Instant coffee consumption may be associated with higher risk of metabolic syndrome in Korean adults

Instant coffee consumption may be associated with higher risk of metabolic syndrome in Korean adults

diabetes research and clinical practice 106 (2014) 145–153 Contents available at ScienceDirect Diabetes Research and Clinical Practice journ al h om...

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diabetes research and clinical practice 106 (2014) 145–153

Contents available at ScienceDirect

Diabetes Research and Clinical Practice journ al h ome pa ge : www .elsevier.co m/lo cate/diabres

Instant coffee consumption may be associated with higher risk of metabolic syndrome in Korean adults Hyo-Jin Kim a,1, Seongbeom Cho b,1, David R. Jacobs Jr.c, Kyong Park a,* a

Department of Food and Nutrition, Yeungnam University, Gyeongsan, Gyeongbuk, Republic of Korea College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, Republic of Korea c Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, MN, USA b

article info

abstract

Article history:

Aims: Cumulative evidence suggests that coffee consumption may have beneficial effects

Received 29 August 2013

on metabolic diseases; however, few previous studies have considered the types of coffee

Received in revised form

consumed and the additives used. We investigated the relationship between coffee con-

12 February 2014

sumption and metabolic syndrome (MetSyn) and its components.

Accepted 4 July 2014

Methods: We analyzed 17,953 Korean adults, aged 19–65 years, using cross-sectional data

Available online 22 July 2014

from the Korean National Health and Nutrition Examination Survey (KNHANES, 2007–2011). Coffee consumption level, types of coffee consumed, and the additives used were assessed

Keywords:

based on a food frequency questionnaire and 24-h recall. Demographic and lifestyle factors

Instant coffee

were assessed using self-administered questionnaires. Data on metabolic biomarkers were

Metabolic syndrome

obtained from a health examination. Multivariable logistic regression was used to deter-

Korean adults

mine the odds ratios of prevalent metabolic syndrome and its components according to frequency and type of coffee consumption. Results: We found that 76% of the subjects were habitual coffee drinkers, most of whom consumed instant coffee mix containing sugar and powder creamer. After multivariable adjustment, the odds ratios (95% CI) comparing those who consumed coffee 3 times/day with those who consumed coffee <1 time/week were 1.37 (1.15–1.63) for obesity, 1.33 (1.11–1.59) for abdominal obesity, 1.28 (1.09–1.51) for hypo-HDL cholesterolemia, and 1.37 (1.10–1.72) for metabolic syndrome. Instant-coffee drinkers were observed to have elevated risks of these metabolic conditions. Conclusions: Consumption of coffee, particularly instant coffee mix, may have harmful effects on MetSyn, perhaps partly deriving from excessive intake of sugar and powder creamer. # 2014 Elsevier Ireland Ltd. All rights reserved.

* Corresponding author at: Department of Food and Nutrition, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 712-749, Republic of Korea. Tel.: +82 53 810 2879; fax: +82 53 810 4768. E-mail address: [email protected] (K. Park). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.diabres.2014.07.007 0168-8227/# 2014 Elsevier Ireland Ltd. All rights reserved.

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1.

