Why Does Everything I Eat Taste Bitter?

If a person has a bitter taste in his mouth when he eats, then he may have GERD, dental or gum problems, mouth yeast infection, respiratory tract infection, dehydration or an autoimmune condition according to WebMD and the Telegraph. GERD is a gastroesophageal reflux disease that causes symptoms of heartburn, chest pain, trouble swallowing, nausea and extra saliva with a bitter taste, according to WebMD.