Nuts have a high nutrient density, and numerous studies have reported their cardiometabolic benefits. Although observational studies in adults have indicated a potential link between nut consumption and improved mental health, there is still insufficient evidence from experimental studies to draw firm conclusions about this association.
Nuts are widely recognized for their high nutrient density and their multiple reported cardiometabolic benefits. They are rich in monounsaturated (MUFAs) and polyunsaturated (PUFAs) fatty acids (including omega-3 alpha-linolenic acid and omega-6 linoleic acid) as well as antioxidants and compounds with anti inflammatory properties. Observational studies in adults have suggested a potential association between nut consumption and improved mental health, including a reduced risk of depression and enhanced mood. However, evidence from experimental studies remains limited and often inconclusive. Early adulthood (ages 18-24) represents a critical developmental period marked by substantial physical, psychological, and social changes, and it is also a stage during which mental health problems commonly emerge. The Nuts4Brain-RCT will investigate the impact of a 6-month mixed-nut intervention on mental health symptoms, cognitive functioning, sleep quality, overall well-being, health-related quality of life, and biochemical mediators of brain function and mental health in young adults.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
135
Participants will be instructed to consume a single daily dose of nuts (30 g/day of mixed nuts). Nuts will be provided free of charge for the entire study period (6 moths). The participants will be instructed to incorporate nuts into their regular diet and consume them in any way they prefer. Upon completion of the intervention, participants will be instructed to continue their usual dietary and lifestyle habits, without any specific restrictions or incentives directed toward nut consumption. After 6 months have passed since the end of the intervention, all participants will be called for a final session (12 months) in which all data evaluated throughout the study will be collected
Participants will be instructed to consume two daily doses of nuts (60 g/day of mixed nuts). Nuts will be provided free of charge for the entire study period (6 months). The participants will be instructed to incorporate nuts into their regular diet and consume them in any way they prefer.Upon completion of the intervention, participants will be instructed to continue their usual dietary and lifestyle habits, without any specific restrictions or incentives directed toward nut consumption. After 6 months have passed since the end of the intervention, all participants will be called for a final session (12 months) in which all data evaluated throughout the study will be collected
Participants will be instructed to maintain their regular diet without any specific dietary instructions or intervention.
Health and Social Research Center. University of Castilla-La Mancha
Cuenca, Cuenca, Spain
RECRUITINGDepression
Changes in symptoms of depression assessed with the Beck Depression Inventory Version II (BDI-II). Each of the 21 items includes four statements of increasing severity, and a total score (ranging from 0 to 63) is calculated, with higher scores indicating more severe depression.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Anxiety
Changes in symptoms of anxiety assessed with The Generalized Anxiety Disorder 7-item (GAD-7). The GAD-7 consists of seven questions asking individuals to rate the frequency and severity of specific anxiety symptoms over the past two weeks.The total score ranges from 0 to 21, calculated by summing the scores of all seven items. A score of 10 or greater is considered a reasonable cut-off point for identifying possible cases of GAD that may require further clinical evaluation
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Stress
Changes in symptoms of stress assessed with The Perceived Stress Scale (PSS-10). The PSS-10 is a widely used, 10-item self-report questionnaire that measures an individual's perception of stress over the past month. Scoring involves reverse-scoring four positive items and summing all 10. Total scores range from 0 to 40, with higher scores indicating more perceived stress. Scores can be interpreted generally as low (0-13), moderate (14-26), or high (27-40) stress.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Episodic memory
The Picture Sequence Memory Test assesses episodic memory by requiring participants to encode and recall the temporal order of a sequence of visually presented everyday events. After presentation, individuals are asked to reconstruct the sequence in its original order, allowing evaluation of visual episodic memory and learning across trials. Test time: 7 minutes. This test is one of the measures included in the NIH Toolbox Cognition Battery, which is administered on an iPad by qualified personnel.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Working memory
The List Sorting Working Memory Test (LSWM), part of the NIH Toolbox Cognition Batery, assesses working memory by having individuals recall and sequence visually and auditorily presented stimuli (like animal/food pictures) in size order (smallest to largest). Test time: 7 minutes.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Cognitive flexibility
