Article in press - uncorrected proof Clin Chem Lab Med 2010;48(6):xxx-xxx 2010 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2010.161
The relationship of coffee and green tea consumption with high-sensitivity C-reactive protein in Japanese men and women
Takako Maki1,*, Ngoc Minh Pham1, Daigo Yoshida1, Guang Yin1, Keizo Ohnaka2, Ryoichi Takayanagi3 and Suminori Kono1
Keywords: alcohol intake; coffee consumption; high sensitivity C-reactive protein; obesity; smoking.
1
Department of Preventive Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan 2 Department of Geriatric Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan 3 Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
Abstract Background: Circulating high-sensitivity C-reactive protein (CRP) is a good marker of chronic low-grade inflammation. The few studies that have addressed the relationship between coffee consumption and CRP concentrations report inconsistent findings. The authors of this study examined the relationship between coffee and green tea consumption and serum concentrations of CRP, and the interaction with alcohol consumption, smoking, and obesity in a large population of free-living Japanese men and women. Methods: Study subjects were 10,325 men and women, 49–76 years of age, living in Fukuoka City who participated in a baseline survey of a cohort study on lifestyle-related diseases. Coffee and green tea consumption and other lifestyle characteristics were assessed using a structured questionnaire. Anthropometric measurements and venous blood samples were also included. Results: CRP concentrations were progressively lower with increasing levels of coffee consumption, after adjustment for smoking and other covariates (p for trends0.03) in men, but not in women. Stratified analysis indicated that this inverse association was primarily limited to men with a high consumption of alcohol (G50 g/day). Green tea consumption showed no measurable relationship with CRP concentrations in either men or women. Conclusions: Coffee may be protective specifically against alcohol-induced hepatic inflammation. Further studies are warranted in different populations. Clin Chem Lab Med 2010;48
Introduction Chronic inflammation has been implicated in the pathogenesis of diverse diseases including cancer, atherosclerotic disease, and type 2 diabetes mellitus (1–3). Considerable attention has recently been drawn to not only the association of inflammatory biomarkers with disease risk, but also to determinants of circulating inflammatory biomarkers (4). Creactive protein (CRP) is one of the acute-phase proteins, and circulating CRP is synthesized and secreted by hepatocytes in response to proinflammatory cytokines (5). Serum concentrations of high-sensitivity CRP are a good biomarker of chronic low-grade inflammation (6). Several behavioral and clinical correlates of circulating CRP have been reported. Obesity and smoking have most consistently been related to increased concentrations of circulating CRP (4, 6). CRP concentrations are also increased in women undergoing hormone replacement therapy (7). However, moderate alcohol consumption has generally been related to lower CRP concentrations (8, 9). While a possible protective effect of coffee consumption has been suggested in relation to inflammation-related diseases (10–12), the few studies that have addressed the relationship between coffee consumption and CRP concentrations have reported inconsistent findings (13–16). Coffee and coffee compounds, such as chlorogenic acids and caffeic acid have potent in vitro and in vivo antioxidant activities (17–19). Green tea is an important source of antioxidant flavonoids in Japan (20), but the relationship between habitual consumption of green tea and inflammatory markers has not been examined previously. In the study reported here, we examined the relationship of coffee and green tea consumption with serum concentrations of high-sensitivity CRP in a large population of freeliving men and women. We also explored the interaction of coffee consumption with smoking, obesity, and alcohol intake in relation to CRP concentrations.
Materials and methods *Corresponding author: Takako Maki, MD, Department of Preventive Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan Phone: q81-92-642-6113, Fax: q81-92-642-6115, E-mail:
[email protected] Received November 5, 2009; accepted January 19, 2010
Study subjects The study subjects were participants in the baseline survey of the Kyushu University Fukuoka Cohort Study. Eligible persons were residents of the East Ward of Fukuoka City aged 50–74 years at the time of recruitment. All participants gave written informed con-
2010/584
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sent before participation in the survey. The study was approved by the Ethics Committee of the Kyushu University Faculty of Medical Sciences. Between February 2004 and August 2007, a total of 12,949 subjects (5817 men and 7132 women) participated in the baseline survey, with a participation rate of 24%. Age at the time of the survey ranged from 49 to 76 years; three women aged 49 years were included because of a mistake in recording the date of birth. We excluded 1495 subjects who were under current medical care for coronary artery disease (ns534), arteriosclerosis obliterance (ns36), stroke (ns251), chronic liver disease (ns265), chronic renal failure (ns29), cancer (ns498), or alcohol abuse (ns4); some participants had two or more conditions for exclusion. Further excluded were 301 subjects who reported a prior history of myocardial infarction or coronary angioplasty (ns32), stroke (ns132), or chronic liver disease (ns143); again, some participants had two or more conditions. Also excluded were 677 subjects currently using analgesics, 138 subjects with a CRP concentration of G10 mg/L, and 13 subjects with missing information on the covariates being studied. Thus, a total of 10,325 subjects (4407 men and 5918 women) remained in the present analysis.
