Caffeine is the most widely used psychoactive substance in the world.

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Caffeine

Caffeine, sometimes called theine when found in tea, is a xanthine alkaloid found in the leaves and beans of the coffee tree, in tea, yerba mate, guarana berries, and in small quantities in cocoa, the kola nut and the Yaupon holly. In plants, caffeine acts as a natural pesticide that paralyzes and kills many insects feeding upon them. more...

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Caffeine is a central nervous system (CNS) stimulant, having the effect of warding off drowsiness and restoring alertness. Caffeine-containing beverages, such as coffee and tea, enjoy great popularity, making caffeine the world's most popular psychoactive substance.

Sources of caffeine

Caffeine is a plant alkaloid, found in numerous plant varieties. The most commonly used of which are coffee, tea, and to some extent cocoa. Other, less commonly used, sources of caffeine include the plants yerba mate and guaraná, which are sometimes used in the preparation of teas and, more recently, energy drinks. Two of caffeine's alternative names, mateine and guaranine, are derived from the names of these plants.

The world's primary source of caffeine is the bean of the coffee plant, from which coffee is brewed. Caffeine content in coffee varies widely depending on the variety of coffee bean and the method of preparation used, but in general one serving of coffee ranges from about 40 mg for a single shot of espresso to about 100 mg for strong drip coffee. Generally, dark roast coffee has less caffeine than lighter roasts since the roasting process reduces caffeine content of the bean.

Tea is another common source of caffeine in many cultures. Tea generally contains somewhat less caffeine per serving than coffee, usually about half as much, depending on the strength of the brew, though certain types of tea, such as black and oolong, contain somewhat more caffeine than most other teas.

Caffeine is also a common ingredient of soft drinks such as cola, originally prepared from kola nuts. Soft drinks typically contain about 10 mg to 50 mg of caffeine per serving. By contrast, energy drinks such as Red Bull contain as much as 80 mg of caffeine per serving. The caffeine in these drinks originates either from the ingredients used or is an additive derived from the product of decaffeination or chemical synthesis.

Chocolate derived from cocoa is a weak stimulant, mostly due to its content of theobromine and theophylline, but it also contains a small amount of caffeine . However, chocolate contains too little of these compounds for a reasonable serving to create effects in humans that are on par with coffee.

Finally, caffeine may also be purchased in most areas in the form of a pill that containing from 50 mg to 200 mg. Caffeine pills are regulated differently among various nations. For example, the European Union requires that a warning be placed on the packaging of any food whose caffeine exceeds 150 mg per litre. In many other countries, however, caffeine is classified as a flavouring and is unregulated.

Caffeine equivalents

In general, each of the following contains approximately 200 mg of caffeine:

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The influence of caffeine on pain
From Townsend Letter for Doctors and Patients, 1/1/05 by Melvyn R. Werbach

The primary application of caffeine supplementation in pain control has been as an analgesic adjuvant when combined with certain analgesic drugs. This practice is supported by a number of double-blind studies. One of these studies found the potentiating action of caffeine on acetaminophen-induced pain relief to be similar to that experienced when an analgesic with a peripheral action (such as acetaminophen) is combined with another with a central action, in this case dextroproxyphen. By combining the peripherally-acting analgesic with caffeine instead of a centrally-acting analgesic, the side effects of central analgesics (such as drowsiness, constipation and nausea) can be avoided. (1)

[ILLUSTRATION OMITTED]

In a review of 30 clinical trials involving over 10,000 patients, the authors concluded that 40% higher dosages of aspirin, acetaminophen or salicylamide would be needed if they were not given in combination with a small dose of caffeine. (2) A similar adjuvant effect was found when caffeine was added to propyphenazone, (3) or to ibuprofen, a non-steroidal anti-inflammatory drug. (4) However, two recent meta-analyses of randomized controlled trials have questioned the efficacy of caffeine as an adjuvant as they found that caffeine added little to the analgesic effect of acetaminophen, (5) and was ineffective in enhancing the analgesic effect of aspirin. (6)

Studies have also investigated the efficacy of caffeine intake by itself, in treating acute pain. In a double-blind crossover study of 53 patients with non-migrainous headaches, subjects received 2 doses of caffeine, acetaminophen, 2 combinations of caffeine with acetaminophen, and placebo. Caffeine appeared to have an independent analgesic effect that remained significant when statistical adjustments were made for prior caffeine consumption and caffeine's effects on mood. Sixty-five milligrams of caffeine was just as effective as 648 milligrams of acetaminophen in relieving non-migrainous headache symptoms. (7)

However, when data on 131 patients with chronic back pain were reviewed, there were no significant differences between low, moderate and high caffeine users on subjective measures of pain severity or affective distress, (8) suggesting that chronic caffeine intake may be ineffective as a pain reliever.

