Trehalose is a naturally occurring sugar, or disaccharide, composed of two glucose molecules joined together by a distinctive alpha, alpha-1,1-glycosidic bond. This chemical arrangement gives trehalose stability and a lower chemical reactivity compared to other common sugars. First discovered in 1832 in an ergot of rye, and later isolated in 1859 from a sugary substance produced by weevils, trehalose has a long history in nature. This compound is now recognized for the role it plays in allowing organisms to survive extreme environmental conditions, a property that has led to its growing use in food, medicine, and industry.
Trehalose in Nature: The Survival Sugar
Trehalose is synthesized by a wide variety of organisms, including bacteria, fungi, plants, and invertebrate animals, and functions primarily as a stress protectant and energy source. Its presence is highly concentrated in organisms that possess the ability to enter a state of suspended animation called anhydrobiosis. These organisms accumulate large quantities of the sugar when they experience desiccation, freezing, or high temperatures.
The sugar is found in organisms like baker’s yeast, certain desert plants known as resurrection plants, and the microscopic tardigrades, often called water bears. For instance, the resurrection plant Selaginella lepidophylla can dry out to a fraction of its mass and then spring back to life when rehydrated, a feat enabled by trehalose. In insects, trehalose also serves as the main carbohydrate energy storage molecule, providing a rapid energy source for activities such as flight.
The Science of Bioprotection
The ability of trehalose to stabilize biological structures is rooted in two physicochemical mechanisms that distinguish it from other sugars like sucrose. One of these mechanisms is the “water replacement” hypothesis, which describes how trehalose effectively substitutes for water molecules that surround proteins and cell membranes. In the absence of water, trehalose forms hydrogen bonds with polar groups on these macromolecules, satisfying their structural needs and preventing them from unfolding or denaturing.
This direct interaction helps maintain the native three-dimensional structure of proteins and the integrity of cell membranes during drying. The other mechanism involves the formation of an amorphous “glassy” matrix, a process known as vitrification. When moisture levels drop significantly, trehalose forms a non-crystalline, highly viscous solid that physically immobilizes and encases cellular structures.
Because trehalose has a significantly higher glass transition temperature than other disaccharides, this glassy state remains stable even under moderate heat. This mechanical entrapment prevents the molecular movement and chemical reactions that would otherwise cause decay, allowing the biological material to be preserved over extended periods. Both the water replacement and vitrification mechanisms work together to confer protection to fragile biological molecules and entire cells.
Commercial Uses in Food and Industry
The natural stabilizing properties of trehalose have been leveraged for commercial application. In the food industry, trehalose is utilized as a preservative and a low-sweetness sweetener, possessing about 45% of the sweetness of table sugar. Its non-reducing nature means it resists chemical reactions like the Maillard browning reaction, which helps maintain the color and flavor of foods.
Trehalose is also effective at preventing starch retrogradation, which is the process that causes baked goods to become stale. This anti-staling effect extends the shelf life and preserves the texture of products like bread and noodles. Beyond food, the sugar is used extensively in the pharmaceutical and biotechnology sectors.
Trehalose is commonly used as an excipient in formulations to preserve vaccines, therapeutic proteins, and blood products, ensuring their stability outside of refrigeration. The compound is also included in cosmetics for skin hydration, drawing on its ability to retain water.
How the Body Processes Trehalose
When consumed, trehalose is digested in the small intestine by the enzyme trehalase, which breaks the disaccharide into its two constituent glucose molecules. This digestive process is relatively slow compared to other sugars, resulting in a lower and more gradual rise in blood sugar. As a result, trehalose is considered to have a lower glycemic index than sucrose, making it a more moderate source of carbohydrate energy.
However, some individuals have a genetic variation resulting in a trehalase deficiency, which can limit the enzyme’s activity. For these people, consuming trehalose can lead to digestive discomfort because the undigested sugar passes into the large intestine, where it is fermented by gut bacteria. This fermentation process can produce gas, bloating, and other gastrointestinal symptoms.
Beyond its role in digestion, trehalose has generated significant interest in research for its potential to induce autophagy, a cellular process. Autophagy involves the breakdown and removal of damaged cells, proteins, and organelles. Preliminary, non-dietary research suggests trehalose may promote this cellular cleanup independently of the main nutrient-sensing pathways.
This laboratory finding has led to investigations into trehalose’s potential therapeutic application in neurodegenerative disorders, such as Huntington’s and Alzheimer’s diseases. Laboratory studies on trehalose and autophagy show promise, but these findings generally involve high-dose, non-oral administration. The direct health effects of dietary trehalose consumption in humans for these specific conditions are still subject to ongoing investigation into the precise mechanisms of this induction.