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What You Should Know About Caffeine
Reprinted from the International Food Information Council Foundation, (June 1992).

Whether waking up to a steaming mug of coffee, enjoying lunch with an ice cold cola, or relaxing in the afternoon over a cup of tea, these daily pleasures often have a common ingredient - caffeine.

Caffeine is a naturally occurring substance found in the leaves, seeds or fruits of more than 60 plants. These include coffee and cocoa beans, kola nuts and tea leaves, which are used to make many favorite beverages such as coffee, tea and cola drinks, and foods such as chocolate. Caffeine also is extracted from plants and manufactured synthetically for use as a flavor in some food products.

People have enjoyed caffeine-containing beverages since ancient times. As long ago as 2700 B.C., the Chinese Emperor Shen Nung sipped hot brewed tea. Coffee originated in Africa around 575 A.D. where beans were used as money and consumed as food. Eleventh century Arabians were known to have coffee beverages. And while exploring the New World, Spanish conquistadors were treated to a chocolate drink by Aztec Emperor Montezuma in 1519.

Why caffeine?
The longstanding popularity of beverages that naturally contain caffeine attests to its appealing qualities. In some soft drinks, caffeine is added in small amounts as a key ingredient in the subtle flavor profile that provides each product's unique taste. Because caffeine consumption is so widespread, it is one of the most well-studied ingredients in the food supply.

How does the body react to caffeine?
Caffeine is a mild stimulant. People differ greatly in their innate sensitivity to caffeine. Whereas many individuals can drink several cups of coffee within an hour and notice no effects, others may feel some effect after one serving.

Caffeine does not accumulate in the bloodstream or body and is normally excreted within several hours following consumption.

In sensitive individuals, tests show that caffeine can quicken reaction time and prolong vigilance of various demanding tasks. Many people, such as shift workers and college students studying late at night, find caffeine-containing beverages can help them stay alert to finish their work.

Although a widespread belief, caffeine-containing foods and beverages will not actually help "sober up" an individual who has consumed too much alcohol.

Does caffeine pose health concerns?
During the past decade, extensive research on caffeine in relation to cardiovascular disease, fibrocystic breast disease, reproductive function, behavior in children, birth defects, and cancer has identified no significant health hazard from normal caffeine consumption.

The U.S. Food and Drug Administration (FDA) has conducted research and reviewed the extensive scientific literature on caffeine. In a Federal Register notice published in May 1987, FDA stated that the agency had reviewed "studies on teratology, reproduction behavior, carcinogenicity, and cardiovascular disease...but found no evidence to show that the use of caffeine in carbonated beverages would render these beverages injurious to health."

The American Medical Association (AMA) has examined the research on caffeine and come to a similarly confident position on its safety. A 1984 report from the AMA Council on Scientific Affairs stated, "Moderate tea or coffee drinkers probably need have no concern for their health relative to their caffeine consumption provided other lifestyle habits (diet, alcohol consumption) are moderate, as well."

How has caffeine been studied?
Caffeine has been studied extensively in both animals and humans. Research has established that any biological effects of caffeine in either animals or humans depend strongly on the dose, method of administration and duration of exposure.

Human studies have included both direct biological tests, as well as epidemiological research examining data from surveys of human populations.

Because such extensive human data are available on caffeine, experts advise careful evaluation of high-dose animal experiments before they are interpreted as immediately relevant to human safety.

Can caffeine intake hamper sleep?
The effect of caffeine on sleep varies widely among the population. Individual sensitivity and frequency of consumption seem to determine which individuals feel some effect. Studies at Vanderbilt University have found many individuals feel no effects from caffeine on sleep, while others report delayed, reduced or poorer quality sleep.

Does caffeine increase the risk of cancer?
Speculation that caffeine could be a possible cancer risk has not been confirmed by scientific investigations. A number of human epidemiological studies have examined the increased risk of developing cancer at different locations in the body. Two recent studies of large numbers of people in Norway (16,600) and Hawaii (7,350) found no relationship between coffee consumption and cancer risk.

