D-Psicose (C6H12O6), also known as D-allulose, or simply allulose, is a low-calorie epimer of the monosaccharide sugar fructose, used by some major commercial food and beverage manufacturers as a low-calorie sweetener. First identified in wheat in the 1940s, allulose is naturally present in small quantities in certain foods.
The U.S. Food and Drug Administration (FDA) has accepted a petition for Generally Recognized As Safe (GRAS) for allulose as a sugar substitute in various specified food categories. Because it is absorbed and metabolized differently from other sugars, the FDA has exempted allulose from the listing of total and added sugars on the Nutrition and Supplement Facts labels, but requires the labeling of 0.4 kcal/g as carbohydrate.
A meta-analysis was conducted of the effect on postprandial glucose and insulin responses of adding a median of 5 grams of allulose (range, 2.5-10 g) to a fixed carbohydrate-containing drink or meal, versus the same meal alone. Five studies were included, with a median of 18 largely middle-aged participants, including nondiabetic subjects in three studies and subjects with pre-diabetes and/or Type II diabetes in the other two. Three of the 5 studies used a reference 75 gram oral glucose tolerance test (OGTT) for at least one comparison; some studies used other glucose-containing foods either as the sole comparison or as an additional arm along with the OGTT, for a total of ten comparisons. To control for sweetness, aspartame was added to the control preparation in two of the five studies. Overall, compared to the carbohydrate-containing meal alone, the same meal with a small dose of added allulose resulted in a 10% lower integrated area under the curve (iAUC) of postprandial glucose. The quality of the evidence was rated as moderate.
The sweetness of allulose is estimated to be 70% of the sweetness of sucrose. It has some cooling sensation and no bitterness. Its taste is said to be sugar-like, in contrast to certain other sweeteners, like the high-intensity artificial sweeteners aspartame and saccharin. The caloric value of allulose in humans is about 0.2 to 0.4 kcal/g, relative to about 4 kcal/g for typical carbohydrates. In rats, the relative energy value of allulose was found to be 0.007 kcal/g, or approximately 0.3% of that of sucrose. Similar to the sugar alcohol erythritol, allulose is minimally metabolized and is excreted largely unchanged. The glycemic index of allulose is very low or negligible.
Allulose is a weak inhibitor of the enzymes ?-glucosidase, ?-amylase, maltase, and sucrase. Because of this, it can inhibit the metabolism of starch and disaccharides into monosaccharides in the gastrointestinal tract. Additionally, allulose inhibits the absorption of glucose via transporters in the intestines. For these reasons, allulose has potential antihyperglycemic effects, and has been found to reduce postprandial hyperglycemia in humans. Through modulation of lipogenic enzymes in the liver, allulose may also have antihyperlipidemic effects.
Due to its effect of causing incomplete absorption of carbohydrates from the gastrointestinal tract, and subsequent fermentation of these carbohydrates by intestinal bacteria, allulose can result in unpleasant symptoms such as flatulence, abdominal discomfort, and diarrhea. The maximum non-effect dose of allulose in causing diarrhea in humans has been found to be 0.55 g/kg of body weight. This is higher than that of most sugar alcohols (0.17–0.42 g/kg), but is less than that of erythritol (0.66–1.0+ g/kg).
D-allulose was found to be more reactive than fructose and glucose in glycation reactions. wikipedia
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