Baseline survey Details of the baseline survey were described previously (21). In brief, each participant completed a self-administered questionnaire which inquired about food and beverage intake, smoking habit, alcohol use, physical activity, diseases under current or previous treatment, use of drugs and supplements, parental history of selected diseases, and others. Unfilled answers in the questionnaire were confirmed by in-person interview. Anthropometric measurements (height, body weight, and waist and hip circumferences) and venous blood sampling were also included. With respect to the consumption of coffee and green tea, individuals answered closed-ended questions with eight options (almost nill, 1–2 cups/week, 3–4 cups/week, 5–6 cups/week, 1–3 cups/day, 4–6 cups/day, 7–9 cups/day, and G10 cups/day) on average intake over the previous year. Types of coffee and use of milk or sugar were not ascertained. Past alcohol drinkers were separated from lifelong non-drinkers, and current drinkers reported consumption frequencies and quantities of five different alcoholic beverages (sake, shochu, beer, whiskey/brandy, and wine) on average in the past year. Total daily ethanol intake (g/day) was calculated by using the approximate concentration of ethanol in each beverage. Consumption of alcohol, coffee, and green tea estimated by similar questions were reported to have fairly high validity in comparison with a 28day record (22). For smoking habits, past smokers were distinguished from lifelong non-smokers, and past and current smokers reported the average number of cigarettes smoked per day. Questions on physical activity ascertained the amount of time spent on four types of workrelated physical activities (standing, bicycling, walking, and strenuous labor) and for three types of leisure-time physical activities (light, moderate, and heavy) over the previous year. The intensity of each physical activity was determined in terms of metabolic equivalent (MET) value and expressed as a sum of MET multiplied by the time (in hours) spent performing each activity. Body mass index (BMI) (kg/m2) and waist-to-hip ratio (WHR) were calculated.
Measurement of high-sensitivity CRP Non-fasting or fasting venous blood samples were drawn into vacuum tubes, and serum was separated by centrifugation on the same day. The samples were temporally stored in a refrigerator, and then
shipped to an external laboratory (SRL, Hachiohji, Japan) on dry ice the next working day. Serum concentrations of high-sensitivity CRP were measured using a latex-enhanced immunonephelometric assay on a BN II analyzer (Siemens Healthcare Diagnostics, Marburg, Germany). The BN II method was reported to have intra-assay coefficients of variation (CV) of 2.2%–3.4% and inter-assay CV of 3.0%–5.4% using pooled serum samples from healthy subjects (23). It was also shown that CRP is stable on ice for at least 36 h until separation of serum (24). Also, the assay is not subject to interference from samples with gross hemolysis, jaundice, and turbidity due to lipemia (23). The laboratory’s claimed limit of detection was 0.05 mg/L, and a value of 0.025 mg/L was assigned when the value was below the detection limit.
