Caffeine is a naturally occurring stimulant found in coffee, tea, and other herbs. Caffeine is the most socially acceptable drug in the world. Coffee is second only to tea (another caffeine-containing brew) as the most popular beverage in the world.

Despite this, very little is known about how caffeine works, that is, its intracellular mechanism of action. However, recent studies have unveiled many important benefits of caffeine and coffee consumption, particularly for athletes. Many of these benefits have never previously been considered.

At the cellular level, caffeine owes its psychostimulant action to the inhibition of the adenosine A2A receptors. (Adenosine is one of the four building blocks of DNA and an important signaling molecule in the brain.) At concentrations equivalent to a few cups of coffee a day, caffeine binds and blocks nerve cells that normally inhibit voluntary movements in the brain’s movement center, (the striatum). This creates that subtle but very cool “wired” feeling from a jolt of caffeine.

Most athletes know that caffeine gives a workout a serious boost. However, caffeine has recently been shown to be effective at reducing muscle pain produced during exercise [1].

Drinking a cup of coffee is more likely to reduce muscle pain during a workout than taking aspirin . . .

Although aspirin is commonly used to treat muscle pain, a team of researchers at the University of Georgia have previously shown that aspirin does not reduce muscle pain produced during vigorous exercise. Muscle contraction produces a host of biochemicals that can stimulate pain. It was discovered that aspirin blocks only one of those chemicals. Apparently, the biochemical blocked by aspirin has no role in exercise-induced muscle pain.

Now, the same team of scientists discovered that a shot of caffeine before training reduced thigh muscle pain during intense exercise [1]. In this study, 16 healthy men cycled intensely for 30 minutes on two separate days. The exercise intensity was the same on both days and purposefully set to make the riders’ thigh muscles hurt. Participants in the study took either caffeine (10 milligrams per kilogram of body weight) or a placebo one hour before the exercise.

The participants reported feeling substantially less pain in their thigh muscles after taking caffeine compared to taking the placebo. Prior reports show that caffeine improves exercise performance. The researchers suggest that caffeine’s ability to reduce leg muscle pain during exercise might be explained partially by its hypoalgesic properties.

Not all analgesics or combinations (acetaminophen and caffeine) are effective for every type of pain or every individual. Much of this is due to biological variation among people in receptors for the drugs as well as variation in pain receptors in different body tissues. For instance, brain tissue has no pain receptors so surgery can be done on the brain without anesthesia. Obviously, it will hurt getting through the skin and cranium.

The next step is to learn how caffeine helps athletes feel less muscle pain during exercise. Scientists don’t know yet whether caffeine is acting on muscles or the brain.

Coffee compounds alter glucose absorption . . .

For effective fat loss and lean mass gains, a low glycemic response (controlled blood glucose and insulin levels) needs to be maintained. A small study carried out in Great Britain has shown that coffee consumption may delay gastric emptying of glucose from the stomach and slow the absorption of glucose into the bloodstream [2]. These researchers showed that not only caffeine but another compound in coffee, chlorogenic acid, lowers the glycemic response of carbohydrate consumption [2].

In a three-way, randomized, crossover study, nine healthy volunteers consumed either a control glucose solution, or 25 grams of glucose in a 400 milliliter caffeinated or decaffeinated coffee after fasting. Blood was frequently tested over the following three hours.

Both caffeinated and decaffeinated coffee significantly slowed the secretion of glucose-dependent insulinotropic polypeptides compared with the control group. Glucose and insulin profiles were consistently lowered with coffee consumption, and gastrointestinal hormone profiles revealed delayed intestinal glucose absorption. The differences in plasma glucose, insulin, and gastrointestinal hormone profiles shown in this research confirm the potent biological action of coffee on glucose transport.

The researchers suggest that a novel function of coffee consumption may be to slow intestinal glucose absorption rates into the blood as well as shift the site of glucose absorption to more distal parts of the intestine.

Some reports in the media have suggested that coffee consumption negatively affects insulin metabolism and glucose transport into muscle. However, the latest research that has specifically examined this aspect demonstrates that caffeine has a minimal (if any) impact on glucose transport into muscles [3]. Results from other studies have shown that the components of coffee could be beneficial for glucose metabolism and may even help prevent type-2 diabetes [4].

