Thursday, May 10, 2007

Energy Drinks, Sport Bars & Gels

Nutrition – Energy Drinks, Sport Bars & Gels
by Charlene Boudreau,
From USA Swimming
The use and selection of energy bars, sports drinks and gels has grown considerably over the past few years. For athletes, reasons for using these products are typically based on their convenience and potential performance-improving effects. Bars, drinks and gels provide a quick and easy means of supplying the body with calories and micronutrients (vitamins and minerals) when conventional foods are not available or feasible. Since swimmers typically workout and/or race in the morning when they may choose not to eat, and an overnight fast would force them to perform in a partially glycogen-depleted state, bars, drinks and gels may provide a compact, more tolerable “meal” substitution. In some cases, the addition of certain ingredients promises results.

Energy bars fall into 3 main categories, depending on their nutrient composition:
-High Carbohydrate Bars (>30 g carbohydrate)
-High Protein Bars (>12 g protein)
-Mixed Bars (usually >20 g carbohydrate, >10 g protein, 2.5-10 g fat).

High carbohydrate bars provide the fuel needed for tough endurance workouts. High protein bars are often promoted for post-workout recovery. Mixed bars make a healthy snack during the day when time is short and hunger is big.

Gels are typically high in carbohydrate (>30g) and low in fat (<1g) and protein (<12 g). They include mainly simple sugars, as opposed to complex carbohydrates. Since simple sugars reach the bloodstream faster than complex carbohydrates, which take longer to digest and be absorbed, gels are typically used in situations when carbohydrates are needed quickly. For swimmers, breaks between sets present an opportunity to provide the body with the energy (carbohydrate) it needs for long workouts.

Sports drinks have traditionally been comprised of carbohydrate and electrolytes in amounts that enhance fluid absorption and minimize gastrointestinal distress. Over the past 5 years, sports drinks have expanded to include those with added amino acids, herbal ingredients and herbal mental “boosters.” Many products have been marketed to a consumer base that goes beyond the competitive athlete and into the realm of the recreational and leisure activity participants.

In addition to the convenience factor, many energy bars, sports drinks and gels have direct scientifically proven benefits both during and following exercise. The two basic reasons why researchers suggest that athletes turn to these types of fuels are:
Fluid replenishment (drinks).
Energy provision (bars, drinks, gels).

Maintaining Hydration During Exercise - The daily sweat loss for elite level athletes can range from 1 to 1.5 liters per hour. Depending on the intensity and duration of the workouts, the daily water requirement for these athletes ranges from two to six liters per day. In extreme cases, this requirement may be as high as 16 liters per day if the climate is hot. Failure to maintain a hydrated state can lead to detrimental changes in the cardiovascular response to exercise, over-heating of the body and decreases in both maximal power and work capacity. Just a 2% drop in body weight due to dehydration can have an overall negative impact on exercise performance.

The collection of research addressing sports drinks is extensive and has evolved quite dramatically over the years. Studies have indicated that the ingestion of a 6-8% carbohydrate beverage (ex. Gatorade, Powerade) during prolonged strenuous exercise can delay fatigue and improve performance. The theory is that the carbohydrate drink provides sugar (glucose) to the blood, which spares glycogen (the body’s internal reserve of carbohydrate) during prolonged exercise. And we know that how well a fluid (sports drink or water) works depends on (1) how much is ingested (fluid ingestion), (2) how long it takes for that fluid to move from the stomach to the intestine (gastric emptying…the faster the better), (3) how long it takes to be absorbed from the intestine into the bloodstream (intestinal absorption) and (4) whether it weakens or enhances the body’s utilization of carbohydrate as a fuel (fuel utilization).

Providing Energy During Exercise - In addition to staying hydrated, athletes are faced with the task of fueling their bodies for performance. For activities lasting less than one hour, this can usually be accomplished with the pre-exercise meal or snack.

For longer-duration activities, this usually means “eating on the run.” Given the environment, swimmers face the added obstacle of the water. Conventional “dry” foods are not feasible, making products such as water, sports drinks, energy bars and gels their only options. This also leads to the questions of what, when, why and how much?

The use of bars, drinks and gels as fuel sources during exercise is based on their typically high carbohydrate content. Providing the body with carbohydrate during prolonged activity maintains blood sugar levels. The availability of this “fuel” during exercise allows the body to spare glycogen and can prolong the time an athlete can exercise before tiring. The well-researched sports drink (also called carbohydrate electrolyte drink) has traditionally been recommended for endurance events lasting
more than 90 minutes. However, recent research suggests that sports drinks can improve high intensity and sprint-interval sessions lasting less than an hour. This suggests a benefit to using sports drinks for fuel during workouts to a broader segment of the athletic community, including sprinters.

