Participants are being invited to take part in a research study. Before deciding whether to take part, it is important for participants to understand why the research is being done and what it will involve.

Purpose: This study will investigate whether a multi-ingredient nutritional supplement containing magnesium and melatonin can improve sleep quality in adults who experience disrupted sleep due to nighttime leg cramps.

What participation involves: Participation lasts 8 weeks. Participants will be randomly assigned to take either the nutritional supplement or a placebo (inactive look-alike) every night before bed for 6 weeks. Participants will wear an Oura Ring wearable device on one finger continuously for 8 weeks throughout the study and complete short questionnaires using a smartphone app. The Oura Ring and study supplement will be sent to the participant's home address. Participants will never need to travel to a research centre; all contact with the research team will be by video call, phone, messaging, or email.

How long: Total involvement will be 8 weeks, made up of a 2-week baseline period and a 6-week supplementation period. Each day, participants will complete a short app-based questionnaire (approximately 1 minute). At the end of weeks 2, 4, 6, and 8, participants will complete additional app-based questionnaires (approximately 10 minutes).

Inclusion Criteria:

• Adults aged 40-75 years
• Self-reported poor sleep quality (PSQI >5) at screening
• Self-reported nocturnal leg cramp averaging ≥4 episodes per fortnight at screening
• Capacity to understand and provide electronic informed consent
• Willing to wear an Oura Ring wearable device continuously throughout the study period
• Access to a smartphone/tablet with iOS 15 or higher and Android 9 or higher and willing to install and use the Oura and Trialflare applications
• Be a resident of and permanently living in Florida with no planned travel across more than one time zone for at least 1 night during the study period

Exclusion Criteria:

• Current or recent (within 4 weeks of randomisation) use of melatonin, magnesium, or other supplements specifically taken for sleep or leg cramps or listed as an ingredient of the intervention supplement.
• Current use of any prescription medication
• Diagnosed sleep disorder (e.g. obstructive sleep apnoea, restless legs syndrome, insomnia disorder)
• Known or suspected secondary cause of nocturnal leg cramps (e.g. peripheral vascular disease, neurological condition, renal impairment, thyroid disorder)
• Any current or prior diagnosis of:
• Cancer or malignancy of any kind (prior malignancy is not exclusionary if the participant is in confirmed remission and has completed all treatment)
• Cardiovascular disease (e.g. hypertension, coronary artery disease, heart failure, arrhythmia, stroke, peripheral vascular disease)
• Autoimmune disorder (e.g. rheumatoid arthritis, lupus, multiple sclerosis)
• Gastrointestinal disorder (e.g. IBS, malabsorption syndromes)
• Neurological disorder (e.g. epilepsy, Parkinson's disease, dementia)
• Hepatic or renal impairment
• Diabetes mellitus (type 1 or type 2)
• Severe psychiatric disorder (e.g. schizophrenia, bipolar disorder)
• Myasthenia Gravis
• Known hypersensitivity or allergy to any ingredient in the active or placebo product
• Rotating shift work or irregular sleep patterns
• Current participation in another interventional clinical trial
• Inability to comply with study procedures or remote visit schedule
• Breastfeeding, pregnant, or planning to become pregnant during the study period