Soft Drinks, Hard Facts

Though the soft drink industry admits that soda contributes to tooth decay, most data suggest it is just one of several contributors, and a less important one in developed countries than elsewhere in the world. In the United States, cavities have decreased while soda consumption has increased.

Here's one health effect that even the soft drink industry admits, grudgingly, has merit. In a carefully worded statement, the NSDA says that "there's no scientific evidence that consumption of sugars per se has any negative effect other than dental caries." But the association also correctly notes that soft drinks aren't the sole cause of tooth decay.

In fact, a lot of sugary foods, from fruit juices to candy and even raisins and other dried fruit, have what dentists refer to as "cariogenic properties," which is to say they can cause tooth decay.

Okay, so how many more cavities are soft drink consumers likely to get compared with people who don't drink soda? This is where it gets complicated.

A federally funded study of nearly 3,200 Americans 9 to 29 years old conducted between 1971 and 1974 showed a direct link between tooth decay and soft drinks. (Numerous other studies have shown the same link throughout the world, from Sweden to Iraq.) But here's the rub: In the last 25 years, tooth decay in the United States and other developed countries has actually declined -- at the same time that soft drink use and obesity have risen dramatically.

The scientific explanation for this phenomenon appears to come from a number of studies. One of the most illustrative is a 1994 British study of tooth decay among 12-year-olds in 90 countries. Conducted by statisticians at the University of Reading, the study found that throughout the world, dental decay rises proportionally with sugar consumption. But when researchers examined data from 29 industrialized nations, there was no evidence of a link between sugar and tooth decay.

"These results suggest," the researchers reported in the British Dental Journal, "that in addition to sugar, other factors" -- including improved diet, fluoridated water and even genetics -- play an important role in reducing tooth decay.

But sugar isn't the only ingredient in soft drinks that causes tooth problems. The acids in soda pop are also notorious for etching tooth enamel in ways that can lead to cavities. "Acid begins to dissolve tooth enamel in only 20 minutes," notes the Ohio Dental Association in a release issued earlier this month.

Caffeine Dependence

The stimulant properties and dependence potential of caffeine in soda are well documented, as are their effects on children. While health advocates argue that childhood use of caffeine can lead to dependence later in life -- and that regular doses of caffeine can have negative effects on brain development -- there is no conclusive science to demonstrate this.

Ever tried going without your usual cup of java on the weekend? If so, you may have experienced a splitting headache, a slight rise in blood pressure, irritability and maybe even some stomach problems. These well-documented symptoms describe the typical withdrawal process suffered by about half of regular caffeine consumers who go without their usual dose, according to Kenneth S. Kendler, professor of psychiatry and human genetics at Virginia Commonwealth University (VCU) in Richmond.

Research on caffeine's effects in children is more limited, but it suggests that kids also experience caffeine dependence and withdrawal. At the University of Minnesota, child psychiatrist Gail Bernstein and her colleagues gave 8- to 12-year-old children the equivalent of two to three cans of Diet Coke daily for 13 days. Then they substituted caffeine-free soft drinks without telling the children and measured withdrawal symptoms.

During a computerized test 24 hours later, the children showed signficantly decreased attention, a classic symptom of withdrawal, Bernstein says.

The soft drink industry agrees that caffeine causes the same effects in children as adults, but officials also note that there is wide variation in how people respond to caffeine. The simple solution, the industry says, is to choose a soda pop that is caffeine-free. All big soda makers offer products with either low or no caffeine.

That may be a good idea, though it raises the question of whether soda machines in schools should be permitted to offer caffeinated beverages or at least be obligated to offer a significant proportion of caffeine-free products. It also raises the question of how one determines a product's caffeine content. Nutrition labels are not required to divulge that information. If a beverage contains caffeine, it must be included in the ingredient list, but there's no way to tell how much a beverage has, and there's little logic or predictability to the way caffeine is deployed throughout a product line.

Okay, so most enlightened consumers already know that colas contain a fair amount of caffeine. It turns out to be 35 to 38 milligrams per 12-ounce can, or roughly 28 percent of the amount found in an 8-ounce cup of coffee. But few know that diet colas -- usually chosen by those who are trying to dodge calories and/or sugar -- often pack a lot more caffeine. A 12-ounce can of Diet Coke, for example, has about 42 milligrams of caffeine -- seven more than the same amount of Coke Classic. A can of Pepsi One has about 56 milligrams of caffeine -- 18 milligrams more than both regular Pepsi and Diet Pepsi.

Even harder to figure out is the caffeine distribution in other flavors of soda pop. Many brands of root beer contain no caffeine. An exception is Barq's, made by the Coca-Cola Co., which has has 23 milligrams per 12-ounce can. Sprite, 7-Up and ginger ale are caffeine-free. But Mountain Dew, the curiously named Mello Yellow, Sun Drop Regular, Jolt and diet as well as regular Sunkist orange soda all pack caffeine.