Presentation on theme: "Ergogenic Aids: Caffeine. Caffeine Characterization – Member of methylxanthine group of compounds Mild stimulant that affects multiple organ systems."— Presentation transcript:
Caffeine Characterization – Member of methylxanthine group of compounds Mild stimulant that affects multiple organ systems – Absorbed rapidly from the gastrointestinal tract – Blood half-life of 3 to 6 hours Sources – Found in many food, beverage, and pharmaceutical sources – Occurs naturally in coffee beans, tea leaves, cocoa, and cola nuts
Caffeine Sources Data from product labels and manufacturers, and National Soft Drink Association. 1997. a Brewing tea or coffee for longer periods slightly increases the caffeine content. b Prescription, 1 oz; 30 mL. Reprinted from Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:338. SubstanceCaffeine content (mg) Beverages and foods Coffee a Coffee, Starbucks, decaf, 12 oz10 Coffee, Starbucks, grande, 16 oz550 Coffee, Starbucks, tall, 12 oz375 Coffee, Starbucks, short, 8 oz250 Caffe, Starbucks, Americano, grande, 16 oz105 Caffe, Starbucks, Americano, tall, 12 oz70 Caffe, Starbucks, Americano, short, 8 oz35 Caffe, Starbucks, latte or cappucino, grande, 16 oz70 Caffe Mocha, Starbucks, short (8 oz) or tall (12 oz)35 Espresso, Starbucks, 8 oz280 Brewed, drip method110-150 Brewed, percolator64-124 Instant40-108 Espresso100 Decaffeinated, brewed or instant; Sanka2-5 Coffe Frappuccino, Starbucks, grande, 16 oz170 Tea, 5 oz cup* Brewed, 1 min9-33 Brewed, 3 min20-46 Brewed, 5 min20-50 Nestea Sweetened Lemon Ice Tea20 Iced tea, 12 oz; instant tea12-36 Green tea, 8 oz30 Chocolate Baker's semi-sweet, 1 oz; Baker's chocolate chips, 1/4 cup13 Cocoa, 5 oz cup, made from mix6-10 Milk chocolate candy, 1 oz6 Sweet/dark chocolate, 1 oz20 Baking chocolate, 1 oz35 Chocolate bar, 3.5 oz12-15 Jello chocolate fudge mousse12 Ovaltine0 Soft drinks 7-Eleven Big Gulp Cola, 64 oz190 Jolt100 Sugar Free Mr. Pibb59 Mellow Yellow, Mountain Dew53-54 Tab47 Table 1. Caffeine Content (mg) of Some Common Foods, Beverages, and Over-the-Counter and Prescription Medications SubstanceCaffeine content (mg) Coca Cola, Diet Coke, 7-Up Gold46 Shasta-Cola, Cherry Cola, Diet Cola44 Dr. Pepper, Mr. Pibb40-41 Dr. Pepper, Sugar Free40 Pepsi Cola38 Diet Pepsi, Pepsi Light, Diet RC, RC Cola, Diet Rite36 Red Bull, 8 oz80 Frozen Desserts Ben and Jerry's no fat coffee fudge frozen yogurt, 1 cup85 Starbucks coffee ice cream, assorted flavors, 1 cup40-60 Haagen-Dazs coffee ice cream, 1 cup58 Haagen-Dazs coffee frozen yogurt, fat free, 1 cup42 Haagen-Dazs coffee fudge ice cream, low fat, 1 cup30 Starbucks frappuccino bar, 1 bar (2.5 oz)15 Healthy Choice cappuccino, chocolate chunk, or cappuccino mocha fudge ice cream, 1 cup 8 Over-the-counter products Cold remedies Dristan, Coryban-D, Triaminicin, Sinarest30-31 Excedrin65 Actifed, Contac, Comtrex, Sudafed0 Diuretics Aqua-ban200 Pre-Mens Forte100 Pain remedies Vanquish33 Anacin; Midol32 Aspirin, any brand; Bufferin, Tyelenol, Excedrin PM0 Stimulants Vivarin tablet, NoDoz maximum strength caplet, Caffedrine200 NoDoz tablet100 Enerjets lozenges75 Weight control aids Dexatrim, Dietac200 Prolamine140 Pain drugs b Cafergot100 Migrol50 Fiorinal40 Darvon32
Caffeine and General Health No consistent evidence for adverse effects on the cardiovascular system – Pre-existing heart arrhythmias or high blood pressure should limit consumption – Potential interactions with other compounds (eg, ephedrine) may increase risk of side effects Sleeplessness and jitters are well-recognized side effects, especially in people not used to caffeine Stomach irritation may occur with caffeinated beverages that increase stomach acid No convincing links between caffeine and cancer or osteoporosis Stimulant effects of caffeine on metabolic rate are minor and should not greatly affect weight control Coffee may help to protect against type 2 diabetes and diseases such as Parkinson’s – Data are mainly observational and the relationships are not exceedingly strong Abstinence or moderation of intake (≤ 2 cups per day) is advisable during pregnancy and lactation Williams MH. Nutrition for Health, Fitness, & Sport. 9th ed. New York, NY: McGraw Hill; 2010:539-542.
