Caffeine is widely consumed by the general public and athletes, and moderate levels can improve athletic performance. Caffeine does not cause dehydration, but it can interfere with sleep. Caffeine in coffee does not seem as effective, so other sources should be used.
Man has been searching for ways of improving athletic performance since at least 400 BC, when the hearts of lion were believed to impart benefits. Today, caffeine can improve performance in endurance running, and three of every four elite athletes take caffeine when competing. Caffeine is one of the most widely used drugs in the world, with average daily intakes worldwide of 70mg/day, but higher in the US (~200mg/day) and the UK (~400mg/day). Caffeine has many effects on many different tissue types, directly and through its metabolites, as well as stimulating adrenaline release.
Studies have shown caffeine can improve performance by ~2%. Though much greater improvements (~12%) have been shown in laboratory conditions, these are not likely to be seen in real world race conditions. That ~2% represents 3.5 minutes on a 3 hour marathon, nearly 5 minutes on a 4 hour marathon. For the 5K, that represents 25 seconds on a 21 minute 5K, or 18 seconds on a 15 minute 5K. Caffeine tends to benefit fitter individuals more. Caffeine may improve performance by reducing the RPE and Muscle pain.
2.1 Green Tea and Performance
There is relatively little research concerning the effect of tea on athletic performance. However, one study did show that the green tea extract increased fat burning and glucose tolerance during cycling at 60% V̇O2max without affecting Heart Rate or overall energy consumption.
2.2 Coffee and Performance
When you take caffeine as coffee, it may not improve performance as it does when taken in other forms. One study showed that caffeine in coffee does not give a performance improvement where isolated caffeine does and another showed no benefit from caffeinated coffee over decaffeinated coffee. Some studies show a performance benefit from caffeinated coffee, but did not compare with caffeine alone. This may be because coffee contains hundreds if not thousands of compounds besides caffeine. Some of these extra compounds of been shown to affect glucose metabolism. It is been observed that decaffeinated coffee can reduce the absorption of glucose.
3 How much?
Most studies use 3-13mg/Kg, average 6mg, but within that dose range there was no obvious dose response. A smaller intake of 3 to 5 mg/kg dose before exercise and then 1 to 2 mg/kg intakes during prolonged exercise has been recommended. Too much caffeine (9 mg/kg), especially for those that do not regularly take caffeine, can cause impairment, such as becoming talkative, giddy, and unable to perform simple tasks such as telling the time. Low levels of exercise (30% V̇O2max) seem to increase the metabolism of caffeine, but higher intensities have no impact. Below is a listing of caffeine in common beverages.
|Brewed coffee||100-150+ per 8oz|
|Brewed decaf coffee||5 (range: 3-12)|
|Starbucks Espresso||75 per shot|
|Black Tea||28-46 per 8Oz|
|Oolong Tea||12-55 per 8Oz|
|Green Tea||8-36 per 8Oz|
|Soda - Cola||35 per 12oz Can (see 'soda' for details)|
|Soda – Mountain Dew||54 per 12oz Can|
|Red Bull||80 per 8.3oz Can|
4 Caffeine and Dehydration
Caffeine does not impact performance in hot/humid conditions, nor act as a diuretic when running. Caffeine at 360mg is a diuretic at rest, but not at 180mg or less. Caffeine does not cause long term dehydration, and black tea has been shown to hydrate as well as water. Caffeine does result in increased sodium excretion in the urine, but the significance of this unclear.
5 Caffeine Habituation
Surprisingly, there is no clear evidence that the performance benefits of caffeine vary with habitual caffeine usage. Caffeine impacts caffeine naive more at rest than those habituated to caffeine, but the difference is far less during exercise. Caffeine habituation has been shown to reduce the adrenaline response to caffeine, but most other responses remain similar . Animal studies have shown that some tissues adapt to long term use of caffeine but other tissues do not appear to change at all.
6 Caffeine and DOMS
Caffeine has been shown to not only reduce the pain of Delayed Onset Muscle Soreness (DOMS), but also reduces the associated weakness. This reduction in weakness is important because although the soreness is delayed 24-72 hours after exercise, the muscle damage and resulting weakness happens within 30 minutes.
7 Caffeine Withdrawal
Withdrawal from Caffeine generally produces a headache and fatigue, with some evidence of anxiety. Onset of withdrawal is typically 12-24 hours after the last intake, though occasionally as quickly as 3-6 hours, with symptoms after peaking 20-48 hours and lasting a week. Small amounts of caffeine can help with withdrawal.
8 Caffeine and Sleep
Not surprisingly given it's a stimulant, caffeine interferes with sleep. Taking 100mg caffeine just before bedtime significantly interferes with sleep. More significantly, taking 200 mg early in the morning will also significantly interfere with sleep. This suggests that caffeine should be taken as early in the day as is practical, and those with sleep problems should reduce caffeine or avoid it completely.