Laboratory studies have investigated the mechanism by which caffeine may reduce pain. In vitro, instant coffee powders were shown to compete with naloxone for binding to opiate receptors. (9) This finding was not confirmed in vivo, however, as an animal study found that high doses of coffee, whether or not they contained caffeine, failed to show opiate-antagonizing activity. (10) More recent animal work has provided evidence suggesting that the antinociceptive effect of caffeine is mediated instead by central amplification of cholinergic transmission. (11) Moreover, adenosine is suspected to be the metabolite responsible for ischemic muscle pain, and caffeine is an adenosine receptor antagonist. (12)

A Warning

Caffeine can also have negative effects on pain. Acute caffeine withdrawal can cause distress due to "somatic dysfunction." (A term common to osteopathic physicians, somatic dysfunction refers to "impaired or altered function of related components of the somatic (body framework) system: skeletal, arthrodial, and myofascial structures, and related vascular, lymphatic and neural elements." (13)) Subjects in one study regularly consumed 300 mg or more of caffeine a day (found in about 2 eight-ounce cups of coffee or 6 eight-ounce cups of tea) and then abstained from caffeine for 4 days. The number of somatic dysfunctions were found to increase significantly during caffeine withdrawal. Even by day 4, most of the subjects had not fully returned to baseline. (14)

Also, a double-blind crossover study has found that caffeine ingestion may reduce the effectiveness of transcutaneous electrical nerve stimulation (TENS). (15) This finding suggests that patients trying TENS should avoid caffeine for a few days prior to the trial.

More information on the influence of nutrition on pain associated with a variety of illnesses can be found in the second edition of Dr. Werbach's classic SourceBook, Nutritional Influences on Illness--and in his updated and expanded CD-ROM with the same title. A free brochure on his books is available from Third Line Press Inc., 4751 Viviana Drive, Tarzana, California 91356, USA. (Phone: 800-916-0076; 818-996-0076; Fax: 818-774-1575; e-mail: tlp@third-line.com; Internet: www.third-line.com.)

References

1. Kuntz D, Brossel R. [Analgesic effect and clinical tolerability of the combination of paracetamol 500 mg and caffeine 50 mg versus paracetamol 400 mg and dextropropoxyphene 30 mg in back pain.] Presse Med 25(25):1171-4, 1996 (in French)

2. Laska EM et al. Caffeine as an analgesic adjuvant. JAMA 251(13):1711-18, 1984

3. Kraetsch HG et al. Analgesic effects of propyphenazone in comparison to its combination with caffeine. Eur J Clin Pharmacol 49(5):377-82, 1996

4. Forbes JA et al. Effect of caffeine on ibuprofen analgesia in postoperative oral surgery pain. Clin Pharmacol Ther 49(6):674-84, 1991

5. Zhang WY, Li Wan Po A. Analgesic efficacy of paracetamol and its combination with codeine and caffeine in surgical pain--a meta-analysis. J Clin Pharm Ther 21(4):261-82, 1996

6. Zhang WY, Po AL. Do codeine and caffeine enhance the analgesic effect of aspirin?--A systematic overview. J Clin Pharm Ther 22(2):79-97, 1997

7. Ward N, Whitney C, Avery D, Dunner D. The analgesic effects of caffeine in headache. Pain 44(2):151-5, 1991

8. Currie SR et al. Caffeine and chronic low back pain. Clin J Pain 11(3):214-19, 1995

9. Boublik JH et al. Coffee contains potent receptor binding activity. Nature 301:246-8, 1983

10. Strubelt O et al. Failure of coffee to inhibit the pharmacodynamic activity of morphine in vivo. Experientia 42(1):35-7, 1986

11. Ghelardini C et al. Caffeine induces central cholinergic analgesia. Naunyn Schmiedebergs Arch Pharmacol 356(5):590-5, 1997

12. Myers DE et al. Hypoalgesic effect of caffeine in experimental ischemic muscle contraction pain. Headache 37(10):654-8, 1997

13. Glossary of Osteopathic Terminology. Glossary Review Committee, Educational Council on Osteopathic Principles of the American Association of Colleges of Osteopathic Medicine. Revised April 2002

14. Reeves RR et al. Somatic dysfunction increase during caffeine withdrawal. J Am Osteopath Assoc 97(8):454-6, 1997

15. Marchand S et al. Effects of caffeine on analgesia from transcutaneous electrical nerve stimulation. Letter. N Engl J Med 333(5):325-6, 1995

by Melvyn R. Werbach, MD

4751 Viviana Drive * Tarzana, California 91356 USA

Phone 818-996-0076 * Fax 818-774-1575

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