Effect of Walnuts on Cognitive Function and Gut Microbiome in Older Adults

Launched by OREGON STATE UNIVERSITY · Apr 16, 2025

Keywords

ClinConnect Summary

This clinical trial is looking at how eating walnuts every day for 12 weeks may affect brain function, inflammation levels, and gut health in healthy adults aged 55 and older. Researchers want to see if walnuts can help improve thinking and memory skills, as well as how the body responds to inflammation, which is a natural process that can affect health as we age.

To participate, you need to be 55 years or older, able to understand spoken instructions, and willing to follow specific eating guidelines, which include avoiding certain nuts and some fruits for the duration of the study. Participants will also complete some cognitive tests to check their thinking abilities. If you meet these criteria and are interested, keep in mind that the study has not started recruiting yet, so there may be more information coming soon.

Gender

ALL

Eligibility criteria

• Inclusion Criteria:
• • Age 55 years or older
• • Able to hear well enough to understand spoken instructions and questions
• • Able to see well enough to read and respond to printed instructions and fill out questionnaires (corrective lenses are allowed)
• • Able to write legibly and move a computer joystick with at least one hand (i.e., no injury or connective tissue or joint disorder that would impair ability to write or make hand movements)
• • Able to speak, read, and understand English
• • Score of greater than 79 on water maze learning task
• • Willing to maintain current eating patterns
• • Willing and able to complete the cognitive tests
• • Willing to stop consuming almonds, Brazil nuts, cashews, chestnuts, hazelnuts, macadamia nuts, peanuts, pecans, pistachios, walnuts, persimmons and pomegranates for 14 weeks. - are nuts or contain ellagitannins or ellagic acid - compounds/foods of interest for this study
• • Willing to limit oak aged wines and spirits to 1 serving/day and limit blackberries (including similar berries like boysenberries, marionberries, and olallieberries), cloudberries, cranberries, currants, elderberries, lingonberries, raspberries, strawberries, wolfberries, other native berries; guava, mango, muscadine grapes, nectarines, peaches, plums, pluots to 1 cup/day for 14 weeks; REMAIN CONSISTENT (consistent intake levels of): Coffee, tea, apple, apricots, blueberries, cherries, grapes (table/common)
• • Willing to stop probiotic supplements 2 weeks prior to and during the study (14 weeks)
• Exclusion Criteria:
• • Consumption of walnuts, pecans, and chestnuts combined greater than 2 oz / week in the past 3 months.
• • Use of oral antibiotics in the past month
• • Regular use of oral anti-inflammatory medications in the past month
• • Nut, wheat, or gluten allergy/intolerance
• • Pregnant or planning to become pregnant during the study period
• • Weighs less than 110 pounds
• • Diagnosis of sickle cell disease
• • Susceptibility to motion sickness
• • Consumes 3 or more alcoholic drinks daily
• • History of smoking tobacco products, including e-cigarettes and vaporizers in the past 2 years (smokeless tobacco use not exclusionary)
• • Use of psilocybin or cannabis products (including CBD-only products) in the past 2 years
• • Current treatment for alcohol or other substance use disorder
• • History of heart attack, heart failure, or stroke, including transient ischemic attack
• • History of liver disease or kidney disease requiring dialysis
• • History of cancer in the past 5 years (Skin cancer that was only surgically treated is not exclusionary)
• • History of bariatric surgery (e.g., gastric bypass, gastric banding, sleeve gastrectomy, etc.) or disorders (e.g., Crohn's disease, unmanaged celiac disease, ulcerative colitis)
• • History of thyroid disorder that requires medication, but subject is not taking medication
• • History of chronic bronchitis or emphysema
• • Diagnosis of dementia or Alzheimer's disease
• • History of head injury requiring hospitalization or loss of consciousness \> 5 minutes
• • History of chronic migraines (for at least 3 months, headache occurring on 15 or more days per month, where at least 8 of those headache days have migraine symptoms)
• • Blood pressure above 159 (systolic) or 99 (diastolic) mm Hg
• • Corrected vision worse than 20/50
• • Score of less than 10/15 on Ishihara color vision test or diagnosis of color blindness
• • Score of less than 26/30 on Mini-Mental State Exam
• • Score of greater than 15 on Center for Epidemiologic Depression survey
• • History of disease or disorder which causes cognitive impairment, including but limited to: attention-deficit/hyperactivity disorder (ADHD), amyotrophic lateral sclerosis, autism, bipolar disorder, Down's syndrome, encephalitis, epilepsy/seizures, human immunodeficiency virus (HIV), Huntington's disease, Korsakoff's psychosis, multiple sclerosis, Parkinson's disease, or psychotic disorders (e.g., schizophrenia, schizoaffective disorder, schizophreniform disorder)
• • Current and regular use of any of the following medications: insulin, opioids, anti-seizure medications, psychotropic medications: stimulants, anti-psychotics, or medications that cause daytime drowsiness or difficulty concentrating