9 Caffeine and Cramping
10 Caffeine as a Pain killer
Caffeine is frequently added to over-the-counter pain medication to boost its effectiveness; without caffeine 40% more pain medication is required to have the same results. Caffeine adds slightly to the relief of surgical pain from Acetaminophen (Paracetamol) and caffeine can reduce headaches to an equivalent level as Acetaminophen (Paracetamol). Caffeine reduces muscle pain during exercise in both those that habitually take caffeine and those that caffeine naïve, though one study suggested this may only occur in hot conditions. As noted above, caffeine can reduce the pain of DOMS.
11 Caffeine at altitude
The general recommendation to avoid caffeine at altitude does not seem to have a scientific basis. In fact, a number of the effects of caffeine have the potential to be beneficial at altitude:
- As noted above, caffeine does not produce dehydration, and there is little evidence that dehydration contributes to altitude sickness.
- Caffeine tends to increase Breathing, which may offset the depressed Breathing seen at altitude.
- The risk of a brain or lung edema at altitude is a serious concern, and there is the possibility that caffeine may help by constricting blood vessels without restricting oxygenation.
- Caffeine may help alleviate the headache that is common with altitude sickness.
- The lassitude seen at altitude may be offset by caffeine, and the exercise performance improvements at altitude may be even greater than at sea level.
- While caffeine could reduce the altitude problems that prevent sleep, the stimulant nature of caffeine may offset these benefits.
Caffeine has a shorter duration of effect at high altitude, possibly due to increased blood flow to the liver, and withdrawal from caffeine would likely make altitude problems more severe.
12 Glucose Absorption, Insulin Resistance and Glycemic index
Caffeine changes the way glucose is absorbed, but this effect is different for those at rest compared with those exercising.
12.1 At Rest
Caffeine reduces glucose absorption at rest. In tests on lean, obese, and Type 2 Diabetics, glucose absorption was impaired by caffeine, though exercise mitigated the reduction slightly in non-diabetics.
12.2 During Exercise
Unlike the effect of caffeine on sedentary or resting individuals, caffeine increases the absorption, uptake and metabolism of glucose during exercise. Caffeine taken during exercise does not change Glycogen replenishment post-exercise, but caffeine taken with carbohydrate after exercise increased Glycogen replenishment and insulin levels compared with just carbohydrate. One hypothesis for this difference is that caffeine reduces the effect of insulin, and non-insulin dependent glucose pathways predominate during exercise. Caffeine taken 2 hours after exercise impairs glucose absorption, but to a lesser extent than in a completely rested state.
13 Sources of Caffeine
There are various sources of caffeine that are sometimes used by athletes.
While coffee is a very common source of caffeine, there is evidence that caffeine taken in coffee is not as effective as other forms (see above for details). Also, coffee may cause Stomach Problems and Lower GI Problems in some individuals. Typical brewed coffee contains 100-150mg per cup which compounds the problem of using coffee in sports. I would recommend using other sources of caffeine before or during runs.
It is claimed that tea is the second most popular drink after water, but it does not appear to be commonly used by athletes. Because the level of caffeine can vary dramatically with different types of tea, and different brewing methods, it is difficult to know how much caffeine is in a particular drink of tea. Generally black tea has more than oolong tea which has more than green tea. Typically black tea contains 28 to 46mg of Caffeine per 8oz cup. This unpredictability makes tea a problematic source of caffeine, though using the same tea and brewing for the same time will give reproducible levels, but you won't know the absolute caffeine intake.
13.3 Gels ($2-8/100mg)
Gels are available with and without caffeine, and the caffeinated variety normally has 25mg, though some go as high as 100mg. The higher caffeine concentrations often include a coffee extract, which may limit the benefits. Given that gels typically cost $1-2 per gel, the caffeine cost is $2-8/100mg. See Comparison of Energy Gels for more details.
The caffeine levels in soda vary widely, with some common values shown below.
|Soda||Caffeine per 12oz|
|Diet Dr Pepper||44.1mg|
|Diet Mountain Dew||55.2mg|
Typically soda makes a poor sports drink as it contains too much sugar, is too carbonated and additives like phosphoric acid can upset the digestive system. However, ultrarunners used to regularly use soda that had been left to go flat and then often diluted with water. This is something to practice in training before using during a race.
13.5 Energy Drinks
There are many different types of energy drink available on the market today. Frequently they are a mixture of many different substances that are believed in some way to be stimulating. Energy drinks should be used with caution, as the substances they contain may not have been scientifically evaluated, especially in the combinations provided. Energy drinks often contain carbohydrate, but the specific types of carbohydrate and the concentration used may not be appropriate to athletic events. The caffeine content of energy drinks is often 200-300mg per can, which is quite high, but lower than a Starbucks Venti brewed coffee which typically has 400+mg.
