Saccharin:
Subsequent studies in rats showed an increased incidence of urinary bladder cancer at high doses of saccharin, especially in male rats. However, mechanistic studies (studies that examine how a substance works in the body) have shown that these results apply only to rats. Human epidemiology studies (studies of patterns, causes, and control of diseases in groups of people) have shown no consistent evidence that saccharin is associated with bladder cancer incidence.
Because the bladder tumors seen in rats are due to a mechanism not relevant to humans and because there is no clear evidence that saccharin causes cancer in humans, saccharin was delisted in 2000 from the U.S. National Toxicology Programs Report on Carcinogens, where it had been listed since 1981 as a substance reasonably anticipated to be a human carcinogen (a substance known to cause cancer). More information about the delisting of saccharin is available at
http://ntp.niehs.nih.gov/ntp/roc/eleventh/append/appb.pdf on the Internet. The delisting led to legislation, which was signed into law on December 21, 2000, repealing the warning label requirement for products containing saccharin.
Aspartame
In 2005, a laboratory study found more lymphomas and leukemias in rats fed very high doses of aspartame (equivalent to drinking 8 to 2,083 cans of diet soda daily) (1). However, there were some inconsistencies in the findings. For example, the number of cancer cases did not rise with increasing amounts of aspartame as would be expected. An FDA statement on this study can be found at
http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2006/ucm108650.htm on the Internet.
Subsequently, NCI examined human data from the NIH-AARP Diet and Health Study of over half a million retirees.
Increasing consumption of aspartame-containing beverages was not associated with the development of lymphoma, leukemia, or brain cancer (2).
Acesulfame potassium, Sucralose, and Neotame
Before approving these sweeteners, the FDA reviewed more than 100 safety studies that were conducted on each sweetener, including studies to assess cancer risk. The results of these studies showed
no evidence that these sweeteners cause cancer or pose any other threat to human health.
Cyclamate
Because the findings in rats suggested that cyclamate might increase the risk of bladder cancer in humans, the FDA banned the use of cyclamate in 1969. After reexamination of cyclamates carcinogenicity and the evaluation of additional data, scientists concluded that cyclamate was not a carcinogen or a co-carcinogen (a substance that enhances the effect of a cancer-causing substance). A food additive petition was filed with the FDA for the reapproval of cyclamate, but this petition is currently being held in abeyance (not actively being considered).
The FDAs concerns about cyclamate are not cancer related.