The Metabolic Effect of Walnuts in Healthy Subjects

The objectives of the proposed study are to assess whether the metabolic effects of walnut consumption depends on which food components the walnuts substitute (i.e. carbohydrates; saturated fatty acids) and whether it is important to consume walnuts as snacks or with meals.

The metabolic effects of walnut consumption may not only relate to the ingested walnuts but also to what is not eaten when walnuts are consumed. We want to evaluate whether the metabolic changes are more pronounced if study participants are instructed to reduce carbohydrates or saturated fatty acids to remain on an isocaloric diet. In a third group we will test what food is omitted if no specific instructions are given. Furthermore half of the subjects in each group will be instructed to eat walnuts with meals and half as snacks.

Inclusion criteria

• Postmenopausal healthy women and healthy men
• Age >50 yrs
• Written informed consent prior to study participation

Exclusion criteria

• Known allergy to nuts
• Evidence of alcohol (women >70g/week, men >140g/week), tabacco or drug abuse
• Obesity ≥35 kg/m2
• Diabetes mellitus
• Hypertension >140/90 mmHg or history of hypertension
• LDL-cholesterol >190 mg/dl, Triglycerides > 350 mg/dl
• History of atherosclerotic disease
• Liver disease of any etiology
• Kidney disease of any etiology (GFR < 60 ml/min/1.73)
• Uncontrolled thyroid disease or other endocrine diseases
• Acute or chronic inflammatory diseases
• Active malignancy
• Current or previous (within 3 months) treatment with antidiabetic drugs, hypolipidemic drugs, antihypertensive drugs, anti-inflammatory drugs, vitamin E, hormonal replacement therapy
• major surgical intervention within 3 months (or planned)