13.6 Red Bull ($3-6/100mg)
I've tried a few different energy drinks, and the only one I use now is Red Bull. Red Bull is only lightly carbonated, is not too sweet for my taste, and while the mixture of glucose and sucrose is not great for sports drink, it's better than many of the alternatives. One study has shown that the added Taurine, B vitamins and other ingredients do not add any benefit over the just taking the caffeine. However, I like the taste, and my expectation of a benefit provides a useful placebo. Red Bull contains about 80mg of caffeine per 8oz can, which is slightly less than the equivalent volume of coffee.
13.7 Energy Shots
Energy shots are more convenient than energy drinks due to their small size and portability. However, they concentrated form can easily cause stomach upsets in addition to the problems noted in energy drinks above.
13.8 Caffeine Tablets ($0.03/100mg)
Caffeine tablets have the advantage of low-cost, predictable caffeine content, and portability. Compared with other sources of caffeine, these tablets are 1/100th the cost. I use Natrol tables, which are 200mg per tablet. I cut them into halves using a Pill Cutter, then it's easy to bite off a smaller amount as needed. I carry these in my Portable Pharmacy.
14 Tea and Theanine
Theanine is an amino acid found in tea, primarily green tea. Theanine calms the mind without inducing drowsiness, achieving a relaxed but alert mental state. Theanine has a number of benefits:
- It has been shown to improve and sustain long term attention, acting as a stimulant, even without caffeine.
- When combined with caffeine, theanine reduces distractions.
- Theanine reduces blood pressure and can offset the rise in blood pressure that comes from caffeine.
- Three components of green tea (Catechins, Caffeine and Theanine) reduce obesity in mice.
- Tea may help reduce dementia, and tea improves learning in rats.
- Theanine and cystine may help reduce the immune system depression of high intensity training.
15 Caffeine, Running and Sudden Death
While rare, the sudden death of a runner does occur and often makes the news. Running is estimated to have a mortality rate of about 1 in 7,000 runners, or one death per 396,000 man-hours. Sudden death during a marathon is rarer, at less than 1 in 50,000.
15.1 Primary Causes of Sudden Death in Athletes
15.2 Myocardial Blood Flow and Heart Attacks
The heart not only pumps blood but, like any muscle, it requires its own supply of blood as well. If this blood supply, called myocardial blood flow, is interrupted the result is a Myocardial infarction or heart attack. Coronary artery disease, which reduces the myocardial blood flow, is the most common cause of sudden death worldwide.
15.3 Caffeine and Myocardial Blood Flow
A moderate amount of caffeine does not change the myocardial blood flow at rest, but during exercise the caffeine significantly reduces the flow. This decrease in myocardial blood flow is worse at altitude and in people with Coronary artery disease. (These changes were seen with 200mg of caffeine, but the studies did not try other amounts to see of the effect varies with dose.) The change in myocardial blood flow is not a risk factor for healthy individuals, but for those with Coronary artery disease the combination of caffeine and exercise may exacerbate their condition.
15.4 Caffeine and Irregular Heart Beats
Cardiac arrhythmias (irregular heartbeats) are a group of conditions where the heart does not beat normally and can be a life threatening emergency. There is a common belief that caffeine is linked to some types of arrhythmias, but this does not seem scientifically supported for . In fact, an animal study showed that moderate caffeine reduces the risk of atrial fibrillation. A study giving recent heart attacks 450mg of caffeine showed no change in the risk of arrythmia. Giving 200mg of caffeine before a bicycle stress test to patients who have malignant ventricular arrhythmias made no difference. However, there are anecdotal reports of people having arrhythmia triggered by caffeine. Note that a caffeine overdoes can result in heart problems.
15.5 Evaluating the risks
Because coronary artery disease may not have any initial symptoms, risk evaluation is tricky. Some runners who died suddenly had high cholesterol, high blood pressure or chest pains. Other risk factors include diabetes, smoking, family history of heart attacks, obesity, long term alcohol use. If you have any risk factors for coronary artery disease, it would be prudent to talk to a healthcare professional.
16 Caffeine and health
For most people, caffeine is generally taken as tea or coffee, to the bulk of the scientific evidence around the health impact of caffeine is based on these beverages.
Both green and black tea contain similarly high levels of antioxidants. Green tea contains high levels of EGCG, which has been shown to inhibit cancer cell proliferation. This EGCG may help trigger natural cell death which in turn may help treat both obesity and osteoporosis. Green tea consumption has been linked to a reduction in upper GI cancers and green team may also help with lung, liver, prostate and breast cancers.
16.2 Coffee and Cancer
Caffeine intake (coffee and other forms) is linked to lower rates of the most common type of skin cancer and coffee drinking is associated with a reduced risk of bladder, breast, buccal and pharyngeal, colorectal, endometrial, esophageal, hepatocellular, leukemic, pancreatic, and prostate cancers.
16.3 Coffee and Type 2 Diabetes
Coffee drinking is associated with a substantially lower risk of type 2 diabetes, including decaffeinated. However, coffee drinking is associated with a number of lifestyle risks, such as smoking, inactivity, and poor diet, and adjustments for these risks may overly strengthen the potential anti-diabetic benefits of coffee drinking. There are a number of possible mechanisms behind the reduction in type II diabetes:
- In postmenopausal women, coffee increases the hormone SHRB that may account for the diabetes reduction .
