Concerned about weight control and fearful of obesity, Americans have turned in increasing numbers to "diet" foods and beverages made with low-calorie artificial sweeteners—first cyclamate, then saccharin, then aspartame, and most recently acesulfame K. But the widespread use of artificial sweeteners has brought with it a raft of health concerns. People are still asking, "Is any sweetener safe?"
Thoughtful scientists generally address safety questions as a trade-off between risks and benefits. So far, any health benefit from artificial sweeteners remains largely a matter of conjecture. One might assume that artificial sweeteners are useful for weight control. But some authorities suggest that many people who use artificial sweeteners tend to increase their food consumption, leaving total calorie intake roughly unchanged or even increased. For some people, that diet soda may be a license for a slice of cake.
Surprisingly few studies have been undertaken to see whether artificial sweeteners actually help people control weight, and those few have been inconclusive. For example, the National Academy of Sciences/National Research Council assessed five studies concerning the "management of obesity with non-nutritive sweeteners." It found the design for all five studies "inappropriate" for reaching any firm conclusion on the efficacy of sweeteners in weight control.
Still, many people crave an alternative to sugar. For the nation's more than 11 million diabetics, that desire is especially compelling.
What's Wrong With Sugar?
The average American consumes 67 pounds of assorted sugars per year. About half is sucrose, or table sugar. Most of the rest is made up of corn sweeteners, which are popular with food and beverage companies because they're cheap. But in calorie content, sucrose, corn sweeteners, and other sugars are equivalent. A teaspoon of sugar contains 16 calories, a can of sugar-sweetened soda, about 160.
Sugar is a natural suspect in obesity. Many grams of sugar fit into a small space; hence, candy and other sugar-laden foods pack a heavy load of calories. These carbohydrate calories are "empty," in that simple sugars provide only calories and no other nutrients to the body.
Weight gain results when one eats more calories—in any form—than one burns in exercising and carrying out normal activities. If you're trying to control your weight, sugar is only part of the picture. Fats have nine calories per gram, compared with four for sugar and other carbohydrates. But cutting down on consumption of simple sugars can certainly contribute to weight control.
Sugar has long been associated with tooth decay. Laboratory experiments have shown that forms of sugar that cling to the teeth—such as candy, honey, granulated sugar, and the like—are more damaging than the liquid forms, such as sugared beverages.
Among other charges leveled against sugar are that it promotes heart disease and that excessive sugar consumption may cause diabetes. An extensive review by the FDA recently concluded that there was no scientific basis for such assertions.
Though people with diabetes should watch their consumption of sugar, there is no evidence that excess sugar consumption causes diabetes. If sugar plays any role at all, it is an indirect one; it may contribute to obesity, which can in turn trigger the onset of diabetes in susceptible individuals. As for heart disease, any connection with sugar consumption remains speculative and unproved.
Overall, we see little harm in moderate sugar consumption.
Cyclamate: Banned but Not Forgotten
Cyclamate (Sucaryl), which is 30 times sweeter than an equal weight of sugar but calorie-free, was the dominant artificial sweetener in this country in the 1960s. Then tests with laboratory animals raised the possibility that it might cause cancer. The U.S. Food and Drug Administration (FDA) banned the use of cyclamate as a food additive in 1969. But it continues to be sold over-the-counter in drugstores in Canada and is also used in some 40 other countries.
To test the safety of a food additive, large doses are fed to small groups of animals. If it produces cancer or other toxic effects under laboratory conditions, the substance is presumed to pose some risk of causing similar effects in humans if very large numbers of users are exposed to low doses over many years. Direct evidence that a food additive causes adverse health effects in people is almost impossible to obtain, because people's eating habits are so complex and so many other variables influence people's health. Thus, animal data are usually the best evidence the FDA has available when evaluating the safety of an additive.
Though humans don't usually consume enormous doses of artificial sweeteners, many people do consume small amounts, day after day, year after year. And since nearly 70 million Americans use artificial sweeteners in one form or another, even a small risk could threaten a large number of people.
