Note: Although the following is about treating pain from an injection, I have witnessed the same effect when I perform a traditional Bris using the Mogen clamp (which takes under 20 seconds). I give the baby a gauze pad dipped in a concentrated sugar solution to suck on immediately prior to the Bris. After the Bris, the baby sucks on a gauze pad dipped in sweet wine or grape juice. The results are wonderful. In my opinion, this is the safest and least invasive way to reduce the discomfort for a baby during a Bris.
— Cantor Philip L. Sherman, Mohel
December 17, 2012
By NICHOLAS BAKALAR
Researchers reviewed data from 14 randomized trials using a sweet-tasting solution to treat pain from injections in babies under a year old. Over all, babies who tasted a sweet solution cried less than those given a placebo, but the studies were difficult to compare because of their varying methodologies.
Some studies tested a sweet solution against a placebo, some one sweet solution against another. Others tested sugar against a topical anesthetic or against a distraction like sucking on a pacifier.
The analysis, published last week in The Cochrane Database of Systematic Reviews, concludes that sugar is an effective anesthetic in reducing the amount of crying time. But there was no strong evidence for which sweet substance worked best, or for the ideal concentration or dosage. The one study that tested sugar against a topical anesthetic found no difference between the two in duration of crying time.(emphasis mine)
"The effect of the sugar will last only about two minutes, so it should be given during the administration of the shot," said the lead author, Manal Kassab, an assistant professor at the Jordan University of Science and Technology. "Giving small amounts of sugar is a very safe intervention."
The reason for the effect is unclear, but some experts suggest sugar releases natural opioids, or that stimulating the taste receptors induces a feeling of comfort.