Walnuts to Achieve Lasting NUTrition to Prevent Diabetes

Prediabetes is a precursor of type 2 diabetes and an independent risk factor for cardiovascular disease, and currently affects one-quarter of the population of the United States. Individuals of overweight or obese BMI are at particular high risk for incident diabetes. A major modifiable risk factor for type 2 diabetes is poor dietary quality, and improvement of dietary quality can effectively delay and even prevent type 2 diabetes. Interventions to improve dietary quality thus far, however, rely on short-term intensive clinically designed meals replacing the entire diet which have poor sustainability. Persistent improvements to daily dietary patterns are often difficult without directed guidance, and overall dietary quality in the United States remains poor. The identification of a practical, daily dietary intervention to improve dietary quality and prevent diabetes in those at high risk remains unknown. The investigators propose to enroll 40 individuals with diagnosed prediabetes into a randomized controlled pilot study and provide a daily walnut supplementation intervention to determine feasibility and acceptability of the supplement. The investigators will then determine preliminary efficacy on metabolic markers and will investigate associations between dietary quality and circulating levels of branched-chain amino acids. The goal is to implement a whole-food supplement to improve dietary quality in patients with prediabetes as a tool for future type 2 diabetes prevention.

Will receive and be instructed to consume 1-oz individually wrapped daily walnut supplement packages for 12 weeks during intervention.

Will receive diet and exercise guidance at beginning of study. At end of study, will receive 12 weeks of a walnut supply to be consumed at their discretion after the study is complete.

1 ounce of individually wrapped, raw walnuts to be consumed daily replacing a high-refined carbohydrate food.

Adherence to the intervention was determined through daily food diaries. Participants detailed daily consumption of the walnut supplement on a calendar provided at the outset of the study. Percentage was determined as number of days consuming supplement over 84 days total.

Palatability was measured using a visual analog scale, the scale range is 0-100, with 100 being the "Most Pleasant."

Change in diet quality measured by Healthy Eating Index-2010 Score (0 - 100). Higher scores indicate better diet quality.

Plasma metabolomics performed as an exploratory outcome for all participants. This outcome represents number of participants who had a successful blood draw at both baseline and 12 weeks sent to the laboratory with usable data recovered.

Inclusion Criteria: Male or female between 18-65 years of age at baseline living in the San Francisco Bay area. BMI>25 m/kg2 (or >23 m/kg2 for individuals of Asian or South Asian ethnicity) Documentation of prediabetes diagnosis as evidenced by the following criteria: A fasting glucose 100-125 mg/dL, or a HbA1c measurement of 5.7-6.4%, OR a diagnosis of "prediabetes" or "impaired fasting glucose" in the past 6 months, identified through an electronic medical record query from patients at UCSF and through outside recruitment in the surrounding community We will confirm eligibility of potential participants by repeating fasting capillary blood glucose measurements at the baseline visit to ensure that they have prediabetes Written informed consent and ability for subject to comply with the requirements of the study. Exclusion Criteria: Pregnant or breastfeeding women at enrollment. Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data, such as diverticulosis or diverticulitis. Tree or peanut allergies Unwilling to consume a daily walnut supplement. Diagnosis of diabetes On glucose lowering medications Dietician-managed dietary intake, or personal or medical dietary restrictions that do not allow consumption of walnuts Malabsorptive conditions including intestinal bypass surgery, pancreatitis, inflammatory bowel disease