diabetes research and clinical practice 106 (2014) 145–153

Introduction

Coffee is one of the most frequently consumed beverages worldwide [1]. In 2010, the average annual coffee consumption in Korea was 2.06 kg per capita, and the consumption of coffee in Korea continues to increase [2]. Recent data showed that Koreans drink coffee approximately 10 times per week, making coffee the third most frequently consumed food or beverage item after rice (17 times/week) and cabbage (14 times/week) [3]. Previous studies reported that coffee consumption may be inversely associated with metabolic risk factors such as blood pressure (BP) [4,5] and fasting blood glucose (FG) [6,7]. In addition, cumulative evidence suggests that frequent coffee consumption may be linked to a lower risk of incident diabetes [8–12]. However, few studies have investigated the effects of the types of coffee consumed and the use of coffee additives on the risk of metabolic syndrome (MetSyn) or type 2 diabetes mellitus [8,10,13–16]. In addition, data on the Korean population are extremely limited [17–19], and the prevalences of MetSyn and type 2 diabetes have recently been increasing in Asian populations, including Koreans, reaching similar levels as Western countries [20,21]. Studies from other nations cannot be directly generalized to the Korean population because Koreans have unique coffee drinking habits. For example, filtered coffee is the most common type of coffee consumed in Europe and the United States, where the majority of the previous studies were conducted [8–11]. In contrast, coffee prepared using instant coffee mix (usually including powder creamer and sugar) is the most common type of coffee consumed in Korea, constituting over 90% of the domestic coffee market [22]. Therefore, we designed the present cross-sectional study to analyze coffee consumption patterns among Korean adults using nationally representative data from the Korean National Health and Nutrition Examination Survey (KNHANES). We specifically sought to investigate possible associations of the risk of MetSyn with the frequency of coffee intake and the type of coffee consumed.

2.

Materials and methods

2.1.

Study population

The KNHANES used a complex, stratified, multistage, probability-cluster sampling method, which enabled the collection of extensive and representative data concerning health and nutritional status in the non-institutionalized civilian Korean population. Data were collected through health interviews, health examinations, and dietary interviews administered by trained personnel. We analyzed data from KNHANES 2007–2011, which included a total of 42,347 participants. Subjects were excluded from this study if they were aged <19 or >65 years (n = 17,326); self-reported a diagnosis of diabetes, stroke, myocardial infarction, angina pectoris, or were taking medications to control diabetes, myocardial infarction, or angina pectoris (n = 1910); had missing information on sampling weights

(n = 1512); had missing frequency information on the coffee item of the food frequency questionnaire (FFQ) (n = 236); did not report 24-h recall dietary information (n = 3258); or had a daily energy intake <25% or >300% of estimated energy requirements (n = 152). In total, 17,953 subjects were included in the analysis of this study. We also conducted a sub-sample analysis of a total of 13,313 subjects, after excluding KNHANES respondents who provided insufficient information on coffee types or additive intakes. The Institutional Review Board (IRB) of Korea Centers for Disease Control and Prevention (KCDC) provided formal ethics approval for the KNHANES data sets (IRB number: 2007-02-CON-04-P, 2008-04EXP-01-C, 200901CON-03-2C).

2.2.

Measurements

Education level was classified into 3 groups: middle school graduation or less, high school graduation, and at least college graduation. Smoking status was classified as never, former, or current smoker. Alcohol consumption was categorized based on the frequency of consumption per week. Level of physical activity was estimated using answers to 3 survey questions, and was categorized as vigorous-intensity physical activity, moderate-intensity physical activity, or walking. Metabolic equivalents (METs) h/week were calculated based on the subjects’ responses to the physical activity questionnaires [23]. Food intake was assessed with a 63-item FFQ that included coffee. For each food item, there were 10 categories for the frequency of consumption, with responses that ranged from ‘‘rarely’’ to ‘‘3 times a day’’; however, the amount consumed was not assessed. The frequency of coffee consumption was classified into 5 groups (<1 time/week, 1–6 times/week, 1 time/day, 2 times/day, 3 times/day). Dietary intake was also assessed using a single 24-h dietary recall. In this data, a total of 87 food codes were classified as ‘‘drink and tea.’’ Among them, we selected 14 food codes that contained ‘‘coffee.’’ To minimize the misclassification of coffee consumption status, and to identify the types of coffee and coffee additives consumed, we classified coffee drinkers using data from both the 24-h recall and the FFQ as follows: (1) non-drinkers were defined as individuals who drank less than once per week; (2) filtered-coffee drinkers were defined as individuals who consumed only filtered coffee with a frequency of coffee consumption greater than or equal to once per week; and (3) instant-coffee drinkers were defined as individuals who consumed only instant coffee or coffee prepared using instant coffee mix with a frequency of coffee consumption greater than or equal to once per week. Decaffeinated or boiled coffee is rarely consumed in South Korea, so it was not considered in our analysis. Because intake levels of sugar/syrup, coffee creamer, and milk were not included in the FFQ, we analyzed and categorized these using data from the 24-h recall. Participants were asked to fast overnight before the health examination. Body weight and height were measured in light clothing with no shoes, and body mass index (BMI) was calculated as weight (kg) divided by height squared (m2). ‘‘Overweight/obesity’’ was defined based on 2000 statement from the World Health Organization for Asian population [24]. Waist circumference (WC) was measured as the abdominal girth midway between the costal margin and the iliac crest at

