Caffeine is a central nervous system stimulant that temporarily increases attention, alertness and motor activity, reports the University of Michigan Health Service. Alcohol is a depressant, which serves to slow down brain and motor activity. Individually, the two substances serve completely opposite functions. However, in combination, they can magnify negative effects in the body such as increased heart rate, blood pressure and urine elimination. Preventing damage to the body when using the individual or combination of alcohol and caffeine requires understanding how each substance impacts bodily functions with increased dosage, as well as maintaining moderation to limit harmful use.
Heart Rate
Heart rate refers to how many times the heart beats per minute. Normal or resting heart rate ranges from 60 to 100 beats per minute, notes MayoClinic.com. Due to the stimulating effect of caffeine, heart rate is increased. The higher caffeine content consumed, the more prolonged the effects of increased heart rate. Alcohol, however, also causes a rise in heart rate, even though alcohol has a sedative effect on the body. A 2002 study reported in Heart indicates the relationship is unclear, yet the association between alcohol and heart-rate increase may result from increased vasodilation, when the blood vessels are widened and cause more blood to flow through the arteries and calcium to enter the cardiac chambers. Truman State University notes that because of the enhanced effects caused by the combination use of alcohol and caffeine, heart strain is likely the result.
Blood Pressure
The University of Michigan Health Service indicates that caffeine increases body temperature and blood flow, which impacts blood pressure. Alcohol can initially lower blood pressure, however, individuals using alcohol excessively tend to have high blood pressure. The combination of alcohol and caffeine results in opposing effects due to the stimulant verses depressant nature of each substance, notes Truman State University. This ultimately leads to a rise in blood pressure because the heart must work harder to accommodate the excess blood flow from alcohol dilating, or opening, blood vessels while simultaneously managing the effect of caffeine constricting, or narrowing, the blood vessels.
Diuretic Effect
Alcohol and caffeine increase urine output and fluid loss, known as the diuretic effect. The kidneys are responsible for filtering fluids and sending waste through the digestive system for elimination. Alcohol and caffeine compromise kidney functions due to having a dual diuretic effect when used in combination. The Coffee Science Information Center notes that moderate use of caffeine alone is not harmful and does not lead to dehydration. However, increased dosage with alcohol depletes the body of essential electrolytes such as sodium, potassium and calcium. Electrolytes are important for maintaining hydration, nerve and heart function. Truman State University further warns that the diuretic effect of caffeine and alcohol also promotes hangovers, fatigue and lethargy due to dehydration.
References
- Alcohol Health and Research World: Alcohol's Impact on Kidney Function
- Mayo Clinic: Heart Rate: What's Normal?
- Truman State University: Trendy Combination Leads to Heart Strain, Dehydration
- University of Michigan Health Service: Caffeine
- Heart; Relations Between Alcohol Consumption, Heart Rate and Heart Rate Variability in Men; J. M. Ryan and L. G. Howes; December 2002
- Coffee Science Information Center: Coffee and Kidney Function
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