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

Abstract

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.

Keywords: CVD; LDL oxidation; MUFA; antioxidants; avocado; lipid; lipid transfer proteins; lipoprotein; small dense LDL.

FIGURE 1

Study design: a randomized, crossover, controlled trial to evaluate the effect of a moderate-fat diet including 1 avocado per day on lipids and lipoproteins in healthy adults with overweight and obesity (aged 21–70 y). AAD, average American diet; AV, avocado diet; BD/VS, clinical visit—fasting blood draw and vital signs; LF, lower-fat diet; MF, moderate-fat diet; RM, randomization for diet treatment sequence (3 of the 6 randomized diet sequences are shown in the diagram).

FIGURE 2

The percentage change of plasma antioxidants after 5 wk of consumption of LF, MF, and AV diets compared with baseline in healthy adults with overweight and obesity (aged 21–70 y). All values are means ± SEMs (n = 42–45). *The concentrations are significantly higher compared with the baseline (P < 0.05). Labeled means without a common letter differ, P < 0.05. Statistical models were run on the raw change values. AV, avocado diet; LF, lower-fat diet; MF, moderate-fat diet.

FIGURE 3

The percentage change of plasma oxidative markers after 5 wk of consumption of LF, MF, and AV diets compared with baseline in healthy adults with overweight and obesity (aged 21–70 y). All values are means ± SEMs (n = 42–45). *Values are significantly different from the baseline (P < 0.05). Labeled means without a common letter differ, P  < 0.05. Statistical models were run on the raw change values. The percentages of changes from baseline are shown for visualization. AV, avocado diet; LF, lower-fat diet; MF, moderate-fat diet.

FIGURE 4

The correlation between changes in oxidized LDL (oxLDL) and LDL subclasses caused by all 3 diets in healthy adults with overweight and obesity (aged 21–70 y). (A) The correlation between changes in oxLDL and small LDL-P. (B) The correlation between changes in oxLDL and large LDL-P. AV, avocado diet; LDL-P, LDL particles; LF, lower-fat diet; MF, moderate-fat diet.

FIGURE 5

Correlations between change in CETP activity and change in LDL and HDL subclasses for the 3 diets in healthy adults with overweight and obesity (aged 21–70 y). (A) Correlation between change in CETP activity and change in small LDL-P. (B) Correlation between change in CETP activity and change in large HDL-P. AV, avocado diet; CETP, cholesteryl ester transfer protein; HDL-P, HDL particles; LDL-P, LDL particles; LF, lower-fat diet; MF, moderate-fat diet.