- Coffee (including decaffeinated) is correlated with reduced markers of insulin secretion, especially in obese and overweight women.
- One study found the T2DM risk was only reduced in tea and coffee drinkers who had previously lost weight.
17 Restrictions on Caffeine for Competition
Caffeine was removed from the World Anti-Doping Agency (WADA) list in 2004; prior to that it was restricted at high levels based on urine concentration. It is still restricted by the NCAA at similarly high concentrations. The level of caffeine intake required to exceed the NCAA threshold varies dramatically (x16) between individuals, and for a given individual at different times, with some people at risk of exceeding the permitted level on 3 cups of regular coffee per day and others able to take excessive levels. A study of caffeine showed that even 9mg/kg was less than the NCAA threshold for the test subjects, but another study showed that doses of 9mg or above could result in a positive test for some individuals.
18 Ethics of Caffeine
At its most simplistic level, caffeine is permitted for use in competition, so if we consider "ethics" as simply "following the rules", then caffeine is ethical. If we look at the broader ethical implications of caffeine however, things become a little more nebulous. The World Anti-Doping Agency (WADA) may consider controlling a substance or method if it meets two of these three conditions:
- It has the potential to improve performance
- It has the potential to harm the health of the athlete
- It violates the "spirit of sport"
Clearly caffeine meets criteria #1, but not #2 (if anything, caffeine may be beneficial to health). So does the use of caffeine violate the spirit of the sport? Let's compare the use of caffeine with the use of carbohydrate:
- Both caffeine and carbohydrate have been shown to improve performance
- Neither caffeine nor carbohydrate are essential for life
- The vast majority of people routinely take caffeine, and nearly everybody takes carbohydrate
- There are few health risks with caffeine, and other than Fructose, carbohydrate is generally considered safe
- While both caffeine and carbohydrate are found naturally in plants, it is common for them to be consumed in highly refined forms
- Athletes frequently consume caffeine and/or carbohydrate for the sole purpose of improving performance
- Any athlete that does not effectively use either caffeine or carbohydrate is at a distinct disadvantage
This comparison indicates to me that caffeine is not against the spirit of the sport, or unethical.
19 Newborn babies and Caffeine
Newborn babies may be subject to higher levels of caffeine from breast milk than one would expect. If we assume:
- A 3 Kg baby (6.6Lb)
- A milk intake of 500 to 900 ml/day
- The nursing mother's caffeine intake of 200mg/day (one double shot espresso),
We get a resulting caffeine concentration in the milk of 4ug/ml to 8ug/ml, which is a total caffeine intake of between 2mg to 13mg, or 0.6 to 4 mg/Kg body weight. The upper end of that level is quite high. However, the baby's half-life for caffeine is 31-132 hours (average 82 hours), compared with an adult's 2-10 hour half-life, so the caffeine will build up over time. A 24 hour half live (which is easier to calculate) would result in about a 3mg to 26mg, which is 1 to 8 mg/Kg. I'm guessing that would result in the baby not sleeping well! Conversely, a baby whose mother takes caffeine during pregnancy and is then given formula milk may undergo caffeine withdrawal after birth. Even if the mother breast feeds, the varying levels of caffeine may cause withdrawal symptoms. Also, caffeine has been shown to increase fetal Heart Rate.