The initial evidence of cyclamate's possible health risks seemed damning at the time. In recent years, however, many scientists, manufacturers, and food and beverage companies have talked of getting the FDA to rescind its ban on cyclamate. The second thoughts arise out of a reevaluation of the original data, as well as more recent studies.
In 1984, the FDA's Cancer Assessment Committee reported on its review of more than two dozen studies on laboratory animals—mice, rats, dogs, and monkeys—that had been fed cyclamate for long periods. The committee said that some results could not be duplicated even by the authors of the studies and concluded that those studies showing a carcinogenic effect for the substance were open to question. It also said that "there is very little credible data to implicate cyclamate as a carcinogen at any organ tissue site... "
On the strength of such reassessments, the makers of cyclamate, Abbott Laboratories, and a trade organization called the Calorie Control Council have petitioned the FDA to lift its ban on cyclamate.
Nevertheless, reasons for concern about other potential health effects of cyclamate remain. Various experiments have shown that a breakdown product of cyclamate, called cyclohexylamine (CHA), can cause high blood pressure and atrophy (shrinkage) of the testicles in rats.
In 1985, a committee of the National Academy of Sciences/National Research Council reviewed all the data assembled to date. It concluded that cyclamate and CHA are probably not carcinogens by themselves. It found the evidence "suggestive," however, that those substances may promote the effects of other cancer-causing substances or cause mutations. The committee also said that such other adverse side effects as testicular atrophy and toxicity to embryos must be fully investigated before cyclamate can be restored to use in the nation's food supply.
Saccharin: The Endless Moratorium
Some 300 times sweeter than sugar, and calorie-free, saccharin had taken over from cyclamate as the most commonly used artificial sweetener even before cyclamate was banned.
Numerous studies over the years have shown that saccharin is a weak carcinogen in laboratory animals. Rats fed large doses of saccharin showed an increased incidence of bladder cancer. The most influential of the many studies to date, a 1977 Canadian study, demonstrated that it was saccharin itself, not a contaminant or other factor, that produced cancer in test animals. In large part, it was this study that led the FDA in 1977 to propose banning saccharin in the U.S.
However, since cyclamate had already been banned in 1969, a ban on saccharin would have left the marketplace devoid of artificial sweeteners. A public outcry, eagerly fanned by the soft-drink industry, ensued. Congress, listening to the protests, imposed a moratorium on the saccharin ban. It has extended the moratorium every few years since.
Proponents of saccharin, including saccharin's only U.S. manufacturer, the Sherwin-Williams Company, note that people have been using saccharin for most of a century with no clear indication of ill effects, such as an increased incidence of bladder cancer in users. However, that does not necessarily mean that saccharin is without harm to humans.
Late in 1977, researchers at Johns Hopkins School of Medicine reported that pure saccharin did not cause genetic mutations in bacteria. (Many substances that cause such mutations are carcinogens, and most carcinogens cause mutations.) But the urine of mice fed saccharin did cause bacterial mutations, which suggests that a breakdown product of saccharin may be carcinogenic.
In 1978, Melvin Reuber, of the National Cancer Institute's Chemical Carcinogenesis Program, summarized many animal studies to date. He found that bladder cancer was not the only problem with saccharin. Various animal studies had reported cancers in the reproductive and blood-forming systems, in the lungs, and elsewhere. Reuber's judgment was that saccharin "likely is carcinogenic in human beings."
In 1983, Japanese researchers confirmed that saccharin promotes the action of a known carcinogen on the urinary bladder in rats. This finding added strength to previous evidence that saccharin, even if it is not cancer-causing in itself, may heighten the risk from substances that are. Such cancer promoters are called "co-carcinogens."
Also in 1983, the FDA's Frank Cordle and Sanford Miller said that even though saccharin is a known carcinogen and co-carcinogen in rodents, "the results of human epidemiologic studies tend to support the conclusion that human users of artificial sweeteners—saccharin and cyclamate—do not have an increased risk of cancer of the lower urinary tract." Cordle has said that he "would see very little hazard with humans" from exposure to saccharin and cyclamate.
