Development and Evidence Base

Abstract This chapter outlines the core studies in which the Portfolio diet was tested and developed. They focus on (1) the creation of the Portfolio diet, (2) the addition of monounsaturated fatty acids to increase high-density lipoprotein (HDL) levels, and (3) testing the efficacy of the Portfolio diet under real-world settings. Subsequent updates to the Portfolio diet are also discussed. Major findings include Study 1. Testing the concept: portfolio foods vs. Lovastatin ● First study to test the combined ability of specific foods (nuts, plant sterols, viscous fibers, soy protein) to lower levels of low-density lipoprotein (LDL-C). ● Consumption of Portfolio diet foods result in reductions in LDL-C to the same degree as Lovastatin (drug treatment for high cholesterol). Study 2. Raising High density lipoprotein (HDL-C) (the “good” cholesterol) ● Addition of high levels of monounsaturated fatty acids found in nuts and plant sterols, further increases the effectives of the Portfolio diet by increasing HDL. Low ratios of LDL: HDL have been shown to reduce risk of CVD. Study 3. Testing its real-world applicability ● Even when study foods are self-selected and when patients are only given minimal instructions, the Portfolio diet can achieve meaningful reductions in LDL-C. Overall CVD reductions seen in these three core studies would be expected to be greater in the general population if they implemented a Portfolio diet as the patients who participated in these studies were already following a heart healthy diet before starting the Portfolio diet. Additional studies: ● Supplementation of strawberries to the Portfolio resulted in decreased oxidized LDL levels, a type of LDL which is more reactive and thought to lead to more arterial damage. ● Seeds and Plant Based Protein. Seeds added to “Nuts” category to make more inclusive to those with nut allergy’s and plant based protein replacing the “Soy” category to similarly improve inclusiveness. ● Enhanced glycemic control seen with Portfolio diet components have potential benefits in the treatment of type 2 diabetes. ● Food component updates. “Soy protein” was changed to “plant based protein” to include foods such as legumes. “Seeds” were added to the “Nuts” category to make it more inclusive to those with nut allergies who may not be able to eat tree nuts or peanuts. Berries have been added to the viscous fiber section, the plant sterol pillar has been broadened to include supplements and other plant sterol fortified foods such as orange juice and spreads.