Table 1 – General characteristics according to the frequency of coffee consumption. N

Frequency of coffee consumption 1–6/week

<1/week

1/day

2/day

3/day

Mean or N

(SD) or %

Mean or N

(SD) or %

Mean or N

(SD) or %

Mean or N

(SD) or %

Mean or N

(SD) or %

17,953 17,953 17,953 17,953

3163 2122 36.9 9.73

18 55 (17.2) (51.9)

2865 1839 36.5 59.0

17 53 (16.3) (143.3)

4344 3026 40.9 133.3

23 60 (16.7) (179.3)

4065 2550 42.5 225.4

22 54 (14.8) (222.8)

3516 1537 41.7 384.5

21 35 (13.3) (404.6)

<0.001 <0.001 <0.001

17,953 17,953 17,953 16,606 17,800

0.46 0.34 0.93 373 0.75

(2.73) (2.07) (15.8) 18 (1.35)

(10.20) (7.42) (33.6) 26 (1.51)

16.5 12.6 2.48 1384 1.20

(18.54) (14.06) (30.6) 51 (1.64)

<0.001 <0.001 0.02 <0.001 <0.001

39 56 5

1435 1847 193

42 52 6

2.59 1.90 1.60 474 0.87

(7.49) (5.37) (23.6) 24 (1.39)

5.19 3.92 2.60 638 0.87

(8.63) (6.13) (29.0) 22 (1.44)

8.82 6.65 2.57 737 1.00

17,773

<0.001 1116 1662 353

34 55 12

1028 1551 263

35 55 10

1590 2419 296

37 56 7

1495 2295 230

16,270

0.01 1340 555 955

45 20 35

1190 539 876

43 21 36

1841 758 1331

46 20 34

1766 682 1229

48 19 34

1455 567 1186

44 18 38

814 741 810 741

27 25 25 22

679 674 728 739

25 24 26 25

987 1052 1137 1112

24 24 26 26

859 1046 1045 1070

22 27 26 25

806 893 876 884

24 27 25 24

829

19

654

16

1199

22

1021

22

754

19

1277 1036

47 35

1229 965

49 35

1654 1470

42 37

1608 1406

42 36

1478 1257

44 37

17,693

0.004

17,837

17,869 17,877

<0.001

22.9 78.6

(4.38) (12.9)

23.3 80.2

(4.39) (39.7)

23.5 79.8

(4.06) (12.7)

23.6 80.6

(4.10) (11.7)

23.8 81.8

(4.22) (13.2)

<0.001 <0.001

17,468

5.01

(0.70)

5.05

(0.79)

5.08

(0.72)

5.14

(0.70)

5.14

(0.81)

<0.001

17,460

1.34

(1.55)

1.36

(1.40)

1.40

(1.35)

1.45

(1.56)

1.52

(1.32)

<0.001

17,460

4.64

(1.13)

4.68

(1.12)

4.74

(1.20)

4.84

(1.14)

4.89

(1.02)

