A recent University of Saskatchewan study indicates a pulse-based diet improves soccer players’ cholesterol levels and may help them run greater distances.

By Dario Bard

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Kinesiology professor Phil Chilibeck is out to prove something: that a pulse-based diet can give an athlete that winning edge. It is an idea that was first suggested to him by fellow University of Saskatchewan professor Bert Vandenberg.

“Bert, a lentil researcher and also a master soccer player, came to me and said, ‘I eat my lentils before my games and it seems to improve my performance. Can we do a study together on this?’” recalls Chilibeck.

Intrigued by the possibility, Chilibeck embarked on a series of studies. The first three, published from 2009 to 2012, had athletes run several treadmill trials following varying diet conditions: a meal featuring mashed potatoes and egg whites (high glycemic index); a meal featuring boiled whole red lentils (low glycemic index); and no meal at all (control). Although none of these studies found significant differences in the performance indicators when consuming a low versus a high glycemic index meal, there was evidence that, unlike high glycemic index foods, low glycemic index foods do not cause a sugar rush, and therefore do not impair the burning of fat during aerobic exercise, a trait which could improve an athlete’s aerobic performance over the long haul.

“In most of those studies, we saw improved metabolism,” says Chilibeck. “But it was a very controlled lab experiment. We received some criticism during the peer review process that pointed out that running on a treadmill is not the same as playing an actual soccer game. So we moved the next study into the gym where we had players run back and forth, stop and jump to head a ball supported by a tether, dribble around cones and take shots on a target. Again, everything was controlled and recorded. And once more, we saw improvement in metabolism during the running drills and we saw improvement in some of the performance measures, like the ability to run an agility course late in the ‘game’. In the second half, we saw increased running speed and also jumping height in the simulated heading drill. Overall, participants appeared to have more energy in the second half of the ‘game’ when they were on the pulse-based diet.”

The gym experiment took the research one step closer to actual game conditions. Its results showed enough promise for Chilibeck to take it to the next level. He prepared a research proposal to study the performance and metabolism of soccer players during an actual game and submitted it to the University of Saskatchewan’s Agriculture Development Fund, which found two sponsors for the study: the Saskatchewan Pulse Growers and the Western Grains Research Foundation.

With funding in hand, Chilibeck took his hypothesis out onto the soccer pitch last soccer season. Preliminary results are now in and IFT had the chance to speak with Chilibeck about his early findings.

IFT: Can you describe your latest study? How were you able to record performance measures during actual game conditions and what are your preliminary findings?

Chilibeck: The study lasted for two months and involved nine soccer players from both the men’s and women’s University of Saskatchewan soccer teams. For one month, we put players on a pulse-based diet that featured lentils, beans, peas and chickpeas. That included a variety of foods like chili, baked beans, salads with chickpeas in them, and pasta sauces with chickpeas or lentils in them. So for that month, the players ate two pulse-based meals a day with about a cup of pulses per meal. Then for the other month, they were on their regular diet and could eat whatever they wanted to eat. It was a randomized study, so we started half the players out on the pulse-based diet and the others on their regular diet. During both phases, participants filled out food diaries. In the non-pulse phase, most of the players ate a typical North American diet, which features foods with a high glycemic index; pulses are not included all that often if at all. Therefore, the quality of the carbohydrates they received was quite different.

We evaluated game performance over the two months. I should add that when players were in the pulse-phase of the study, we gave them a pulse-based energy bar called the Megabite before the game. The Megabite is a concept energy bar that Pulse Canada developed. It is one of the better energy bars I’ve tried. It is very tasty and has a low glycemic index, so it supplies sustained energy.

When players were on the regular-diet phase, we gave them a standard, commercially-available sport nutrition bar that has a relatively high glycemic index.

During the game, we used a GPS system that players wore under their shirts in a harness on their backs. The system tracks the distance the player covers during a game. That allowed us to get all the performance measures during actual game play.