- ↑ Search for the Competitive Edge: A History of Dietary Fads and Supplements http://jn.nutrition.org/content/127/5/869S.full
- ↑ Prevalence of caffeine use in elite ... [Appl Physiol Nutr Metab. 2011] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21854160
- ↑ Gilbert RM. Caffeine consumption. In : Spiller GA, editor. The methylxanthine beverages and foods, Alan R. Liss; 1984. p. 185-213
- ↑ 4.0 4.1 4.2 Psychopharmacology, Volume 94, Number 4 - SpringerLink http://www.springerlink.com/content/wl412194360xj32t/
- ↑ 5.0 5.1 5.2 5.3 5.4 Caffeine and exercise: metabolism and per... [Can J Appl Physiol. 1994] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/8081318
- ↑ 6.0 6.1 6.2 6.3 6.4 Effects of caffeine ingestion o... [Int J Sport Nutr Exerc Metab. 2004] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15657469
- ↑ Effects of caffeine ingestion on rati... [Scand J Med Sci Sports. 2005] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15773860
- ↑ 8.0 8.1 Effect of caffeine on quadricep... [Int J Sport Nutr Exerc Metab. 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/19478340
- ↑ MC. Venables, CJ. Hulston, HR. Cox, AE. Jeukendrup, Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans., Am J Clin Nutr, volume 87, issue 3, pages 778-84, Mar 2008, PMID 18326618
- ↑ Metabolic and exercise endurance effects of coffee and caffeine ingestion http://jap.physiology.org/content/85/3/883.abstract
- ↑ Butts and Crowell (1985) Effect of caffeine ingestion on cardiorespiratory endurance in men and women http://www.getcited.org/pub/103341768
- ↑ Effect of caffeinated coffee on running speed, respiratory factors, blood lactate and perceived exertion during 1500-m treadmill running. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478936/
- ↑ Effects of caffeine ingestion on metabolism a... [Med Sci Sports. 1978] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/723503
- ↑ Failure of caffeine to affect substrate... [Med Sci Sports Exerc. 1985] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/3982273
- ↑ 15.0 15.1 BMC Cancer | Full text | Coffee consumption and risk of cancers: a meta-analysis of cohort studies http://www.biomedcentral.com/1471-2407/11/96/
- ↑ 16.0 16.1 16.2 JAMA Network | JAMA: The Journal of the American Medical Association | Coffee Consumption and Risk of Type 2 DiabetesA Systematic Review http://jama.jamanetwork.com/article.aspx?articleid=201177
- ↑ Coffee acutely modifies gastrointestinal hormone secretion and glucose tolerance in humans: glycemic effects of chlorogenic acid and caffeine http://www.ajcn.org/content/78/4/728.abstract
- ↑ Effects of moderate exercise on the pha... [Eur J Clin Pharmacol. 1991] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/2060565
- ↑ Effects of exercise and thermal stress on caf... [J Appl Physiol. 2002] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/12235049
- ↑ Myth buster: caffeine does not exhibit a di... [Indian J Med Res. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20693584
- ↑ Renal and cardiovascular effects of caffeine... [Clin Sci (Lond). 1987] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/3297472
- ↑ Fluid, electrolyte, and renal i... [Int J Sport Nutr Exerc Metab. 2005] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/16131696
- ↑ Black tea is not significantly different from wate... [Br J Nutr. 2011] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21450118
- ↑ Natriuretic effect of caffeine: assessment o... [Clin Sci (Lond). 2002] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/12401118
- ↑ European Journal of Applied Physiology and Occupational Physiology, Volume 62, Number 6 - SpringerLink http://www.springerlink.com/content/u37082130426tl56/
- ↑ Caffeine metabolism and epinephrine responses during exercise in users and nonusers http://jap.physiology.org/content/75/2/805.abstract
- ↑ 27.0 27.1 The effects of caffeine on perceived pain of muscles http://scholarsresearchlibrary.com/ABR-vol2-iss6/ABR-2011-2-6-16-21.pdf
- ↑ Caffeine Attenuates Delayed-Onset Muscle Pain and Force Loss Following Eccentric Exercise http://www.jpain.org/article/S1526-5900%2806%2901023-6/abstract
- ↑ Excitation-contraction uncoupling: major... [Exerc Sport Sci Rev. 2001] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/11337828
- ↑ Intracellular calcium and force in single mouse mu... [J Physiol. 1995] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/8568662
- ↑ Comparison of the symptoms of exercise-induced muscle damage after an initial and repeated bout of plyometric exercise in men and boys http://jap.physiology.org/cgi/content/full/99/3/1174
