Adding monounsaturated fatty acids to a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia

Abstract

Background: Higher intake of monounsaturated fat may raise high-density lipoprotein (HDL) cholesterol without raising low-density lipoprotein (LDL) cholesterol. We tested whether increasing the monounsaturated fat content of a diet proven effective for lowering LDL cholesterol (dietary portfolio) also modified other risk factors for cardiovascular disease, specifically by increasing HDL cholesterol, lowering serum triglyceride and further reducing the ratio of total to HDL cholesterol.

Methods: Twenty-four patients with hyperlipidemia consumed a therapeutic diet very low in saturated fat for one month and were then randomly assigned to a dietary portfolio low or high in monounsaturated fatty acid for another month. We supplied participants' food for the two-month period. Calorie intake was based on Harris-Benedict estimates for energy requirements.

Results: For patients who consumed the dietary portfolio high in monounsaturated fat, HDL cholesterol rose, whereas for those consuming the dietary portfolio low in monounsaturated fat, HDL cholesterol did not change. The 12.5% treatment difference was significant (0.12 mmol/L, 95% confidence interval [CI] 0.05 to 0.21, p = 0.003). The ratio of total to HDL cholesterol was reduced by 6.5% with the diet high in monounsaturated fat relative to the diet low in monounsaturated fat (-0.28, 95% CI -0.59 to -0.04, p = 0.025). Patients consuming the diet high in monounsaturated fat also had significantly higher concentrations of apolipoprotein AI, and their C-reactive protein was significantly lower. No treatment differences were seen for triglycerides, other lipids or body weight, and mean weight loss was similar for the diets high in monounsaturated fat (-0.8 kg) and low in monounsaturated fat (-1.2 kg).

Interpretation: Monounsaturated fat increased the effectiveness of a cholesterol-lowering dietary portfolio, despite statin-like reductions in LDL cholesterol. The potential benefits for cardiovascular risk were achieved through increases in HDL cholesterol, further reductions in the ratio of total to HDL cholesterol and reductions in C-reactive protein. (ClinicalTrials.gov trial register no. NCT00430430.).

Figure 1:

Flow of patients through the study. *Of the 12 people who chose not to participate, four had a medical issue, two wanted to lose weight, one was not willing to stop statin therapy, one was not willing to stop vitamin supplements, one was not willing to give blood samples for analysis, one was not willing to undergo kinetics testing, one had a family issue, and one was not interested. F = female, M = male, MUFA = monounsaturated fatty acid, R = randomization.

Figure 2:

Mean percentage change (and standard deviation) from baseline in (A) high-density lipoprotein (HDL) cholesterol (p = 0.003), (B) apolipoprotein AI (p = 0.001), (C) low-density lipoprotein (LDL) cholesterol (p = 0.43) and (D) apolipoprotein B (p = 0.50) with dietary portfolios having high and low levels of monounsaturated fatty acid (MUFA). Significance of differences between treatments was determined by repeated-measures analysis.