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An intervention study showed that increased coffee consumption (up to 7 cups a day) for 14 days reduced fasting plasma glucose levels in healthy people, whereas substitution of regular coffee for decaffeinated coffee for 20 days did not affect plasma glucose. These results suggest that coffee and caffeine could be beneficial for glucose metabolism [4].

Drinking strong coffee may help prevent cancer . . .

A team of German researchers who have identified a potent antioxidant compound in coffee has shown that coffee consumption increased protection against colon cancer [5].

Scientists have suspected for years that coffee could offer some protection against cancer thanks to its high antioxidant content, but for the first time, these scientists identified a specific, highly active anticancer compound in coffee that boosts the activity of phase II enzymes. Activation of phase II enzymes dramatically upgrades protection against free radical damage, and this important process is thought to protect our DNA against cancer-causing damage.

The study revealed that coffee contains the anticancer compound methylpyridinium, not found in significant amounts in other foods and beverages. Its anticancer activity was unknown until now. Methylpyridinium is not present in raw coffee beans but is formed during the roasting process from its chemical precursor, trigonelline, which is common in raw coffee beans. It is present in both caffeinated and decaffeinated coffee, and even instant coffee.

Coffee consumption was shown to boost activity levels of phase II enzymes in a dose-dependent manner. In other words, the higher the quantity of coffee, the higher the increase in the activity level of the enzymes. Analysis of the extract showed that the most active anticancer compound was methylpyridinium. The results provide strong support for coffee as a cancer fighter in living systems.

Until human studies are done, no one knows exactly how much coffee is needed to have a protective effect against colon cancer. However, the results from these studies suggest that drinking coffee may offer real protection, especially if the coffee is strong! Espresso coffee contains about two to three times more of the anticancer compound than a medium roasted coffee beverage. The researchers also suggested that a dietary supplement could be developed to offer the benefits of the coffee chemical to those not keen on the beverage.

The healthy brew . . .

The results from another large study involving over 51,000 people suggest that drinking three cups of coffee daily may reduce the risk of mortality from liver cirrhosis [6].

Other research studies have shown that coffee could also boost male fertility [7]. In tests on 750 men awaiting vasectomy operations, Brazilian researchers showed that coffee drinkers had better sperm motility. The scientists have proposed research on coffee-based treatments for fertility problems.

Caffeine boosts fat metabolism and stamina in athletes . . .

Athletes use caffeine mainly for its fat-burning, performance-enhancing effects. It appears that a relatively small dose of caffeine before your workout will boost performance and increase the amount of fat utilized during exercise.

An Australian team of researchers has shown that athletes who consumed a small dose of caffeine before exercise (approx 200 milligrams) could continue to exercise at a high-capacity for up to 30% longer than those who had not taken the stimulant. The caffeine supplement enabled the athletes to perform up to 3.5% beyond their normal capacity in a series of performance tests.

The researchers suggested that substances in caffeine triggered the muscles to use fat to fuel exercise instead of the usual carbohydrate stores, thus enabling better endurance performance. In other tests performed by these scientists, drinking Coca-Cola© helped cyclists go faster for longer than those who were given caffeine-free beverages.

Keeping habitual caffeine consumption to a minimum appears to be important to obtaining caffeine’s performance-enhancing effects. However, regarding burning unwanted body fat, no research has shown a reduced effect from frequent caffeine consumption. In other words, while caffeine’s stimulating effects may be blunted by frequent use, caffeine’s potent fat-burning effect may not necessarily be reduced by frequent caffeine consumption.


1. Journal of Pain, August, vol 4, no 6.
2. American Journal of Clinical Nutrition, Vol. 78, No. 4, 728-733.

3. Canadian Journal of Applied Physiology 28; 3.
4. Lancet 360: 1477–78.
5. Journal of Agricultural and Food Chemistry, No 5
6. Annals of Epidemiology, July; 7: 2003.
7. Presented at The Annual American Society for Reproductive Medicine conference; Texas, August 2003.

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Caffeine – Performance Enhancer, Fat-Burner, Pain Reliever, and Anti-Cancer Compound

by Paul Cribb Ph.D. CSCS. time to read: 7 min