and marketing behind the sports drink industry, slamming the science and the marketing. (1)

The article, in brief, is VERY damning to the sports drink industry, claiming that corporate concerns have artificially created an unnecessary market. In the process, the article claims that many of the scientists (including my post-doctoral supervisor and other respected scientists I know well) are hopelessly mired in conflicts of interest positions. Another major claim is that “dehydration” has been artificially promoted as a disease, with sports drinks as the therapeutic drug of choice. Finally, the study claims to take a critical look at hydration research and finding it severely lacking in scientific rigour.

For the Prosecution
This is a pretty long list of charges. Let’s look at each in a bit more detail the specific charges from BMJ:

1. Many of the scientists involved in hydration research are either directly funded by sports drink companies, or else their institutions (e.g. US military) are major customers for sports drinks. This may be OK, in and of itself, if these conflicts are noted and declared.

2. What BMJ took issues with was that many of these same scientists are the same ones writing public policy concerning hydration and the use of sports drinks. For example, many of the scientists mentioned above were the co-authors of the American College of Sports Medicine’s position statement on fluid replacement during exercise (both the 1996 and updated 2007 documents). (2)

3. The ACSM, the pre-eminent exercise physiology society internationally, has among its major sponsors Glaxo-Smith Kline (Lucozade), Coca-Cola (Powerade) and PepsiCo (Gatorade).

4. The scientific message promoted by ACSM is largely that thirst is not a reliable indicator of thirst, and therefore individuals must pre-empt thirst and instead drink as much as possible to prevent any dehydration from occurring.

5. Other scientific evidence, namely that thirst can indeed be an accurate measure for the need to drink, exists. In recent years, this has been spearheaded by Professor Tim Noakes, a physiologist from South Africa. This research is claimed to have largely been ignored by ACSM and other policy makers.

6. Hyponatremia (low blood salt concentrations), which can occur from drinking too much water, is a bigger physiological and clinical danger than mild to moderate dehydration.

7. Apart from the necessity for hydration, a separate issue is that the ideal fluid replacement has been changed from water to a specific sports drink, as it’s harder to sell bottled water than a sports drink.

8. Much of the marketing for sports drinks is directly targeted at children and the general public, rather than heavy exercisers. This is claimed to stem from the need to develop a larger market beyond just the relatively limited target of heavy exercisers.

9. In reviewing hydration research, the report claims that much of the existing literature is of low quality, with inadequate sample sizes, inappropriate performance tests, and many other research design and statistical issues.

My Interpretation
The above is my paraphrasing the BMJ report, and not my interpretation necessarily. I will note that I am likely one of the very few scientists in the field of exercise physiology and hydration research with no conflicts of interests. Apart from my doctoral research in the mid 1990s being funded by contracts with the Canadian Forces, I have had no direct or indirect interactions with any companies related to sports drinks.

I also know well many of the scientists involved on both sides of the argument as friends and colleagues for many years. Therefore, I think I’m well placed to give a hopefully objective perspective to this controversial field (feel free to comment otherwise and provide your own insight). You can find a detailed chapter on hydration and also supplements in Peaks Coaching Group

Conflicts of Interests
The field of exercise physiology is actually a very small world and the funding pales in comparison to big medical or pharmaceutical fields. Therefore, it is VERY hard to find scientists who have no conflicts of interests to create an “independent” oversight group. Knowing many of these scientists in and out of the lab, I certainly do not buy into a conspiracy theory approach that there is deliberate misrepresentation going on.

I do agree with the charge about large policy making bodies, like ACSM, making position statements about hydration while being directly supported by sports drink companies. If nothing else, the optics are very, very murky this way.

Summary: a draw on this one. I believe in the scientists on both sides of the issue, but I have a harder time trusting large organizations.

Dehydration vs Hyponatremia
I think this issue is wracked by imprecise arguments, with me arguing one idea, you arguing a separate idea, and both of us incorrectly thinking we’re arguing the same idea. Let’s look at what I see:

– Would I err on the side of dehydration or hyponatremia? This is simple – both are not desired and should be avoided!

– Do indeed listen to your thirst. It is an important psychophysiological signal to guide your behavior. This is exactly analogous to using Ratings of Perceived Exertion (RPE) as a gauge for your workload. Is it perfectly accurate? Not nearly compared to direct measurement of power output. However, can it be trained to be more accurate and reliable? Absolutely. Listen to your thirst, use it with pre/post exercise weighing to get an idea of fluid loss, and drink a reasonable amount to avoid too much fluid loss or too much drinking.

– How much is too much loss? Keep track of how your perform and feel with different levels of drinking during exercise, and keep track of your weight over multiple days to make sure you can train yourself to drink enough to recover day-to-day.

Water vs Sports Drinks
Going for a relatively easy and short ride of 60-90 min? You’re likely fine with water, as it’s hard even with high-intensity exercise to deplete your glycogen to dangerous levels to risk bonking or inadequate day-to-day recovery. The report does raise a good point – if your goal with cycling is weight loss, why handicap the 500 kcal you burned off on the ride by stuffing yourself with 250 kcal during the ride itself?

I know my constant theme is experience and to experiment with your own responses with nearly everything related to fitness and training. But again, experience is the key. Personally, if I’m riding in the afternoon for 60 min or more, I’ll usually have a bottle of sports drink with me, as I find that I’m usually famished about 4-5 pm, even with a big lunch. For me, I just don’t seem to get lunch into my system that well no matter how much or often I eat over the course of the workday.

Weak Hydration Science?
This argument fro the report I don’t really buy into, but I’ll admit that this might be because I’m too embedded into my field and its style of research. The field is again much smaller than big medical or pharmaceutical research, and there are no “standard” protocols for exercise testing, subject selection, statistics, etc. Therefore, it’s completely expected that there be wide disparity across study designs. You just have to examine things as they are.

I also don’t buy into the small sample size issue. This is absolutely part and parcel of exercise physiology research, and I find the statistics and analysis, in general, sound and appropriate for the majority of studies.

Summary
I know I absolutely sound like a broken record, but ignore the hyperbole from the extreme arguments on both sides, and the moderate path is usually a safe and good one.

There IS a role for sports drinks for cyclists. It’s not a magic bullet but it’s also not fool’s gold either. Try out different drinks to see which ones tastes good to you and seems to work well for your gut and your performance. Then use them on the bike the way that’s best for you.

Ride fast and have fun!

Reference

1. Cohen D. The truth about sports drinks. BMJ 2012, Aug 15;345.
2. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American college of sports medicine position stand. Exercise and fluid replacement. Medicine and Science in Sports and Exercise 2007;39(2):377-90.




About Stephen:
Stephen Cheung is a Canada Research Chair at Brock University, and has published over 60 scientific articles and book chapters dealing with the effects of thermal and hypoxic stress on human physiology and performance. Stephen’s Cutting-Edge Cycling, a book on the science of cycling, came out April 2012, and he can be reached for comments at stephen@pezcyclingnews.com .

 

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