The Dimensional Change Card Sort Test is a standardized measure of cognitive flexibility. Participants are required to sort cards according to different rules (e.g., color or shape) and to adapt their responses when the sorting dimension changes. Test time: 5 minutes. This test is one of the tests that will be determined using the NIH Toolbox Cognition Battery, which will be administered on an iPad by qualified personnel.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Processing speed
The Pattern Comparison Processing Speed Test is a standardized measure of processing speed. Participants are asked to quickly determine whether two visual patterns are the same or different, emphasizing speed and accuracy of visual perception and decision-making. Test Time: 4 minutes. This test is one of the tests that will be determined using the NIH Toolbox Cognition Battery, which will be administered on an iPad by qualified personnel.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Inhibitory control and attention
The Flanker Inhibitory Control and Attention Test is a standardized measure of inhibitory control and selective attention, core components of executive function. Participants are required to focus on a central target stimulus while inhibiting interference from surrounding distractor stimuli. Performance reflects the ability to maintain attention, suppress competing responses, and resolve cognitive conflict. Test Time: 3 minutes. This test is one of the tests that will be determined using the NIH Toolbox Cognition Battery, which will be administered on an iPad by qualified personnel.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Brain Derived Neurotrophic Factor
Changes in blood concentration of brain-derived neurotrophic factor (BDNF), a biochemical mediator of brain functioning
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Sleep quality
Changes in quality of sleep assessed with the Pittsburgh Sleep Quality Index (PSQI). The PSQI consists of 19 individual self-rated questions (and 5 optional questions for a roommate/bed partner) that are grouped into seven component scores. Each of the seven components is scored on a scale of 0 to 3, where 0 indicates no difficulty and 3 indicates severe difficulty. The scores of these components are summed to produce a global PSQI score, which ranges from 0 to 21. Higher scores indicate poorer sleep quality.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Health-related quality of life (HRQL)
Changes in health-related quality of life assessed with the SF12 questionnaire. It consists of 12 questions that cover the same eight health domains as the longer SF-36: Physical Functioning, Role Physical, Bodily Pain, General Health, Vitality, Social Functioning, Role Emotional, and Mental Health. The 12 items are used to create two main summary measures through a complex, norm-based scoring algorithm: Physical Component Summary (PCS): A single score representing physical health status. Mental Component Summary (MCS): A single score representing mental and emotional health status. Interpretation of Scores: Scores for both PCS and MCS typically range from 0 to 100, where higher scores indicate better health and functioning.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Inflammatory biomarkers
Changes in blood inflammatory markers (e.g. hs-CRP) to examine underlying mechanisms
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Concentration of vitamins and minerals
Changes in blood concentration of specific vitamins and minerals (e.g., vitamins B9, B12, D, iron, and magnesium) to examine underlying mechanisms
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Body image
Changes in body image perception using The Standard Figural Stimuli (SFS). Measurement Purpose: Perceived Body Image: The figure the individual selects as most representative of their current body size. Ideal Body Image: The figure the individual would like to have. Body Dissatisfaction: The discrepancy between the perceived image and the ideal image. A larger difference indicates greater body dissatisfaction.
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Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Screen time
Screen time will be assessed using an ad hoc questionnaire that records the number of hours of leisure time participants spend watching television, using a mobile phone, using a computer for work-related purposes, or engaging with other electronic devices, both on weekdays and during weekends.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Social media addiction
Changes in social media addiction through Social Network Addiction Questionnaire, 6-item version (ARS-6). The scale typically consists of 6 items, with one item representing each of the six components of addiction. Response Scale: Responses are typically given on a 5-point Likert scale (e.g., from 1 = Not at all to 5 = Always). Scoring: Item responses are summed to obtain a total score, ranging from 6 to 30. Higher scores indicate a greater risk or severity of social media addiction.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Sociodemographic
Sociodemographic information such as age, sex, date of birth, country of origin, marital status, housing type, medication use, and family history of mental or cardiovascular disorders.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Drugs consumption
Changes in drugs consumption assessed with the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST). The ASSIST generates substance-specific risk scores that categorize use into low, moderate, or high-risk categories. Higher scores indicate a greater risk of substance-related health and social problems, guiding the type of intervention needed (e.g., brief intervention or referral to specialist treatment).