<0.001

diabetes research and clinical practice 106 (2014) 145–153

147

Subjects Women Age (years) Coffee consumption (ml/day) Coffee additives Sugar/syrup (g/day) Creamer (g/day) Milk (g/day) Current smokers Alcohol consumption (n/week) Sleeping time (h/day) <7 7–8 >8 Physical activity MET-h/week <20 20–39 40 Income level Low Mid-low Mid-high High Education level Middle school graduation or less High school graduation College or more Metabolic bio-markers BMI (kg/m2) Waist circumference (cm) Fasting blood glucose (mmol/l) Triglyceride (mmol/l) Total cholesterol (mmol/l)

p-Value or p trenda

148

<0.001 <0.001 (19.2) (14.1) 114.6 76.5 (20.3) (14.2) 114.3 75.9

(0.35) 1.22 (0.39) 1.26

Mean or N (SD) or % Mean or N

Abbreviations: SD, standard deviation; MET, metabolic equivalent; BMI, body mass index; HDL, high-density lipoprotein. p-Value for categorical variable, and p trend for continuous variables. a

(19.1) (13.2) 113.3 74.6 (18.1) (14.3) 111.9 74.1 (19.4) (14.0) 112.1 73.8 17,920 17,920

(0.39) (0.42)

HDL-cholesterol (mmol/l) Systolic blood pressure (mm Hg) Diastolic blood pressure (mm Hg)

13,799

1.28

(0.37)

1.27

1.26

(SD) or % (SD) or % Mean or N

(SD) or %

Mean or N

Mean or N

1/day <1/week

N Table 1 (Continued )

the end of a normal expiration with each participant’s weight distributed equally on both feet. BP was measured in a sitting position following a 5-min rest period, and 3 repeated measurements were averaged for the analysis. The serum concentrations of glucose, cholesterol, and triglycerides were measured using a Hitachi automatic analyzer 7600 (Tokyo, Japan) at the Neodin Medical Institute in Korea. Metabolic syndrome was defined based on the National Cholesterol Education Program Adult Treatment Panel III (NCEP APT III) criteria [25] with a modified waist circumference cutoff for Asian population [24,26] as at least three of the following: (1) abdominal obesity: WC 90 cm for men and 80 cm for women; (2) high fasting glucose: FG 100 mg/dl (5.5 mmol/l); (3) hyper-triglyceridemia: triglyceride (TG) 150 mg/dl (1.7 mmol/l); (4) hypo-high-density lipoprotein (HDL) cholesterolemia: HDL <40 mg/dl (1.0 mmol/l) for men and <50 mg/dl (1.3 mmol/l) for women; and (5) hypertension (HTN): systolic blood pressure (SBP) 130 mm Hg or diastolic blood pressure (DBP) 85 mm Hg.

2.3.

1–6/week

Frequency of coffee consumption

2/day

3/day

(SD) or %

<0.001

p-Value or p trenda

diabetes research and clinical practice 106 (2014) 145–153

Statistical analysis

Statistical analyses were performed using survey procedures in SAS software (version 9.2, SAS institute Inc, Cary, NC, USA) in accordance with the KNHANES complex sampling design. Statistical significance was defined as a 2-sided p value of <0.05. We compared general characteristics according to the status and frequency of coffee consumption using chi-squared tests (for categorical variables) and ANOVA (for continuous variables). Odds ratios of abnormal metabolic risk factors and metabolic syndrome were estimated using multivariable logistic regression.

3.

Results

The characteristics of the study subjects are presented in Table 1, as stratified by the frequency of coffee consumption. Frequent coffee drinkers tended to be older, currently smoke, sleep less, consume more alcohol, and use more coffee additives, particularly sugar/syrup and powder creamer. In addition, the frequency of coffee consumption was associated with higher levels of BMI, WC, FG, TG, total cholesterol (Tchol), systolic blood pressure, and diastolic blood pressure. Frequent coffee consumption was also associated with lower levels of HDL. Approximately 76% of the study subjects were habitual coffee drinkers, most of whom consumed instant coffee (Table 2). Filtered-coffee drinkers were mostly women, and had higher income and education levels than instant-coffee drinkers or non-drinkers. In contrast, instant coffee consumption was more prevalent among older subjects, current smokers, and persons who frequently consumed alcohol. In addition, instant-coffee drinkers consumed substantially higher levels of sugar/syrup and powder creamer. We found that instant-coffee drinkers were more likely to have higher levels of BMI, WC, FG, TG, Tchol, and BP than filtered-coffee drinkers, but lower levels of HDL. We examined trends in coffee consumption according to age (Fig. 1). The percentage of filtered-coffee drinkers

