The U.S. Food and Drug Administration approved the non-absorbable, non-caloric fat substitute for use in snacks in January 1996 and reviewed its approval last June. A report on the new study is being published Tuesday (Feb. 16) in the Annals of Internal Medicine, a medical journal.

"Olestra is composed of sucrose, which is table sugar, and soybean oil," said Dr. Robert Sandler, professor of medicine at the University of North Carolina at Chapel Hill School of Medicine. "Olestra is not digested or absorbed and passes through the gastrointestinal tract essentially unchanged.

"There's been a lot of interest in it because it allows people to eat certain snacks with fewer calories from fat," he said. "Interest also is high because of anecdotal reports in the past year or so saying it caused unpleasant and sometimes painful symptoms such as diarrhea and abdominal cramping."

What is perplexing about the reports is that they conflict with extensive clinical testing, said Sandler, study principal investigator and co-director of UNC-CH's Center for Gastrointestinal Biology and Disease. They also contradict a recent large study in which people consumed a single serving of olestra-based chips in a movie theater.

The new research involved recruiting more than 3,200 volunteers to eat either regular corn and potato chips or those made with olestra for six weeks and to keep records. They recorded how much they ate and whether they suffered any symptoms.

Participants, who lived in Phoenix and St. Petersburg, Fla., received up to eight free bags of chips per household once a week for six weeks. They did not know which bags contained the fat substitute, and neither did the researchers until the study closed.

"Overall, people in both the olestra group and the control group ate a lot of chips," Sandler said. "We found no difference between the two groups overall or for any of the symptoms we asked about."

Analysis showed no significant differences either by age or sex or in the number of days volunteers reported any kind of abdominal symptoms, he said. One of the few differences was that people in the olestra group reported an average of one more day during the six weeks of more frequent bowel movements.

Olestra-eaters in the top 10 percent of chip consumption had somewhat more frequent bowel movements than other volunteers, while those in the top 10 percent of regular chip consumption had somewhat fewer than average.

The only subject who withdrew from the study because of gastrointestinal symptoms was in the control group, the physician said. Neither group visited doctors more than the other.

"We asked people if they had any symptoms and asked them to evaluate the impact of the symptoms on their daily activity," Sandler said. "The vast majority said those symptoms had no impact."

At the study's end, researchers asked participants what kind of chips they thought they were eating. Many guessed wrong. Interestingly, he said, the type of chips people thought they were eating had a significantly greater effect on symptoms they reported than did the chips themselves.

"The bottom line here was that meaningful gastrointestinal effects were not associated with eating olestra corn or potato chips," Sandler said. "There is evidence from other work that olestra decreases absorption of the fat-soluble vitamins A, D, E and K, and so the companies that use olestra supplement their products with those vitamins."

If people experience severe symptoms after eating olestra chips, those symptoms come not from the chips but from something else, the physician said.

Proctor and Gamble, one of the manufacturers of olestra-based chips, supported the new study. Other companies that produce and promote olestra products are Frito-Lay and Nabisco.

Sandler, who does not own stock in the companies, agreed to conduct the research with the understanding that he would refuse to publish any conclusions he did not support.

Note: If no author is given, the source is cited instead.

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