WASHINGTON -- A huge federal study takes the fizz out of arguments that the diet soda sweetener aspartame might raise the risk of cancer.
No increased risk was seen even among people who gulped down many artificially sweetened drinks a day, according to researchers who studied the diets of more than half a million older Americans.
A consumer group praised the study, done by researchers independent of any funding or ties to industry groups.
''It goes a fair way toward allaying concerns about aspartame," said Michael Jacobson, head of the Center for Science in the Public Interest, which had urged the government to review the sweetener's safety after a troubling study with rats last year.
Findings were reported yesterday at a meeting of the American Association for Cancer Research.
Aspartame came on the market 25 years ago and is found in thousands of products -- sodas, chewing gum, dairy products, even many medicines. NutraSweet and Equal are popular brands.
Research in the 1970s linked a different sweetener, saccharin, to bladder cancer in lab rats. Although the mechanism by which this occurred does not apply to people and no human risk was ever documented, worries about sugar substitutes in general have persisted.
They worsened after Italian researchers last year reported results of the largest animal study ever done on aspartame, involving 1,800 lab rats. Females developed more lymphomas and leukemias on aspartame than those not fed the sweetener.
The new study, by scientists at the National Cancer Institute, involved 340,045 men and 226,945 women, ages 50 to 69, participating in research by the National Institutes of Health and the AARP, formerly known as the American Association of Retired Persons.
From surveys they filled out in 1995 and 1996 detailing food and beverage consumption, researchers calculated how much aspartame they consumed, especially from sodas or from adding the sweetener to coffee or tea.
Over the next five years, 2,106 developed blood-related cancers such as lymphoma or leukemia, and 376 developed brain tumors. No link was found to aspartame consumption for these cancers in general or for specific types, said Unhee Lim, who reported the study's findings.
The dietary information was collected before the cancers developed, removing the possibility of ''memory bias" -- faulty recollection influenced by knowing you have a disease.