A still unpublished Canadian study has for the first time concluded that use of artificial sweeteners by human males increases their risk of bladder cancer.
The study, according to reliable sources, found that men who used non-nutritive artificial sweeteners in pill form - including saccharin and cyclamate - had a 60 per cent greater chance of getting bladder cancer than men who did not use the sweeteners.
Using smaller test groups, the study also found no increased risk of bladder cancer for females using artificial sweeteners.Smoking was found to be eight times more important as a determinant of bladder cancer than use of the non-nutritive artificial sweeteners, according to a source familiar with the study.
The study was a joint venture of the National Cancer Institute of Canada as well as epidemiologists from the University of Toronto, the University of British Columbia, Dalhousie University in Nova Scotia and Memorial University in St. John's, New-foundland. It has not been released pending publication in Lancet, the British medical journal.
Donald Kennedy, commissioner of the Food and Drug Administration, said in a telephone interview that the Canadian study is "a very convincing looking study" and that "it makes it virtually certain that saccharin is a human carcinogen."
Kennedy, who has read a draft of the study, said, "It's hard to overstate its significance . . . It overturns completely in my mind the argument that the saccharin risk is something that's only present in animals."
From a preliminary analysis of the study, Kennedy said, the risk of human males getting cancer is "more than we guessed," based on projections from animal studies.
The FDA first announced its intention to ban saccharin in March after another Canadian study found that saccharin caused cancer in rats, especially among the males tested. The period for comment prior to FDA's drafting an order on saccharin ended June 14, but Kennedy indicated that the process may be re-opened "considering this very important piece of new information."
A spokesman for Edward M. Kennedy (D-Mass.), chairman of the Senate Human Resources health subcommittee, said that the results "are of great concern to him" and that he has decided to take no action on legislation to suspend any ban on the sale of saccharin until he hears from FDA. Commissioner Kennedy and Sen. Kennedy met Thursday to discuss the study.
The Canadian study involved 480 males who had bladder cancer. The research retrospectively studied this group using questionnaires to determine age, environmental conditions and other factors that might influence their health. A control group of 480 males similar in composition to the study group was constructed for comparison.
The results, according to those familiar with the findings, showed increased incidence of bladder cancer as the amount of saccharin and other artificial sweeteners increased. The data, according to one source, show a higher incidence of bladder cancer among males who used saccharin exclusively.
A smaller group of females - 152 in each group - found no increased risk of bladder cancer from using the artificial sweeteners.
Original calculations of the incidence of bladder cancer, based on animal studies, concluded that if every American drank one can of diet soda daily over a lifetime, 1,200 additional cases of bladder cancer might result annually. The FDA's Kennedy said yesterday that the new study indicates that at least twice as many cases, and perhaps more, could be attributed to that same level of consumption.
Kennedy said he gave "incomparably more weight" to the new study compared to past reports because it involved a larger group, because it confirmed the Canadian rat study's finding of male sensitivity to artificial sweetners and because it shows a relationship between dosage and incidence of cancer.
A spokesman for the Calorie Control Council of America said he could not comment on the study without analyzing it in detail.