Monday, April 23, 2012

Sugar Showdown: Science Responds to "Fructophobia"

The scientific community lashed out against "sugar is toxic" sensationalism on Sunday, April 22, identifying it as a distraction from more meaningful areas of research and debate on the causes of obesity and disease.

In a highly attended debate at Experimental Biology 2012 in San Diego sponsored by the Corn Refiners Association, scientists expressed clear frustration about the repeated assaults on sugar both in recentnews reports and in the scientific literature.

"You don't often see this at a meeting," said John White, Ph.D., of White Technical Research, to me after the event, referring to what he said was "the groundswell of researchers pushing back" against inflammatory remarks and overstatements.

The symposium organized by the American Society for Nutrition showcased both sides of the controversy surrounding the metabolic effects and health implications of sugar—fructose, sucrose, and high-fructose corn syrup—using latest available and emerging scientific findings.

As the first presenter, White presented data from the National Health and Nutrition Examination Surveys showing that no correlation existed between total fructose and the prevalence of obesity and that total added sugars and intake of sugar-sweetened beverages have declined for more than a decade.

"The support for fructose as a metabolic threat at current levels of intake is weak," White affirmed.

White also made the point that high-fructose corn syrup and sucrose are not different, suggesting the former might've been more appropriately called "medium-fructose corn syrup" because of its similarity to table sugar and other sugars.

Presenting a contrasting view, George Bray, M.D., chief division of clinical obesity and metabolism, showed data that soft drink consumption had increased from 1950 to 2000. Sugar-sweetened beverages, he argued, provide add-on calories that lead to weight gain, particularly from intra-abdominal fat.

In what promised to be a highly charged attack on sugar, characteristic of his appearance in media reports, Robert Lustig, M.D., began with a title slide displaying: "Fructose: alcohol without the 'buzz'". He argued that fructose metabolism was similar to that of ethanol's and that a "beer belly" was not far off from a "soda belly."

In his limited time, fast-talking Dr. Lustig quickly explained metabolic pathways and repeated remarks that fructose may be addicting to the brain like ethanol, based on animal research, and that fructose may be several times more likely than glucose to form advanced-glycation end products (a hallmark feature of uncontrolled diabetes).

Next to speak was cardiologist James Rippe, M.D., who presented a convincing argument that while fructose alone may have "qualitative differences," they were not "quantitative differences." He argued that research comparing pure fructose to pure glucose was not relevant to human nutrition. 

Sharing White's viewpoint, Dr. Rippe added that there were no metabolic differences between the sugars or fructose by itself—that is, there are no clinically meaningful effects on blood lipids at levels consumed by people normally, and no effects on uric acid or blood pressure.

He said the hot topic was an emotional issue creating a "perfect storm" for mistaken identity.

Dr. Rippe said afterward that Dr. Lustig's logic about fructose being uniquely responsible for disease was like going into "an alternate universe" that just did not stand up to scientific scrutiny. Yet it garners attention because of the public's habit of playing "the blame game" mixed with misconceptions about high-fructose corn syrup.

"People called him on it today," Rippe told me. By going to the media directly, he said, Dr. Lustig didn't have to have the same standards of proof that scientists usually must have. 

The last presenter was David Klurfeld, Ph.D., of the United States Department of Agriculture, who rounded out the debate again affirming that there was no evidence suggesting that sugar presented a unique metabolic danger.

"Is there a metabolic difference between sugars? Of course," Klurfeld said, "Is it biologically meaningful?" The answer was that it wasn't, according to the available evidence.

"The dose makes the poison," Klurfeld added. Should there be sugar regulation or taxation? There is insufficient data to justify any decision, Klurfeld said, quipping that whole milk would be next.

A question-and-answer period followed the debate giving a voice to disgruntled attendees who called Dr. Lustig out for suggesting that sugar was a metabolic danger. Dr. Lustig agreed that "everything can be toxic" at a dose, but sugar is abused and addictive.

One commenter (later identified as Richard Black, Ph.D., of Kraft Foods) responded saying that media should stop comparing sugar to cocaine by showing images where the brain lights up in the same areas. "The brain is supposed to light up in response to food," he said.

In an amusing but perhaps humbling moment for Dr. Lustig, he singled out the commenter asking if he had children. The commenter responded that he did. Dr. Lustig then asked him if as infants his children more easily liked sweet foods. The commenter said that, yes, of course they did because breast milk was sweet. Dr. Lustig replied that it was not. His reply caused an immediate reaction (notably, from mostly women) in the room who voiced in unison, "Yes, it is!"

John Sievenpiper, M.D., of St. Michael's Hospital told me after the event he was pleased that the speakers framed their arguments in a way that put the controversy in perspective. As shown in recent meta-analyses of which he co-authored, fructose demonstrated no significant effect on body weight or blood pressure in calorie-controlled trials. Fructose also demonstrated improvement of glycemic control at levels comparable to that obtained in fruit.

"It's hard to change people's minds," Dr. Sievenpiper said, stating concern that people would reduce intake of fruit in response to fears about the metabolic effects of fructose.

Don't miss this Storify story from folks on Twitter using the #sugarshowdown hashtag during the debate. Also, check out video blogger Emily Tomayko's recap on the ASN blog here.

Update 24-May-12: As a follow-up to this report, I've posted an interview with Dr. Sievenpiper here. Hopefully, it will help bring more clarity to the issues and answer several questions people have. If you wish to comment, please do so after reading that post. I've now closed comments on this blog post. 

Update 8-June-12: Check out videos (just published) of each of the talks. Here they are: White, Lustig, Bray, Rippe, and Klurfeld. Oh, and there is a video of the Q&A too.