Trehalose is a disaccharide composed of glucose, differing from the dietary sugar known as maltose which is also comprised of two glucose molecules due to differing bonds. Trehalose is found mostly as a component of mushrooms in the diet, with limited exposure in the human diet otherwise.
It has been investigated for a variety of therapeutic purposes due to its ability to induce apoptosis (controlled cellular death) via an atypical mechanism, and in these therapeutic settings using trehalose injections it appears to be effective.
Unfortunately, not only is trehalose initially poorly absorbed from the intestines but within the intestinal wall there is an enzyme (trehalase) which can rapidly degrade trehalose into glucose. For the trehalose that bypasses this enzyme and gets absorbed, the threhalase present in the liver and the blood appears to finalize the digestion leaving little to no trehalose able to reach a cell and exert its therapeutic effects.
The only way to preserve the effects of trehalose is to avoid oral ingestion by applying the compound topically leading to the promise of trehalose in protecting cellular function being exclusive to the skin, eyes, and hair. It has already shown therapeutic promise for the treatment of dry eye symptoms when used as eye drops, with a potency greater than commercially available products.