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diabetes research and clinical practice 106 (2014) 145–153

Table 2 – General characteristics according to the type of coffee consumed. N

Type of coffee consumed Non-drinkers

Subjects Women Age (years) Coffee consumption (ml/day) Coffee additives Sugar/syrup (g/day) Creamer (g/day) Milk (g/day) Current smokers Alcohol consumption (n/week) Sleeping time (h/day) <7 7–8 >8 Physical activity MET-h/week <20 20–39 40 Income level Low Mid-low Mid-high High Education level Middle school graduation or less High school graduation College or more Metabolic bio-markers BMI (kg/m2) Waist circumference (cm) Fasting blood glucose (mmol/l) Triglyceride (mmol/l) Total cholesterol (mmol/l) HDL-cholesterol (mmol/l) Systolic blood pressure (mm Hg) Diastolic blood pressure (mm Hg)

13,313 13,313 13,313 13,313

13,313 13,313 13,313 12,304 13,189

Filtered-coffee drinkers

p-Value or p trenda Instant-coffee drinkers

Mean or N

(SD) or %

Mean or N

(SD) or %

Mean or N

(SD) or %

3152 2117 36.9 0

24 55 (17.4) (0)

580 444 36.0 371.9

5 69 (13.7) (326)

9581 5661 42.3 260.3

71 49 (16.3) (289)

<0.001 <0.001 <0.001

(8.75) (0.42) (17.7) 17 (1.35)

12.5 9.57 2.63 2238 1.01

(13.9) (10.5) (32.1) 33 (1.61)

<0.001 <0.001 <0.001 <0.001 <0.001

40 55 5

3606 5292 581

39 55 6

0.46 0.34 0.94 370 0.75

(2.73) (2.07) (15.8) 18 (1.35)

1.11 0.03 1.97 75 0.79

13,171

<0.001 1114 1656 350

34 55 12

223 320 29

12,113

0.4 1334 554 953

45 21 35

259 119 171

47 21 32

4071 1634 3018

46 19 35

811 738 806 740

28 25 25 23

77 104 164 225

16 18 30 36

2208 2457 2459 2335

24 26 26 24

828

19

46

6

2542

22

1273 1030

47 35

225 304

41 53

3782 3191

42 35

13,124

<0.001

13,221

13,252 13,260

<0.001

22.9 78.6

(4.38) (12.8)

23.2 77.7

(4.46) (12.2)

23.6 80.8

(4.22) (13.3)

<0.001 <0.001

12,950

5.01

(0.70)

5.00

(0.66)

5.13

(0.82)

<0.001

12,945 12,945

1.34 4.64

(1.55) (1.12)

1.20 4.66

(0.96) (1.09)

1.46 4.84

(1.46) (1.16)

<0.001 <0.001

10,124

1.28

(0.37)

1.33

(0.40)

1.24

(0.39)

<0.001

13,286

112.1

(19.5)

110.3

(16.5)

114.4

(22.5)

<0.001

13,286

73.8

(14.0)

73.7

(12.7)

75.8

(16.2)

<0.001

Abbreviations: SD, standard deviation; MET, metabolic equivalent; BMI, body mass index; HDL, high-density lipoprotein. p-Value for categorical variable, and p trend for continuous variables.

a

increased over time and was higher among younger subjects in all survey years. In contrast, young subjects tended to consume less instant coffee, and the percentage of young instant-coffee drinkers decreased over time. Table 3 includes adjusted odds ratio (OR) for obesity, abnormal metabolic risk factors, and MetSyn according to the frequency of coffee consumption. We observed that subjects who consumed coffee 3 times/day had significantly higher odds of obesity (OR 1.28, Confidence Interval [CI] 1.09–1.50),

abdominal obesity (OR 1.24, CI 1.05–1.40), hypo-HDL-cholesterolemia (OR 1.18, CI 1.02–1.37), and MetSyn (OR 1.25, CI 1.02– 1.53) than those who consumed coffee <1 time/day in multivariable models, adjusting for age, sex, smoking, physical activity, alcohol, total energy, education, and income. A multivariable analysis of coffee consumption status indicated that instant-coffee drinkers had significantly higher risks of obesity (OR, 1.29; 95% CI, 1.11–1.47), abdominal obesity (OR, 1.18; 95% CI, 1.01–1.36), hypo-HDL-cholesterolemia (OR,