- ↑ HP. Landolt, DJ. Dijk, SE. Gaus, AA. Borbély, Caffeine reduces low-frequency delta activity in the human sleep EEG., Neuropsychopharmacology, volume 12, issue 3, pages 229-38, May 1995, doi 10.1016/0893-133X(94)00079-F, PMID 7612156
- ↑ HP. Landolt, E. Werth, AA. Borbély, DJ. Dijk, Caffeine intake (200 mg) in the morning affects human sleep and EEG power spectra at night., Brain Res, volume 675, issue 1-2, pages 67-74, Mar 1995, PMID 7796154
- ↑ Judith Stern, Coffee and muscle cramps, Neuromuscular Disorders, volume 21, issue 5, 2011, pages 375, ISSN 09608966, doi 10.1016/j.nmd.2011.03.007
- ↑ Victor Dubowitz, Muscle cramps and coffee, Neuromuscular Disorders, volume 21, issue 3, 2011, pages 235, ISSN 09608966, doi 10.1016/j.nmd.2011.01.004
- ↑ N.C. Voermans, B.G. van Engelen, Coffee and muscle cramps, Neuromuscular Disorders, volume 21, issue 12, 2011, pages 832, ISSN 09608966, doi 10.1016/j.nmd.2011.07.006
- ↑ JAMA Network | JAMA: The Journal of the American Medical Association | Caffeine as an Analgesic Adjuvant http://jama.jamanetwork.com/article.aspx?articleid=392180
- ↑ Analgesic efficacy of paracetamol and its combination with codeine and caffeine in surgical pain–a meta-analysis - Zhang - 2008 - Journal of Clinical Pharmacy and Therapeutics - Wiley Online Library http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2710.1996.tb01148.x/abstract
- ↑ The analgesic effects of caffeine in headache. [Pain. 1991] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/2052380
- ↑ Caffeine lowers muscle pain during exercise in... [Physiol Behav. 2011] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21163281
- ↑ 41.0 41.1 Caffeine at high altitude: java at base cAMP. [High Alt Med Biol. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20367483
- ↑ Coffee acutely modifies gastrointestinal hormone secretion and glucose tolerance in humans: glycemic effects of chlorogenic acid and caffeine http://www.ajcn.org/content/78/4/728.abstract
- ↑ Caffeine Can Decrease Insulin Sensitivity in Humans http://care.diabetesjournals.org/content/25/2/364.abstract?ijkey=0d78b20406d1b0da6a363f1b00847b0434751e49&keytype2=tf_ipsecsha
- ↑ Effects of caffeine on glucose tolerance: a ... [Eur J Clin Nutr. 1998] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/9846599?dopt=Abstract
- ↑ ingentaconnect Caffeine ingestion elevates plasma insulin response in humans dur... http://www.ingentaconnect.com/content/nrc/cjpp/2001/00000079/00000007/art00002
- ↑ Caffeine Ingestion Is Associated With Reductions in Glucose Uptake Independent of Obesity and Type 2 Diabetes Before and After Exercise Training http://care.diabetesjournals.org/content/28/3/566.short
- ↑ Caffeine ingestion increases the insulin response to an oral-glucose-tolerance test in obese men before and after weight loss http://www.ajcn.org/content/80/1/22.short
- ↑ Caffeine increases exogenous carbohydrate oxidation during exercise http://jap.physiology.org/content/99/3/844.full
- ↑ Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine http://jap.physiology.org/content/89/3/1079.full
- ↑ 50.0 50.1 Caffeine ingestion does not impede the resynthesis of proglycogen and macroglycogen after prolonged exercise and carbohydrate supplementation in humans http://jap.physiology.org/content/96/3/943.full
- ↑ High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine http://jap.physiology.org/content/105/1/7.long
- ↑ High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine http://www.jappl.org/content/105/1/7.full
- ↑ Caffeine-Induced Impairment of Insulin Action but Not Insulin Signaling in Human Skeletal Muscle Is Reduced by Exercise http://diabetes.diabetesjournals.org/content/51/3/583.full
- ↑ 54.0 54.1 ML. Bunker, M. McWilliams, Caffeine content of common beverages., J Am Diet Assoc, volume 74, issue 1, pages 28-32, Jan 1979, PMID 762339
- ↑ Yoko Shishikura, Santosh Khokhar, Factors affecting the levels of catechins and caffeine in tea beverage: estimated daily intakes and antioxidant activity, Journal of the Science of Food and Agriculture, volume 85, issue 12, 2005, pages 2125–2133, ISSN 0022-5142, doi 10.1002/jsfa.2206
- ↑ Alan Macfarlane, Iris Macfarlane !!coauthors!!, The Empire of Tea, publisher The Overlook Press, isbn 1-58567-493-1, 32 !!page!!, 2004
- ↑ YS. Lin, YJ. Tsai, JS. Tsay, JK. Lin, Factors affecting the levels of tea polyphenols and caffeine in tea leaves., J Agric Food Chem, volume 51, issue 7, pages 1864-73, Mar 2003, doi 10.1021/jf021066b, PMID 12643643
- ↑ K.-H. Chou, L.N. Bell, Caffeine Content of Prepackaged National-Brand and Private-Label Carbonated Beverages, Journal of Food Science, volume 72, issue 6, 2007, pages C337–C342, ISSN 0022-1147, doi 10.1111/j.1750-3841.2007.00414.x
