By Leslie Bonci
Leslie Bonci, MPH, RD, is Director of the Sports Medicine Nutrition Program at the University of Pittsburgh Medical Center Health System, and a consultant to the University of Pittsburgh Department of Athletics, the Pittsburgh Steelers, Pittsburgh Ballet Theater, and several Pittsburgh-area high schools.
Training & Conditioning, 11.3, April 2001, http://www.momentummedia.com/articles/tc/tc1103/bigdrop.htm
One of the greatest challenges in sports is building and maintaining adequate energy stores. Whatever diet we choose, the bottom line is having enough glucose in the blood at all times to ensure that the muscles have an adequate supply. When blood or muscles are running a deficit, we become hypoglycemic.
A small percentage of the general population is naturally hypoglycemic, and thus prone to dips in their blood glucose related to certain dietary factors. While the actual number of athletes with diagnosed hypoglycemia may be low, it is still important that all athletes modify their diets to decrease the likelihood of hypoglycemic symptoms, since exercise, especially prolonged activity, can lower blood glucose levels.
Hypoglycemia can cause symptoms that can impair performance and even curtail participation in athletic events. By following a few simple guidelines, and being prepared to handle serious episodes, hypoglycemia can be easily prevented and treated.
What and Who
Dietary carbohydrate is stored in the liver and muscles as glycogen. If liver glycogen stores are low due to exercise or decreased carbohydrate intake, the liver is unable to maintain circulating glucose concentrations, which can lead to hypoglycemia. Hypoglycemia is defined as a blood glucose level less than 70 mg/dl. Symptoms include shakiness, sweats, tingling lips, sudden mood swings, irritability, hunger, fatigue, weakness, impaired coordination, paleness, loss of concentration, and unconsciousness.
Since hypoglycemia can also impair temperature regulation, the hypoglycemic athlete is more susceptible to hypothermia and hyperthermia. Therefore, precautions must particularly be taken to prevent an athlete from experiencing hypoglycemic episodes in extreme weather conditions.
Individuals with reactive or post-prandial hypoglycemia may experience a fall in blood glucose two to five hours after a meal. The symptoms will be the same as listed above. Insulin-dependent diabetic athletes also are prone to late hypoglycemia after exercise. By properly timing meals, ingesting extra carbohydrate before activity, and having quick-acting carbohydrates at hand, these athletes can decrease their risk of hypoglycemic episodes (see Sidebar, “Hypoglycemia and the Diabetic Athlete,” at the end of this article).
Maintaining adequate blood glucose levels during activity can be a challenge for any athlete. Athletes participating in prolonged exercise following several hours without food or after an overnight fast, or those who have been restricting carbohydrate intake, will be more likely to experience problems.
Adequate carbohydrate intake (a minimum of three to 3.6 grams per pound body weight, up to six grams per pound body weight for those exercising four or more hours per day) is necessary to ensure optimal glycogen stores. Bread, rice, pasta, bagels, crackers, sweets, fruits, fruit juices, vegetables, milk, yogurt, and sports bars, drinks, and gels are all excellent sources of carbohydrate. Dairy foods and certain sports drinks and bars will provide protein and, in some cases, fat, in addition to carbohydrate.
Table One (at the end of this article) shows a meal plan that would provide adequate carbohydrate for an active individual exercising one to two hours a day. Athletes should be reminded that consuming carbohydrate at every meal and snack can be an easy way to meet their needs. Eating frequent meals is a great way to stabilize blood glucose and provides an opportunity to ingest carbohydrate throughout the day. For those with reactive hypoglycemia, larger meals can increase the likelihood of a reaction, so establishing an eating schedule can be very helpful.
There is no scientific rationale behind consuming carbohydrates early in the day and restricting carbohydrate intake at night. An evening meal of only protein and vegetables may precipitate a hypoglycemic reaction during the night. Mixed nutrient meals that include protein and fat in addition to carbohydrate are preferred, especially in those with reactive hypoglycemia. Soluble fiber foods (oats, barley, fruits, vegetables, and dried beans and peas such as kidney, pinto, split peas, and lentils) may help stabilize blood glucose and should be included throughout the day as part of overall carbohydrate consumption.
With some athletes, it may be advisable to delay carbohydrate intake until pre-exercise warmups or five minutes before exercise. Since most athletes will not want large volumes of food in the stomach at the onset of exercise, a liquid supplement, such as those targeted toward diabetics, or a glass of milk and a sports bar made with longer-acting carbohydrates may be recommended.
Consuming carbohydrate during exercise can help prevent hypoglycemia by supplementing the liver’s ability to maintain blood glucose levels. In addition, carbohydrate consumption during exercise can delay the rate of muscle glycogen depletion, and therefore delay fatigue. Research has shown that the body can effectively use solid or liquid carbohydrate sources during exercise. Athletes should experiment to find what is most comfortable and palatable.
