Caffeine is a stimulant present in soda, tea and coffee. Stimulants, like caffeine, increase heart rate and blood pressure by causing a series of chemical reactions in your heart and adrenal gland. After drinking or eating caffeine, you feel increased energy and focus. These reactions are associated with your "fight or flight" response.
Cyclic Adenosine Monophosphate
Caffeine inhibits phosphodiesterase (PDE). PDE is a chemical that breaks down second messengers responsible for helping hormones and neurotransmitters pass through cell membranes. Cyclic adenosine monophosphate (cAMP) is a second messenger. Caffeine stops PDE from breaking down cAMP. Neurotransmitters, like norepinephrine and epinephrine, cannot pass through cell membranes. This causes neurotransmitters to build up and affect heart rate.
Norepinephrine and Epinephrine
Without cAMP to help norepinephrine and epinephrine pass through cell membranes, the neurotransmitters increase your heart rate and blood pressure. Blood pumps faster and harder moving more oxygen to the brain, organs and tissues. You feel an increase in energy, but the body feels the effects of the "fight or flight" reaction. "Fight or flight" is a natural reaction to stress that preserves body tissues in case of harm and prepares the body to run or attack.
Adenosine
Caffeine and adenosine share many chemical characteristics. Adenosine naturally occurs in your brain. It works as a neurotransmitter. When caffeine enters your brain, it binds with adenosine. Nerve cells no longer recognize the adenosine and your brain reacts by speeding up nerve cells. Adenosine helps your body fall into deep sleep. With nerve cells racing, your brain does not recognize the adenosine and you feel more awake. The adenosine reaction stops fatigue, not increased heart rate.
Dangers of Caffeine
The effect of caffeine on your heart depends on the amount of caffeine you consume and your tolerance to caffeine. The average cup of coffee contains about 100 mg of caffeine and over-the-counter "no sleep" medications contain 200 mg of caffeine. In large doses of caffeine, 10 g or more, death can occur. You would have to consume about 100 cups of coffee, drinking one cup after another, to consume 10 g of caffeine.
Naturally-Occurring vs. Added Caffeine
Caffeine naturally occurs in coffee and tea. The average cup of coffee contains about 100 mg of caffeine per 5-oz. serving. Tea contains about 80 mg of caffeine per 5-oz. serving. Caffeine is added to some sodas. Caffeine content in soda ranges from 0 mg of caffeine in Sprite and 7-Up to 64 mg of caffeine per 12-oz. serving of Coca-Cola.
Lasting Effects
The effect of caffeine lasts 12 hours in your body. When you drink one cup of coffee with 100 mg of caffeine at 10 a.m., the caffeine affects PDE, cAMP, norepinephrine, epinephrine and adenosine until 10 p.m. Your heart rate stays elevated for 12 hours.
Member Comments