The effect of coffee consumption on serum lipids: a meta-analysis of randomized controlled trials

Abstract

BACKGROUND/OBJECTIVES: Numbers of epidemiological studies assessing coffee consumption and serum lipids have yielded inconsistent results. We aimed to evaluate the effects of coffee intake on serum lipids. SUBJECTS/METHODS: We searched several English and Chinese electronic databases up to September 2011 for randomized controlled trials of coffee on serum lipids. Weighted mean effect size was calculated for net changes in serum lipids by using random-effect models or fixed-effect models. Subgroup and meta-regression analyses were conducted to explore possible explanations for heterogeneity among trials. RESULTS: Twelve studies conducted in Western countries with a total of 1017 subjects were identified. Meta-analyses showed, on average, drinking coffee for 45 days was associated with an increase of 8.1 mg/dl (95% confidence interval (CI): 4.5, 11.6; Po0.001) for total cholesterol (TC), 5.4 mg/dl (95% CI: 1.4, 9.5; P ¼ 0.009) for low-density lipoprotein cholesterol (LDL-C) and 12.6 mg/dl (95% CI: 3.5, 12.6; P ¼ 0.007) for triglyceride (TG). The increase in TC were greater in trials using unfiltered coffee and caffeinated coffee as the treatment group. Those who had hyperlipidemia were more sensitive to the cholesterol-raising effect of coffee. Meta-regression analysis revealed a positive dose-response relation between coffee intake and TC, LDL-C and TG. CONCLUSION: The intake of coffee especially unfiltered coffee is contributed significantly to the increase in TC, LDL-C and TG, and the changes were related to the level of intake. Studies of coffee intake on serum lipids in Asian populations should be performed. Keywords: coffee; caffeine; lipids; meta-analysis; randomized controlled trials INTRODUCTIONCoffee is one of the most commonly consumed beverages and even small health effects of coffee could have considerable public health consequences. Controversies regarding its risks and benefits still exist as substances in coffee may have either unfavorable or beneficial effects on the cardiovascular system. 1 A large body of epidemiology studies, including recent studies, [2][3][4][5] examining the association between coffee consumption and serum lipids have yielded inconsistent results.A meta-analysis of nine randomized controlled trials (RCTs) published before December 1998 concluded that consumption of unfiltered, but not filtered, coffee increased serum levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C). 6 However, this meta-analysis was only based on English-language literature and the authors failed to include two important RCTs, 7,8 which included 345 participants. In addition, the active factors such as caffeine and coffee oils, which were responsible for the plasma lipoprotein-increasing effect of coffee, were not determined.To determine the effect of caffeinated coffee and decaffeinated coffee consumption on plasma lipoprotein cholesterol levels in healthy men, Fried et al. 9 performed a RCT by three intervention coffee including 720 ml/day of caffeinated coffee, 360 ml/day o...

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