Andrea Janus, CTVNews.ca Thursday, June 27, 2013
Chocoholics trying to hide their habit may want to keep dark glasses at hand, suggests a new study, which found the brain’s pleasure response to food can actually be seen in the eyes.
In a small study of nine patients, U.S. researchers measured dopamine levels in the eyes of their subjects after they had tasted chocolate.
Dopamine is the chemical associated with the brain’s reward, pleasure and addiction centre. Dopamine is also released in the eye in response to light exposure.
The researchers used electroretinography (ERG), a tool used by ophthalmologists to look for retinal damage, to measure increases of dopamine in the retina. They found a surge in dopamine activity when the eye was exposed to a flash of light just as the subject ate a piece of brownie. A similar spike was noticed when subjects were given the drug methylphenidate to trigger a dopamine response.
These spikes were far greater than when subjects were exposed to light while only drinking water.
“What makes this so exciting is that the eye’s dopamine system was considered separate from the rest of the brain’s dopamine system,” lead researcher Dr. Jennifer Nasser, associate professor of Nutrition Sciences at Drexel, said in a statement.
“So most people – and indeed many retinography experts told me this – would say that tasting a food that stimulates the brain’s dopamine system wouldn’t have an effect on the eye’s dopamine system.”
The findings are published in the journal Obesity.
Nasser cautions that the study is small, and the findings must be replicated in larger studies. However, if replicated, the research may lead to the use of ERG to study food addiction, which could lead to new ideas for obesity prevention. If a doctor or nutritionist can identify foods that cause a huge dopamine spike in a patient, then they can help devise a diet that avoids those triggers.
“My research takes a pharmacology approach to the brain’s response to food,” Nasser said.
“Food is both a nutrient delivery system and a pleasure delivery system, and a ‘side effect’ is excess calories. I want to maximize the pleasure and nutritional value of food but minimize the side effects. We need more user-friendly tools to do that.”