L-tryptophanCombination of L-tryptophan + Ca-500Combination of L-tryptophan + Ca-1000Control
L-tryptophan: L-tryptophan, an aromatic amino acid and one of the building blocks of protein, is a part of our daily diet. The load of L-tryptophan (0.1 kcal/minute) is based on our previous study, in which L-tryptophan represented a submaximal load.
Combination of L-tryptophan + Ca-500: Calcium, an essential mineral and a key component of dairy products, is a regular part of our daily diet. In this condition, both L-tryptophan and calcium will be administered as 'active'. Recent studies have shown that calcium in a dose of 500 mg enhances the effects of L-tryptophan to stimulate gut functions and reduce energy intake. This dose of calcium will be considered 'lower dose'.
Combination of L-tryptophan + Ca-1000: In this condition, both L-tryptophan and calcium will be administered. In our study calcium in a dose of 1000 mg enhances the effects of L-tryptophan to stimulate gut functions and reduce energy intake. This dose of calcium will be considered 'higher dose'.
Control: An isotonic solution containing 2.5 g of NaCl, dissolved in 225 mL of distilled water.
Study summary
The intervention in this study consists of 75-minute intraduodenal infusions of isosmotic solutions containing either saline (control), L-tryptophan, or calcium combined with L-tryptophan. Participants enrolled into the study will receive, in a randomised, double-blind fashion either (i) saline (control), (ii) L-tryptophan at a rate of 0.1 kcal/minute, (iii) combination of L-tryptophan (0.1 kcal/minute) + 500 mg calcium, or (iv) combination of L-tryptophan (0.1 kcal/minute) + 1000 mg calcium in four separate sessions, each of which will be separated by at least 4 (and up to 10) days. Each study session will be 4-6 hours. Studies will be carried out in the Clinical Research Facility of the Adelaide Medical School, the University of Adelaide, by staff and students trained in the required techniques.
Eligibility
Sex
MALE
Min age
18 Years
Max age
70 Years
Healthy volunteers
Accepted
Inclusion Criteria:
* Healthy, lean males (only men will be included in the study to avoid the confounding effects of the menstrual cycle on gastric emptying).
* BMI: 19-25 kg/m2,
* Weight-stable (i.e. \<5% fluctuation) at study entry, which will be ascertained by a stable body weight in the preceding 3 months.
Exclusion Criteria:
* Significant GI symptoms, or history of GI disease or surgery
* Current gallbladder or pancreatic disease
* Cardiovascular or respiratory diseases
* Any other illnesses as assessed by the investigator (including chronic illnesses not explicitly listed above)
* Use of prescribed or non-prescribed medications (including vitamins and herbal supplements) which may affect energy metabolism, GI function, body weight or appetite (e.g. domperidone, cisapride, anticholinergic drugs (e.g. atropine), metoclopramide, erythromycin, hyoscine, orlistat, green tea extracts, Astragalus, St Johns Wort etc.)
* Lactose intolerance/other food allergy(ies)
* Individuals with low ferritin levels (\<30 ng/mL), or who have donated blood in the 12 weeks prior to taking part in the study
* High performance athletes
* Current intake of \> 2 standard drinks on \> 5 days per week (\>140g/week)
* Current smokers of tobacco (cigarettes, cigars, pipes, sheesha, chewing, vaping etc.)
* Current use of recreational drugs, e.g. marijuana
* Current intake of any illicit substance
* Vegetarians
* Inability to tolerate nasoduodenal tube
* Inability to comprehend study protocol
* Restrained eaters (score \>12 on the 3-factor eating questionnaire)
Primary outcome measure(s)
Plasma glucose concentrations — Blood samples will be collected over 4.5 hours: at baseline (time = -30 minutes), then at regular intervals before and after drink administration (times = -25, -15, 0, 10, 20, 30, 45, 60, 75, 90, 120, 180, and 240 minutes). Plasma glucose concentrations (mmol/L) will be assessed using the glucose oxidase method.
Trial sites (1)
Facility
City
Region
Status
Clinical Research Facility, Adelaide Health and Medical Sciences Building
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
We use cookies to analyse site traffic and improve your experience. With your consent, we may also use cookies for advertising. You can change your choice at any time.