Sweetest Taboo

Monell scientists are studying the way one food additive affects your body's secret taste receptors.

by Lauren F. Friedman

Evan M. Lopez

Ian 1984, Domino Sugar Corp. filed an unusual patent. While other companies competed to develop the perfect artificial sweetener, Domino sought to protect a process that produced the opposite effect. By coating sugar with lactisole — a compound that blocks the tongue's receptors for sweetness — Domino's food scientists had invented a substance of dubious value: not sugar-free sweetener, but a sweet-free sugar.

While casual consumers might fail to grasp the practical applications of a high-calorie, zero-flavor additive, processed food companies were hungry for a bulking agent that could improve the texture of a product without adversely affecting its taste.

More than 20 years have passed since Domino's original patent, and now, on its food industry Web site devoted to specialty ingredients, the company suggests its lactisole-coated sugar as an additive for more than 30 different kinds of food — everything from pizza crust to salad dressing. Lactisole excels as a blocker of sweetness, but before biting into that muffin, know this: The taste receptors that lactisole affects are not just on the tongue.

Within the past few years, research from the Monell Chemical Senses Center in University City has shown that the human taste system is spread all throughout the body. In fact, some of the most important taste receptors are on the gut and the pancreas, where — preliminary findings suggest — they help regulate carbohydrate absorption and insulin release.

"Domino limited the quantity of lactisole ... so it would be deemed nontoxic to humans," explains Bedrich Mosinger, a senior research associate at Monell. "However, when the lactisole was studied by itself, no one knew about these receptors being on endocrine cells." He pauses, and chooses his next words carefully: "There may be a different view now on how safe these compounds really could be."

For a long time, lactisole — which has been tested on rodents and is generally accepted as safe — was the only compound known to block the sweet receptors. But that just changed. While searching for other substances that might suppress taste, Mosinger realized lactisole was structurally almost identical to two other compounds humans already ingest a lot of — though not always on purpose. The first is a phenoxy herbicide best-known as the popular weed killer 2,4-D, released into the environment at a rate of approximately 55 million pounds per year in the United States alone. The second compound, known as a fibrate, is sold as a prescription drug that treats lipid disorders like high cholesterol and triglycerides. Both blockers, Mosinger found, affect the receptors of humans but not rodents, and both are up to 10 times as potent as lactisole.

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In his paper on the study, published in The Journal of Medicinal Chemistry this past October, Mosinger — along with co-authors Emeline L. Maillet and Robert F. Margolskee — wrote: "Long-term biological effects of these compounds in humans are largely unknown. ... We think it prudent to evaluate effects of acute and chronic exposure to these compounds specifically on human metabolism and development."

People taking fibrates often report some problems with taste, but since the study of chemosensory receptors on the pancreas and gut is still relatively new, it's difficult to guess what the implications are at an intestinal level. But messing with the body's natural regulatory system might be ill-advised: There have been several published reports that show high rates of gestational diabetes in agricultural areas with high 2,4-D contamination.

Still, Mosinger urges caution. "Health officials might have some statistical correlation between the millions of pounds of these compounds used and incidents of certain disease, but you can correlate number of telephone poles to increased number of diseases," he says. It's still too early to say. But while large quantities of phenoxy herbicides and fibrates may foster diabetes and obesity, it's equally possible they could be used in the treatment of these very same disorders. In fact, some naturally occurring plants with similar anti-sweet properties have been folk remedies for diabetes for more than 2,000 years.

For now, there are no answers, just more questions. What happens if the body's system for processing carbohydrates is thrown off by a fraud: a lactisole-coated sugar pretending to be something else entirely? What if these frauds are already all around us? And what if a cause of the diabetes epidemic may also be its cure?

Mosinger has an answer: "I can't speculate on that."

(lauren.friedman@citypaper.net)