- ↑ Fueling Properly for an Ultra | Running Times Magazine http://runningtimes.com/Article.aspx?ArticleID=21791
- ↑ Caffeine Content of Drinks http://www.energyfiend.com/the-caffeine-database
- ↑ The Complete Guide to Starbucks Caffeine http://www.energyfiend.com/the-complete-guide-to-starbucks-caffeine
- ↑ RW. Pettitt, JD. Niemeyer, PJ. Sexton, A. Lipetzky, SR. Murray, Do the non-caffeine ingredients of energy drinks affect metabolic responses to heavy exercise?, J Strength Cond Res, Oct 2012, doi 10.1519/JSC.0b013e3182736e31, PMID 23037611
- ↑ Nutrition Facts and Analysis for Energy drink, RED BULL, with added caffeine, niacin, pantothenic acid, vitamins B6 and B12 http://nutritiondata.self.com/facts/beverages/7399/2
- ↑ L-theanine, a natural constituent in te... [Asia Pac J Clin Nutr. 2008] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18296328
- ↑ The effects of L-theanine on alpha-band oscilla... [Brain Topogr. 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18841456
- ↑ Source density analysis of the human E... [Nutr Neurosci. 2007 Jun-Aug] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18019399
- ↑ Psychological effects of dietary components of tea:... [Nutr Rev. 2008] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/18254874
- ↑ 68.0 68.1 ScienceDirect.com - Trends in Food Science & Technology - L-theanine—a unique amino acid of green tea and its relaxation effect in humans http://www.sciencedirect.com/science/article/pii/S0924224499000448
- ↑ Time for tea: mood, blood pressure... [Psychopharmacology (Berl). 2008] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/17891480
- ↑ Anti-obesity Effects of Three Major Components of Green Tea, Catechins, Caffeine and Theanine, in Mice http://iv.iiarjournals.org/content/18/1/55.short
- ↑ Tea and cognitive health in late life: c... [J Nutr Health Aging. 2012] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/22237999
- ↑ Effects of oral supplementation wi... [Biosci Biotechnol Biochem. 2009] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/19352043
- ↑ Cystine and Theanine Supplementation Restores High-Intensity... : The Journal of Strength & Conditioning Research http://journals.lww.com/nsca-jscr/Abstract/2010/03000/Cystine_and_Theanine_Supplementation_Restores.34.aspx
- ↑ PD. Thompson, EJ. Funk, RA. Carleton, WQ. Sturner, Incidence of death during jogging in Rhode Island from 1975 through 1980., JAMA, volume 247, issue 18, pages 2535-8, May 1982, PMID 6978411
- ↑ Barry J. Maron, Liviu C. Poliac, William O. Roberts, Risk for sudden cardiac death associated with marathon running, Journal of the American College of Cardiology, volume 28, issue 2, 1996, pages 428–431, ISSN 07351097, doi 10.1016/0735-1097(96)00137-4
- ↑ William O. Roberts, Barry J. Maron, Evidence for Decreasing Occurrence of Sudden Cardiac Death Associated With the Marathon, Journal of the American College of Cardiology, volume 46, issue 7, 2005, pages 1373–1374, ISSN 07351097, doi 10.1016/j.jacc.2005.07.008
- ↑ Barry J. Maron, Stephen E. Epstein, William C. Roberts, Causes of sudden death in competitive athletes, Journal of the American College of Cardiology, volume 7, issue 1, 1986, pages 204–214, ISSN 07351097, doi 10.1016/S0735-1097(86)80283-2
- ↑ 78.0 78.1 Bruce F. Waller, William C. Roberts, Sudden death while running in conditioned runners aged 40 years or over, The American Journal of Cardiology, volume 45, issue 6, 1980, pages 1292–1300, ISSN 00029149, doi 10.1016/0002-9149(80)90491-9
- ↑ 79.0 79.1 79.2 M. Namdar, T. Schepis, P. Koepfli, O. Gaemperli, PT. Siegrist, R. Grathwohl, I. Valenta, R. Delaloye, M. Klainguti, Caffeine impairs myocardial blood flow response to physical exercise in patients with coronary artery disease as well as in age-matched controls., PLoS One, volume 4, issue 5, pages e5665, 2009, doi 10.1371/journal.pone.0005665, PMID 19479069
- ↑ 80.0 80.1 80.2 M. Namdar, P. Koepfli, R. Grathwohl, PT. Siegrist, M. Klainguti, T. Schepis, R. Delaloye, CA. Wyss, SP. Fleischmann, Caffeine decreases exercise-induced myocardial flow reserve., J Am Coll Cardiol, volume 47, issue 2, pages 405-10, Jan 2006, doi 10.1016/j.jacc.2005.08.064, PMID 16412869
- ↑ 81.0 81.1 Abdul Rashid, Mujahid Hines, Benjamin J. Scherlag, William S. Yamanashi, William Lovallo, The effects of caffeine on the inducibility of atrial fibrillation, Journal of Electrocardiology, volume 39, issue 4, 2006, pages 421–425, ISSN 00220736, doi 10.1016/j.jelectrocard.2005.12.007
- ↑ MB. Katan, E. Schouten, Caffeine and arrhythmia., Am J Clin Nutr, volume 81, issue 3, pages 539-40, Mar 2005, PMID 15755819
