Trehalose is a very interesting sugar, it is a disaccharide made up of two molecules of glucose. It occurs in some seeds and fungi though it is not common in plants. Mushrooms contain up to 10–25 % by dry weight.

It is the main fuel used by insects in flight. Because their wings beat so fast and in order to enable them to produce sudden bursts of power nature has chosen this sugar for their blood. It is estimated that insects can use it twice as efficiently as Glucose.

It protects organisms from extremes of weather, such as freezing and drying out. The Resurrection Plant can withstand months without water because it contains abundant amounts of this sugar which protects the cells against damage in the difficult conditions.

Benefits:
No great benefit as a sweetener, it is less than half as sweet as sugar and has a similar glycemic index. However it has a multitude of other uses and applications. It is an antioxidant, it acts as a natural preservative, it keeps food moist and helps preserve texture and flavour. In nature it has amazing qualities which seem to prevent damage to cells from drying out or freezing.

These properties can have advantages in the production of cosmetics, pharmaceuticals and foodstuffs. It has an important application as a constituent in solutions for the protection of organs during transplant operations. It is useful as a component of frozen foods and ration packs etc. It is temperature stable and can be used in cooking.

It has been shown to inhibit the degradation of carbohydrates, proteins, and fatty acids in foods. Thus it can act as a safe preservative. In addition it has been found to inhibit the development of bacteria that cause body odor, so it may find use as a cosmetic.

Eye drops containing this sugar have proved useful in the treatment of dry eye syndrome.

It may even help to mitigate against insulin resistance and become a useful tool against the onset of diabetes. It has a hypoinsulinemic effect, the exact opposite of fructose.  showed significant improvement in triglyceride levels and insulin response in mice.

Concerns:
As with most other sugars it is harmful to teeth. It has a fairly high glycemic index, though unlike ordinary sugar it is only broken down into glucose - there is no fructose component. Fine in moderation.

Safety:
There is no recommendation from the FDA or the CSPI on this sugar. It would be well to follow the and restrict intake of all sugars, including Trehalose to 50g per day. 

Production:
In 1994 Japanese firm Hayashibara developed a low cost of producing it from starch. Before that it was not widely available.

Sold As:
Not usually sold on its own. A new product has arrived on the market called NewSweet. It consists of Trehalose sweetened with Stevia so that it can be used one for one with ordinary sugar. This would give it an effective glycemic index of 35, and it contains no fructose. However it still is sugar, so moderation is essential.