Editor’s Note: Last month’s Physiology & Nutrition post, OSMO co-founder Stacy Sims’ regular column, discussed why she thinks gels are a poor choice for fueling endurance athletes. It’s a good read and generated a lot of comments and questions. It also piqued the interest of several brands known for their gels, one of which sent a rebuttal. As did one of the Peaks Coaching coaches, which serves as their column for this month. Both responses are posted below unedited, as was Sims’ post.
As an introduction and a little background, we’ve interviewed Sims when OSMO launched. We’ve also interviewed Allen Lim when he launched Skratch and asked similar questions. Then, in preparation for last year’s TSEpic, I interviewed Sims again about food choices. That post has a primer about why solids work when gels may not, which was one of the common questions in the comments. And Sims has already prepared Part 2 of “Why No Gels” which expands on that. Look for it this Friday. In the meantime, here are a few counterpoints to the original.
My name is Magda Boulet. I have been a pro athlete since 1997, training and competing with GU product for 17 years now. As the VP of Innovation and R&D at GU Energy Labs, I work closely with athletes of all walks of life who train and compete with gels every day at the highest competitive level. Understanding fueling strategies is essential to my long lasting success as an Olympic distance runner.
As an athlete, a scientist, and a consumer, I am passionate about formulating products and delivering research that are supported by experts in the scientific community and validated by athletes in the field. Having said this, I was disappointed to read the recently published article on “Why Not Gels?” in which the author misrepresented scientific facts and concluded that gels are “the most detrimental fuel sources for performance.”
There are many physiological and nutritional challenges faced by athletes that can have a profound effect on athletic performance. After decades of scientifically validated research and practical athletic experience, I know GU’s sports nutrition products provide a performance benefit to athletes. It is my responsibility as a sports scientist and coach to answer the daily questions of “When, how and what to fuel with?” To be honest, I don’t have one recipe that fits everyone, which is why a comprehensive endurance sports nutrition strategy will take into account an athlete’s current fitness level, environmental conditions, exercise intensity, type of activity, body size, gender, and portability and palatability of sports nutrition products.
GU Energy Gel was developed because endurance runners were facing GI distress from eating solid foods that were not easily ingested and digested during demanding efforts. Gels were designed to be concentrated for a reason, and when consumed with enough water, do not compromise the gut, as the author believes. The article referenced a study that claimed that maltodextrin in the small intestine promotes a hyperosmolar environment similar to that of fructose. However, the study referenced by Lambert, et al., did not use maltodextrin, but instead had athletes consume a 6% isotonic sucrose and glucose solution compared with water in the gut (1).
Maltodextrin is not broken down to any significant extent in the stomach and therefore does not increase osmolality, nor does it promote water influx into the stomach and cause dehydration as claimed by the athor (3). In fact, the beauty of maltodextrin is that the glucose molecules are linked together like cars on a train, and deliver a significant amount of carbohydrates to the body in a way that does not negatively increase osmolality the way free glucose does.
Also misrepresented in the article is the premise that gels cause high osmolality and draw in water. A packet of GU consumed with only 10oz of water contains 22 grams of carbohydrates and 100 calories, and has an osmolality of only 200 mOsmoles. If we chose to formulate our products with only simple sugars the osmolality would be much higher. Osmolality is also not the only factor to consider in intestinal absorption. Carbohydrate composition and the rate of flow of particles in a solution (solute flux) has been shown to be twice as important as osmolality in determining water absorption (2).
Gels have a significant place in the athlete’s nutrition plan. GI distress and dehydration are important issues facing many athletes, but gels are not to blame. Our bodies are not well equipped to consume calories during intense exercise (especially when dehydrated) due to limitations in blood flow to the gut. An athlete’s intensity level during exercise primarily dictates the source of fuel intake that can be tolerated.
Athletes all over the world perform with GU Energy Gels formulated with a blend of carbohydrates and branched-chain amino acids. These are ingredients that are scientifically validated and field tested by athletes of varying abilities. There is not one recipe that works perfectly for everyone, but gels are an option that works for many. I always recommend that athletes balance fuel intake and fluids by training with a combination of drinks, gels, chews, and solids.