- ↑ 83.0 83.1 DJ. Pelchovitz, JJ. Goldberger, Caffeine and cardiac arrhythmias: a review of the evidence., Am J Med, volume 124, issue 4, pages 284-9, Apr 2011, doi 10.1016/j.amjmed.2010.10.017, PMID 21435415
- ↑ MG. Myers, L. Harris, High dose caffeine and ventricular arrhythmias., Can J Cardiol, volume 6, issue 3, pages 95-8, Apr 1990, PMID 1692755
- ↑ TB. Graboys, CM. Blatt, B. Lown, The effect of caffeine on ventricular ectopic activity in patients with malignant ventricular arrhythmia., Arch Intern Med, volume 149, issue 3, pages 637-9, Mar 1989, PMID 2465748
- ↑ Coronary artery disease: Symptoms - MayoClinic.com http://www.mayoclinic.com/health/coronary-artery-disease/DS00064/DSECTION=symptoms
- ↑ Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods – 2007 http://www.webcitation.org/query?url=http%3A%2F%2Fwww.ars.usda.gov%2FSP2UserFiles%2FPlace%2F12354500%2FData%2FORAC%2FORAC07.pdf&date=2009-05-23
- ↑ Apoptotic effect of EGCG in HT-29 colon cancer cells via AMPK signal pathway http://www.sciencedirect.com/science/article/pii/S0304383506001960
- ↑ Apoptotic effect of green tea polyphenol (EGCG) on cervical carcinoma cells - Asif Siddiqui - 2010 - Diagnostic Cytopathology - Wiley Online Library http://onlinelibrary.wiley.com/doi/10.1002/dc.21434/abstract
- ↑ ingentaconnect Novel Treatments for Obesity and Osteoporosis: Targeting Apoptoti... http://www.ingentaconnect.com/content/ben/cmc/2005/00000012/00000019/art00003
- ↑ Tea and cancer prevention: epidemiological stu... [Pharmacol Res. 2011] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/21419224
- ↑ Increased Caffeine Intake Is Associated with Reduced Risk of Basal Cell Carcinoma of the Skin http://cancerres.aacrjournals.org/content/72/13/3282.abstract
- ↑ Annals of Internal Medicine | Coffee Consumption and Risk for Type 2 Diabetes Mellitus http://annals.org/article.aspx?volume=140&issue=1&page=1
- ↑ Coffee, Caffeine, and Risk of Type 2 Diabetes http://care.diabetesjournals.org/content/29/2/398.abstract?ijkey=0aa1ab4745bc811da4ab34ed66604d4462b97615&keytype2=tf_ipsecsha
- ↑ Coffee and Caffeine Consumption in Relation to Sex Hormone–Binding Globulin and Risk of Type 2 Diabetes in Postmenopausal Women http://diabetes.diabetesjournals.org/content/60/1/269.short
- ↑ Caffeinated Coffee, Decaffeinated Coffee, and Caffeine in Relation to Plasma C-Peptide Levels, a Marker of Insulin Secretion, in U.S. Women http://care.diabetesjournals.org/content/28/6/1390.abstract?ijkey=3d4c0a5aa75e45f1690789634957ab9f0a6f0e13&keytype2=tf_ipsecsha
- ↑ Coffee, tea and diabetes: the role of weig... [Int J Obes (Lond). 2005] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/15925959?dopt=Abstract
- ↑ 2012 Prohibited List - World Anti-Doping Agency http://www.wada-ama.org/en/Resources/Q-and-A/2012-Prohibited-List/
- ↑ NCAA Banned Drug List - NCAA.org http://www.ncaa.org/wps/wcm/connect/public/NCAA/Health+and+Safety/Drug+Testing/Resources/NCAA+banned+drugs+list
- ↑ Caffeine renal clearance and urine caffe... [Br J Clin Pharmacol. 1991] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/2049248
- ↑ TE. Graham, LL. Spriet, Performance and metabolic responses to a high caffeine dose during prolonged exercise., J Appl Physiol, volume 71, issue 6, pages 2292-8, Dec 1991, PMID 1778925
- ↑ WJ. Pasman, MA. van Baak, AE. Jeukendrup, A. de Haan, The effect of different dosages of caffeine on endurance performance time., Int J Sports Med, volume 16, issue 4, pages 225-30, May 1995, doi 10.1055/s-2007-972996, PMID 7657415
- ↑ How much expressed milk will my baby need? : KellyMom http://www.kellymom.com/bf/pumping/milkcalc.html
- ↑ S. Stavchansky, A. Combs, R. Sagraves, M. Delgado, A. Joshi, Pharmacokinetics of caffeine in breast milk and plasma after single oral administration of caffeine to lactating mothers., Biopharm Drug Dispos, volume 9, issue 3, pages 285-99, PMID 3395670
- ↑ Parsons, William D., and Allen H. Neims. "Prolonged half-life of caffeine in healthy term newborn infants." Journal of Pediatrics 98.4 (1981): 640-641.
- ↑ JD. McGowan, RE. Altman, WP. Kanto, Neonatal withdrawal symptoms after chronic maternal ingestion of caffeine., South Med J, volume 81, issue 9, pages 1092-4, Sep 1988, PMID 3420441
- ↑ I. Martín, MA. López-Vílchez, A. Mur, O. García-Algar, S. Rossi, E. Marchei, S. Pichini, Neonatal withdrawal syndrome after chronic maternal drinking of mate., Ther Drug Monit, volume 29, issue 1, pages 127-9, Feb 2007, doi 10.1097/FTD.0b013e31803257ed, PMID 17304161
- ↑ G. Buscicchio, M. Piemontese, L. Gentilucci, F. Ferretti, AL. Tranquilli, The effects of maternal caffeine and chocolate intake on fetal heart rate., J Matern Fetal Neonatal Med, volume 25, issue 5, pages 528-30, May 2012, doi 10.3109/14767058.2011.636104, PMID 22502981