In selecting supplements, the hypoglycemic athlete should avoid high-carbohydrate energy bars sweetened primarily with sugar (sucrose) or dextrose, which can cause a rapid peak in blood glucose followed by a sharp decline. Conversely, a high-protein bar is not advisable either, since it does not provide sufficient glucose as a fuel for the exercising muscle (see Sidebar, “Glycemic Index,” at the end of this article).
A moderate-carbohydrate energy bar (less than 50 percent of the calories from carbohydrate) whose ingredients include rice, corn or cornstarch, and fructose as the primary sweetener, may be of benefit. These products are intended to prevent hypoglycemia, but are not for use as a treatment for an athlete who is experiencing a hypoglycemic reaction.
Athletes may need to be cautioned about the way three common substances—sugar, caffeine, and alcohol—affect the body’s sugar levels. Some athletes get confused by the word “sugar” on a nutrition label assuming that that food product is bad or should be avoided. Sugar is one type of carbohydrate, and does not need to be avoided in all cases. Although sucrose or refined sugar should be limited, sugar on a label can correspond to “lactose” in milk, “fructose” in fruit, and “maltose” in grain products. In a fruit yogurt with 35 grams of sugar, this figure is mostly a composite of the lactose and fructose in the product. Labels should be used to calculate total carbohydrate intake for the day, without agonizing over the grams of sugar in the food item.
Further, although some athletes may be drawn to artificial sweeteners, it is important to note that the majority of these products are not metabolized and therefore non-caloric. Therefore, the athlete using these products may not be taking in enough calories for exercise. Acesulfame-K, saccharin, and sucralose are all non-calorie sweeteners. Aspartame is metabolized as a protein, but is a very low-calorie item. If an athlete chooses to use artificially sweetened foods or beverages, he or she should use them after exercise, or on a rest day, and not before or during activity.
In some individuals, sensitivity to caffeine and alcohol may be a problem. Caffeine consumption should be less than 200 mg/day (an eight-ounce cup of coffee has roughly 130 mg, a 12-ounce cola has about 40 to 45 mg, a 1.5-ounce bar of chocolate has 10 to 30 mg, and two Excedrin have 130 mg). Even if the athlete does not drink beverages containing caffeine, it is important to inquire about any caffeine consumed through supplements (typically in the form of guarana, mate, or kola nut).
An athlete who has fasted, or who has not eaten sufficiently for several hours, is more likey to experience hypoglycemia in response to alcohol consumption than someone who has maintained an adequate diet. Since alcohol blocks the production of glucose by the liver, normal blood glucose levels cannot be maintained, resulting in hypoglycemia. Alcohol should never be consumed on an empty stomach.
If an athlete is experiencing a hypoglycemic reaction, administering 15 grams of quickly absorbed carbohydrate may help reduce symptoms. After strenuous exercise, 35 to 40 grams of carbohydrate may be necessary. Table Two (at the end of this article) lists foods that contain 15 grams of quick-acting carbohydrate. If the athlete is not feeling better after 15 to 20 minutes, test his or her blood glucose, and if the reading is still less than 70 mg/dl, administer another 15 grams of carbohydrate. (Having a glucometer at the ready is becoming more and more important as an increasing number of diabetics play sports.)
If the athlete is unconscious, call an ambulance. Do not attempt to give food or beverages. An emergency option for treating an unconscious athlete who you know to be prone to hypoglycemic episodes is to place a small amount of glucose gel or cake decorating gel between his or her cheek and gums, and rub the cheek from the outside until the gel dissolves. A glucagons injection may be necessary if blood glucose levels do not start to improve.
• Encourage the hypoglycemic athlete to experiment with low-glycemic-index food choices before exercising to determine if blood glucose levels stabilize.
• Encourage carbohydrate consumption during exercise, especially endurance-type activities.
• Diets that advocate protein intake to the exclusion of all else, or that severely curtail carbohydrates, are never recommended for athletes.
• Make sure the hypoglycemic athlete does not come to practice or competition without having eaten; if necessary, provide food for the athlete before he or she is permitted to exercise.
• The athlete should meet with a registered dietitian who can assist in developing a meal plan he or she can follow.
• Diabetic athletes may need to experiment with their insulin dosing before exercise, and should test blood glucose during exercise.
• Ask athletes about alcohol and supplement use, especially caffeine-containing products and “energy-boosting” products, which can contain significant amounts of high-glycemic index carbohydrates that can exacerbate hypoglycemia.
• Keep quick-acting carbohydrate foods on hand (see Table Two, at the end of this article).
By following these recommendations, you will be able to prevent most athletes from ever experiencing hypoglycemic episodes. And you will be able to keep athletes with hypoglycemia in the game and at the peak of their abilities.
