Several studies indicate that the brain regions responsible for taste overlap the areas responsible for detecting pain.
However, Dana Small and A. Vania Apkarian noted that little research has been conducted on the relationship to taste sensitivity and pain. They developed a simple experiment to see if there was a relationship.
Eleven volunteers with chronic back pain were matched with 11 normal volunteers, of similar age, gender, and education backgrounds. Each person was tested separately for sensitivity to four different kinds of tastes: bitter, salty, sweet, and sour. They each sampled a small cup of water with each of the four flavors, rating them on a scale of 0 to 100 for the strength of the taste sensation. Here are the results:
For salty, sweet, or sour tastes, as well as the overall average, people with chronic back pain rated the flavors as significantly more intense than normal individuals. There’s clearly a relationship between these two phenomenona.
But perhaps people with chronic back pain simply rate the flavors as more intense, but aren’t actually sensing anything different. Small and Apkarian designed two tests to see if this could explain the discrepancy. In the first, the sour flavor was presented in a highly diluted form, undetectable by all participants. The concentration of flavor was gradually increased until it was detected. Again, there was a trend towards people with back pain detecting the flavor at a lower concentration than normal individuals. Though the trend was not significant, the researchers argue that it suggests that people with chronic back pain are indeed more sensitive to taste.
In the second test, participants were shown cards colored different shades of gray and asked rate their their blackness on a scale of 0 to 100. There was no difference between people with back pain and healthy people, again suggesting that people with back pain aren’t merely biased towards more intense ratings.
Small, D.M., & Apkarian, A.V. (2006). Increased taste intensity perception exhibited by patients with chronic back pain. Pain, 120, 124-130.