Dietary Intake of Whole Walnuts in Adult Subjects Under Low Cardiovascular Risk

Recent literature data raise important questions on the beneficial effect of dietary fats. Dietary intake of nuts, although with high caloric burden, is however characterized with high intake of fatty acids with known beneficial health effects. Those fatty acids include mono- (MUFA) and polyunsaturated fatty acids (PUFA), to whom beneficial health effects are ascribed. Among nuts, walnuts are characterized with comparatively high levels of MUFA and PUFA, especially content of alpha-linolenic PUFA, considered essential fatty acid, since not synthesized endogenously in humans. Dietary intake of alpha-linolenic acid is shown to be inversely related with cardiovascular risk factors, both in interventional studies and epidemiological cohorts. Molecular background of alpha-linolenic actions is bidirectional, and includes the action itself, as well as beneficial endogenous conversion towards long-chain fatty acids, including eicosapentaenoic and docosahexaenoic fatty acid. Although high caloric intake is indicated with intake of walnuts, literature data suggest that consumption of walnuts does not increase body weight. Dietary intake of walnuts has been shown to decrease cholesterol fractions, triglycerides and apolipoproteins in adult population. Also, consumption of walnuts was associated with decrease in blood pressure. The study design is cross-over, controlled, randomized nutritional intervention. The participants are randomly assigned to receive either study treatment, or no treatment, and are crossed after five weeks. The study subjects are instructed to continue with their habitual diet and physical activity. Additionally, study subjects are instructed to avoid walnuts and nuts other then study treatment, during the complete study period of 10 weeks. Sample size calculation was conducted by use of online calculators, and was based on the low density lipoprotein (LDL) cholesterol. Namely, in order to achieve decrease in 0.5 mmol/L, in a sample with projected standard deviation of 0.7 mmol/L, and type I and II errors being 0.2 and 0.05, respectively, 62 subjects are needed.