150

diabetes research and clinical practice 106 (2014) 145–153

Fig. 1 – Trends in (A) the percentage of filtered-coffee drinkers and (B) the percentage of instant-coffee drinkers among all study subjects, according to age and survey years, 2007–2011.

1.19; 95% CI, 1.04–1.30), and MetSyn (OR, 1.21; 95% CI, 1.02–1.43) than non-drinkers. However, filtered-coffee drinkers were not observed to be at a statistically significant excess risk for any of these markers or conditions, including MetSyn (Table 4).

4.

Discussion

In this examination of coffee consumption in Korean adults aged 19–65 years, coffee prepared using a coffee mix (containing sugar and powder creamer) was the most frequently consumed type of coffee. A high coffee consumption was associated with higher risks of obesity, abdominal obesity, hypo-HDL-cholesterolemia, and MetSyn. Because most coffee drinkers specifically consumed instant coffee, we examined the associations between metabolic risk factors and the type of coffee that was consumed. We found that instant-coffee drinkers were more likely to have obesity, abdominal obesity, hypo-HDL-cholesterolemia, and MetSyn than non-drinkers. However, we did not observe any adverse markers or

conditions that were significantly associated with the consumption of filtered coffee. Several previous studies have shown that coffee consumption is not associated with greater obesity indexes, such as increased BMI or WC [27,28]. The 2003–2004 United States National Health and Nutrition Examination Survey (NHANES) data indicated that the frequency of coffee consumption was not associated with BMI or WC in crude or adjusted analyses for demographic, lifestyle, and dietary factors [27]. Similar results were observed in the Amsterdam Growth and Health Longitudinal Study, which reported that frequent coffee consumption among persons aged 27–42 years was not related to WC in either crude or multivariable analyses [28]. However, positive associations between coffee consumption and BMI have been reported in other studies [29–31]. In our study, frequent instant-coffee drinkers had higher BMI and WC than non-drinkers, suggesting that they may be at risk for general obesity as well as abdominal obesity. This observed association may be, in part, due to excessive calorie intake from the added sugar and creamer in their instant coffee, but our

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Table 3 – Crude and adjusted odds ratio (95% CI) for metabolic biomarker levels and metabolic syndrome by the frequency of coffee consumption. Frequency of coffee consumption <1/week

