When Dr. Morando Soffritti ... saw the results of his team's seven-year study on aspartame, he knew he was about to be injected into a bitter controversy over this sweetener. Aspartame is sold under the brand names Nutra-Sweet and Equal and is found in such popular products as Diet Coke, Diet Pepsi, Diet Snapple and Sugar Free Kool-Aid. Hundreds of millions of people consume it worldwide. Dr. Soffritti ... oversees 180 scientists and researchers in 30 countries. Dr. Soffritti's study concluded that [aspartame] was associated with unusually high rates of lymphomas, leukemias and other cancers. The study ... involved 1,900 laboratory rats and cost $1 million. Soffritti said he was inspired to look at aspartame because of what he calls "inadequacies" in the cancer studies done by Searle in the 1970's. Others have also challenged Searle's studies. Years before the F.D.A. approved aspartame, the agency had serious concerns about the accuracy and credibility of Searle's aspartame studies. From 1977 to 1985 -- during much of the approval process -- Searle was headed by Donald H. Rumsfeld, who is now the secretary of defense. Searle was acquired by Monsanto in 1985. Dr. Soffritti said ... more research and open debate were needed on whether aspartame was a carcinogen. "It is very important to have scientists who are independent and not funded by industry looking at this."