Previous research had suggested that only sugary substances protect against pain but Chicago scientists have published a paper claiming that plain old water may be just as effective, if not more so.
Writing in the Journal of Neuroscience the neurobiologists presented research that recorded how rats responded to heat when eating and drinking different things.
As a rat swallowed, a light-bulb beneath the cage was switched on, providing a heat stimulus that normally caused the animal to lift its paw off the floor. Rats turned out to be far slower to react during a meal than they were when awake, but not eating.
Surprising result
This finding was true not only with chocolate but also with water. Given that previous research had indicated that only sugary substances were protective against pain, this was a surprise to the researchers.
“This really shows it has nothing to do with calories,” said neurobiology professor Peggy Mason. “Water has no calories, saccharine has no sugar, but both have the same effect as a chocolate chip. It’s really shocking.”
Appetite was also found to have no effect on how the rats reacted. Mason and research associate professor Hayley Foo suggested this may be explained by evolution.
Pain relief may help animals in the wild avoid distraction while eating scarce food even when they are not hungry. This effect is less useful to modern humans who enjoy readily available food and struggle to avoid overeating and obesity.
“We’ve gotten a lot more overweight in last 100 to 150 years,” said Mason. “We’re not more hungry; the fact of the matter is that we eat more because food is readily available and we are biologically destined to eat what’s readily available.”
Water instead of candy
But the discovery that water may be just as good as chocolate could have implications for public policy. Mason said water could be a replacement for the practice of using candy to calm children – or even adults – in the doctor’s office.
“Ingestion is a painkiller but we don’t need the sugar,” Mason said. “So replace the doctor’s lollipop with a drink of water.”
Water could be even more effective than chocolate. When rats were made ill by a drug treatment, eating chocolate no longer delayed their reaction but drinking water still caused a reduced pain response.
Not all food and drink sparked a slowed pain response in the rats. Mason and Foo gave the rats quinine, a bitter drink that causes them to make an expression that translates to “yuck” in human terms.
During quinine administration, the rats reacted to heat as quickly as when not eating. This, the scientists said suggested that an unpleasant food or drink fails to trigger pain relief.
Source: Journal of Neuroscience
October 14
“Analgesia accompanying food consumption requires ingestion of hedonic foods”
Authors: P. Mason, H. Foo