Caffeine Reduces Myocardial Blood Flow During Exercise
Caffeine (1,3,7-trimethylxanthine) is one of the most widely used pharmacologically active drugs in the world and is found in products such as colas, coffee, tea, energy beverages, dietary supplements, over-the-counter medications, and chocolate. It has been estimated that worldwide caffeine consumption is approximately 76 mg/d per person; in the United States and other developed countries, the average consumption rate exceeds 230 mg/d.(1)
As the popularity and consumption of energy beverages has increased, sudden cardiac death has been reported in teenagers and young athletes who have consumed these products.(2) Most energy beverages also contain guarana, a rainforest vine with seeds that contain high levels of caffeine.(3) High levels of caffeine, especially in individuals who do not consume caffeine on a regular basis, may play a role in caffeine toxicity and possible cardiac death.(3) The use of energy beverages is often advertised in conjunction with amateur and professional sports, and cardiac arrest in the setting of caffeine use and exertion has been described.(4)
On October 17, 2012, a California Superior Court lawsuit was filed against Monster Energy (Monster Beverage Corporation, Corona, Calif) by the parents of Anais Fournier, a 14-year-old Maryland teenager who died after drinking two 24-ounce Monster Energy Drinks in 24 hours. After autopsy, the cause of death was noted as “cardiac arrhythmia due to caffeine toxicity.”5 Energy beverages have been shown to acutely reduce endothelial function; however, energy beverages also may contain a variety of constituents, and the contribution of caffeine alone is unclear.(6)
Given the increase in caffeine availability and reports of adverse events, an understanding of the cardiac effects of caffeine is urgently required. This review summarizes the available medical literature specifically relating to caffeine ingestion and reduced exercise coronary blood flow, suggesting possible mechanisms. This review specifically focuses on the effects of caffeine on the coronary arteries, especially the reduced coronary blood flow noted with exercise.(7, 8, 9)
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– John P. Higgins, MD, MBA, MPhil, Kavita M. Babu, MD
This article originally appeared in the August 2013 issue of The American Journal of Medicine.
