Cardiovascular Diseases
Conditions
Keywords
heart health, gut microbiota, Mediterranean diet, cardiometabolic health, gut health, diet
Brief summary
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut.
Detailed description
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut. Overweight/obese adults between the ages of 45 and 70 yo with elevated LDL-C levels are eligible to participate. The study involves 5 visits (1 initial screening and 4 study visits) and will last about 10 weeks. There is a 1-week run-in period before starting the study, followed by two diet intervention periods each lasting 3 weeks, separated by a 3-week washout period. Participation in this study will involve an initial 1-week run in period to become accustomed to the study diet. After this 1 week period, participants will be randomly selected to start either a walnut or a no-nut diet. During each phase of the study, participants will be asked to come to the University of California, Davis campus after a 10-12 hour overnight fast. At each visit, body measurements will be taken; blood, urine and fecal samples will be collected. During the 10 weeks of the study, all nuts and nut-derived products will need to be avoided. The study will provide walnuts to be eaten at home for each intervention phase. Additionally, the investigators will ask that ellagitannin-rich foods, high-fiber and fermented foods be avoided in the diet. Detailed food diaries will be filled out and brought to study visits.
Interventions
DIETARY_SUPPLEMENTWalnuts
Participants will consume 56 g of walnuts daily for 3 weeks. Participants will also follow a diet devoid of ellagitannin-rich, high fiber, and fermented foods.
DIETARY_SUPPLEMENTNo-nut diet
Participants will exclude all nuts and nut-derived products; high-fiber, fermented and ellagitannin-rich foods will also be excluded.
Sponsors
University of California, Davis
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
45 Years to 70 Years
Healthy volunteers
No
Inclusion criteria
* Overweight and obese men and postmenopausal women between 45-70 years of age, BMI range of 25.0-39.9 kg/m2 and elevated LDL-C levels (130-189 mg/dL).
Exclusion criteria
* Adults unable to consent, individuals who are not yet adults (infants, children, teenagers), pregnant or lactating women, women planning to become pregnant in the next four months and prisoners will be specifically excluded. Additional
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Assessing the influence of walnut consumption on blood lipid measurements. | Through study completion, an average of 10 weeks | Measure for changes in the levels of HDL and LDL in separated plasma; measured in units of mg/dL. Blood will be assessed for the fasting (baseline) sample at each of the 4 study visits. |
| Assessing the influence of walnut consumption on circulating inflammatory markers: PAI-1, VCAM-1 and ICAM-1. | Through study completion, an average of 10 weeks | Measure circulating inflammatory markers in separated plasma at each of the 4 study visits. Commercially available ELISA kits will be used: PAI-1, VCAM-1, ICAM-1. |
| Assessing the influence of walnut consumption on blood pressure. | Through study completion, an average of 10 weeks | Measure blood pressure (mmHg) before the start of drawing blood on study day protocols. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Assessing the influence of walnut consumption on fecal pH. | Through study completion, an average of 10 weeks | Measure fecal pH via pH meter at each of the 4 study visits. |
| Assessing the influence of walnut consumption on stool consistency. | Through study completion, an average of 10 weeks | Assess fecal consistency using Bristol Stool Scale at each of the 4 study visits. The scale runs from Type 1 (the lowest) to Type 7 (the highest). The desirable Type is either 3 or 4. Types 1 and 2 may be indicative of constipation, while Types 5, 6, and 7 may indicative diarrhea. |
| Assessing the influence of walnut consumption on fecal moisture. | Through study completion, an average of 10 weeks | Measure fecal moisture by weighing wt and vacuum dried feces in grams at each of the 4 study visits. |
| Assessing the influence of walnut consumption on the levels of gut inflammatory markers: Lipocalin-2 and calprotectin. | Through study completion, an average of 10 weeks | Measure fecal levels of Lipocalin-2 and calprotectin at each of the 4 study visits. Commercially available ELISA kits will be used: lipocalin-2, calprotectin. |
| Assessing the influence of walnut consumption on plasma and urine levels of walnut-derived metabolites - urolithins. | Through study completion, an average of 10 weeks | Measure urolithin levels in separated plasma and urine via metabolomics analysis at each of the 4 study visits. |
Countries
United States
Outcome results
None listed