But other scientists, including sonic on a National Research Council committee, find Cordle's assessment too optimistic. They point out that consumption of artificial sweeteners was relatively low until the last 20 years or so, and that many forms of cancer have a long latency period. Though no one has produced any proof that saccharin has been responsible for human cancer cases, at least one study has found that it can boost or promote the effects of known carcinogens on human cells in the test tube. Saccharin thus is a definite carcinogen in certain lab animals and may pose some risk as a carcinogen or co-carcinogen in humans. Research continues.
Aspartame: The Challenger
Aspartame (Nutrasweet) is a chemical combination of two amino acids, aspartic acid and phenylalanine. Both substances are building blocks of ordinary proteins and are essential nutrients. The FDA approved aspartame for certain uses in 1981 and for use in soft drinks in 1983.
Per gram, aspartame has just as many calories as sugar. However, since it is roughly 200 times sweeter than sugar, it contributes only 1/200 as many calories to the diet. Some aspartame preparations, such as the tabletop sweetener Equal, use glucose as a carrier for the aspartame. That adds a few calories, but the total remains much lower than in an equivalent portion of sugar.
Toxicity tests have shown a short-term "no effect level" of 5000 milligrams per kilogram of body weight. That is, when test animals are given a single dose of up to 5000 milligrams (about a sixth of an ounce) of aspartame for every kilogram (2.2 pounds) they weigh, they show no signs of ill effects. The FDA has multiplied this figure by 100 as a safety factor and obtained a "maximum allowable daily intake" of 50 milligrams of aspartame per kilogram of body weight. That amounts to about 17 aspartame-sweetened sodas a day for a 150-pound adult, 8 or 9 such sodas for a 75-pound child.
The FDA has required aspartame's manufacturer, G. D. Searle, to monitor consumption levels. With the FDA's approval, Searle has contracted with the Market Research Corporation of America to survey users and calculate their levels of consumption of aspartame. Their reports show consumption levels for all age groups to be well within the FDA's limits. In assessing health hazards, the practice is to focus on the 1 percent of users who consume the largest quantities of the sweetener.
One of the two components of aspartame, phenylalanine, poses problems for some people—roughly one in 15,000—who suffer from a metabolic disorder called phenylketonuria (PKU). These people lack an enzyme needed to process this amino acid properly, which can build up to toxic levels in their blood and tissues. If the condition is not diagnosed at birth, mental retardation can result. Fortunately, screening at birth is now routine.
To make sure that people afflicted with PKU know of the phenylalanine in aspartame, the FDA requires that aspartame-containing products be labeled with a warning.
When aspartame breaks down, either before or after consumption, it releases a substance called diketopiperazine (DKP) and methyl alcohol. The latter is simple wood alcohol, famous for causing blindness and brain damage in drinkers of bootleg liquor and Sterno.
But early concern about the products of aspartame breakdown seems to have eased. The FDA concluded that at doses considerably above any likely dietary intake, DKP is not toxic to adults, children, or fetuses, and does not cause mutations in bacteria. As for methyl alcohol, many foods contain more of it than aspartame produces. The aspartame in one can of diet soda, for example, provides only about half as much methyl alcohol as eight ounces of tomato juice—and both sources contain much less than the body can process without ill effects.
Perhaps more worrisome have been concerns raised by John Olney, of Washington University in St. Louis, and Richard Wurtman, a professor of biochemistry at M. I. T. They have warned that, because aspartame's components are related to neurotransmitters—chemicals that pass signals from nerve cell to nerve cell—and since aspartic acid and phenylalanine levels in the blood do rise at least a little after a person consumes aspartame, the sweetener might adversely affect the brain.
The FDA, after an analysis of Dr. Wurtman's studies and others, disagreed with his conclusions, saying that the evidence for behavioral effects is not significant and that no further behavioral testing seems necessary. The British government has reached a similar conclusion.
In 1983, the FDA said that it is reasonably certain that aspartame does not cause brain tumors, brain damage, or behavioral changes in humans.
