Almonds and Health Effects on Metabolism, Vascular Function and Cognition

The primary objective of the proposed study is to examine and understand the impact of long-term almond consumption on chronic glucose metabolism in subjects with impaired glucose tolerance and/or impaired fasting glucose.

Objectives:

Secondary objectives are to investigate if improved chronic glucose metabolism in subjects with impaired glucose tolerance and/or impaired fasting glucose after long-term almond consumption translates into improved peripheral and brain vascular function, and enhanced cognitive performance. In addition, the investigators will address to what extent improved chronic glucose metabolism in subjects with impaired glucose tolerance and/or impaired fasting glucose after long-term almond consumption can be explained by (combined) effects of lowered hepatic lipid accumulation and inflammation, skeletal muscle characteristics, visceral and subcutaneous fat accumulation, pancreatic function or fecal microbiota composition.

Study design:

The proposed study will be a 12 months randomised, controlled trial with a cross-over design. Two experimental periods of five months will be separated by a two months washout period.

Study population:

Forty-three impaired glucose tolerant and/or impaired fasting glucose subjects, with overweight and mild obesity (BMI 25-35 kg/m2), aged 40-70 years.

Intervention:

During the intervention period of 5 months, subjects will receive daily 50 gr almonds, but not in the 2 months washout and 5 months control periods.

Eligibility Criteria:
Inclusion Criteria:

* Aged between 40-70 years
* Men and women
* BMI between 25-35 kg/m2 (overweight and obese)
* Being classified as having impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG). IGT is defined according the criteria of the WHO and American Diabetes Association (ADA) as two-hour glucose concentrations of 7.8 to 11.0 mmol/l (140 to 199 mg per dL) during the 75-g oral glucose tolerance test. IFG is defined as having a fasting plasma glucose between 6.1 and 7.0 mmol/l (110 to 125 mg per dL) and a two-hour glucose concentration below 7.8 mmol/l (140 mg per dL).
* Serum total cholesterol \< 8.0 mmol/L (further testing is recommended for excessive hyperlipidemia \[serum total cholesterol ≥ 8.0 mmol/L\] according to the Standard for cardiovascular risk management of the Dutch general practitioners community \[NHG\])
* Serum triacylglycerol \< 4.52 mmol/L
* No current smoker
* No diabetic patients
* No familial hypercholesterolemia
* No abuse of drugs
* Not more than 4 alcoholic consumption per day with a maximum of 21 per week
* Stable body weight (weight gain or loss \< 3 kg in the past three months)
* No use of medication known to treat blood pressure, lipid or glucose metabolism
* No use of an investigational product within another biomedical intervention trial within the previous 1-month
* No severe medical conditions that might interfere with the study, such as epilepsy, asthma, kidney failure or renal insufficiency, chronic obstructive pulmonary disease, inflammatory bowel diseases, auto inflammatory diseases and rheumatoid arthritis
* No active cardiovascular disease like congestive heart failure or cardiovascular event, such as an acute myocardial infarction or cerebrovascular accident
* Willingness to give up being a blood donor from 8 weeks before the start of the study, during the study and for 4 weeks after completion of the study
* No difficult venipuncture as evidenced during the screening visit
* Willing to comply to study protocol during study
* Informed consent signed

Exclusion Criteria:

* Allergy or intolerance to almonds
* Serum total cholesterol ≥ 8.0 mmol/L
* Serum triacylglycerol ≥ 4.52 mmol/L
* Current smoker, or smoking cessation \<12 months
* Diabetic patients
* Familial hypercholesterolemia
* Abuse of drugs
* More than 4 alcoholic consumptions per day or 21 per week
* Unstable body weight (weight gain or loss \> 3 kg in the past three months)
* Use medication known to treat blood pressure, lipid or glucose metabolism
* Use of an investigational product within another biomedical intervention trial within the previous 1-month
* Severe medical conditions that might interfere with the study, such as epilepsy, asthma, kidney failure or renal insufficiency, chronic obstructive pulmonary disease, inflammatory bowel diseases, auto inflammatory diseases and rheumatoid arthritis
* Active cardiovascular disease like congestive heart failure or cardiovascular event, such as an acute myocardial infarction or cerebrovascular accident
* Not willing to give up being a blood donor from 8 weeks before the start of the study, during the study or for 4 weeks after completion of the study
* Not or difficult to venipuncture as evidenced during the screening visit
* Use of over-the-counter and prescribed medication or supplements, which may interfere with study measurements to be judged by the principal investigator;
* Use of oral antibiotics in 40 days or less prior to the start of the study;
* Blood donation in the past 3 months before the start of the study
* Not willing to comply to study protocol during study or sign informed consent