Pahurat Kongmuang. Effects of caffeine on anorectal function in Thai health volunteers. Master's Degree(Physiology). Mahidol University. : Mahidol University, 2009-07-28.
Effects of caffeine on anorectal function in Thai health volunteers
Abstract:
The effect of caffeine at the dose of 3.5 mg per kg body weight on anorectal
function was evaluated in ten normal Thai adult subjects (5 men and 5 women). Each
subject drank 200 ml of water then caffeine. The anorectal manometric study was
divided into 3 periods, basal / water / caffeine. Each period lasted 45 minutes without
any adverse events.
In this study the basal anal sphincter pressure of 10 normal adult Thai subjects is 36.4
mmHg (range 18.4 to 54.5 mmHg). The basal anal sphincter pressure after caffeine
consumption tended to increase especially at 15 minutes (50.4 mmHg, range 6.7 -97.4
mmHg, p=0.05). At 5, 10 and 45 minutes, after either water or caffeine consumption, no
difference in the basal anal sphincter pressures was found. The average basal anal sphincter
pressure though out the whole 45 minutes, was slightly increased but not statistically
significant after drinking water. After caffeine, the pressure increased significantly compared
to drinking water (p= 0.02).
The maximum squeeze pressure in the control period was 105.7 mmHg (range 10.9 to
234.9 mmHg), after water consumption it was slightly higher (116.0 mmHg, range 12.9 to 234.6
mmHg, p=0.12). After caffeine consumption, the maximum squeeze pressure increased
significantly (134.7 mmHg, range 17.9 to 243.7 mmHg, p=0.02) comparing to that at control
period.
The sustained squeeze pressure in control period was 102 mmHg (range 14 to 234.5
mmHg). It remained unchanged after water consumption (105.8 mmHg, range 12.3 to 198.6
mmHg, p=0.69). After caffeine, the pressure tended to rise (124.9 mmHg, range 19 to 215.9
mmHg, p=0.09) and was significantly higher after caffeine than after drinking water (p = 0.04).
Either water or caffeine consumption caused a decrease in rectal sensory
threshold for the desire to defecate tested by intrarectal air inflation. This might be
partly due to the gastrocolic reflex response.
This study indicated that drinking caffeine 3.5 mg per kg body weight in 200 ml of
water resulted in a tendency to stronger anal sphincter contractions both at basal period and
during voluntary squeeze. But the sensory threshold was also decreased leading to an earlier
desire to defecate. So caffeine consumption can result in an earlier desire to defecate leading
to easier defecation if the anal sphincter can relax voluntarily. Further study with larger
number of subjects of different age groups or different anorectal symptoms should be carried
out in order to obtain more understanding in the effects of caffeine on anorectal function or
physiology in health and diseases.