This confirms the earlier position of the American Cancer Society, which stated, "Available information does not suggest a recommendation against the moderate use of coffee. There is no indication that caffeine, a natural component of both coffee and tea, is a risk factor in human cancer."

Does caffeine contribute to breast diseases?
All clinical studies to date suggest that caffeine consumption does not increase the risk of breast cancer. Researchers in a worldwide examination of 100,000 deaths due to breast cancer concluded that the data do not support an association between caffeine intake and the development of breast cancer.

Research has also shown that caffeine intake is not related to the development of fibrocystic breast disease (FBD), a condition with benign fibrous lumps in the breast. Both the American Medical Association's Council on Scientific Affairs and the National Cancer Institute have published reports stating there is not an association between caffeine intake and the incidence of FBD.

Does caffeine cause high blood pressure?
After reviewing the results of 17 studies, scientists reported in the Archives of Internal Medicine that coffee, tea and other caffeinated beverages do not cause any persistent increase in blood pressure.

Some individuals sensitive to caffeine may experience a very small, short-lived rise in blood pressure, usually not lasting more than several hours. Studies show any rise in blood pressure is less than that normally experienced when climbing stairs.

Does caffeine increase the risk of cardiovascular disease?
The bulk of scientific research does not support a link between caffeine consumption and cardiovascular disease.

The comprehensive 1989 report of the National Research Council on Diet and Health stated, "evidence linking coffee consumption to the risk of coronary heart disease...is weak and inconsistent."

A 1989 report from the well-respected Framingham Heart Study stated that after examining all potential links between coffee intake and cardiovascular disease, there was "no deleterious or salutary effect of coffee consumption." A 1990 Harvard University study confirmed this report, concluding that caffeine intake does not "appreciably increase the risk of coronary heart disease or stroke." Finally, a recent review of studies on caffeine consumption of the equivalent of five to six cups of coffee a day did not increase the frequency or severity of cardiac arrhythmias.

Is moderate caffeine consumption harmful during pregnancy?
Three major studies involving more than 15,000 women have found no birth defects associated with caffeine consumption. Even offspring of the heaviest coffee drinkers were not found to be at higher risk of birth defects.

Similarly, evidence from other human studies continues to support the conclusion that moderate consumption of caffeine by pregnant women does not predispose the mother to spontaneous abortion or preterm delivery, nor the fetus to low birth weight.

The most recent FDA animal studies have found no birth defects when rats are given high doses of caffeine in their drinking water. These results contradict earlier FDA research in 1980 that had triggered an advisory to pregnant women to avoid caffeine. The earlier study force-fed rats high doses of caffeine all at once through stomach tubes (gavage). In the later research, rats sipped similar doses of caffeine in their drinking water, but with no effects.

FDA has stated that scientific evidence does not indicate caffeine adversely affects reproduction in humans. The agency does continue to advise that pregnant women consume caffeine in moderation.

Can caffeine affect fertility?
The largest and most thorough study of women's caffeine consumption and fertility found that caffeine was not linked to fertility problems. This study of almost 3,000 women was reported by researchers at the Centers for Disease Control and Harvard Medical School in early 1990.

Other studies have suggested that caffeine intake might reduce a woman's chance of becoming pregnant, but these did not examine other aspects of lifestyle that may affect fertility, such as exercise level, dietary habits, stress, etc.

Is it possible to consume too much caffeine and become "addicted"?
Several important benchmarks show that caffeine consumption patterns differ sharply from drugs of dependence. First, caffeine intake does not result in steadily increaseed doses. Second, it is not difficult to stop consumption of caffeine.

Some sensitive individuals may experience mild, temporary effects, including headache, irritability and nervousness when their daily intake is quickly and substantially altered. These symptoms usually can be avoided if intake is decreased slowly over several days. Third, the antisocial behavior provoked by drug abuse is not associated with caffeine consumption. Finally, unlike drugs of dependence, caffeine is not associated with any chronic health problems.

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Last modified: July 28, 1998