Cola drinks are carbonated soft drinks that contain some extract of the kola nut in their syrup. Kola nuts are the chestnut-sized and -colored seeds of the African kola tree (Cola nitida or Cola acuminata). For the soft-drink industry, the trees are, as of 2008, grown on plantations throughout the tropics. Historically, kola nuts were valued highly among African societies for their stimulating properties. Kola nuts were cracked into small pieces and chewed for the effect, which increased energy and elevated mood in extremes of heat, hunger, exhaustion, and the like. European colonists in Africa learned of the effect and some chewed the nuts. In the 1800s, Europeans brought kola nuts to various strenuous endeavors in Africa and in other regions, and they began to increase the areas under cultivation. Kola nuts were soon finely powdered and made into syrups for ease of use, with no loss of effect, it was claimed.
The active ingredient responsible for these stimulatory properties is caffeine, a powerful brain stimulant, which is also present in other plants such as coffee, cocoa, tea, and maté. Besides reversing drowsiness and fatigue, a heightened awareness of stimuli and surroundings may occur. Studies have shown that less energy may be expended by the musculature with equal or greater results—in animals as well as humans—but excess use causes tolerance and dependence, often unrealized until deprivation results in severe headaches. Large doses can cause nervous irritation, shaking, sleep disturbances, insomnia, and aggravation of stomach ulcers or high blood pressure.
In the late 1800s, in the United States, cola drinks came onto the market with other carbonated or phosphated (fizzy) drinks. Coca-Cola, one of the first and most popular, contained extracts of both the coca plant (cocaine) and the kola nut (caffeine), but by the early 1900s, with the realization of its dangers, cocaine was removed and replaced by additional caffeine and a decocainized extract. Drinking cola is common in the United States and emulated worldwide, with many brands competing for a huge and growing consumer market.
As of 2008, colas were available with sugar or artificial sweeteners, with or without caffeine, with or without caramel coloring (clear), thus indicating that people seem to like the flavor regardless of the specific ingredients or the effect.
David Courtwright’s historical study of the origins of the worldwide use of kola points out that the makers of Coca-Cola faced litigation in the United States as early as 1911 on the grounds that the caffeine in the drink was habit-forming and an unlabeled additive in a product advertised to children and adults alike. The result of the trial forced Coca-Cola to reduce caffeine amounts by half, but by then the product was available throughout the United States. During World War II, American soldiers introduced Coke to Europe and Japan, and dozens of bottling plants were built immediately after the war ended. By 1991, Coke was available in 155 nations.
Despite the truthful claims by soft-drink companies of responsible improvements to their products by removing kola extract, caffeine remains the key psychoactive ingredient of these soft drinks. Courtwright argues that products such as Coca-Cola are not only stimulating drugs, but cultural and political symbols that never would have become so in the absence of caffeine or a like stimulant.
Several medical studies conducted in the late twentieth century linked the consumption of cola drinks by physically active adolescent girls to increased bone fractures as compared to those who abstained from colas. A Harvard University School of Public Health study could not determine the exact cause, but speculated that phosphoric acid contained in cola drinks adversely affects calcium metabolism and bone mass. Coupled with the belief that many teens replace milk with soda in their diets increased the likelihood of a decrease in bone density. In addition, research indicates that adolescents who consume excessive amounts of colas (1.5 liters per day or eleven liters per week) or other caffeinated beverages experience daily or near–daily headaches. Public health officials have also noted a dramatic increase in calorie consumption among adolescent cola drinkers.
Phosphoric acid in cola has also been linked to weakened bone density in older women. A 2006 Tufts University study found that regular consumers of cola drinks were likelier to experience decreased bone mineral density in the hip. Such a decrease could lead to osteoporosis and, ultimately, fractures of the hip that are often debilitating or even fatal among older women. However, critics of the 2006 study noted that while the corollaries between phosphoric acid in cola and bone deterioration are quite plausible, research comparing bone loss over time between cola drinkers and non-cola drinkers is necessary to confirm a connection.
Written by Michael J. Kuhar (revised by Matthew May) in "Encyclopedia of Drugs, Alcohol and Addictive Behavior", MacMillan Reference USA (a part of Gale, Cengage Learning), USA, 2009, Pamela Korsmeyer and Henry R. Kranzler, Editors in Chief, excerpts volume I, pp. 337-338. Digitized, adapted and illustrated to be posted by Leopoldo Costa.