But Wurtman, despite all signs of safety, has maintained that the FDA showed "unseemly haste" in approving aspartame. Florence Graves, as vice president of Common Cause, has expressed the same concern. She has stated that aspartame was approved for use in soft drinks in large part because of the antiregulatory stance of the Reagan administration—and perhaps because of a wish to reduce saccharin consumption by providing an alternative.
The FDA began monitoring the growing number of complaints from consumers about possible side effects of aspartame use. In 1984, the FDA asked the Centers for Disease Control (CDC) for help in analyzing and evaluating these complaints. By the end of the year, the CDC said that the reported symptoms—including stomach upset, hives, headaches, menstrual problems, insomnia, and uncontrollable behavior—fit no specific pattern. Furthermore, the CDC said, the symptoms were generally mild, common even among people who did not use aspartame, and most abundant in Arizona, where adverse publicity had been especially prominent. The CDC's position is that while some people may be unusually sensitive to aspartame, the data "do not provide evidence for the existence of serious, widespread, adverse health consequences," especially since similar complaints have not surfaced in other countries where aspartame is being used. The CDC's report also stated that a thorough evaluation of the complaints would require "focused clinical studies," several of which are now planned or under way.
Despite the uncertainty, aspartame received an impressive endorsement in 1985. The Council on Scientific Affairs of the American Medical Association stated: "Available evidence suggests that consumption of aspartame by normal humans is safe and is not associated with serious adverse health effects. Individuals who need to control their phenylalanine intake should handle aspartame like any other source of phenylalanine."
Acesulfame K: The Latest Entry
A new artificial sweetener entered the U.S. marketplace more recently, having previously been used in 20 countries, including Australia, Britain, France, Israel, Sweden, Switzerland, the Soviet Union, and West Germany. In 1988, the FDA approved acesulfame potassium—or acesulfame K—as a table sugar substitute and for use in dry food products. The manufacturer expects to win approval for use in liquids, baked goods, candies, and, ultimately, soft drinks. The sweetener is marketed in the United States under the brand name Sunette.
Acesulfame K, like aspartame, is about 200 times sweeter than sugar. Like saccharin, it has no calories. Acesulfame K's reported advantages over the other two include greater stability, lack of an aftertaste, and lower cost.
But even before the product was approved by the FDA, its safety had been challenged by the Center for Science in the Public Interest, a nutrition-oriented consumer advocacy group that has often challenged the safety of artificial sweeteners. The organization asserted that some studies showed an increased incidence of tumors and a rise in blood cholesterol among laboratory animals that were fed the sweetener. The FDA, however, concluded that the animals' health problems "were typical of what could routinely be expected and were not due to feeding with acesulfame potassium."
Clearly, the acesulfame K story has only just begun.
With the exception of diabetics, few people really need artificial sweeteners. Sugar, used in moderation, has no serious adverse health effects, and it has fewer calories than some people assume.
Saccharin's demonstrated carcinogenicity in laboratory animals is a serious problem, in CU's view. We believe that Congress should rescind its moratorium and let the FDA make an independent decision about saccharin, which it proposed to ban in 1977.
A reexamination of the evidence suggests that cyclamate is not itself a carcinogen and has no adverse effect on brain function. However, there remain unresolved concerns about its overall safety, including whether it may act as a co-carcinogen to promote the effects of some known carcinogens. In addition, since it is only 30 times as sweet as sugar, it is harder to keep its consumption down to levels presumed safe. We think there are too many unresolved questions to put cyclamate back on the market.
Although some questions remain about aspartame's safety, and about the soundness of the process that led to its approval, it seems to be acceptably safe for most people when used in moderation. It does not appear to cause or promote cancer. But it may, as the label warns, pose a potential risk for people with PKU. For the time being, an objective weighing of the evidence suggests that aspartame is the artificial sweetener to be preferred on safety grounds.
As of this writing, it is still too early to reach firm conclusions about the long-term safety of the just-approved acesulfame K.
On the road to ideal weight, sugar-free products can take you only so far. To go the distance, you'll have to rely on a carefully planned, and persistent, regimen that provides fewer total calories and more vigorous exercise.