If you let a piece of candy melt in your mouth, but did not swallow it, would the sugar be absorbed through the walls of your mouth?
Simple sugars such as glucose, fructose and galactose will be absorbed.
- They are most probably transported by a common carrier, which is why if you present both glucose and galactose, the presence of one will inhibit the absorption rate of the other.
- Uptake rate also seems to partly depend on the concentration of sodium ions in the buccal cavity. This was identified and explored subsequently.
- It seems that at the cellular level, absorption is not the quickest but there is a lot of vascularization which allows it to enter the bloodstream quickly, regardless.
Here's a back-of-the-envelope calculation: about 10mg is absorbed in 5 minutes when you hold a solution of 3.6g/l in your mouth. A normal gulp volume is around 10ml. That's 36mg of sugar in a mouthful. Result: you can absorb 10mg of sugar from a theoretical maximum of 36mg. In other words, within 5 minutes, you absorb ~30% of all available sugar. That's pretty good, given that a sugar solution is not a more concentrated, solid sugary food!
Worthy to note that most complex sugars will not be absorbed. Note that many complex sugars actually won't be uptaken even in rest of the GI tract, like cellulose.
The absorption of sugar from the mouth is possible and it was successfully tested for treatment of hypoglycemia. In all mentioned studies, they used D-glucose (dextrose), which is a common natural or added sugar in foods and beverages.
Sixty-nine children with glucose concentrations of < 0.8 g/L were assigned randomly to 1 of 4 methods of administration, 1 with 3 different doses of sugar, as follows: oral group (OG) (n = 15): 2.5 g of sugar; sublingual group (SG) (n = 27): 2.5 g of sugar under the tongue, with 3 treatment subgroups, ie, 0.1 g/kg, 0.15 g/kg, and 0.2 g/kg; intravenous group (IG) (n = 8): 8 mL of 30% dextrose in a single bolus; water group (n = 11)...Bioavailabilities were 84% and 38% in the SG [sublingual group] and OG [oral group], respectively. The sublingual administration of sugar proved to be effective among moderately hypoglycemic children.
Analysis of regression coefficients after 30 min compared to the control session, demonstrated an increase in PG [plasma glucose] with the sachet of liquid sugars (0.068 mmol/l/min, p = 0.001) which was greater than a single dextrose tablet (0.052 mmol/l/min, p = 0.002), but no significant PG increase was found after buccal glucose spray. Liquid sugars or dextrose tablets, but not the buccal glucose spray, are effective means to increase PG within 10 minutes after ingestion.
Our findings show that treatment with 40% dextrose gel is more effective than feeding alone for reversal of neonatal hypoglycaemia in at-risk late preterm and term babies in the first 48 h after birth....Our study is the first report in babies showing that buccal dextrose gel is a safe effective treatment for management of hypoglycaemia.
We showed that sublingual absorption was faster than the oral route. An increase of 2 mmol/L in blood glucose concentration was achieved in 10 min, and 64% of children had a blood glucose concentration of more than 3·3 mmol/L after 20 min.
Providing sugar under the tongue (sublingual) resulted in a greater rise in blood glucose after 20 minutes than giving the sugar orally, but this was in a specific setting including children with hypoglycaemia and symptoms of concomitant malaria or respiratory tract infection. On the other hand, giving glucose by the buccal mucosa route resulted in a lower plasma glucose concentration than with the oral route. For dextrose gel (where uptake of the glucose occurs through a combination of oral swallowing and via the buccal mucosa), no clear benefit was shown compared to oral glucose administration (glucose tablets or glucose solutions).
Important: Currently, buccal glucose is not recommended to treat hypoglycemia, except in uncooperative children who refuse to swallow glucose (International Liaison Committee on Resuscitation, 2019) .