Caffeine is a naturally occurring central nervous system stimulant that falls under the methylxanthine class of compounds. It is the most widely consumed psychoactive substance globally and is commonly found in coffee beans, tea leaves, kola nuts, and cacao pods¹².

Effects of Caffeine

1. Stimulation and Alertness

   • Caffeine stimulates the central nervous system, enhancing alertness and reducing the sensation of fatigue³.

2. Blood Pressure

   • Caffeine can cause a brief increase in blood pressure, particularly in those who do not consume it regularly⁴. This rise occurs as caffeine may block a hormone that helps keep arteries widened or cause the adrenal glands to release more adrenaline⁴.

3. Diuretic Effect

   • It acts as a diuretic, increasing urine production and helping the body eliminate excess salt and water³.

4. Stomach Acid and Heartburn

   • Caffeine increases the release of acid in the stomach, which can lead to heartburn or upset stomach³.

5. Calcium Absorption

   • It may interfere with the absorption of calcium in the body³.

Safety and Consumption

• For most adults, up to 400 milligrams of caffeine per day is considered safe and typically does not pose long-term health risks⁴.
• Sensitivity to caffeine varies widely. Some individuals may experience side effects such as insomnia, heartburn, urinary symptoms, palpitations, or anxiety even at lower doses⁴.
• People who are pregnant, breastfeeding, or dealing with specific health concerns should consult with a healthcare provider about their caffeine consumption.

Therapeutic Uses

• FDA-Approved Uses:

  • Caffeine is approved for treating apnea of prematurity in newborns and for temporarily restoring wakefulness in cases of fatigue or drowsiness².

• Off-Label Uses:

  • It is sometimes used for treating migraines and post-dural puncture headaches².

Sources of Caffeine

• The caffeine content varies significantly across different beverages:
  • An 8-ounce cup of coffee: 95-200 mg
  • A 12-ounce can of cola: 35-45 mg
  • An 8-ounce energy drink: 70-100 mg
  • An 8-ounce cup of tea: 14-60 mg⁵.

Metabolism and Absorption

• Caffeine is absorbed within about 45 minutes after consumption and peaks in the blood within 15 minutes to 2 hours. It is metabolized primarily in the liver and can remain in the bloodstream for 1.5 to 9.5 hours².
• Various factors, including pregnancy, oral contraceptives, and smoking, can influence the metabolism of caffeine².

In summary, while caffeine can be a useful stimulant that many people consume daily without issue, individual responses can vary. It is essential to be aware of personal limits and potential side effects.

Footnotes

1. NCBI Bookshelf, StatPearls ↩

2. MedlinePlus ↩ ↩² ↩³ ↩⁴ ↩⁵

3. Harvard T.H. Chan School of Public Health, Nutrition Source ↩ ↩² ↩³ ↩⁴

4. Mayo Clinic ↩ ↩² ↩³ ↩⁴

5. FDA Guidelines ↩