1–6/week

1/day

2/day

3/day

Obesity [BMI  23] 1 1.29 (1.10–1.51) 1.26 (1.10–1.45) 1.25 (1.09–1.45) Age and sex-adjusted Multivariable model 1 1.40 (1.18–1.66) 1.32 (1.13–1.54) 1.30 (1.11–1.52) Abdominal obesity [WC 90 cm for men and 80 cm for women] 1 1.20 (1.04–1.40) 1.15 (1.00–1.32) 1.09 (0.95–1.25) Age and sex-adjusted 1 1.22 (1.03–1.45) 1.18 (1.02–1.38) 1.10 (0.93–1.30) Multivariable model High fasting glucose [FG 100 mg/dl (5.5 mmol/l)] 1 1.10 (0.91–1.34) 1.17 (0.98–1.40) 1.19 (1.00–1.40) Age and sex-adjusted 1 1.05 (0.85–1.31) 1.10 (0.91–1.33) 1.12 (0.92–1.36) Multivariable model Hyper-triglyceridemia [TG 150 mg/dl (1.7 mmol/l)] 1 1.05 (0.89–1.24) 1.12 (0.96–1.30) 0.96 (0.83–1.11) Age and sex-adjusted 1 1.01 (0.85–1.21) 1.06 (0.89–1.25) 0.96 (0.82–1.13) Multivariable model Hypo-HDL cholesterolemia [HDL <40 mg/dl (1.0 mmol/l) for men and <50 mg/dl (1.3 mmol/l) for women] 1 1.05 (0.91–1.20) 1.15 (1.01–1.31) 1.07 (0.93–1.22) Age and sex-adjusted 1 1.05 (0.90–1.22) 1.18 (1.02–1.37) 1.13 (0.97–1.32) Multivariable model Hypertension [SBP 130 mmHg or DBP 85 mmHg] 1 1.06 (0.87–1.30) 1.14 (0.95–1.36) 1.09 (0.90–1.30) Age and sex-adjusted Multivariable model 1 1.17 (0.94–1.47) 1.17 (0.96–1.43) 1.13 (0.92–1.40) Metabolic syndrome 1 1.09 (0.89–1.32) 1.23 (1.04–1.44) 1.16 (0.98–1.36) Age and sex-adjusted 1 1.11 (0.90–1.38) 1.28 (1.07–1.53) 1.23 (1.02–1.49) Multivariable model

1.22 (1.06–1.40) 1.28 (1.09–1.50) 1.19 (1.03–1.37) 1.24 (1.05–1.40) 1.12 (0.93–1.33) 1.05 (0.86–1.29) 1.09 (0.94–1.26) 1.00 (0.84–1.18) 1.12 (0.97–1.28) 1.18 (1.02–1.37) 0.95 (0.78–1.15) 1.07 (0.86–1.34) 1.22 (1.01–1.46) 1.25 (1.02–1.53)

Abbreviations: CI, confidence interval; BMI, body mass index; WC, waist circumference; FG, fasting glucose; TG, triglyceride; HDL, high-density lipoprotein; SBP, systolic blood pressure; DBP, diastolic blood pressure. Multivariable models: adjusted for age, sex, smoking status, physical activity, alcohol, total energy, education, and income.

Table 4 – Crude and adjusted odds ratio (95% CI) for metabolic biomarker levels and metabolic syndrome by type of coffee consumed. Type of coffee consumed Non-drinkers

Filtered-coffee drinkers

Obesity [BMI  23] 1 1.25 (0.95–1.65) Age and sex-adjusted Multivariable model 1 1.28 (0.95–1.72) Abdominal obesity [WC 90 cm for men and 80 cm for women] 1 0.98 (0.73–1.31) Age and sex-adjusted 1 1.04 (0.76–1.44) Multivariable model High fasting glucose [FG 100 mg/dl (5.5 mmol/l)] 1 1.18 (0.80–1.73) Age and sex-adjusted 1 1.19 (0.78–1.83) Multivariable model Hyper-triglyceridemia [TG 150 mg/dl (1.7 mmol/l)] Age and sex-adjusted 1 0.83 (0.58–1.21) 1 0.84 (0.55–1.26) Multivariable model Hypo-HDL cholesterolemia [HDL <40 mg/dl (1.0 mmol/l) for men and <50 mg/dl (1.3 mmol/l) for women] 1 0.94 (0.72–1.22) Age and sex-adjusted 1 0.97 (0.71–1.32) Multivariable model Hypertension [SBP 130 mmHg or DBP 85 mmHg] 1 0.93 (0.66–1.33) Age and sex-adjusted Multivariable model 1 1.09 (0.72–1.64) Metabolic syndrome 1 1.15 (0.78–1.71) Age and sex-adjusted 1 1.15 (0.76–1.78) Multivariable model

Instant-coffee drinkers 1.23 (1.08–1.39) 1.29 (1.11–1.47) 1.14 (1.01–1.29) 1.18 (1.01–1.36) 1.14 (0.98–1.33) 1.11 (0.93–1.33) 1.03 (0.90–1.17) 0.98 (0.85–1.13) 1.11 (0.99–1.25) 1.19 (1.04–1.30) 1.03 (0.88–1.21) 1.09 (0.90–1.31) 1.15 (0.99–1.33) 1.21 (1.02–1.43)

Abbreviations: CI, confidence interval; BMI, body mass index; WC, waist circumference; FG, fasting glucose; TG, triglyceride; HDL, high-density lipoprotein; SBP, systolic blood pressure; DBP, diastolic blood pressure. Multivariable model: adjusted for age, sex, smoking status, physical activity, alcohol, total energy, education, and income.

