My first meeting with (3R,4R,5R)-1,3,4,5,6-pentahydroxyhexan-2-one, less formally known as “psicose” or “allulose,” was way back in my graduate school days. I was studying the molecular structure of simple sugars, a category of carbohydrates to which allulose belongs. I wasn’t interested in its biochemistry or its sweetness, my focus was on distinguishing it from fructose by the then relatively novel technique of carbon-13 nuclear magnetic resonance spectroscopy (C-13NMR). Allulose is a stereoisomer of fructose, meaning the two compounds differ only in the spatial arrangement of their atoms, a subtle feature that makes identification difficult. In any case, it turned out that C-13 NMR was capable of differentiating allulose from fructose and for me, that was that.
Now fast forward some five decades and once again I meet up with allulose. This time not in a lab, but in the grocery store. Well, not exactly in a grocery store, but on a picture taken of a product’s label in a grocery store that was sent to me by someone from Florida. The label described the contents as “granulated sugar replacement that has net zero carbs, zero calories, zero glycemic index, tastes like sugar and can be used like sugar.” The only ingredient listed was allulose. This seemed pretty interesting. I had never before thought about where allulose could be found, as far as I was concerned it came from a bottle in the lab. But now I had to look into this simple carbohydrate further.
It turns out that allulose does occur naturally in small amounts in wheat, figs, raisins maple syrup and molasses. First identified in 1940, it was found to have about 70% the sweetness of sucrose, and interestingly, unlike other sugars, was not metabolized and passed out of the body unchanged. This raised interest in the compound as a potential non-nutritive sweetener, but at the time, isolating it from natural sources was not feasible. Then in 1994, Ken Izumori at Kagawa University in Japan found a way to convert fructose to allulose using an enzyme and since fructose is readily produced from corn, the commercial production of allulose became possible. Studies in humans showed that indeed it was poorly absorbed and did not raise insulin levels. But it did to some degree inhibit the effects of enzymes in the gut that normally break down starch and sugar. As a result, these pass into the colon where they are fermented by bacteria and the products of such fermentation can cause abdominal discomfort, flatulence and diarrhea.
In 2012, a Korean producer of allulose petitioned the U.S. Food and Drug Administration to categorize the substance as “Generally Recognized as Safe” based on its occurrence in nature and no significant side effects expected when used as a sugar substitute in the doses intended. The petition was accepted, and since allulose is absorbed and metabolized differently from other sugars, the FDA also exempted it from being listed as an added sugar on food labels. This opened the way for allulose to be marketed as a bulk sweetener and to be used as an additive in pastries, gum, candies, ice cream, beverages, yogurt and cereals.
Allulose has not been approved in the European Union or in Canada. Under Health Canada's Food and Drug Regulations it is regarded as a novel food ingredient since it has a limited history of use in food. Novel foods must first undergo a pre-market safety assessment before they can be sold in Canada. That doesn’t mean allulose is banned, and purchasing it online from the U.S.is not illegal.
Just about everyone agrees that overconsumption of sugar leads to weight gain and other health problems. And there is no doubt that we are overconsuming. The average North American ingests about nineteen teaspoons of added sugar a day, three times the maximum recommended amount! It is easy to see why non-caloric sugar substitutes are appealing, but so far, every sugar substitute introduced into the marketplace has resulted in controversy of one sort or another. It remains to be seen if allulose will prove to be an exception.