Hydrating the Body at Rest – Quality workouts depend on replenishing fuel stores that were spent during previous sessions. This includes, but is not limited to, fluids. Failure to correct a fluid deficit incurred from one workout before the next workout puts the athlete at risk for a compromised performance. Starting a session in a dehydrated state may cause a faster rise in core body temperature, greater cardiovascular strain and an impaired ability to dissipate heat. These effects may be exaggerated if the workout takes place in a hot environment. Therefore, re-hydrating and maintaining a hydrated state outside of practice times is just as critical to the athlete as hydrating during workouts.

Be aware that thirst is not always an accurate indicator of when an athlete should begin hydrating. For most athletes, by the time they are thirsty, they are already dehydrated. This makes the intake of fluids, including sports drinks, an important part of the daily nutrition program, especially during the recovery phase. It has been suggested that fluids containing sodium are more efficient at hydrating than plain water alone. According to the American College of Sports Medicine, “one should consume adequate fluids during the 24-hour period before an event and drink about 500 ml (about 17 oz) of fluid about 2 hours before exercise to promote adequate hydration and allow time for excretion of excess ingested water.”

Fueling the Body at Rest – As mentioned previously, quality workouts depend on replenishing fuel stores spent during previous sessions. Depending on the extent of depletion, it can take as long as 24 hours to fully replenish glycogen stores, but the first two hours post-workout are the most critical. Given the right fuel, glycogen synthesis during this time can occur as much as 2-3 times faster than normal (i.e. compared to if they were given no fuel at all). This is due to the increased sensitivity of muscle cells to the hormone insulin. It is well known that the ingestion of carbohydrate causes an insulin response (i.e. increasing glucose in blood increases insulin in the blood). The presence of insulin in the bloodstream promotes the uptake of glucose by the muscles. Once moved from blood to muscle, this glucose can then be converted to glycogen for storage. Certain proteins and amino acids have been shown to elicit an insulin response. When ingested with carbohydrate, they can create a “synergistic” effect. In other words, their combined effect is greater than the sum of their individual effects. Those found to have the greatest impact on insulin levels include protein hydrolysate mixtures, leucine, phenylalanine, and arginine.

In addition, insulin itself has been proposed as an important factor in muscle protein balance by increasing synthesis and decreasing degradation. Some researchers believe that when exercise acts as the stimulus and levels of circulating amino acids are high, a more anabolic (muscle-building) state is created. Unfortunately, research in this area is still limited, and questions still remain regarding how nutrition impacts resistance and intermittent activities. The general idea is to take advantage of the body’s natural post-exercise sensitivity to insulin by providing it with food that will (1) raise insulin levels, (2) put glucose in the bloodstream quickly and (3) enhance the conversion of glucose to glycogen.

At rest, such as during the pre- and post-workout periods, the use of energy bars, drinks and gels varies with personal preference, time available to eat, etc. In addition, athletes are compelled to select these products based on claims made by the manufacturers about the addition of various ingredients and which products are “the best.” Some of these claims are related to fat burning capabilities, the roles of electrolytes (sodium, potassium, chloride) and caffeine, and the addition of various carbohydrate/protein hydrolysate combinations. An important point to remember is that because most bars, drinks and gels are considered dietary supplements, they are subject to the less stringent regulation demonstrated within the supplement industry since the passing of the Dietary Supplements Health and Education Act of 1994

For this reason, it is worth the time for athletes and coaches to choose their bars, drinks and gels cautiously.

To address some of the issues mentioned above, I recently reviewed a collection of studies (Oliver & Tremblay, 2002; Kolkhorst, MacTaggart & Hansen, 1998; Haff, Kock, Potteiger, Kuphal, Magee, Green & Jakicic, 2000; Nassis, Williams & Chisnall, 1998; Brouns, Kovacs & Senden, 1998; Van Nieuwenhoven, Brummer & Brouns, 2000; Van Loon, Saris, Kruijshoop & Wagenmakers, 2000). The applications of this research are summarized below:
-Fifteen minutes may not be enough time to reap the benefits of ingesting carbohydrate prior to a workout.
-The claims made by the manufacturers of Sports Nutrition Bars are not always supported by science. An athlete may be better advised to choose a product that has KNOWN scientific benefits.
-Consuming Gatorlode or Gatorade before and during a workout may not enhance the amount lifted, force produced, or time to fatigue, but it can prevent muscle glycogen stores from declining.
-Maintaining this fuel source can have direct implications on a pool workout that closely follows a dryland/lifting session or vice versa. It allows the swimmers to come to workout with more “gas in the tank.”
-There has been some debate on the extent (if any) to which caffeine intake enhances endurance performance. Regardless of the controversy, many manufacturers of sports drinks, energy bars and gels have taken the initiative to add caffeine to their lists of ingredients.
-When given the choice, many athletes will drink more of a sports drink than water because they prefer the taste.
-The inclusion of caffeine in sports drinks may not affect gastrointestinal variables, but using a drink like Coca Cola to rehydrate the body after a tough workout may have an adverse effect on electrolyte balance.
-Since caffeine appears to increase magnesium and calcium loss in urine, rehydration should be accomplished with 6-8% carbohydrate-electrolyte sports drinks that are caffeine-free, rather than any drinks that contain caffeine and/or do not include electrolytes.
-The enhanced insulin response caused by the addition of protein to the carbohydrate-only drink can be achieved just as effectively by adding the same amount of extra carbohydrate.
-Consuming carbohydrate in the amount of 0.8 g/kg/hr (58 grams/hr for a 160 lb male) is not as effective in replenishing glycogen as consuming 1.2 g/kg/hr (87 grams/hr for a 160 lb male). In other words, 0.8 g/kg/hr (32 fl oz of Gatorade for a 160 lb male) is not enough to maximize the repletion process.

