According to the "Information Times," coffee contains caffeine, which, once in the body, stimulates the sympathetic nervous system. This helps to eliminate sleepiness, improve blood circulation, and make the body feel warmer, thus providing an energizing effect. However, stimulation and excitation of the sympathetic nervous system can suppress appetite, so drinking coffee before a meal may lead to a loss of appetite.
Additionally, the stomach is stimulated, causing an increase in gastric juice secretion. This can irritate an empty stomach and is not beneficial for patients with conditions like gastric ulcers.
However, drinking coffee after a meal can aid digestion because the increased gastric juice secretion helps with the digestive process.