An Acute Randomized Dose-finding Equivalence Trial of Small, Catalytic Doses of Fructose and Allulose on Postprandial Carbohydrate Metabolism: The Fructose and Allulose Catalytic Effects (FACE) Study

Diabetes remains one of the most important unmet prevention and treatment challenges. Despite the growing armamentarium of medications, which include six new classes of drugs since metformin was first approved in 1995 in the US, the combined prevalence of impaired glucose tolerance (IGT) and diabetes continues to grow. Although oral antihyperglycaemic agents have been shown to prevent the development of diabetes in high-risk individuals and to reduce the risk of microvascular complications in individuals with type 2 diabetes, they have failed to deliver the anticipated macrovascular benefits.

Some functional food ingredients may hold promise as potential therapies for diabetes. An emerging literature has shown that low-dose fructose and its c-3 epimer, allulose (a non-caloric sugar found naturally in small amounts in foods such as dried fruits, brown sugar, and maple syrup which is generally recognized as safe [GRAS] by the FDA under GRN 400 since 2012 and GRN 498 since 2014) may benefit glycemic control.

Clinical translation of these findings has proven promising. Catalytic doses of fructose at 7.5g and 10g and allulose at 5g, 7.5g, and 10g (but not 2.5g) have been shown to decrease the postprandial glycemic responses to high glycemic index meals (oral glucose, maltodextrins, or mashed potatoes) from ~15-30% in healthy participants and those with prediabetes or diabetes. These acute effects have been shown to be sustainable over the longer term in the case of fructose. In separate systematic reviews and meta-analyses of controlled feeding trials, the investigators showed that both small doses (defined as ≤36g/day based on 3 meals at ≤10g/meal and 2 snacks at ≤3g/snack) and higher doses (median, 60g/day) of fructose in exchange for other carbohydrates decreased HbA1c by 0.4% and 0.53%, respectively, a level of reduction which exceed the clinically meaningful threshold of 0.3% proposed by the Federal Drug Administration (FDA) for the development of new oral anti-hyperglycemic agents.

Although these findings provide a compelling proof of concept, there is an urgent need for replication studies. Whether the effects of fructose and allulose are equivalent is of particular interest, as allulose represents a non-caloric alternative to fructose. The minimum 'catalytic' dose at which improvements in carbohydrate metabolism are observed also remains to be determined for each of the sugars in people with and without diabetes.

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