How It Works: Mechanisms of Action

Abstract The components of the Portfolio diet act in different ways to promote health and reduce the risk of cardiovascular disease (CVD). The mechanisms by which these foods operate have been subject to much debate. This chapter outlines some of the proposed mechanisms and additional health benefits associated with foods in the Dietary Portfolio. Viscous fiber is believed to lower cholesterol by forming a thick, sticky gel in the intestine. This gel has been found to delay absorption of nutrients, like glucose, in the small intestine, resulting in a reduced insulin response and a reduction in cholesterol. The gel may also reduce the reabsorption of bile salts in the small intestine, increasing fecal cholesterol loss, further reducing blood cholesterol. Nuts are a rich source of many beneficial compounds including: plant sterols, fiber, plant proteins, phytochemicals, and most importantly monounsaturated fatty acids (MUFA). The MUFA are thought to foster an environment that decreases C-reactive protein and increases apolipoprotein A1, two predictors of CVD. If carbohydrates are replaced with MUFA, high-density lipoprotein cholesterol (HDL-C) will stay in circulation longer, resulting in a more beneficial ratio of “good” cholesterol to “bad.” Plant sterols are proposed to reduce the absorption of dietary cholesterol and cholesterol produced by the body, resulting in low-density lipoprotein cholesterol (LDL-C) reduction (“bad” cholesterol). This effect is likely the result of plant sterols competing with cholesterol for absorption into cells. Soy contains protein fragments which may in part be responsible for the observed reductions in LDL-C. Together with the role soy plays in replacing other, unhealthy foods, such as red meat, this may have the greatest effect on LDL-C reduction compared with other Portfolio components.