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Adherence to the Mediterranean Diet
Changes in adherence to the mediterranean diet assessed with the MEDAS questionnaire. Scoring: Each item is scored with 1 point if the criteria for adherence to the Mediterranean diet are met, and 0 points if they are not. The total score ranges from 0 to 14 points. Higher scores indicate greater adherence to the Mediterranean diet. A common cut-off point of ≥9 is often used to define good adherence to the diet.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Resilience
Changes in resilience assessed with the Connor-Davidson Resilience Scale (CD-RISC 10). Each item is rated on a 5-point Likert scale ranging from 0 (not true at all) to 4 (true nearly all the time). The total score is calculated by summing the values of all 10 items. Total scores range from 0 to 40. Higher scores on the CD-RISC 10 indicate greater resilience and a better ability to cope with adversity and bounce back from difficult experiences.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Risk of eating disorders
The SCOFF questionnaire (an acronym derived from the initials of its English questions: Sick, Control, One stone, Fat, Food) is a brief and simple, five-question screening tool designed to detect the possible presence of eating disorders (EDs), such as anorexia nervosa and bulimia nervosa. The total score can range from 0 to 5. A score of two or more points is considered a positive screening result and suggests a suspicion of an ED that requires a detailed formal clinical assessment.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Weight
Weight in kilograms will be assessed twice using a calibrated digital scale (Scale Seca® 861) with participants barefoot and in light weight clothing.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Height
Height will be measured twice with a stadiometer (Wall stadiometer Seca® 222), with participants standing upright, barefoot, and with the sagittal midline aligned to the wall.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Body Mass Index (BMI)
BMI will be calculated as weight divided by height squared (kg/m2).
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Body fat percentage
Body fat percentage will be assessed twice using the bioimpedance analysis system under standardized conditions (morning, fasting, post-void, after 15 minutes rest, barefoot, with controlled temperature and humidity).
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Blood pressure
Blood pressure will be measured using an automated device (OMRON® M5-I (Omron Healthcare UK Ltd.)). Systolic and diastolic blood pressure will be assessed twice, with a 5-minute interval between measurements. Participants will be seated in a quiet environment, with the right arm semi-flexed at heart level.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Muscular strenght
Measured through handgrip strength using a calibrated dynamometer (Digital dynamometer TKK 5401 Grip-D (Takey®, Tokyo, Japan), and standing long jump for lower body strength. Handgrip: Kilograms (kg). Horizontal jump: Centimeters (cm).
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Phisical activity
Changes in phisical activity assessed with the The International Physical Activity Questionnaire (IPAQ). The data collected with the IPAQ can be reported as a continuous measure (estimation of total energy expenditure in MET-minutes per week) or categorically (classifying individuals into low, moderate, or high physical activity levels): Continuous Score: Total energy expenditure is calculated using specific formulas that assign MET (metabolic equivalent) values to each activity type (walking=3.3 METs, moderate=4.0 METs, vigorous=8.0 METs). Categorical Score: Participants are classified into three levels of physical activity based on predefined criteria related to the duration, frequency, and intensity of activities.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Lipid profile
Changes in blood lipid profile (Cholesterol (Total, HDL-c, LDL-c), triglycerides)) to examine underlying mechanisms.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Glucose levels
Changes in blood glucose levels to examine underlying mechanisms.
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"
Hemoglobin A1c (HbA1c)
Changes in blood HbA1c levels to examine underlying mechanisms.
Time frame: Day 0", "Month 3", "Month 6", "Month 12"
Adherence verification
Adherence to nut consumption intervention measured by blood levels of vitamin E
Time frame: "Day 0", "Month 3", "Month 6", "Month 12"