Effects of California Walnuts on Vascular Function and Immune Health in Postmenopausal Women

Cardiovascular disease is the leading cause of morbidity and mortality in the United States. The initiation and progression of atherosclerotic vascular disease is multifactoral in nature, and includes endothelial dysfunction, triggered by chronic inflammation. The consumption of foods rich in flavonoids and other phytochemicals has been inversely associated with cardiovascular disease risk in several epidemiological studies.

Aging is physiologically associated with a variable decline in several features of the immune function. In fact, immunosenescence, or aging of the immune system, is characterized by a reduced ability to fight infection and mount an adequate immune response once a novel infection is introduced. Both the innate and acquired immune systems can be affected with immune specific cells, cell signaling, cytokine production, and cell surface marker expression being all subject to age-related changes. The immune system cells within the digestive tract are an accessible and ideal target to stimulate immunity and diet-based nutritional interventions represent a non-invasive, relatively low-cost, and effective method of stimulating the immune function thus ultimately improving the antibody production in subjects at risk for immunosenescence. This is also based on the significant and dynamic interaction between luminal nutrients and the overall immune function. The study of nutritional influences on the immune system represents an area of growing interest to nutritionists, food scientists and immunologists. In general terms, dietary components have the potential to be an accessible and effective immune stimulant given the antigen presenting capacity of the intestine.

Due to their age and menopausal status, postmenopausal women are at a greater risk population for developing CVD. Males tend to show greater rates of CVD than pre-menopausal women, while women following menopause show an increase in CVD development. This increase in CVD for postmenopausal women is associated with endothelial dysfunction that becomes worse with age.

Recent studies have reported that consumption of walnuts is associated with beneficial effects in prevention of chronic diseases, such as cardiovascular disease (CVD), by favorably altering human serum profiles (i.e. decrease in LDL cholesterol and triglycerides and increase in HDL cholesterol and apolipoprotein A1). It has been shown that the consumption of walnuts, which mainly contain α-linolenic acid (ALA), L-arginine, and polyphenols, can beneficially alter vascular function and reduce inflammatory biomarkers. For example, Dr. Ros and his colleagues demonstrated that the addition of walnuts to a high-fat meal could improve endothelial function. This favorable influence on vasoactivity has been attributed to the antioxidant and anti-inflammatory properties of certain biofactors found in the walnuts.

In this study, we will focus on defining the potential role of California walnuts and its effects on vascular health and immune function. We will determine whether short term (4 week) consumption of California walnuts, particularly rich in ALA, L-arginine and polyphenols will improve endothelial function, platelet reactivity and immune function in an at-risk population of postmenopausal women 55-70 years of age.