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Microsoft word - caffeine friend or foe.doc
Caffeine intakes are claimed to improve performance, alertness and cognition - the whole process by which knowledge is acquired, including perception, intuition and reasoning. It also stimulates oxidation of fat which can help in sparing the body’s limited muscle glycogen stores. Caffeine helps in the release of calcium from muscle cells, thereby stimulating muscle contractions more effectively. The stimulating effect of caffeine may even help those golfers who struggle to practice or compete first thing in the morning (the overall importance of breakfast should not be forgotten of course – a cup of coffee is definitely not a substitute for a healthy balanced breakfast. If you have forgotten how important breakfast is, re-read the nutrition newsletter a couple of months ago “Breakfast for all”!) Caffeine belongs to a group of chemicals called methylxanthines and it is found in tea, coffee, cocoa, colas and other soft drinks, energy drinks and chocolate. It is also found in some over-the-counter medicines including cold and flu remedies, pain relief products, anti-histamine tablets and diuretics (things that make you pee more). Caffeine is not a nutrient, even though it is regularly found in the diet, but in fact is classed as a pharmacological agent. It is indeed a socially acceptable drug and the most widely consumed behaviour-influencing substance in the world. It is soluble in water and fat and can therefore appear in all tissues and systems of the body. The liver is mainly responsible for metabolizing caffeine and the kidneys for excreting it. Peak concentrations of caffeine appear in the blood 30 to 60 minutes after consumption though the range is very wide – 15 minutes to 2 hours. Caffeine has a half-life of between 4 to 6 hours. In other words the highest concentration of caffeine will be in the blood about an hour after consumption and this level will have fallen by half, 4 to 6 hours after consumption. A review paper published in 2004 looked at thirty-nine caffeine studies, twenty-one involving endurance exercise, twelve involving short-duration-high intensity exercise and six using a graded exercise test. The longer events produced the biggest effects but improvements were also seen in short-duration, high-intensity exercise. Of particular interest to golfers however was the finding the just a small amount (60mg) of caffeine, equivalent to one cup of coffee was shown to have an effect on decision making, alertness and reaction time. Now you probably don’t think there are many similarities between a golf player and a rugby player! However the results of a study published in 2005, where the subjects were rugby players, could be of interest to golfers. The effects of caffeine in a performance test simulating physical and skill demands of the game were investigated. No need to give all the details here but the paper concluded with a final comment “This effect of caffeine is likely to be important in competitive sports where the ability to perform skills like passing balls, hitting balls or shooting goals with accuracy late in the event is a key to successful performance.” Before you all rush off to get your caffeine fix, there are several things to consider first. Overall the literature suggests that small to moderate intakes of caffeine (around 2mg per kg body weight) – not the traditional larger doses of 6mg per kg body
weight – is all that is needed to reduce perception of fatigue and enhance performance. Individual responses to caffeine intake and the withdrawal of caffeine from the diet are enormous. Frequent high intakes cause a rapid desensitization in people which means that more is then needed to get the same result. A sensible approach for players intending to use caffeine in the match situation would be to moderate their caffeine intake on non-match days so that the effect of a slightly increased intake on match days is maximized. There certainly seems no good evidence that complete caffeine withdrawal is necessary however. Players should be aware that although caffeine was removed from the World Anti-Doping Agency (WADA) list of banned substances early in 2004, its use is being monitored in-competition only and the situation could always change. Caffeine content of a range of beverages: Caffeine content Average cup of instant coffee - 75mg* Average mug of instant coffee - 100mg* Average cup of brewed coffee - 100mg* Average cup of tea - 50mg* Regular cola drink - 11-70mg per can+ Regular cola drink - 16-106mg per 500ml bottle+ Regular energy drink - up to 80mg per can* Lucozade Sport with caffeine boost - 16mg per 500ml bottle# *Source – Food Standards Agency for pregnant women on caffeine, 10 October 2001. + Source – MAFF Food Safety Directorate 1998 # Manufacturer’s data People are often advised by pseudo-nutritionists and journalists to avoid coffee because of the dehydrating effects of caffeine, particularly in situations where fluid balance may be compromised. Back in 2003, Professor Ron Maughan and I looked at the current literature concerning the effect of caffeine ingestion on fluid balance. The conclusion we drew (and others have come to the same one) was that there was no support for the suggestion that consumption of caffeine-containing beverages as part of a normal lifestyle led to fluid loss in excess of the volume ingested. In other words it did not have a diuretic effect. Caffeine consumption was not associated with poor hydration status either. Players who habitually drink caffeine-containing drinks can be reassured that intakes of up to 300mg of caffeine a day will not compromise hydration status. As the table above shows this is roughly equivalent to 3 mugs of coffee or 6 cups of tea. In conclusion, caffeine is relatively safe for healthy players and is now totally legal. However those players who do decide to use caffeine in tournaments must practice and perfect the technique in practice sessions or even low-key tournaments first. Jane Griffin Sports Dietitian and Nutrition Consultant
for old formulas”. What Dr Huang opened us to When one is busy with a clinic year after year, one’s was the logic and intelligence behind the Shang understanding of classical formulas can became myopic Han Lun (Discussion of Cold-Induced Disorders) formulas. One could say he taught us more thoroughly how to understand and utilise the old uses for the old formulas. There have been
Impact of CO2 on human decision making and productivity Usha Satish1,*, William B. Fisk2, Mark J. Mendell2, Katia Eliseeva2, Toshifumi Hotchi2,Douglas Sullivan2, Lisa B. Cleckner3, Krishnamurthy Shekhar1 and Kaeling Teng11SUNY Upstate Medical University, Syracuse, NY2Lawrence Berkeley National Laboratories, Berkeley, CA3Syracuse Center of Excellence, Syracuse, NY Keywords: Performance, IAQ, D