Lecture 15: Caffeine

Introduction to Caffeine

  • Caffeine is recognized as the world's most commonly used psychoactive drug.

  • Daily caffeine consumption estimates suggest that up to 80% of the world's population consumes caffeine in various forms.

Sources of Caffeine

  • Common sources: coffee, tea, cola drinks.

  • Less known sources: Yerba Mate, Guarana, cacao.

    • Yerba Mate: consumed in South America like tea.

    • Guarana: found in energy drinks, contains theophylline and caffeine.

    • Cacao: used to make chocolate, the primary source of theobromine.

Global Caffeine Consumption Statistics

  • Worldwide Average: 70 mg per day.

  • Canada: 210 mg per day.

  • United Kingdom: 450 mg per day.

  • Typical caffeine in coffee (e.g., Tim Hortons): ~100 mg.

    • Worldwide average corresponds to less than one cup of coffee.

    • Consumption in Canada equates to about two cups of coffee.

    • UK consumption is roughly four and a half cups of coffee.

Chemical Composition of Caffeine

  • Caffeine is classified as a methylxanthine.

    • Contains methyl groups added to the xanthine molecule at positions 1, 3, and 7.

    • Other Methylxanthines:

      • Theophylline: equipotent to caffeine for stimulating effects.

      • Theobromine: only one-tenth the potency of caffeine and theophylline.

    • Caffeine's full name: 1,3,7-trimethylxanthine.

The Role of Methylxanthines in Plants

  • Methylxanthines serve a protective function in plants against insects by producing octopamine.

  • Insects consuming xanthine-containing material can die from octopamine accumulation; mammals, including humans, do not metabolize xanthines this way.

Coffee and Its History

  • Coffee consumption dates back centuries; myth about a goat herder discovering coffee.

  • Roasting and grinding processes led to coffee as a beverage.

  • Coffee houses emerged as places for socializing and discussion, referred to as "penny universities".

  • Introduced to Europe by Ottoman trade, coffee replaced wine in Islamic culture due to alcohol prohibition.

Tea and Its Historical Background

  • Tea is believed to be the oldest caffeine-containing beverage used for psychoactive effects.

  • Legend of Emperor Shen Nong accidentally discovering tea.

  • Tea became popular in China and later in Japan; propelled to Europe through Venetian trade routes.

  • Opium Wars primarily about British demand for tea and its trade intricacies.

  • Tea's introduction to Canada in the early 1700s.

  • Typical caffeine content in tea: 50 mg per cup.

Cola Drinks and Energy Beverages

  • Cola drinks are significant sources of caffeine, mostly added rather than natural.

  • Typical caffeine content in cola: 40 mg.

  • Energy drinks like Red Bull vary in caffeine content but are often perceived to have higher caffeine levels than coffee; Red Bull has about 83-85 mg.

Caffeine Pills and Other Sources

  • Over-the-counter caffeine pills (e.g., No-Doz) often contain 100 mg of caffeine.

  • Caffeine is also found in certain pain relievers, cold medicines, and even chewing gum or candies.

Caffeine Absorption and Metabolism

  • Rapidly absorbed in the GI tract; peak blood concentrations in 30-60 minutes.

  • Average half-life: 5 hours, affecting regular consumption patterns (e.g., withdrawal symptoms).

  • Influences on metabolism include medications (antidepressants slow metabolism), smoking (increases metabolism), and pregnancy (slows metabolism).

Neurochemical Effects of Caffeine

  • Acts as an antagonist at adenosine receptors, which normally promote sleepiness and relaxation.

  • By blocking adenosine, caffeine increases alertness and wakefulness, elevates mood and subjective feelings of energy.

Effects and Risks of Caffeine

  • Positive: increases mental alertness, subjective mood elevation, decreases appetite.

  • Negative: decreased quality of sleep, does not counteract alcohol effects, increases calcium excretion which can risk osteoporosis.

  • Acute caffeine intoxication can occur at levels generally regarded as high (around 600 mg), leading to symptoms like restlessness, increased heart rate, insomnia, and headache.

Tolerance and Dependence

  • Tolerance may occur with regular caffeine use but not uniformly across all effects.

  • Dependence is also evident, especially when withdrawal symptoms like headache and irritability present after cessation.

  • Withdrawal symptoms peak between 24-48 hours and remit within 7-10 days.

  • Acutely caffeinated intoxication recognized as a substance-induced disorder with distinct symptomatic profiles.