Table One. Getting Enough Carbs
The following is a sample meal plan that would ensure adequate carbohydrate intake for a typical 180-pound athlete (requiring 594 to 648 grams of carbohydrate per day).
A bagel with 1 Tbs. fruit preserves and
1 Tbs. peanut butter
An 8-oz. fruit yogurt with 1/4 cup
152 grams carbohydrate
A sports bar (not low-carb. type)
46 grams carbohydrate
Turkey sandwich with:
3 slices turkey breast
1 slice mozzarella cheese
Lettuce and tomato
Whole grain 6-inch pita bread
A 4-oz. container of pudding
A 2-oz. bag of pretzels
8-oz. orange juice mixed with seltzer
80 grams carbohydrate
A cereal bar
A 20-oz. sports drink
60 grams of carbohydrate
Stir fry with 2 cups mixed vegetables
and 1 cup chopped chicken
over 2 cups of rice
A 12-oz. glass of low-fat milk
1 cup frozen yogurt
3 sandwich cookies
213 grams of carbohydrate
A fist-sized bowl of toasted oat-type
cereal with 8-oz. low-fat milk
51 grams of carbohydrate
TOTAL: 632 grams of carbohydrate
Sidebar: Hypoglycemia and the Diabetic Athlete
Although diabetes is characterized by hyperglycemia, insulin-dependent diabetic athletes can experience late hypoglycemia after exercise, because exercise increases insulin sensitivity for several hours following exercise. Poorly controlled diabetic athletes should not follow carbohydrate-loading regimens that recommend periods of carbohydrate restriction, as these can increase the risk for hypoglycemia. Further, alcohol blocks hepatic glucose production, which can precipitate late and severe hypoglycemia in the insulin-dependent diabetic athlete. Caffeine in doses greater than 200 mg/day can also increase the incidence of hypoglycemia in athletes with insulin-dependent diabetes.
Insulin-dependent diabetic athletes should consume a large meal one to three hours before exercise, and may need to decrease their insulin dose to prevent hypoglycemia during exercise. If exercise lasts longer than 30 minutes, the athlete may need to consume extra carbohydrate at the pre-activity meal, and have quick-acting carbohydrate sources available, if needed, during exercise. The recommendations for carbohydrate during exercise for an insulin-dependent diabetic athlete are:
• 40 grams of carbohydrate per hour (such as two packets of sports gel and water or a packet of sports gel and a 20-ounce sports drink).
• 70 to 80 grams of carbohydrate per hour during prolonged exercise (greater than two hours). A cereal bar or sports bar (not high protein or high fat), 20 ounces of sports drink, and 1/4 cup of gummy-type candy (spaced over the course of one hour) will provide the required amount.
There is no advantage to exceeding these amounts. Some athletes over-consume food to prevent the onset of hypoglycemia. This can exacerbate symptoms and lead to stomach upset and, possibly, weight gain.
Sidebar: Glycemic Index
Some hypoglycemic athletes may benefit from eating foods with a low glycemic index prior to exercise. The glycemic index of a food is its ability to affect blood glucose levels after ingestion. Eating low-glycemic-index foods may not benefit most athletes, but for those with reactive or chronic hypoglycemia, being selective about the type of carbohydrate consumed prior to exercise, and noting performance levels and physical well being, can help determine whether this regimen is helpful. Low-glycemic-index foods include brown or white rice, chickpeas, plums, pasta, milk, cheese, lentils, yogurt, peaches, apples, kidney beans, nuts, and fructose.
Some acceptable pre-exercise meals with a low glycemic index include:
•Fructose-sweetened yogurt with walnuts and apples
•Lentil soup with rice
•Peanut butter on rice cakes and a plum
•Rice pudding with milk, cinnamon, raisins, and maple syrup for sweetener
•A smoothie made with yogurt, milk, and frozen peaches
•Red beans and rice
Table Two. You Gotta Act Quick
If an athlete is experiencing a hypoglycemic episode, the best recourse is to give him or her 15 grams of quick-acting carbohydrates. The following foods meet these criteria and are easily kept on hand.
4 oz. of carbonated beverage (not sugar-free)
5 gummy-type candies
8 jelly beans
1/2 cup gelatin (not sugar-free)
5 hard candies (small roll size)
8-oz. skim milk
6 1/2-inch sugar cubes
8-oz. sports drink
3 glucose tablets
The following foods are higher in fructose, which has a lesser and slower effect on elevating blood glucose levels:
4 oz. of apple or orange juice
1 Tbs. honey
2 Tbs. raisins
Half a candy bar will also provide 15 grams of quick-acting carbohydrate. Candy bars, however, can be higher in fat content, which can slow digestion, therefore delaying the effectiveness of the carbohydrate.