Mechanistic Effect of Walnut Consumption on Sleep Quality

Columbia University24 enrolled

Overview

Poor sleep quality is very common in modern society. Walnuts contain many nutrients that may be helpful for sleep, including melatonin and polyphenols. Some studies show that eating foods high in melatonin and polyphenols improves sleep quality, but walnuts have not been studied specifically. This study proposes to test if eating walnuts improves sleep compared to a food that lacks these sleep-promoting factors. The investigators expect that walnut consumption for 4 days will increase melatonin levels and lead to better sleep quality compared to a high-carbohydrate, high-sugar food. The study will enroll middle-aged and older adults with sleep complaints to participate in this study. Each person will eat the two different foods for 4 days each in random order. The 4-day periods will be separated by at least 2-3 weeks. Sleep quality will be measured by questionnaire and with a wrist monitor every day. The investigators will also do a sleep study using electroencephalography (EEG) on night 3 and take measures of circadian physiology (natural body rhythms) in the laboratory on day 4 (including overnight) by measuring body temperature and blood and urine melatonin. The study findings may provide new options to improve sleep health from increased walnut consumption.

Walnuts are a nutrient-rich food which provides melatonin and polyphenols. While there is evidence that dietary intakes of foods high in melatonin and polyphenols positively influence sleep quality, the effect of walnuts has not been investigated. The investigators propose to fill this knowledge gap by testing the effects of walnut consumption on serum melatonin and resulting sleep and circadian biology. The study hypotheses are that walnut consumption for 4 days will increase melatonin levels, suggestive of more robust circadian rhythms, and lead to better sleep quality compared to a high-carbohydrate high-sugar (HCHS) equivalent. Using a randomized controlled crossover trial, the study aims to: 1) determine the effect of walnut vs HCHS consumption on melatonin levels; and 2) determine the effect of walnut vs HCHS consumption on sleep and circadian physiology. Adult males and females with poor sleep quality will consume three servings/day of walnuts or an equicaloric HCHS food for 4 days. Sleep quality will be measured nightly using the Karolinska Sleep Diary and wrist actigraphy; sleep architecture from polysomnography will be measured on night 3. Circadian physiology will be assessed on day 4 using body temperature and hourly serum melatonin and on the morning of day 5 from overnight urinary 6-sulfatoxymelatonin. Given the extent of poor sleep, our findings may open new avenues to improve sleep health from increased walnut consumption.

Interventions

Walnut consumptionOTHER

Participants will add one serving (1 oz) of walnuts at their self-defined breakfast, lunch, and dinner for 4 days. The study will provide study foods at 3 main meals each day to evaluate a temporal effect of the food on melatonin concentrations throughout the day.

HCHS consumptionOTHER

Participants will add one HCHS food (one PopTarts® pastry) to each of their 3 main meals of the day for 4 days. The study will provide study foods at 3 main meals each day to evaluate a temporal effect of the food on melatonin concentrations throughout the day. An energy-matched high-carbohydrate, high-sugar (HCHS) alternative, representative of a common US snack food, on sleep quality in adults with habitually poor sleep quality.

Eligibility

Sex: ALLMin age: 45 YearsMax age: 65 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Equal numbers of men and women (12 male and 12 post-menopausal female) * Equal number of individuals with normal weight (18.5-24.9 kg/m2) and overweight (25-29.9 kg/m2) * Participants will self-report poor sleep quality, reflected by a global score \>5 on Pittsburgh Sleep Quality Index Exclusion Criteria: * Diagnosed sleep disorder * Participants with conditions that could affect sleep will be excluded: * smoking, excessive caffeine intake (\>300 mg/day) * shift work * chronic pain * diagnosis of a chronic disease (e.g., uncontrolled hypertension, pre-diabetes, type 2 diabetes, chronic kidney disease, chronic obstructive pulmonary disease), * autoimmune diseases * cardiovascular event or cancer in the past 24 months * psychiatric/neurologic disease or disorder, or sleep disorder (diagnosed or high risk for sleep apnea, chronic insomnia, restless leg syndrome, narcolepsy) * use of medications that influence CYP1A2 enzymes * Allergy/intolerance to nuts, tree nuts, or unwilling to eat study foods

Outcomes

Primary Outcomes

Serum melatonin

Serum melatonin will be measured via last testing of blood samples collected on day 4, in an inpatient setting. Repeated for each phase.

Time frame: Baseline (9AM; Hour 0), Hour 1, Hour 2, Hour 3, Hour 4, Hour 5, Hour 6, Hour 7, Hour 8, Hour 9, Hour 10, Hour 11, Hour 12, Hour 13, Hour 14, Hour 15 (Midnight)

Sleep quality index

Sleep quality will be assessed daily using wrist actigraphy. Variables include sleep fragmentation index and sleep efficiency. Repeated for each phase.

Time frame: Night 1, Night 2, Night 3, Night 4

Slow wave sleep index

Slow wave sleep will be measured using electroencephalography, in the participant's home. Repeated for each phase.

Time frame: Night 3

Secondary Outcomes

6-sulfatoxymelatonin level

This is to measure Melatonin production in urine samples. Repeated for each phase.

Time frame: Night 4 to morning of Day 5 (Approximately up to 12 hours)

Body temperature

Proximal to distal body temperature gradient measured using thermochron devices (iButtons). Repeated for each phase. In patient. Over 24 hours.

Time frame: Day 4

Sleep quality score

Self-reported sleep quality assessed using the Karolinska Sleep Diary (higher score represents better sleep). Repeated for each phase.

Time frame: Days 2, 3, 4, 5