Bitter herbs are used in western herbal medicine for maintaining healthy digestive function. As gastric secretion declines with age, a significant percentage of people aged 65 years or older have abnormally low gastric acidity. Low acidity can lead to poor nutrient absorption and abnormal bowel flora. When bitter substances are tasted at the back of the tongue prior to a meal, they have a priming effect on the upper digestive function - this is most noticeable if digestion is below optimum.