Abstract and Introduction
Background: Low levels of high-density lipoproteins (HDL) are considered an important risk factor for cardiovascular disease and constitute one of the criteria for the Metabolic Syndrome (MetS). Lifestyle interventions promoting a low-fat, plant-based eating pattern appear to paradoxically reduce cardiovascular risk but also HDL levels. This study examined the changes in MetS risk factors, in particular HDL, in a large cohort participating in a 30-day lifestyle intervention that promoted a low-fat, plant-based eating pattern.
Methods: Individuals (n = 5,046; mean age = 57.3 ± 12.9 years; 33.5% men, 66.5% women) participating in a in a Complete Health Improvement Program (CHIP) lifestyle intervention within the United States were assessed at baseline and 30 days for changes in body mass index (BMI), blood pressure (BP), lipid profile and fasting plasma glucose (FPG).
Results: HDL levels decreased by 8.7% (p<0.001) despite significant reductions (p<0.001) in BMI (-3.2%), systolic BP (-5.2%), diastolic BP (-5.2%), triglycerides (TG; -7.7%), FPG (-6.3%), LDL (-13.0%), total cholesterol (TC, -11.1%), TC: HDL ratio (-3.2%), and LDL: HDL ratio (-5.3%). While 323 participants classified as having MetS at program entry no longer had this status after the 30 days, 112 participants acquired the MetS classification as a result of reduction in their HDL levels.
Conclusions: When people move towards a low-fat, plant-based diet, HDL levels decrease while other indicators of cardiovascular risk improve. This observation raises questions regarding the value of using HDL levels as a predictor of cardiovascular risk in populations who do not consume a typical western diet. As HDL is part of the assemblage of risk factors that constitute MetS, classifying individuals with MetS may not be appropriate in clinical practice or research when applying lifestyle interventions that promote a plant-based eating pattern.
Epidemiological studies indicate that low levels of plasma or serum HDL is an important risk factor in the development of cardiovascular disease (CVD). Consequentially, the National Cholesterol Education Program has advocated increasing HDL levels as an important strategy for the primary prevention of CVD. Lowered HDL has also been included as one of the risk factors used to establish a diagnosis of Metabolic Syndrome (MetS).
Lifestyle interventions that promote a low-fat, plant-based eating pattern have been shown to reduce HDL levels.[4–8] Consequentially, it has been suggested that low-fat, plant-based diets may not be ideal for people suffering CVD,[9,10] despite being well established to reduce other CVD risk factors including body mass, BP, TC and LDL.[4–8] Furthermore, long-term intervention studies involving low-fat, plant-based diets have even been shown to regress atherosclerotic plaques[4,7] and reduce cardiac events, despite also lowering HDL levels. This apparently conflicting observation has led to debate surrounding the merits of a low-fat, plant-based diet for the management of CVD. In a recent review of HDL argued that lowered HDL level is not associated with increased risk of coronary heart disease in the absence of other lipid or non-lipid risk factors.
The purpose of this study was to further explore the changes in CVD risk factors, especially HDL, in a large cohort of individuals participating in a lifestyle intervention that advocated a low-fat, plant-based eating pattern—the Complete Health Improvement Program (CHIP). The effect of these changes on the MetS rubic and the implications of this for classifying individuals with MetS were specifically examined.
Nutr Metab. 2013;10(58) © 2013 BioMed Central, Ltd.