Statistical analysis Between-group comparisons of means and medians were performed using an unpaired t-test and Wilcoxon rank sum test, respectively. The x2-test was used for comparisons of proportions. The distribution of CRP values was skewed to the right and the natural logarithm of the values was used. The analysis was performed for men and women separately. In both men and women, coffee consumption was categorized into five groups (nill, -1, 1–3, 4–6, or G7 cups/ day), and green tea intake was categorized into four groups (-1, 1–3, 4–6, or G7 cups/day) because those with almost null consumption (less than one cup per week) were very few (6.8% in men and 3.8% in women). Age-adjusted and multivariate-adjusted means of CRP were calculated according to specified categories of coffee and green tea intake by means of analysis of covariance. Statistical adjustment was made for age (continuous variable), BMI (-20, 20–22.4, 22.5–24.9, and G25 kg/m2), WHR (categorized at quartiles), workrelated physical activity (categorized at quartiles), and leisure-time physical activity (categorized at quartiles). Cigarette smoking was categorized into four groups in men (never, past, and current smoking with a consumption of 0–19 or G20 cigarettes/day) and three groups in women (never, past, and current smoking). Alcohol intake was categorized into five groups in men (never, past, and current drinking with a consumption of -24, 25–49, or G50 g of alcohol/ day) and four groups in women (never, past, and current drinking with a consumption of -10 or G10 g of alcohol/day). Trend of an association was assessed using multiple linear regression analysis with ordinal scores assigned to categorical variables of interest. Effects of alcohol intake, cigarette smoking, BMI, and WHR on the association between coffee consumption and CRP were examined with stratification by each covariate. Daily alcohol intake of G50 g/day in men and G10 g/day in women were defined as high alcohol use, and lesser intakes were defined as moderate use. Lifelong non-drinkers and former drinkers were combined in the analysis because CRP concentrations did not differ in these two groups. Individuals were stratified into those with high BMI (BMI G25.0 kg/m2) and those without, and the upper tertile was used for stratification by WHR (0.95 for both sexes). The significance of interactions was tested by generating a product term of coffee or green tea consumption (ordinal variable) and each of the covariates. Twosided p-values -0.05 were regarded as statistically significant. Statistical analysis was performed with SAS version 9.0 (SAS Institute, Cary, NC, USA).
Results Selected characteristics of the study subjects are summarized in Table 1. At least one cup of coffee per day was consumed
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Table 1 Selected characteristics of the study subjects according to gender. Variable
Men, ns4407
Women, ns5918
p-Valuea
Age, years, mean"SD Body mass index, kg/m2, mean"SD Waist-to-hip ratio, mean"SD Work-related activity, MET-h/day, median (IQR) Leisure-time activity, MET-h/week, median (IQR) Smoking, n (%) Never Past Current No. of cigarettes/day in current users, n, median (IQR) Alcohol drinking, n (%) Never Past Current Alcohol, g/day, in current users, median (IQR) Coffee consumption, cups/day, median (IQR) Green tea consumption, cups/day, median (IQR) CRP, mg/L, median (IQR)
62.3"6.7 23.5"2.7 0.93"0.05 6.0 (2.0–14.0) 5.0 (2.0–15.0)
61.8"6.7 22.5"3.1 0.91"0.08 10.0 (6.0–18.0) 5.0 (1.0–14.0)
0.0001 -0.0001 -0.0001 -0.0001 0.01
1137 (25.8) 1842 (41.8) 1428 (32.4) 20 (15–30)
5260 (88.9) 301 (5.1) 357 (6.0) 15 (10–20)
-0.0001 -0.0001
933 (21.2) 269 (6.1) 3205 (72.7) 29.0 (14.0–46.0) 2.0 (0.5–2.0) 2.0 (2.0–5.0) 0.48 (0.26–1.01)
4180 (70.6) 134 (2.3) 1604 (27.1) 9.0 (5.0–16.0) 2.0 (0.5–2.0) 5.0 (2.0–5.0) 0.37 (0.20–0.76)
-0.0001 -0.0001 0.19 -0.0001 -0.0001
p-Value was calculated by using t-test, Wilcoxon rank sum test, or x2-test. SD, standard deviation; MET, metabolic equivalent; IQR, inter quartile range; CRP, C-reactive protein.