Helping athletes find their own ideal nutrition plan so they can pursue and enjoy their endurance lifestyle is my passion. Thanks for reading and keeping an open mind while thinking critically about your performance nutrition options.
VP of Innovation, Research & Development – GU Energy Labs
- Lambert GP, Chang RT, Xia T, Summers RW, and Gisolfi CV. Absorption from different intestinal segments during exercise. J Appl Physiol (1985) 83:204-212, 1997.
- Shi, X, Summers RW, Schedl HP, Flanagan SW, Chang R, and Gisolfi CV. Effects of carbohydrate type and concentration and solution osmolality on water absorption. Medicine and science in sports and exercise 27:1607-1615, 1995.
- Vist GE, and Maughan RJ. The effect of osmolality and carbohydrate content on the rate of gastic emptying of liquids in man. J Physiol 486 (pt 2):523-531, 1995.
PEAKS COACHING RESPONSE
By Chris Myers, PCG Elite Coach
As a triathlon/cycling coach, exercise physiologist, and researcher, I firmly believe my athletes should have all the information possible in order to make educated decisions to optimize their training. In the field of exercise nutrition, science can prove one thing with one body of research while disproving the same point with another, so when my athletes look for nutrition supplements, I try to give them as much data as I can.
Any nutritional supplement needs to be used within its boundaries. For example, you shouldn’t drink a carbohydrate (CHO) mix as a substitute for eating to get calories during a long workout. There is a saying that “one should drink to drink and eat to eat.” What this means is that during exercise we should drink liquids to stay hydrated and eat food for calories to make energy. The use of gels is a staple for many endurance athletes as a quick source of energy, because gels offer the dual avenues of energy transport via maltodextrin and fructose absorption combined with proper hydration for moderate to high moderate exercise.
Gels are sometimes given a bad rap as a common source of dehydration. This is not the case, however. Both dehydration and hypovolemia (decreased blood flow) are mainly caused by thermoregulation of body temperature during prolonged exercise and environmental factors, not gels, and I’d like to explain why I advise my athletes to use gels.
As part of any endurance exercise at or below threshold (usually <75% of VO2Max) for an extended period of time, dehydration becomes an issue. Loss of water, whether from environmental or biological factors, reduces blood volume, more particularly blood plasma (hypovolemia), thus increasing the viscosity (thickness) of your blood. Hypovolemia causes a decrease in venous blood return (end diastolic volume, or EDV) to the heart, which causes a decrease in the amount of blood ejected from the heart to the arteries in a single heartbeat (stroke volume, or SV) (Oöpik, Timpmann, Burk, & Hannus, 2013). Overall, this decreases the most important factor, cardiac output (Q) (Powers & Howley, 2011; Smith & Fernhall, 2011).
Cardiac output (Q) is defined as the amount of blood ejected from the left ventricle of the heart in a minute’s time. Mathematically, Q looks like this:
Q = heart rate (BPM) x SV
(Powers & Howley, 2011)
During exercise this becomes very important. Q needs to be kept at a high rate during prolonged endurance exercise to meet your body’s respiratory demands. When your stroke volume drops, your heart rate increases to compensate to keep Q at the required levels to meet your exercise intensity (Myers, 2001). If a decrease in blood volume causes a significant decrease in stroke volume, your heart won’t be able to compensate and performance will decrease (Bassett & Howley, 2000; Myers, 2001).
The maltodextrin and fructose in a gel do require water for digestion, but not in excessive amounts. This is why it’s important to read the instructions for each product and understand the implications. For example, the printed instructions for GU gels state:
1. Wash down GU down with a few gulps of GU Brew© or water.
2. As a guideline, drink 20-24 unces of fluid per hour throughout training and racing.
Hammer Nutrition gives similar instructions for their gel product:
“Consume 0.5-2.5 servings per hour, along with 16-28 ounces (approximately 475-830 ml) of plain water per hour from a separate source.” (http://www.hammernutrition.com/products/hammer-gel.hg.html?gclid=COuCwfiWrr4CFWsS7Aod4jwANg)
Other products include similar language. Essentially you need to drink 2-4 ounces of water with a gel for initial digestion of the gel. However, each product’s instructions also specifically state that you should continuously consume water, not just when you initial take the gel.
