The caffeine contained within coffee is the main culprit in the effect your morning cup of joe has on your cardiovascular system. Caffeine works as both a stimulant and diuretic. Though you may be drinking coffee for a quick wake-up, it may be doing more than stimulating your brain. Cardiovascular side effects of coffee include an increase in blood pressure and heart rate.
Cardiovascular Changes
When you drink a cup of coffee, the caffeine inside the coffee causes changes to your cardiovascular system which increase your blood pressure. When you take in caffeine, your arteries constrict, making your blood pressure rise. The theory is that caffeine blocks a hormone that keeps your arteries widened. Caffeine, since it is a stimulant, also increases your heart rate.
Hormonal Response
Coffee can also alter your hormones, according to a study conducted by the Duke University Medical Center in 1999. This study took 72 regular coffee drinkers. For two weeks, the individuals were told to either drink coffee as normal or to abstain from it and blood hormones were monitored throughout the day. Consistently stress hormones, adrenaline and noradrenaline, were elevated on the days that coffee was consumed. These two hormones evoke a stress response by the body that also increases blood pressure. In fact, on average blood pressure readings rose by 3 mmHg.
Chronic Hypertension
Though coffee acutely raises your blood pressure, there is no concrete evidence that regular coffee consumption will lead to chronic hypertension. A meta-analysis published in the "American Journal of Clinical Nutrition" in 2011 looked at results of studies involving over 170,000 people for up to 33 years. Those that consume even a large amount of coffee each day are no more likely to be diagnosed with hypertension than those that do not drink any coffee. Scientists believe that coffee is not a risk factor but that more research needs to be done on the subject.
Safety
The consensus is that coffee is safe for most people. According to Sheldon G. Sheps, M.D., of the website MayoClinic.com, 200 mg of caffeine per day, or about two to three cups of coffee, is perfectly safe for most. But be careful, food and even some medications also contain caffeine. If you have been diagnosed with hypertension, speak with your doctor about the safety of coffee for you. Excessive caffeine intake can raise your systolic pressure by 3 to 14 mmHg and your diastolic pressure by 4 to 13 mmHg.
References
- "Nutrition: Concepts and Controversies"; Frances Sizer and Eleanor Whitney; 2004.
- Medline Plus: Caffeine in the Diet; David C. Dugdale, III, MD; May 2, 2009
- MayoClinic.com: Caffeine: How Does It Affect Your Blood Pressure; Sheldon G. Sheps, M.D.; November 14, 2009
- Science Daily.com: Morning Coffee Boosts Blood Pressure, Stress Hormones All Day; March 1999
- Reuters.com: No Evidence Coffee Ups Risk of High Blood Pressure; Genevra Pittman; April 2011
