According to International Society of Rare Sugars and Centre of Food Safety, unlike cane sugar, rare sugars are found in extremely rare quantities in nature from milk, corn, wheat or wood.

Only a few types of rare sugars are marketed for consumer use, like D-Tagatose, D-Xylose, D-Allulose / Psicose, D-Arabinose, etc.

Research studies on rare sugars have been conducted since the 1970s. Owing to extremely high extraction costs, these sugars were not put into mass production until recent years when manufacturers finally achieve a significant technological breakthrough which makes rare sugars affordable for the consumer market.

In Japan, different brands of rare sugars vary in content. For example, a certain brand of liquid rare sugar contains only 15% of rare sugar (allulose). 85% of its content is actually glucose and fructose which will be absorbed into the bloodstream even faster and easier. Consumers must pay attention to the content labels before making a purchase.

Another brand, a powder-form “rare sugar”, is actually made from エリスリトール(erythritol) via fermentation. The Centre of Food Safety in Hong Kong actually classifies erythritol as just a carbohydrate, not a sugar or rare sugar; therefore, the Chinese character of “sugar”, which is incorporated in the product name of this Japan-made erythritol, is greatly misleading.