|MadSci Network: General Biology|
Hi Julia, Well as you know the chemical in coffee that is resposible for all of its effects is caffeine. Some basic info on caffeine is that it is a stimulant, causing such effects in people such as restlessnes, agitation and tachycardia. It is also listed as a class C drug for pregnancy meaning that it may have some tumor causing effects in the fetus but significant human/animal studies have not been done. With that aside you specifically asked if drinking cold vs hot coffee ( I assume that it is not decaffeinated)would have different effects on blood pressure. In any case caffeine is not a chemical that is changed by the heat of the beverage so that would have no effects necessarily on it. Also the heat of the beverage would also have little to do with absorption rate into by the GI tract. There are several studies, which I have referenced below, that show differing results on caffeine's effect on blood pressure. In a nutshell the jury is still out. However, most studies did feel that people who do not regularly consume caffeine may have a slight increase in blood pressure when exposed to caffeine acutely. This tolerance develops rapidly and the blood pressure returns to baseline. Hope this helps. 1. Birkett NJ & Logan AG: Caffeine-containing beverages and the prevalence of hypertension. J Hypertens 1988; 6:S620-S622. 2. Hodgson JM, Puddey IB, Burke V et al: Effects on blood pressure of drinking green and black tea. J Hypertens 1999; 17:457-463. 3. Shirlow MJ, Berry G & Stokes G: Caffeine consumption and blood pressure: an epidemiological study. Int J Epidemiol 1988; 17:90-97. 4. Atkinson,: The cardiovascular effects of caffeine in various forms. Arzneimittelforschung 1977;27(11):2070-2 Mark Sullivan Admin note: also see the following post on the virtues of hot vs. cold drinks in general (not specifically coffee): Does drinking a hot beverage cool down body temperature?
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