In this study the investigators will test a nutritional supplement called betaine hydrochloride to see if it can temporarily increase the stomach acid in healthy volunteers who have decreased stomach acid because they take a medicine called rabeprazole.

Investigators will evaluate the extent and time course of gastric re-acidification after oral betaine HCl in healthy volunteers with pharmacologically-induced hypochlorhydria. After betaine HCl dose, gastric pH will be continuously monitored for 2 hours.

Inclusion Criteria:

• Healthy adult with no active medical problems or significant chronic diseases as determined by the study doctor based on history, physical exam;
• BMI between 18.5 - 35 kg/m2;
• Taking no medications 2 weeks before and during the study enrollment, including drugs of abuse, prescription or OTC medications (except acetaminophen);
• Subjects must be able to maintain adequate birth control during the study independent of hormonal contraceptive use;
• Be able to provide written informed consent and comply with requirements of the study;
• Avoid eating grapefruit and drinking grapefruit juice from 7 days before the first study day until completion of the entire study;
• Abstinence from alcoholic beverages, caffeinated beverages and orange juice from 6pm the night before a study day until completion of that study day;
• Fast from food and beverages at least 8 hours prior to the study day;
• Be able to read, speak and understand English

Exclusion Criteria:

• Subjects with a history of gastrointestinal disease including gastroesophageal reflux disease, gastritis, peptic ulcer disease or dyspepsia.
• Subjects with a fasting gastric pH of > 4 (i.e. hypochlorhydria)
• Subjects with history of dysphagia, achalasia, or difficulty swallowing capsules, tablets or pills.
• Subjects on prescription or chronic over-the counter medications (including hormonal contraceptives);
• Subjects with known allergy to study interventions;
• Subjects who smoke tobacco;
• Subjects with ongoing alcohol or illegal drug use;
• Subjects who are pregnant, lactating or attempting to conceive;
• Subjects unable to maintain adequate birth control during the study;
• Subjects unable to follow protocol instructions or protocol criteria.

2 hours after betaine HCl dose, or by report of subject