When we looked at the data from these systems, what we found is that, on average, players covered about 4% more distance when they were in the pulse phase of the study compared to the regular-diet phase. This result was not statistically significant, however, considering our small sample size and that on average, male players ran a bit over 10 km per game and women ran nearly 8 km per game, which would mean an increase of only about 400 m and 320 m, respectively. The study is ongoing, though, and this soccer season we are repeating the experiment with more players.

Now, besides the readings from the GPS system, we also took blood measurements before and after each diet phase. And there we did have a statistically significant finding: players’ cholesterol levels improved significantly when they were on the pulse-based diet. The total cholesterol to HDL ratio decreased because total cholesterol, which is bad for your health, decreased while HDL cholesterol, which is good for your health, increased.   

IFT: Could you talk a bit about the science behind the idea that pulses can improve sports performance?

Chilibeck: Pulses have a low glycemic index, so they provide a more sustained energy source because, when you eat pulses, your blood sugar levels rise very gradually. And because of that gradual rise, your body does not release much insulin. That is vital, especially for any kind of aerobic exercise, because when there is insulin in your blood, it inhibits the use of fat by the muscles. This is precisely what happens when you eat foods with a high glycemic index; your body releases more insulin in response to the sugar rush. As a result, your muscles are inhibited from burning fat and instead start burning the carbohydrates that are stored in the muscles. Once the muscles run out of carbohydrates, your exercise performance is adversely affected. During aerobic performance, you want your muscles to be using fat as an energy source. In that way you preserve your muscle carbohydrate stores and can run longer distances at greater speeds. So in a sport like soccer, the sustained energy delivered by pulses has benefits throughout the game, but especially in the second half.  

IFT: What has been the reaction of the teams to this study?

Chilibeck: I think one of the big bonuses for the players, who are all university students, is that we provide them with two meals a day for a month at our cost. For the coaches, they know it is going to be beneficial to the players’ health and possibly performance, so they have been very supportive and even involved with the study. I have a graduate student who goes on all the road trips with the team and they treat him like part of the coaching staff. I cover some of the travel costs and the team provides the accommodations.

The coaches also like the GPS system we are using to monitor player performance; it allows the coaching staff to get a really good evaluation of their players.

IFT: I understand the current study is ongoing, but have you thought of where you would like to take this line of research in the future?

Chilibeck: I would like to see this research applied to other sports with similar demands. For example, we would like to apply it to hockey, especially during the collegiate playoffs. In western Canada, to save as much as possible on travel costs, teams play a three-game series over a single weekend. The first game is Friday night and then they have day games on Saturday and Sunday. That’s a lot of games over a really short time. A specific example of when a pulse-based diet might have been very beneficial was last year, when the women’s hockey team had all three playoff games in a series go into overtime. The second game even went into three or four overtime periods. These girls ended up playing the equivalent of five or six regular games over two and a half days. So you have situations like that in hockey, where athletes are struggling to keep their energy levels up and that is when you can really see a pulse-based diet make a difference.

IFT: Are you involved in other research that involves pulses?

Chilibeck: My research interest is in the health area. One of my specific interests is the prevention of diabetes and metabolic syndrome. Pulse-based foods are very good for preventing those conditions because of their low glycemic index. That is actually my main area of research, but as a kinesiology researcher, I am always interested in doing some research with high-performance athletes on the side.

IFT: The United Nations has officially designated next year as the International Year of Pulses. Do you see that furthering your work?

Chilibeck: That kind of widespread promotion of pulses can only help elevate our work. I would think that the pulse producer groups, like the Saskatchewan Pulse Growers, who have traditionally funded us in the past, will be even more supportive in 2016 because of the International Year. So it definitely represents an opportunity to expand this work to other athlete groups, like hockey players. Personally, I am interested in rugby. I’ve been playing rugby now for 20 years and, like soccer, it involves a lot of running and requires large amounts of energy. I would love to study the effects of a pulse-based diet on rugby players.

Also, I should point out that we chose to focus on soccer first for this study because it is the most popular sport in the world. The pulse industry likes that because if we show pulses are beneficial for soccer players, it has the potential to open a very big market for them.

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Dario Bard, IFT Journalist