A Moderate-Fat Diet with One Avocado per Day Increases Plasma Antioxidants and Decreases the Oxidation of Small, Dense LDL in Adults with Overweight and Obesity: A Randomized Controlled Trial

BACKGROUND: Avocados are a nutrient-dense source of MUFAs and are rich in antioxidants. Avocados have an additional LDL cholesterol (LDL-C) lowering effect beyond that observed when their MUFAs are substituted for SFAs, especially on small, dense LDL (sdLDL) particles, which are susceptible to in vivo oxidation and associated with increased risk of cardiovascular disease (CVD). OBJECTIVES: We investigated whether a healthy diet with 1 avocado daily decreased the following secondary outcomes: circulating oxidized LDL (oxLDL) and related oxidative stress markers. METHODS: A randomized, crossover, controlled feeding trial was conducted with 45 men and women, aged 21–70 y, with overweight or obesity and elevated LDL-C (25th–90th percentile). Three cholesterol-lowering diets were provided (5 wk each) in random sequences: a lower-fat (LF) diet (24% calories from fat—7% SFAs, 11% MUFAs, 6% PUFAs) and 2 moderate-fat (MF) diets (34% calories from fat—6% SFAs, 17% MUFAs, 9% PUFAs): the avocado (AV) diet included 1 Hass avocado (∼136 g) per day, and the MF diet used high oleic acid oils to match the fatty acid profile of 1 avocado. A general linear mixed model was used to analyze the treatment effects. RESULTS: Compared with baseline, the AV diet significantly decreased circulating oxLDL (−7.0 U/L, –8.8%, P = 0.0004) and increased plasma lutein concentration (19.6 nmol/L, 68.7%, P < 0.0001), and both changes differed significantly from that after the MF and LF diets (P ≤ 0.05). The change in oxLDL caused by the AV diet was significantly correlated with the changes in the number of sdLDL particles (r = 0.32, P = 0.0002) but not large, buoyant LDL particles. CONCLUSIONS: One avocado a day in a heart-healthy diet decreased oxLDL in adults with overweight and obesity, and the effect was associated with the reduction in sdLDL. This trial was registered at http://www.clinicaltrials.gov as NCT01235832.