Saccharin: An Unnecessary Risk

We feel that saccharin, nitrites, and hundreds of other food additives are perfectly safe at the levels currently used in our foods --Feedback, September 1977

In sharp conflict with the view of the U.S. Food and Drug Administration (FDA), Feedback, a newsletter published by the Harvard University Food Services, encourages students to use the artificial sweetener, saccharin. In a statement we believe to be unwarranted, the September issue of Feedback states that "saccharine, nitrites, and hundreds of other food additives are perfectly safe at the levels currently used in our foods." The publication and distribution of this document under the imprimatur of the University's Food Services raises serious questions. We shall comment here only on certain scientific and policy questions.

Carefully designed studies have raised questions about the safety of saccharin. While research has produced no direct evidence that saccharin causes in the doses to which humans are exposed, the data are not available to prove that it does not. If the uses of saccharin were associated with tangible benefits, as, for example, some suggest for diabetics, one might be willing to accept the risks that animal studies tell us might be involved. But many uses of saccharin are trivial and without tangible benefits. Why accept a risk unnecessarily in such circumstances?

Of course, public policy decisions are often made on the basis of information which is suggestive rather than conclusive. The FDA's proposed ban on saccharin is a case in point. The FDA acted in response to a Canadian study which demonstrated that male rats exposed to saccharin in utero and throughout their lives exhibited a 24 per cent increase in bladder tumors in comparison to controls. A smaller increase was observed in male rats exposed only following birth.

Critics of the Canadian study have pointed out that the experimental animals were exposed to doses of saccharin far in excess of human consumption levels. The relevance of animal studies to man has also been questioned. Several facts must be kept in mind when evaluating these criticisms:

First, when a chemical at high dose is found to cause tumors in animals, decreasing doses of the chemical generally induce progressively fewer tumors. This dose-response relationship enables scientists to overcome the practical problems of large-scale studies by conducting high-dose experiments with a small number of animals to amplify any responses, and extrapolating the findings to lower dosages.

Second, most chemicals do not cause cancer in rats, mice, or other species, even when given in very large amounts over a lifetime. Further, with the possible exception of trivalent arsenic, all chemicals that have been shown to cause cancer in man are carcinogenic in rats or mice. Therefore, positive findings in an animal system must not be taken lightly.

Third, rapid and inexpensive tests have been developed in recent years to measure the capacity of chemicals to induce mutations in bacteria. Of the chemicals that have been tested in one microbial system, 90 per cent of those that scored positive for mutagenicity were also found to induce tumors when studied in animals. In light of this high correlation between mutagenicity and carcinogenicity, test systems for mutagenicity are being used increasingly to identify potentially toxic substances early in product development. Recent reports do indicate that saccharin-containing products produce mutations in test systems.

Fourth, although studies of human populations to date have not provided evidence linking saccharin with bladder cancer, it must be rembered that heavy intake of this additive in diet drinks has only occurred in relatively recent years. In man, a latent period measured sometimes in years and sometimes in decades is often observed between exposure to a carcinogen and clinical evidence of cancer. In the case of cigarette smoking, its relation to lung cancer was established only after decades of exposure by human populations.

While one cannot extrapolate automatically from animal studies to man, the Canadian, findings on saccharin should lead a prudent person to avoid unnecessary consumption of this artificial sweetener. Although the magnitude of the risk entailed by exposure to saccharin will likely not be known for many years, it must be asked whether this is a risk worth taking. There are, of course, cases where the risks are outweighed by the potential benefits--for example, certain chemotherapeutic drugs are used to treat advanced cancer, even though they carry a risk of inducing cancer. However, artificial sweeteners and many other food additives clearly are not essential for most people.

Moreover, since saccharin is contained not only in diet drinks but also in large numbers of foods and toothpastes, it is difficult for the individual to avoid ingestion of this additive without governmental intervention. The FDA's action on saccharin is therefore well advised as prudent preventive medicine. Its further decision to permit the sweetener to be sold as a nonprescription drug recognizes the fact that there may well be people for whom the benefits of taking the sweetener exceed its possible risks.

Howard H. Hiatt is dean of the School of Public Health.

Brian MacMahon is chairman of the Epidemiology Department at the School of Public Health.

Jay A. Winsten is head of the Office of Health Policy Information at the School of Public Health.

The authors are expressing personal views.