Again, I’ve got to apologize for the big gap between posts here recently. The recent sell of our home in Boulder and move to new temporary quarters combined with two book projects and travel has left me a bit tight for time. But, as promised a couple of weeks ago, here is a post on carbohydrate-protein drinks.
It’s been a while since I wrote about this topic, a relatively new one with roots back in the 1990s. That may seem like a long time ago, but in the big scheme it’s not that long since we used carbohydrate as the only fuel source in our sports drinks. (The electrolytes we typically add to sports drinks are another post altogether, which I’ve written about before. )
Over the past 15 to 20 years there has been a lot of interest in protein intake during exercise. The attention this topic gets in the endurance sports media seems to have plateaued in the last couple of years. It seems we don’t hear as much about this subject any more. Perhaps that means it’s come to be commonly accepted and therefore isn’t in need of as much promotion any longer. It seems that many of the athletes I talk with use carb-protein drinks now, especially in shorter events taking less than 3 hours. For the longer events there seems to be fewer users, or at least that’s my impression. Many of the Ironman triathletes I’ve spoken with tell me they have experienced stomach shutdown when using carb-protein drinks. (Adding protein to your drink slows the processing of the gut’s contents.) I don’t know if they are typical of all Ironman athletes or not, however.
I noticed in the last couple of years that there were several new studies on the topic. I’ve been collecting them and finally set down to start reading. This turned out to be a much bigger project than I expected.
The original studies I had read on such products several years ago all seemed to have the same issues. The typical study had athletes exercise to exhaustion (failure) on 3 or more occasions. On one they drank a carb-only solution. On another they drank a carb-protein drink. And for the third they usually used an artificially sweetened placebo. These studies typically found that the carb-protein drink produced a significantly longer time to exhaustion than the carb-only or the placebo.
There are there issues I’ve seen with these studies. The first is that athletes don’t exercise to failure at a fixed and unwavering effort in a race. I’d prefer to see a more racelike standard used, such as a time trial, actual race or something similar.
The second issue is a bigger one. These studies nearly always have had more total calories in the carb-protein drink than in the carb-only drink. That, it seems to me, is a significant flaw which tilts the field in favor of the carb-protein drink.
And in some of the studies there is even a third important issue. These studies use a carb-protein drink in which the carb is a mix of several sources, such as fructose, maltodextrin and sucrose. Mixing multiple carbs together in a sports drink has been shown to improve the carb uptake significantly (like 44% more) when compared with the same amount of calories from a single-source carb (see the Sawka [11] and Jentjens [5] studies below).
These seem to me to be critical issues. So I’ve found it hard to accept the position that there is a definite benefit to using carb-protein drinks, especially if there is the possibility of gut problems as some athletes have suggested. It may be that they do work better than carb-only, but the studies aren’t convincing given their issues.
So with this in mind I set out to read the more recent research to see what was being discovered. Basically, I didn’t see much of a change. Below I’ve listed the studies I could find that go back to 2003 and include 5 from 2010 and 2011. (By clicking on these you can go directly to the abstracts on PubMed should you want to read a few more details and draw your own conclusions.)
Rather than go through all of these, which would be a rather tedious blog post, I’ll instead offer the details from only one – a review of the literature from Stearns and associates at the University of Connecticut which was published last year [12].
The UConn paper examined 11 studies which met their standards for inclusion in the project. Three of these selected studies had time trials as the measured standard. Eight of them used time to exhaustion to gauge the results of the drinks used. Only 3 of the studies cited had equal calories for the carb-only and carb-protein drinks. The others had more calories in the carb-protein solutions. (Stearns et al did not address the mixed-carb issue.)
So what did the UConn review find? The 3 time trial studies showed no significant difference in performance between the two drinks. Of the 8 studies that used time to exhaustion, those with equal calories had no performance difference. It was only in the time to exhaustion studies that also provided more calories in the carb-protein drinks where there was a significant difference in performance.
The benefits found for carb-protein drinks in these few studies, according to the UConn researchers, “may be because of a generic effect of adding calories (fuel) as opposed to a unique benefit of protein.”
So should you use a carb-protein drink or a carb-only drink in your longer workouts and races? (There is no benefit from either for short sessions – those lasting no longer than an hour or so.) If you haven’t experienced any stomach problems from using a carb-protein drink then I see no reason to make a change. There’s no other apparent downside. But if you have, or you have no experience with such products, then I’d suggest sticking with carb-only as it has a long and successful history.
I might add that there is one missing piece here: Some of the studies examined the benefits of carb-protein during and after exercise for the rate of recovery. This could be an important matter that stands apart from performance. I hope to address that in a future post here.
References