a
by more than half of the men and women (58%), and daily users of green tea accounted for 78% in men and 88% in women. Cigarette smoking and alcohol use was more frequent in men. CRP concentrations were higher in men than in women. Spearman’s correlation coefficients between coffee and CRP were –0.01 for men and –0.02 for women. The corresponding values for green tea and CRP were 0.002 for men and 0.02 for women. The concentrations of CRP according to coffee and green tea consumption in men and women are shown in Table 2. Age-adjusted geometric means of CRP did not vary according to coffee consumption, but concentrations were progressively lower with increasing levels of coffee consumption after adjustment for the covariates (p for trends0.03). The inverse association in terms of the multivariate-adjusted means was largely attributed to an allowance for smoking; with adjustment for age and smoking, geometric means from the lowest to the highest categories of coffee consumption were 0.54 (0.50–0.59), 0.53 (0.50–0.57), 0.51 (0.48–0.53), 0.50 (0.45–0.55), and 0.46 (0.37–0.57) (p for trends0.05). Neither age-adjusted nor multivariate-adjusted geometric means showed a clear association between green tea and CRP. In women, there was no clear inverse association between coffee consumption and either age-adjusted or multivariateadjusted mean concentrations of CRP. However, CRP concentrations were slightly decreased in the highest category of coffee consumption. Pre-menopausal and post-menopausal women numbered 423 and 5495, respectively. Coffee intake was unrelated to CRP when the analysis was performed according to menopausal status (data not shown). CRP concentrations did not vary measurably with green tea consumption in women. No measurable interaction was noted for smoking (ps0.63 in men and ps0.55 in women), BMI (ps0.62 in
men and ps0.88 in women), and WHR (ps0.60 in men and ps0.63 in women). An inverse association between coffee consumption and CRP was observed in men with a high alcohol intake (G50 g/day), and the inverse trend was statistically significant, although the interaction was not statistically significant (Table 3). Women showed no such interaction between alcohol and coffee consumption on CRP concentrations (p for interactions0.68).
Discussion The present study showed an inverse association between coffee consumption and CRP concentrations in men, but not in women, after adjusting for smoking and other covariates. This inverse association was primarily limited to men with a high consumption of alcohol (G50 g/day). Green tea consumption showed no measurable relationship with CRP concentrations in men or women. The lack of an inverse association between coffee and CRP in women is contrary to results from two cross-sectional studies in the USA (15) and Japan (16). In the former study (15), caffeinated coffee intake divided into four categories from -1 cup/month to G2 cups/day were inversely associated with CRP concentrations in diabetic women, while decaffeinated coffee intake categorized in the same way showed an inverse association in healthy women. When the analysis was repeated with stratification according to diabetes mellitus (drug treatment or hemoglobin A1c G6.5%), similar results as described above were observed, regardless of the presence of diabetes (data not shown). The Japanese study showed approximately 20% lower concentrations of CRP in those consuming at least one cup of coffee per day compared with those consuming less (16). Age is highly correlated with serum CRP. Women in the present study were
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Table 2 Age-adjusted and multivariate-adjusted geometric means of CRP (mg/L) according to coffee and green tea consumption in men and women. Cups/day
Coffee Never -1 1–3 4–6 7q ptrendb Green tea -1 1–3 4–6 7q ptrendb
Men
Women
n
Age-adjusted mean, 95% CI
Multivariateadjusted mean, 95% CIa
n
Age-adjusted mean, 95% CI
Multivariateadjusted mean, 95% CIa
721 1145 1986 469 86
0.51(0.47–0.56) 0.52 (0.49–0.55) 0.51 (0.49–0.54) 0.55 (0.50–0.61) 0.52 (0.41–0.65) 0.57
0.55(0.51–0.59) 0.53 (0.50–0.56) 0.51 (0.49–0.53) 0.50 (0.46–0.55) 0.44 (0.35–0.55) 0.03
892 1578 2944 444 60
0.39 0.39 0.40 0.44 0.33 0.42
(0.36–0.42) (0.37–0.42) (0.38–0.41) (0.39–0.48) (0.26–0.44)
0.40 0.40 0.39 0.41 0.31 0.52
(0.38–0.43) (0.38–0.42) (0.38–0.41) (0.37–0.45) (0.24–0.39)
953 1831 1130 493
0.53 0.52 0.52 0.50 0.38
0.52 0.51 0.53 0.50 0.72
739 1936 1984 1259
0.40 0.40 0.40 0.38 0.28
(0.37–0.43) (0.38–0.42) (0.38–0.42) (0.36–0.40)
0.38 0.40 0.41 0.39 0.71
(0.36–0.41) (0.38–0.41) (0.39–0.42) (0.37–0.41)
(0.50–0.57) (0.49–0.54) (0.49–0.55) (0.45–0.55)
(0.49–0.56) (0.49–0.54) (0.50–0.56) (0.46–0.55)
a Adjusted for age, body mass index, waist-to-hip ratio, work-related and leisure-time physical activities, smoking, alcohol consumption, and either green tea or coffee consumption. bTrend of an association was assessed with ordinal scores assigned to categories of each variable.
