Does Caffeine Affect Blood Pressure?

Many external factors can affect blood pressure, which measures the force of the flow of blood through your body. These factors include nutrition, stress, physical activity, alcohol and smoking. A diet rich in fruits and vegetables and low in fat helps your body to maintain normal blood pressure readings. However, even people who are diet-conscious can experience increased blood pressure from the simple compound known as caffeine.

What is Caffeine?

• Caffeine is an alkaloid, meaning it is a naturally occurring nitrogen-containing compound that is biologically active in animals, including humans. Plants produce caffeine as a defense mechanism, as it paralyzes and/or kills insects trying to feed on them. Caffeine is found in foods such as cacao beans, coffee beans, tea, kola nuts, yerba mate and guarana.

Sources

• The most common sources of caffeine are coffee, tea and colas. Chocolate also has some caffeine, but in much smaller amounts than the other sources. Coffee has the highest level of caffeine, with a typical 6-ounce cup containing one serving, or 100 mg. Tea has about half as much caffeine, with a cup containing only about 50 mg . The amount of caffeine found in teas and coffee can vary considerably depending on the type, strength and brew. Colas usually contain about 25 mg to 50 mg of caffeine. Many "energy" drinks do not really provide energy; they just contain a significant amount of caffeine, which simulates energy in the drinker.

Mode of Action

• Caffeine is considered a stimulant, meaning it temporarily can improve mental or physical functions. Caffeine affects your central nervous system, which can cause you to feel jittery or nervous. It also increases your rate of respiration and your heart rate.
  Caffeine does have the ability to increase blood pressure, but does not have this effect on everyone. The exact mode of action is not yet understood, but according to Dr. Sheldon G. Sheps at the Mayo Clinic, researchers theorize that caffeine can cause your blood vessels to narrow by blocking adenosine. Adenosine is a hormone that acts to keep vessels dilated. Caffeine also may cause your adrenal gland to release more cortisol and adrenaline, both hormones that can increase blood pressure.

Avoidance

• Avoid drinking caffeine at night when it can disturb your sleep. You also should avoid drinking more than 200 mg of caffeine per day, which translates to about two 12-ounce cups of coffee. To avoid the risks associated with increased blood pressure, do not drink caffeine right before partaking in strenuous activities that also can increase your blood pressure.

Determination

• Caffeine does not affect everyone's body the same way. Some will feel the stimulant effects and may not be able to drink it at night, while others will not notice any effects. To determine if caffeine increases your blood pressure, take your blood pressure reading 30 minutes after consuming a cup of a caffeinated beverage. If the reading is five to 10 points higher than your normal reading, your body may be sensitive to caffeine and its blood pressure-raising effects.