THE EFFECT OF COFFEE CONSUMPTION ON SERUM-CHOLESTEROL LEVELS

Objective: Studies investigating the association of coffee consumption and serum cholesterol levels report conflicting results. In an attemp t to resolve this controversy, we reviewed the literature to answer th e question: Is there a true positive association between coffee consum ption and serum cholesterol levels? Data Sources: A Medline database s earch dating back to 1965 was utilized. Key words used in the search w ere coffee, caffeine and cholesterol. Cholesterol was expanded to incl ude lipoproteins and LDL-, HDL- and VLDL-cholesterol. All articles tha t presented cholesterol data in association with coffee consumption we re examined for references missed by Medline. Recently published artic les were located by a hand search through Current Contents and the lat est monthly editions of Index Medicus. Study Selection: Three reviewer s made the decision to include all publications that met the following criteria: a) reported original experimental results; b) reported tota l serum cholesterol levels; and c) were published in peer-reviewed jou rnals. Data Extraction: Two to four articles were read and analyzed ea ch week in chronological order. Independent data extraction was perfor med by three reviewers, who then met as a group once a week to cross-c heck the analyses. Data Synthesis: A trend, representing the associati on between coffee consumption and serum cholesterol, was calculated fo r each study. The trend was based on the percent difference in cholest erol values between subjects drinking four or more cups of coffee per day in comparison to those drinking zero or less than one cup of coffe e each day. In order to compare studies that reported different cup si zes and different levels of intake, weighted mean cholesterol levels w ere calculated. In studies discussing the data in terms of correlation s, trends were established according to the r values provided by the a uthors. Conclusions: The majority of studies demonstrated a positive t rend in at least one subpopulation of their subjects, indicating that serum cholesterol levels increase with increasing coffee consumption. Stronger trends were seen among subjects drinking boiled coffee than i n those drinking filtered, decaffeinated or instant coffee. However, m ost studies were not randomized clinical trials, and results can be co untered by a number of biases prevalent in the studies, indicating the need for additional well-designed investigations to resolve remaining issues.