slightly older than those in previous studies (15, 16); mean ages in the present and previous Japanese studies were 62 years and 58 years, respectively; in the American study they were 59 years in diabetic women and 56 years in healthy women. However, in the Japanese study (16) an inverse association between coffee and CRP was observed in both of the two age groups -60 and G60 years. It is notable that an inverse association between coffee and CRP was evident only in men with high consumption of alcohol. The present findings are compatible with inverse associations between coffee and serum activities of aminotransferase and g-glutamyltransferase (GGT), which have been shown to be more prevalent in men with higher alcohol consumption (25, 26). It is thus hypothesized that coffee may be protective, specifically against alcohol-induced hepatic inflammation rather than systemic inflammation. CRP is synthesized predominantly in the liver, and circulating CRP may be more closely linked to the extent of hepatic inflammation. The lack of an inverse association between coffee
and CRP in women may be explained by their low alcohol consumption in the present study population. In fact, serum GGT was much higher in men than in women; median values were 35 U/L in men and 20 U/L in women. However, this hypothesis contrary to previous observation in Japanese women, in whom the prevalence of alcohol use (G3 days/ week) was no more than 7.6% (16). Green tea was not related to CRP concentrations in the present study. The association between habitual green tea consumption and CRP or other inflammatory markers has not been examined previously. However, habitual black tea consumption was related to lower concentrations of CRP in a cross-sectional study of men in Belgium (27). Black tea drinking was also shown to decrease CRP concentrations in a trial of healthy non-smoking men (28), but not in another smaller trial of healthy men and women who smoked (29). The lack of an inverse association between green tea and CRP in the present study does not necessarily indicate that drinking green tea is less effective than drinking black tea. A batch
Table 3 Multivariate-adjusted geometric means of CRP (mg/L) according to coffee consumption stratified according to alcohol use in mena. Coffee (cups/day)
Nill -1 1–3 4–6 7q ptrendb
Alcohol consumption Never/former
Moderate (1–49 g/day)
High (G50 g/day)
n
Mean, 95% CI
n
Mean, 95% CI
n
Mean, 95% CI
176 286 541 157 42
0.58 0.58 0.58 0.59 0.42 0.48
406 659 1141 247 31
0.52 0.50 0.47 0.47 0.58 0.10
139 200 304 65 13
0.58 0.56 0.55 0.45 0.29 0.04
(0.50–0.69) (0.51–0.65) (0.53–0.64) (0.49–0.70) (0.30–0.59)
(0.47–0.58) (0.46–0.54) (0.44–0.49) (0.41–0.54) (0.40–0.83)
(0.49–0.69) (0.49–0.64) (0.49–0.62) (0.35–0.57) (0.16–0.50)
Interaction ps0.48. aAdjusted for age, body mass index, waist-to-hip ratio, work-related and leisure-time physical activities, smoking, and green tea consumption. bTrend of an association was assessed with ordinal scores assigned to categories of coffee consumption.
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of green tea leaves is usually reused in brewing, and the number of cups of green tea may not have accurately captured the intake of catechins and other bioactive ingredients. Advantages in the present study were the fairly large size of the study population, uniform measurements of lifestyle variables and CRP, and control for important covariates. Several limitations were noted however. A cross-sectional association does not necessarily indicate causality. Prevalent morbid conditions, such as coronary artery diseases and chronic liver diseases with elevated CRP may have resulted in decreased consumption of coffee. For this reason, we excluded some of the participants who had limiting morbid conditions or some inflammatory diseases, as well as those with CRP G10 mg/L. Low participation (24%) in the survey was another concern in interpreting the findings. Selection bias may have been possible if the participation was affected simultaneously by both coffee consumption and CRP concentrations. Phlebotomy for CRP measurement was performed casually during the daytime throughout the year. However, it is known that CRP concentrations show little or no diurnal or seasonal variation (30, 31). The type of coffee (filtered or unfiltered) is a matter of interest in some European countries, but boiled coffee is rarely consumed in Japan. In conclusion, in a large population of free-living men and women in Japan, coffee consumption was inversely associated with CRP concentrations in men, especially in those with high alcohol consumption. Our rarely warrant further investigation in different populations.
Acknowledgements This study was supported by a grant for the 21st Century Center of Excellence Program (Kyushu University) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
Conflict of interest statement Authors’ conflict of interest disclosure: The authors stated that there are no conflicts of interest regarding the publication of this article. Research funding: None declared. Employment or leadership: None declared. Honorarium: None declared.
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