The Final Word
When it comes to choosing an energy bar, sports drink or gel, the most important things to know are: what is in it and how does it work? To help guide your athletes in their selection and use of bars, drinks and gels, offer these tips:

-Check for Effective Ingredients in Drinks. The post-exercise rehydration drink should contain Carbohydrate (30-80 g/L), Sodium (400-1000 mg/L), and Potassium, Chloride in small quantities. If a drink does not contain these ingredients, it may not be effective in providing energy and maintaining hydration.
-Drink Water with Bars. Drink at least 8-16oz (about 1 water bottle full) of water along with every energy bar you eat. For each packet of gel, take about 4oz of water. This helps keep your body hydrated while helping with the digestion of the product and the absorption of its contents.
-Experiment. Swimmers will differ in their preferences when it comes to flavor, texture, palatability (feel of food in the mouth) and digestive tolerance. Test energy bars and gels in real life settings. Avoid mixed bars immediately before and during workout, as the higher fat content may slow digestion and/or upset your stomach. The same applies for bars that are high in fiber, >5 g. Do not wait until meet day to take your first bite. In doing this, you risk experiencing adverse effects, which could include, among other possible side affects, nausea, cramping, and unanticipated bathroom visits!
-Beware of Extra “Stuff.” Many manufacturers claim that the extra vitamins and minerals they have conveniently added to their product are critical for the energy boost. The fact is that the energy a swimmer gets from a sports bar or gel comes from the calories it provides. While the importance of vitamins and minerals for proper body functioning cannot be denied, adequate amounts of these nutrients can be obtained by consuming a variety of foods from all of the foods groups on a daily basis. In addition, many of the “extra” ingredients supplied in these products may not be ones a competitive athlete wants or needs to ingest. Be extra cautious of herbal ingredients.
-Read the Ingredients. This tip is simple, but it is extremely important! You must be aware of what you are eating. Pay particular attention to the ingredients list on every individual package, and avoid products that may contain substances that you know or even think may appear on the prohibited substance list. Sometimes fortified products contain even more than what actually appears on the list. It is possible. It does happen. It is your responsibility.
-Eat “Real Food.” While bars, drinks and gels provide a convenient way to get the extra calories necessary to keep pace with the swimmer’s lifestyle, it is critical to eat a variety of foods from all of the food groups every day. Use energy bars and gels only to compliment a well-balanced diet when energy demands are high and “real food” is not an option.

For additional information on issues related to this review, visit the following web links:
-Laboratory Evaluation of Nutrition Bars:
-Laboratory Evaluation of Powders and Drinks:

Recommended Reading
-American College of Sports Medicine. (1996). American College of Sports Medicine position stand: Exercise and fluid replacement. Medicine and Science in Sports Medicine 28(1):i-vii.
-Coombes, J.S. and K.L. Hamilton. (2000). The effectiveness of commercially available sports drinks. Sports Medicine 29(3):181-209.
-Cunningham, J.J. (1997). Is potassium needed in sports drinks for fluid replacement during exercise? International Journal of Sport Nutrition 7:154-159.
-Gleeson, M. and N.C. Bishop. (2000). Modification of immune responses to exercise by carbohydrate, glutamine and anti-oxidant supplements. Immunology and Cell Biology 78:554-561.
-Green, G.A., D. H. Catlin and B. Starcevic. (2001). Analysis of over-the-counter dietary supplements. Clinical Journal of Sport Medicine 11:254-259.
-Harvard University. (2000). Power in a bar or procey snack? Harvard Women’s Health Watch July:6.
-Leiper, J.B. (1998). Intestinal water absorption – implications for the formulation of rehydration solutions. International Journal of Sports Medicine 19:S129-S132.
-Maughan, R.J. (1998). The sports drink as a functional food: formulations for successful performance. Proceedings of the Nutrition Society 57:15-23.
-Murray, R. (1998). Rehydration strategies – balancing substrate, fluid, and electrolyte provision. International Journal of Sports Medicine 19:S133-S135.
-Ryan, M. (1997). Sports drinks: research asks for reevaluation of current recommendations. Journal of the American Dietetics Association 97(suppl):S197- S198.
-Tufts University. (2001). Why most energy bars should not go home with most people. Tufts University Health and Nutrition Letter 19(5):6.

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