Today, insufficient sleep has become a growing global problem. Sleep is essential to health and changes in sleep patterns are a part of the aging process. Inadequate and low-quality sleep also increases the risk for age-related cognitive decline and disease conditions. More importantly, due to COVID-19 health emergency, there is a significant increase of psychological distress and symptoms of mental illness and a worsening of quality of sleep. Therefore, there is an urgent need to investigate the way of improving sleep quality, in particular during and post COVID-19 period, in older adults.

One of the possible strategies in improving sleep quality with lifestyle modification is having higher-protein diet. However, this effect has not been fully elucidated in older adults. In addition, the effect of type of dietary protein on sleep quality is inconclusive and there is no clinical trial which assessed the differential response in sleep quality between animal-sourced protein vs. plant-sourced protein. Therefore, the purpose of this research project is to assess the impact of different types of higher dietary protein intake on sleep quality in Singapore older adults.

Findings from the proposed research will provide the scientific evidence of the beneficial effects of regularly consuming higher-protein diet on sleep quality in Singapore older adults. In addition, this research may validate the differential effect of different type of dietary protein on sleep quality. The results from the proposed research will also assist a practical guidance of nutritional behaviour changes providing sleep promoting effects to a large proportion of the Singapore population.

During the 16-week intervention, subjects will be randomly assigned to 1 of 3 groups including consuming normal-protein diet, higher-protein diet supplemented with micellar casein protein or higher-protein diet supplemented with soy protein. Recommended Dietary Allowances for healthy Singaporean. Normal-protein diet will be designed following a healthy eating pattern diet, referred to as the "My Healthy Plate" launched by Health Promotion Board and subjects will consume 3 servings of dietary protein. Higher-protein diet will also follow a healthy eating pattern diet while subjects will additionally take either 20 g micellar casein protein isolate or 20 g soy protein isolate. One-on-one dietary counselling and written instructions for each subject will be provided by a research dietitian and trained research staff. Compliance with the diet interventions will be promoted by frequent online and in-person contact and dietary assessment. Blood amino acid concentration will also be assessed as an indicator of compliance to the protein intake.

Inclusion Criteria:

1. Adults 60-85 years old
2. Not following HPB diet

Exclusion Criteria:

1. Weight change > 3kg in the past 3 months
2. Exercise vigorously over the past 3 months
3. Drinking more than 2 alcoholic drinks per day
4. (if applicable) Pre-menopausal women
5. Taking dietary supplements or medications which may impact sleep outcomes (e.g. Nutritional Shakes (e.g. Ensure), Trp, 5-HTP or melatonin supplementations) the past 1 month
6. Taking dietary supplements which may impact the gut microbiota (e.g. antibiotics, prebiotics, probiotics) the past 2 months (a list of fermented foods)
7. Impaired renal function (normal values: estimated glomerular filtration rate ≥ 90 mL/min/1.73 m2 calculated by chronic kidney disease epidemiology collaboration equation; CKD EPI)
8. Soy intolerance and/or allergy or any medical conditions that may be affected by consumption of soy products (e.g. gout)
9. Prescribed and taking antihypertensive/cholesterol-lowering/ type-2 diabetic medication or Chinese medicine herb which started less than 3 years prior to the intervention participation
10. Diagnosed with gut/gastrointestinal issues such as lactose intolerance and irritable bowel syndrome (IBS)

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.