Of all the dietary habits that people find difficult to change, coffee drinking is one of the most challenging because it is so entrenched in cultural habits and caffeine addiction.⁷ Withdrawal symptoms can involve painful headaches, nausea, vomiting, and loose stools.⁸ People whose health problems would be ameliorated if they gave up coffee can improve their chance for successfully quitting coffee if they have both a satisfying alternative and a method to slowly decrease their caffeine intake to reduce withdrawal symptoms.

The following characteristics of coffee have an adverse effect on the upper GI tract:

• Coffee Decreases Pressure in the Lower Esophageal Sphincter
  
  • Coffee has been shown to decrease pressure in the lower esophageal sphincter, contributing to gastroesophageal reflux. This suggests that coffee can either cause or exacerbate heartburn in susceptible individuals.^{9, 10, 11}
  • The type of coffee bean roasting method used does not reduce the tendency of coffee to produce gastroesophageal reflux. Sensitive individuals, even when consuming coffee produced through different roasting processes, while fasting or after a meal, experienced heartburn, regurgitation and dyspepsia.¹²
  • Coffee consumption has been associated with greater incidence of heartburn than drinking other fluids such as water.¹³
  • Both caffeinated and decaffeinated coffee exacerbate gastroesophaeal reflux, and coffee creates more reflux than caffeine added to water, suggesting that other components of coffee contribute to its aggravating effect.¹⁴
  
  
• The Acidity of Coffee Irritates the Stomach
  
  • Coffee is highly acidic and it can stimulate the hypersecretion of gastric acids. Decaffeinated coffee has been shown to increase acidity to a greater degree than either regular coffee or caffeine alone.¹⁵ Both caffeine and coffee stimulate gastric acid secretion and decaffeinated coffee raises serum gastrin levels.^{16, 17} A study comparing the ability of decaffeinated coffee with that of a high protein meal to increase gastric acid secretion and gastrin levels found that decaffeinated coffee was a more powerful stimulant of acid secretion and gastrin release than the high protein.¹⁸
  • Coffee tends to speed up the process of gastric emptying, which may result in highly acidic stomach contents passing into the small intestine more rapidly than normal. This may lead to injury of the intestinal tissue.¹⁹
  • There is a clear relationship between reduction of stomach acid and heartburn relief.²⁰


• Coffee Is a Risk Factor Associated with Ulcer Susceptibility
  
  • Coffee is linked to ulcer susceptibility. Both caffeinated and decaffeinated coffees have an acid-stimulating effect, and therefore it is recommended that people with ulcers restrict not only caffeinated but also decaffeinated coffee intake.²¹


• Coffee Elevates Stress Hormones
  
  • Caffeine in coffee elevates the stress hormones cortisol, epinephrine (also known as adrenaline) and norepinephrine.^{22, 23, 24, 25} These hormones are responsible for increased heart rate, increased blood pressure, and a sense of "emergency alert". Blood is diverted from the digestive system which can cause indigestion. The circulation of oxygen to the brain and extremities is decreased and the immune system is suppressed.
  • The purpose of the body's "fight or flight" response initiated by the release of cortisol, epinephrine and norepinephrine is to provide the body with a temporary energy boost for intense physical activity. With today's sedentary lifestyle, the continual state of increased stress resulting from caffeine consumption may affect symptoms of heartburn and GERD. Although the relationship between stress and symptoms of gastroesophageal reflux is still unclear, evidence suggests that anxiety, along with exhaustion resulting from sustained stress, are both associated with exacerbation of heartburn and esophageal reflux.²⁹


• Coffee Supresses Immune System Function
  • Immune system suppression caused by chronic increased levels of stress hormones induced by caffeine intake can create a situation in which the bacteria Helicobacter pylori can thrive in the stomach. Infection by H. pylori is implicated in ulcers.


• Caffeine Interferes with GABA Metabolism
  • GABA (Gamma-aminobutyric acid) is a neurotransmitter that is naturally produced in the brain and nervous system as well as the GI tract. It plays an important role in mood and stress management and it exerts a calming effect on the GI tract.
  • Caffeine has been found to interfere with binding of GABA to GABA receptors, preventing it from performing its calming function.²⁶ Studies suggest that stimulation of GABA receptors may be beneficial for people with reflux arising from low lower oesophageal sphincter pressure.^{27, 28} In addition to its direct effect on the GI tract, GABA�s role in stress management is also compromised in the presence of caffeine. This is significant as psychological stress has been shown to be an exacerbating factor in heartburn and ulcers.²⁹