The aim of this study is to assess the impact of 5-hydroxytryptophan (5-HTP) supplementation on sleep quality and gut microbiome composition in older adults with normal cognition vs. mild cognitive impairment (MCI) using a randomized controlled trial.

This is a 12-wk parallel, single-bind (investigator), prospective study design with subjects randomly assigned to consume 100 mg of 5-HTP or does not consume 5-HTP. Fifty older men and women (aged 60-85y, approximately half men and half women, approximately half subjects with MCI) will be recruited with the expectation that ≥ 40 subjects (≥ 10 subjects per group) will complete the study. Body size, blood pressure, urinary melatonin, sleep quality, cognitive function and mood (including depression and anxiety), gut microbiome, and short chain fatty acids will be assessed. Blood amino acid concentration will be measured as an indicator of compliance to the 5-HTP consumption from the collected blood samples.

Relevance to Singapore: The results from the proposed research will assist a practical guidance of nutritional behavior changes providing gut and brain health promoting effects to Singapore older individuals with or without MCI and may result in reducing cost and manpower for cognitive decline care.

Inclusion Criteria:

1. Able to give an informed consent
2. Age 60 ≤years ≤ 85 years old
3. Weight change < 3kg in the past 3 months
4. Not exercising vigorously over the past 3 months
5. Not taking protein (e.g. Whey isolate, Ensure), tryptophan, serotonin and/or 5-HTP supplements for the past one month
6. Not taking sleep medication and/or dietary supplements for sleep (e.g. melatonin, GABA) for the past one month
7. Not taking prebiotic, probiotic and/or dietary fiber supplementations for the past one month
8. Not taking cognitive/brain supplementations (e.g. gingko biloba, acetylcholine) for the past one month
9. Not taking prescription anti-depressant or pain medication (e.g. Zoloft, Tramadol etc.)
10. No acute illness
11. If taking antihypertensive/cholesterol-lowering/ type 2 diabetic medication, he/she has been taking the medication for more than 5 years prior to the study participation
12. Not smoking
13. Not drinking more than 2 alcoholic drinks per day

Exclusion Criteria:

1. Unable to give an informed consent
2. Age < 60 years and >85 years old
3. Weight change >3kg in the past 3 months
4. Exercises vigorously over the past 3 months
5. Taking protein (e.g. Whey isolate, Ensure), tryptophan, serotonin and/or 5-HTP supplements for the past one month
6. Taking sleep medication and/or dietary supplements for sleep (e.g. melatonin, GABA) for the past one month
7. Taking prebiotic, probiotic and/or dietary fiber supplementations for the past one month
8. Taking cognitive/brain supplementation (e.g. gingko biloba, acetylcholine) for the past one month
9. Taking prescription anti-depressant or pain medication (e.g. Zoloft, Tramadol etc.)
10. Having acute illness
11. If taking antihypertensive/cholesterol-lowering/ type 2 diabetic medication, he/she has NOT been taking the medication for less than 5 years prior to the study participation
12. Smoking
13. Drinking more than 2 alcoholic drinks/day

Electronic copies of the data with identifiable participant information will be kept on a secure website with access limited to Dr. Kim and her research staff. All data will be de-identified prior to statistical analyses