Why Is Caffeine Possibly Ergogenic? Increased free fatty acids, glycogen sparing – Associated with higher levels of cAMP in adipose cells Adenosine receptor antagonism Phosphodiesterase inhibition (at high doses) Inhibition of glycogen phosphorylase enzyme – Less breakdown of glycogen Links excitation to contraction in muscle cells – Via release of Ca ++ Direct stimulation of central nervous system – Endorphin release causes decreased perception of effort Stimulation of sodium/potassium pumps – Increased nutrient entry into cells by secondary active transport Inhibition of phosphoinositide metabolism – Less signaling effects of insulin Possibly other mechanisms as well Abbreviation: cAMP, cyclic adenosine monophosphate. Magkos F, Kavouras SA. Caffeine use in sports, pharmacokinetics in man, and cellular mechanisms of action. Crit Rev Food Sci Nutr. 2005;45(7-8):535-562.
Effects of Caffeine on Substrate Oxidation During Exercise Subjects: 2 female, 7 male cyclists Exercise: Cycle to exhaustion at 80% VO 2max Design: Crossover Caffeine: Decaffeinated or caffeinated coffee (330 mg caffeine) 1 hour before cycling Time to exhaustion was nearly 15 min longer for caffeine vs placebo Abbreviations: FFA, free fatty acid; SE, standard error; VO 2max, maximal oxygen consumption; R, ratio; VCO 2, carbon dioxide production. Reprinted from Costill DL, et al. Med Sci Sports. 1978;10(3):155-158..22.214.171.124.12.08.04.00 Glycerol, mM 0.5 0.4 0.3 0.2 FFA, mM 1.0 0.9 0.8 R, VCO 2 /VO 2 0102030405060708090 Exercise time, minutes Caffeine trial Decaffeinated trial SE
Effect of Caffeine on 500-m Split Times During a 1,500-m Swim Subjects: 7 male (72.3 kg), 4 female (57.9 kg) swimmers Capable of swimming 1,500 m in < 25 minutes All subjects consumed < 300 mg caffeine/week All subjects abstained from caffeine for 48 hours before study Design: Randomized, double-blind, crossover Caffeine: 6 mg/kg body weight (BW) administered in a fruit juice drink 2.5 hours before the swim Placebo was fruit juice drink alone Reprinted from MacIntosh BR, et al. Can J Appl Physiol. 1995;20(2):168-177. Subjects swam faster after caffeine consumption and reported lower perceived exertion Placebo Caffeine 448 444 440 436 432 428 424 420 416 412 408 0 50010001500 Distance, meters Time, seconds/500 m
Effects of Different Doses of Caffeine on Performance Subjects: 9 well-trained cyclists Caffeine users (100 to 250+ mg/day) Abstained from caffeine for 3 days prior to exercise Exercise: Cycle to exhaustion at 80% VO 2max Caffeine: 0, 5, 9, or 13 mg/kg BW Caffeine given by capsule Abbreviations: BW, body weight; VO 2max, maximal oxygen consumption. Reprinted from Pasman WJ, et al. Int J Sports Med. 1995;16(4):225-230. There was no dose response observed for the dose range evaluated 80 Endurance time, minutes 70 60 50 40 30 20 10 0 05913 mg caffeine/kg BW *P < 0.05 placebo versus caffeine * * * 47 min 58 min 59 min
Urinary Caffeine Levels With Different Doses of Caffeine mg caffeine/kg BW Abbreviations: BW, body weight; IOC, International Olympic Committee. Reprinted from Pasman WJ, et al. Int J Sports Med. 1995;16(4):225-230. Only the 5-mg/kg BW dose always resulted in urine concentrations below previous IOC limits 5913 1 2 3 4 5 6 7 8 9 Subjects 30 25 20 15 10 5 0 Previous IOC limit > 12 doping limit Urinary caffeine, µg/mL 0
What Is the Ergogenic Dose of Caffeine? 3 to 6 mg/kg BW associated with ergogenic benefits for endurance exercise – No further benefits with higher doses May have more pronounced effects on non-users or regular users who abstain from caffeine for several days – These data are not always consistent – There are potential adverse effects in athletes who don’t regularly use caffeine Recommended to try caffeine in practice before competition conditions Abbreviation: BW, body weight. Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:340-341.
Is Caffeine Permissible as an Ergogenic Aid? No longer listed by the World Anti-Doping Agency as a prohibited substance – Remains on their Monitoring List Still on the National Collegiate Athletic Association (NCAA) Banned Substance List at a dose that results in a urine concentration of 15 μg/mL – Equivalent to 9 to 13 mg/kg BW consumed 1 hour before event Equals 630 to 910 mg caffeine/day for a 70-kg person – Roughly 6 to 9 cups of coffee Abbreviations: BW, body weight; NCAA, National Collegiate Athletic Association.
Position of the International Society of Sports Nutrition Caffeine is effective as an ergogenic aid at 3 to 6 mg/kg BW – More effective when consumed in anhydrous state Caffeine may – Enhance vigilance during extended exhaustive exercise or sleep deprivation – Be beneficial for sustained maximal endurance exercise, such as time trial performance – Be beneficial for high-intensity exercise with intermittent activity occurring over a long period of time (eg, team sports such as soccer or rugby) Data are equivocal regarding effects of caffeine on strength and power Scientific literature does not support the notion that caffeine is a diuretic during exercise Abbreviation: BW, body weight. Goldstein ER, et al. J Int Soc Sports Nutr. 2010;7(1):5.