Non-soy legume consumption lowers cholesterol levels: A meta-analysis of randomized controlled trials
Introduction
Worldwide, cardiovascular diseases (CVD) are estimated to be the leading cause of death and loss of healthy life years resulting from disability [1]. In the United States, CVD causes 1 of every 3 deaths [2]. Recent data show that 71.3 million people in the United States have two or more risk factors for heart disease [2]. Studies have consistently shown that risk factor modification can decrease the prevalence of cardiovascular diseases, such as coronary heart disease and strokes [3], [4], [5], [6]. Diet is an important modifiable risk factor for many types of heart disease [7], [8].
Observational epidemiologic studies have strongly indicated an inverse relationship between fruit and vegetable consumption and the incidence of cardiovascular events [7], [9]. So much so that not consuming fruits and vegetables daily may be responsible for up to 13.7% of acute myocardial infarcts in one estimate[10]. Several studies have also shown that persons who consume diets high in whole grains and fiber have lower blood pressure and total cholesterol levels [11], [12]. The Dietary Guidelines for Americans suggest consuming 3 cups of legumes, which are rich in soluble dietary fiber and vegetable protein, per week; however less than a third of the population meets this guideline [13], [14]. Legume consumption has been associated with lower risks of coronary heart disease in observational epidemiologic studies [15], [16] and has been shown to decrease total cholesterol and low-density lipoprotein cholesterol in clinical trials [17], [18]. However, the majority of studies that have evaluated the hypocholesterolemic effects of legume consumption examined soybeans specifically rather than the many non-soy legumes, which are more commonly consumed in the Western hemisphere [19]. Non-soy legumes include a variety of beans such as navy, pinto, kidney, garbanzo and lima beans and peas such as split green peas or lentils. Randomized controlled trials that have examined the potential hypocholesterolemic effects of a diet rich in non-soy legumes have differed in their findings [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], with some finding no effect [22], [24], [31], while other identified a significant cholesterol lowering effect [20], [21], [27]. We conducted a meta-analysis of randomized controlled trials to quantify the direction and magnitude of the potential effect that consumption of non-soy legumes may have on serum cholesterol concentrations.
Section snippets
Study selection
We searched the online databases MEDLINE (from January 1966 through July 2009) using the following terms as medical subject headings and keywords: fabaceae not soybeans not isoflavones and diet or dietary fiber and cholesterol or hypercholesterolemia or triglycerides or cardiovascular diseases. An EMBASE database search (from January 1980 to July 2009) was also performed using the database-specific medical subject headings and keywords: legume or bean not soybean not isoflavone and dietary fiber
Results
Fig. 1 depicts the flow of study selection for the analysis. Of the 140 potentially relevant references identified, 117 were excluded following review of abstract and title. A total of 23 full-text articles were retrieved and reviewed for inclusion. We further excluded 8 articles due to multiple publications from an individual trial, 1 study was shorter than 3 weeks in duration, 1 was excluded due to lack of control diet, 2 articles were excluded because they reported insufficient information
Discussion
CVD remains the leading cause of death in the US and other Western countries despite advances in care [1]. Therefore, modification of risk factors is an essential part of any strategy to decrease the number of CVD events and deaths. Our results indicate that non-soy legume consumption has a significant beneficial effect on serum cholesterol levels, one of the most important risk factors for CVD. Both total and LDL cholesterol decreased, while HDL cholesterol did not change significantly, when
Acknowledgements
The sponsor had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. Dr. Bazzano had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Dr. Tees and Dr. Nguyen assisted in the abstraction of data and writing of the manuscript. Ms. Thompson contributed to the analysis of the data and editorial
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