Walnut Study


Thank you for your interest in the Walnut Study!

The Walnut Study is a research project aimed to investigate the relationship between walnut consumption, the gut microbiome, and health.

Study Description

The study consists of a complete feeding trial for 15-weeks. Participants will receive 3 meals and 2 snacks per day for 3 weeks for 3 conditions for a total of 9 weeks. Between each condition will be a 3-week wash-out period. You will visit the laboratory twice weekly to pick up meals.

We are looking for men and women between the ages of 25-75 years old with a BMI of 30 + to participate.  Adults must not be allergic to nuts, wheat, or eggs. Additional exclusion criteria can be seen below. In addition to the meal consumption, you will be asked to visit the lab three times over the course of the study to complete questionnaires, bone density scans, and blood draws (7 hours per visit). You will also provide 3 urine samples and 7 fecal samples. Participants can receive up to $1,000 after study completion.

Exclusion Criteria

  • BMI less than 30kg/m2 (https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm)
  • Walnut allergy or intolerance
  • Food allergies (nuts, wheat, dairy, eggs)
  • Prior diagnosis of metabolic or gastrointestinal disease (cardiovascular disease and type 1 or type 2 diabetes, chronic constipation, Crohn’s disease, celiac disease, ulcerative colitis, irritable bowel syndrome, hepatitis, HIV, cancer, etc.)
  • Women that are post-menopausal, pregnant, or lactating
  • Individuals that smoke, use tobacco, abuse drugs, or consume > 2 alcoholic beverages per day.
  • > 5% weight change in the past month or > 10% change in the past year
  • Oral antibiotics during the previous 2 months
  • Fasting blood glucose >126 mg/dL, blood pressure >160/100 mm Hg, elevation in serum transaminases or evidence of liver disease, including primary biliary cirrhosis or gallbladder disease, or constipation.
  • Currently taking lipid-lowering medications, oral hypoglycemic agents, or insulin, or medications known to impact bowel function (proton pump inhibitors, laxatives, prokinetic agents, histamine-2 Rc antagonists, anticholinergics, antispasmodics, anticonvulsants, antidepressants, antihypertensives, antipsychotics, bile acid sequestrants, calcium channel blockers, diuretics, and opiates)
  • History of malabsorptive or restrictive bariatric surgeries or gall bladder removal surgery.
  • Are unable to consume the experimental meals/snacks.
  • Allergic to lidocaine or other topical anesthetics
  • Participants who have donated blood within the last 8 weeks
  • Recent diagnosis of anemia
  • Concurrent enrollment in another dietary, exercise, or medication study
  • > 5% weight change in the past month or > 10% change in the past year
Inclusion Criteria

Eligible participants meet the following criteria:

  • 25-75 years of age
  • Body mass index equal to or above 30 kg/m2 (https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm (with no major recent weight change)
  • No physician diagnosis of metabolic or gastrointestinal diseases or anemia
  • Not currently taking lipid-lowering medications, oral hypoglycemic agents, or insulin, or medications known to impact bowel function such as laxatives, bile acid sequestrants, or opiates
  • Not pregnant, lactating, or had a baby in the last 12 months
  • No tobacco use or more than 2 alcoholic beverages a day during the study
  • Not allergic to nuts, dairy, or gluten or an allergy
  • No history of bariatric surgery or gallbladder removal
  • Not taken antibiotics in the past 6 weeks
  • Not donated blood within the past 2 months from the start of your participation

Contact Information

Email: walnut-study@illinois.edu

Phone: 217-300-3523

Location: Freer Hall and Edward R. Madigan Laboratory