The Effect of Protein on Calcium Absorption and Gastric Acid Production

Phase 4

Completed

Conditions: Osteoporosis

Interventions: Drug: esomeprazole
Drug: Placebo

Registration Number: NCT00719160

Lead Sponsor: Yale University

Brief Summary: We have established that dietary protein is an important regulator of intestinal calcium absorption in humans. However, we do not understand the mechanism by which dietary protein is affecting calcium absorption. Therefore, the purpose of this research is to evaluate whether dietary protein-induced changes in gastric acid secretion explain the observed changes in intestinal calcium absorption.

Detailed Description: We have established that dietary protein is an important regulator of intestinal calcium absorption in humans. However, we do not understand the mechanism by which dietary protein is affecting calcium absorption. Therefore, the purpose of this research is to evaluate whether dietary protein-induced changes in gastric acid secretion explain the observed changes in intestinal calcium absorption. We have compelling in vitro data that amino acids can stimulate gastric acid secretion. We have found that this occurs via allosteric activation of the calcium sensing receptor expressed on the gastric acid-secreting parietal cells. At a fixed concentration of extracellular calcium, addition of L but not D isomers of specific amino acids activates the calcium sensing receptor and stimulates parietal cell acid production. We hypothesize that dietary protein induced gastric acid production increases calcium solubility and bioavailability thereby increasing its absorption. We will test this hypothesis in humans by quantifying the impact of dietary protein on intestinal calcium absorption in subjects who cannot make gastric acid. We will measure intestinal calcium absorption in healthy adults as they consume either a high protein diet with concomitant administration of a proton pump inhibiting (PPI) drug or the same high protein diet with a placebo instead of a PPI. The order of the 2 interventions will be randomized, and study will be double-blind and placebo controlled. If our hypothesis is correct, then intestinal calcium absorption will be highest during the high protein diet with placebo, and lowest during the drug intervention.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 12

Inclusion Criteria

Healthy men and women age 18-45 years
Caucasian or Asian descent due to increased risk of Osteoporosis

Exclusion Criteria

gastrointestinal diseases
osteoporosis
diabetes
hypertension
liver disease
thyroid disorders
kidney disease
kidney stones
cancer
heart disease
eating disorders
obesity
hypogonadism
amenorrhea
oligomenorrhea
abnormal serum FSH or estradiol levels
birth control medication or other hormone-altering medications
pregnancy
Lifestyle factors such as:
- smoking
- excessive exercise (although moderate exercise is allowed)
- prescription medications known to influence vitamin D or calcium metabolism or gastric acid
- excessive body weight change during the past 6 months
- food allergies
- unusual eating habits or medically prescribed diets

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	-
Esomeprazole	Placebo	-
Esomeprazole	esomeprazole	-
Placebo	esomeprazole	-

Primary Outcome Measures

Name	Time	Method
Percent Change in Intestinal Calcium Absorption	Day 5 of a high protein diet	This is completed by measuring the amount of calcium absorbed by utilizing dual stable calcium isotopes. It was hypothesized that we would see a percent decrease as a result of the proton pump inhibitor. Previous published data indicated a decline in calcium absorption of 6.6 +/- 5.5% when gastric pH is blocked.

Secondary Outcome Measures

Name	Time	Method
Gastric pH	Day 5 of a high protein diet	The American Heritage Dictionary defines pH as "a measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14." The normal pH range for stomach acid is between 1.5 and 3.5.