Effect of Daily Walnut Consumption on Memory in Subjects With Long-COVID

NCT07429903 | Completed

• 1 other identifier: 23-000654
• Study Type: interventional
• Target: 31
• Locations: 1 country
• Sites: 1

Brief Summary

Approximately 30% of patients experience "Long-COVID" syndrome presenting with symptoms such as cognitive difficulties ('brain fog'), fatigue, dyspnea, autonomic dysfunction, depression and anxiety, lasting beyond 12 weeks causing significant disability, and threaten health and wellbeing of millions around the world. At the current time, there is no effective treatment for long-COVID. Walnuts contain a mixture of nutrients and phytochemicals include monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and alpha-linolenic acid (ALA). Walnut consumption was directly associated with cognitive function. The investigators have shown pomegranate that share the same phytonutrient ellagitannins as walnut and mixed nuts including walnuts could increase blood microbiome metabolites of tryptophan metabolite indole propionate and serotonin levels via change of gut microbiota and therefore play an essential role in gut-brain axis including cognitive function. The proposed pilot study will include 76 adults (ages \>40 years) with diagnosis of SARS-CoV2 infection presenting with long-COVID symptoms lasting longer than 12 weeks. They will be randomized 1:1 to usual care vs. an intervention group that will include 2 oz (57g) of walnuts daily into their habitual diet for 12 weeks. The investigators will compare the improvement in symptoms of cognitive complains of "brain fog", fatigue and depression of the active intervention group vs. usual care. The outcome of the investigation of the benefit of walnut consumption will provide important novel information on using dietary sources of polyunsaturated fatty acids and phytochemicals to mitigate the common symptoms of long-COVID. This application was submitted in response to the California Walnut Commission's commodity board topic.

Conditions

Long-COVID; Brain Fog; Cognition; Memory

Outcome Measures

Primary Outcomes (1)

• Episodic Memory - RAVLT-Revised Long-Delay Free Recall (number of words recalled)

  Change in long-delay free recall score (number of words correctly recalled) on the RAVLT-Revised from baseline to week 12.

  Baseline to Week 12

Secondary Outcomes (12)

• Executive Function

  Baseline to Week 12

• Trail Making Test Part A Completion Time

  baseline and 12 weeks

• Fatigue

  Baseline and 12

• Mood

  baseline and 12 weeks

• NIH Toolbox Cognitive Battery (NIHTB-CB) - Fluid Intelligence Composite

  Baseline to Week 12

Study Arms (2)

Walnuts

EXPERIMENTAL

Other: whole food - walnuts

Control

NO INTERVENTION

Habitual diet while avoiding nuts

Interventions

whole food - walnuts OTHER

Participants randomized to the intervention group will consume (2 oz ) of whole walnuts daily, incorporated into their diet for 12 weeks. Walnuts were provided to participants, and adherence was monitored using dietary records.

Walnuts

Eligibility Criteria

• Age: 40 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age 40 years and older
• History of confirmed SARS-CoV-2 infection
• Presence of long-COVID symptoms lasting longer than 12 weeks, including one or more of the following:
• Cognitive complaints ("brain fog," memory, attention, or processing speed difficulties)
• Fatigue
• Mood symptoms (e.g., depression)
• Consumption of a low-polyphenol (Western) diet
• Adequate visual acuity and hearing to complete neuropsychological testing
• Screening laboratory results without clinically significant abnormalities that would interfere with study participation
• Ability and willingness to provide written informed consent

You may not qualify if:

• Diagnosis of probable Alzheimer's disease or other dementia (e.g., vascular, Lewy body, frontotemporal)
• Other neurological or medical conditions that may cause cognitive impairment
• Evidence of Parkinson's disease based on motor examination
• Uncontrolled hypertension (systolic BP \>170 mmHg or diastolic BP \>100 mmHg)
• Allergy to walnuts
• Regular consumption of more than 5 oz of walnuts per week
• Current diagnosis of a major psychiatric disorder according to DSM-5 criteria
• Alcoholism or substance use disorder
• Any condition that, in the investigator's judgment, would make participation unsafe or interfere with study completion

Sponsors & Collaborators

• University of California, Los Angeles: lead

Study Sites (1)

UCLA Center for Human Nutrition

Los Angeles, California, 90025, United States

Location

MeSH Terms

Conditions

Post-Acute COVID-19 Syndrome; Mental Fatigue

Condition Hierarchy (Ancestors)

COVID-19; Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases; Post-Infectious Disorders; Chronic Disease; Disease Attributes; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Fatigue; Signs and Symptoms; Behavioral Symptoms; Behavior

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: SUPPORTIVE CARE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor of Medicine and Chief of the Division of Clinical Nutrition at the University of California, Los Angeles

Study Record Dates

• First Submitted: January 23, 2026
• First Posted: February 24, 2026
• Study Start: September 21, 2023
• Primary Completion: January 24, 2025
• Study Completion: January 24, 2025
• Last Updated: February 24, 2026

Record last verified: 2026-01

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)