BIRMINGHAM, Alabama -- One word: Constipation.

Before that was brought up, the 250 people packed tonight into the UAB Alumni House to hear a debate on diets were fidgeting a bit.

The arguments were being made: low carbohydrate versus low protein.

There were lots of study citations, bar charts and line graphs, and erudite explications of complex theories on nutrition's effects on human health.

For the longest time it was the picture of decorum in this debate between two scholarly experts.

Then T. Colin Campbell, the 78-year-old professor emeritus from Cornell University and author of a best-selling book on nutrition, "The China Study," mentioned it.

Constipation.

"Here's what happens to people," Campbell said, pointing to his very last slide entitled "Atkins outcomes v. regular eaters."

"Look at constipation compared to the average eater."

Giggles rippled through the audience.

The chart showed that Atkins eaters reported higher levels of, not just constipation, but halitosis, headaches, muscle cramps and diarrhea.

And as if to rub salt in the wounds, Campbell said these outcomes were from a 2004 study paid for by the Atkins Diet company.

Campbell directed his attention at his opponent, Eric Westman, a physician and Duke University assistant professor, who had been up until then, making a calm, measured case for the Atkins concept of a low carbohydrate and high protein diet.

Now the gloves were off.

Using that slide was not fair, Westman charged back.

"If somebody's diabetes is gone and they need some milk of magnesia for constipation, I think they would be happy to do so," Westman said.

Westman, co-author of "New Atkins for a New You," then pointed out that studies are starting to knock down some of the vaunted claims of "ultra-low fat diets" such as promoted by Campbell.

"There's been a dramatic reduction in faith in the low fat diet," Westman said.

Westman earlier had talked about how he uses a low carbohydrate diet to treat his patients for obesity and diabetes. He pointed to what he said are promising studies that low carbohydrate diets reduce the risk for breast cancer.

"Carbohydrate is not an essential nutrient," Westman said.

Campbell opened things up telling everyone he used to be pro-protein before he was against it. He grew up in a dairy farm, he said.

He essentially described the history of protein reverence by everyone from himself to the National Academy of Sciences.

But over time, and participation in large scale epidemiological studies, he changed his view to believe animal protein was not healthful, and that a whole food, plant-based diet is the way to go.

At some points, Westman tried to find common ground.

"I think we are against the same problem which is the typical American diet," he said.

Westman listed areas where the two could agree, such as that obesity, diabetes and cancer are related to nutrition; that sugar and junk food is harmful; and "real food" is healthier.

Areas he thought they disagree are: adequate protein is not harmful; epidemiology cannot be used to determine causation and animal products are not harmful.

But however much they disagree, it wasn't enough to keep them from breaking bread (or something) together. It was reported they were going to dinner together after the debate at Bottega Restaurant and Cafe, where you can bet only one will be tempted by the grilled beef tenderloin.

The debate was presented by the UAB Center for Palliative and Supportive Care and the UAB Comprehensive Cancer Centers. Check UAB's website in coming days for a video of the entire 90-minute exchange.