It is well established within the realm of academia and athletic performance that rate of hydration is dependent on both the intensity of our exercise and environmental factors such as heat, humidity, wind, etc. The constant loss of water via sweat is part of thermoregulation, and dehydration-induced hypovolemia is not caused by the ingestion of gels. It’s typically recommended that we drink a minimum of 16 ounces of water or an 8-10% CHO mix every 30-60 minutes during exercise. This is where the saying “drink to drink” comes into play. You must be aware of your rate of water loss. When you lose water in an amount greater than 3% of your body weight, your endurance performance starts to decrease (Goulet, 2012). For cyclists this means a decrease in wattage, and for triathletes this means an increase in swim and run pace times.
It is ultimately up to each individual athlete to answer the question, “Do the benefits of gel products outweigh the risks?” Gels do use water as part of the digestion process, but it isn’t enough to cause dehydration and hypovolemia. The dual delivery of fast and sustained energy is an attractive benefit of using gels, though as with anything else, they should be used in moderation.
As with any product containing fructose, gels can potentially cause GI issues. When too many gels are ingested in a short period of time, there isn’t enough time for the fructose to digest, which is the main cause for GI issues with gels. So where do we draw the line? Each of us has to answer that for ourselves, but as a coach, I advise my athletes to eat solid food in combination with gels. As an athlete and consumer, I strongly recommend reading each supplement’s instructions prior to using it. As a junior researcher, I advise all my athletes to stay informed and to investigate the research aims (and possible conflicts of interest) of all supplements and over-the-counter nutritional products.
Bottom line? Gels are a good source of energy as long as they’re taken as intended.
Chris Myers, M.S., is a certified TSAC-F (Tactical Strength and Conditioning Facilitator), a USA Cycling Level 2 coach, a USA Swimming Level 2 coach, a USA Triathlon Level 1 coach, and a Peaks Coaching Group Elite Coach. Additionally, he is a second year doctoral student studying exercise physiology in the Department Nutrition, Exercise, and Health Sciences at Florida State University and is the head coach for the FSU Triathlon Team, Trinoles. He and the other PCG coaches create custom training plans for all levels of athletes. Chris can be contacted directly through PeaksCoachingGroup.com.
Bassett, D. R., & Howley, E. T. (2000). Limiting factors for maximum oxygen uptake and determinants of endurance performance. Medicine and Science in Sports and Exercise, 32, 70–84. doi:10.1097/00005768-200001000-00012
Goulet, E. D. B. (2012). Dehydration and endurance performance in competitive athletes. Nutrition Reviews, 70 Suppl 2, S132–6. doi:10.1111/j.1753-4887.2012.00530.x
GU Gels. (2014).
Hammer Gel – Carbohydrate Energy Gel | Hammer Nutrition. Hammer Nutrition. Retrieved May 15, 2014, from http://www.hammernutrition.com/products/hammer-gel.hg.html?gclid=COuCwfiWrr4CFWsS7Aod4jwANg
Myers, J. N. (2001). The physiology behind exercise testing. Primary Care – Clinics in Office Practice. doi:10.1016/S0095-4543(05)70005-1
Oöpik, V., Timpmann, S., Burk, A., & Hannus, I. (2013). Hydration status of Greco-Roman wrestlers in an authentic precompetition situation. Applied Physiology, Nutrition, and Metabolism = Physiologie Appliquée, Nutrition et Métabolisme, 38, 621–5. doi:10.1139/apnm-2012-0334
Powers, S. K., & Howley, E. T. (2011). Exercise Physiology: Theory and Application to Fitness and Performance. Ed Human KineticsPub Champign (8th ed., Vol. 4th, p. 640). New York City.
Smith, D., & Fernhall, B. (2011). Advanced Cardiovascular Exercise Physiology – Denise L. Smith, Bo Fernhall. Champaign, IL: Human Kinetics. Retrieved from http://www.humankinetics.com/products/all-products/the-advanced-cardiovascular-exercise-physiology