There’s no hotter issue in sports nutrition right now than the carbs versus carbs-plus-protein controversy. The battle pits scientist against scientist, small companies against behemoths, and new research against long-held beliefs. At one crucial juncture, it even threatens the foundations of exercise physiology.
This is quite a change from the time, not long ago, when carbohydrate was King of all Exercise Land, and giving nutrition advice to runners was easy: eat carbohydrate before, during, and after your run. Bon appetit!
Protein's first shout
The runner’s perfect nutritional universe started to come apart in 1992 when a University of Texas exercise physiologist, John Ivy, first challenged King Carb. Ivy and colleagues published a study showing that a meal of carbs plus protein (C+P) after exercise boosted the resynthesis of muscle glycogen (your body’s best energy source) more than carbs alone (C). This was an important finding because glycogen resynthesis is the gold standard for measuring recovery, and most coaches and nutritionists believe that recovery is essential in any training programme.
Only one problem: Ivy seemed to make a critical mistake in his research design. He gave more total calories to the C+P group than to the C-alone group. Doh! Of course you’ll recover faster and better if you put a bigger pile of food on your plate.
It took Ivy and friends a few years to regroup, but they eventually designed newer and better studies that confirmed the original C+P results. They even uncovered the reason. Immediately after you exercise, your insulin, which controls your blood sugar levels, is particularly “sensitive”. Give sensitive insulin some carbohydrates, and it will pack them into your muscles as glycogen. Give sensitive insulin some protein, and it will quickly repair any muscle damage. Give it both carbs and protein, and you get the best of both worlds. Who can argue with a double-barrelled success like that?
First truth: the post-training window
The post-exercise research is so compelling that I’ve changed one of my life rules. From now on, I run first, eat second, and shower last. If my friends in the cafeteria don’t like it, too bad. The timing is crucial, because your insulin sensitivity is at its highest in the first 15 to 20 minutes after your workout. Don’t dilly dally.
Having won the post-training skirmish, John Ivy moved into the big war zone. In 2003, he published a performance study that argued for C+P while you exercise. He gave his subjects a three-hour endurance warm-up, and then asked them to sprint hard for as long as they could. The results showed that the subjects who drank a C+P product lasted 36 per cent longer in the sprint than those who drank a C-only beverage, but Ivy used that early design again: the C+P cyclists also received 25 per cent more total calories.
In practice, Ivy and other investigators face a Catch 22-like problem when they design these studies. If one group of subjects receives more carbs than the other, this carb differential will clearly influence the results. On the other hand, if the carbs are equalised, and proteins or fats are added for one group, the total calories consumed won’t be the same.
The new study produced an even bigger problem for Ivy: while his subjects exercised, they showed no increase in insulin sensitivity. This meant that he had achieved a small but positive result – that is, a 36 per cent increase with 25 per cent more calories – with no explanation for it. The research world doesn’t like loose ends like this. It demands results backed by physiological explanations, or at least solid hypotheses.
“This happens all the time in science,” Ivy says. “It was a long time before we could explain why caffeine improves endurance performance, but that didn’t mean caffeine didn’t work.”
The biggest hurdle protein faces is that it violates the laws of nutrition and exercise physiology. Protein as an energy source is like apples that detach from a tree and float upward. I have several 600-page exercise physiology textbooks, and they all contain charts with titles such as “Sources Of Energy During Exercise”. The charts have just two columns, one for carbs and one for fats. Protein doesn’t feature. It’s great for building and repairing muscle tissue, but it isn’t readily available for energy while you’re exercising. At least that’s the traditional scientific view.
Ivy would be dangling on a long, shaky branch except that several other laboratories have produced similar results. A year ago, Michael Saunders, an exercise physiologist and triathlete from James Madison University in the USA, completed a study that found cyclists drinking C+P products lasted 29 per cent longer (on a first ride) and 40 per cent longer (on a second ride 12 to 15 hours later) than C-only cyclists. The subjects drinking C+P also had much lower levels of a muscle-damage enzyme after they exercised.
Saunders, like Ivy, gave his C+P cyclists 25 per cent more total calories, but he also did a painstaking analysis of his results to show that the C+P riders were able to burn 318 more calories than the C riders, despite consuming only 139 more food calories. “They did almost three times more exercise than the extra calories they received,” Saunders says.
Saunders asked one of his students to conduct an “isocaloric” study in which the C+P and C-only riders consumed the same number of calories. The full research paper by Brett Romano hasn’t been published yet, but the abstract appeared last summer in Medicine & Science In Sports & Exercise. The conclusion was that when the riders received isocaloric amounts of C+P and C-only drinks, there was no difference in their performance.
Still, Saunders isn’t deterred. “When we made the beverages isocaloric, that meant the C+P riders were taking in fewer carbs than the riders with the traditional sports drink,” he says. “And yet they performed just as well with fewer carbs. To me, that means something is going on with the protein that’s allowing them to use it as an energy source.”
As runners, this leaves us in a familiar position – captain of our own ship. Science can do its part; the rest is up to us. It’s reasonable that one formulation can work best for one runner under one set of conditions, while another formulation suits another runner/time/condition. To find the sports drink that helps you perform your best, try as many as you like. Be careful to run at your appropriate race pace, and to use each in weather conditions that simulate your most important races. After all, research is only valuable when it mimics real-life situations.