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results showed that this association was still evident when controlling for coffee additives and total energy intake. The possibility of residual confounding cannot be completely excluded, and further studies are thus warranted. The use of coffee additives should be considered when analyzing the effects of coffee consumption on lipid profiles. Our findings suggest that instant-coffee drinkers had lower levels of HDL-cholesterol than non-drinkers. Instant-coffee drinkers also tended to consume higher levels of coffee additives, which may explain their lower levels of HDLcholesterol. Indeed, high dietary sugar intake leads to a high glycemic index, which decreases HDL-cholesterol levels by impairing insulin sensitivity [32]. The high levels of saturated fat in powder creamer have raised concerns. Recently, Lee et al. [33] analyzed the proportions of total fat and saturated fat in 14 different powder creamer products and 11 instant coffee mixes that are available in the South Korean market. They reported that saturated fat levels were markedly high in all the tested products, potentially because of ingredients derived from coconut oil or palm kernel oil. Higher intake of saturated fatty acids has been linked to a decrease in the anti-inflammatory properties of HDL in the human body [34]. Although a variety of studies have consistently shown that coffee consumption is inversely associated with type 2 diabetes mellitus [7–12,29], only a limited number of studies have investigated the relationship between coffee consumption and MetSyn. The results of 3 cross-sectional studies showed that higher coffee consumption was associated with a lower risk of prevalent MetSyn among Japanese adults [35–37]. In 2 cohort studies conducted in the United States and Europe, no significant associations were found between long-term coffee consumption and risk of MetSyn [38,39]. In our study, we found that habitual intake of coffee, mostly in the form of instant coffee mixes, is positively associated with the risk of prevalent MetSyn. The major limitation of this study is its cross-sectional design. Because exposure and outcome information were assessed simultaneously, the direction of causality cannot be determined from our findings. However, we tried to minimize reverse causation bias by excluding those subjects with myocardial infarction, angina pectoris, stroke, and diabetes, as well as those taking medications related to these conditions. A second limitation to this study was the use of a single 24-h recall to estimate consumption of coffee additives, which may have resulted in underestimation of consumption. However, for those who drank coffee at least daily, the 24-h recall was likely both representative of typical behavior and correct. A third limitation to the present study was its observational design, which may have resulted in residual confounding. Because we used nationally representative survey data, our findings are directly applicable to most healthy Korean adults. Coffee mix was found to be the most frequently consumed type of coffee in the Korean population free of CVD and diabetes. This unique consumption pattern may explain the discrepancies between our findings and the results of previous studies. Although previous studies have identified associations between greater coffee consumption and lower risk of metabolic risk factors and MetSyn, these previous studies considered populations that primarily consumed filtered coffee.

In summary, we found that the consumption of instant coffee with sugar and powder creamer may be associated with higher risks of obesity, abdominal obesity, hypo-HDL-cholesterolemia, and MetSyn. Our findings suggest that the association between coffee intake and metabolic health may differ according to the type of coffee consumed and the coffee additives that are used. As much research suggests that there is an inverse association between coffee consumption and MetSyn or type 2 diabetes, we do not exclude the possibility that coffee intake may provide a benefit. However, the direction could be shifted toward harm in those with high consumption of instant coffee mix containing sugar and powder creamer, such as in the Korean population. Further observational studies and randomized trials are required to fully identify the health benefits and risks of different types of coffee.

Conflict of interest None of the authors have financial or personal conflicts of interest

Acknowledgements This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2012R1A1A1009214).

Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at http://dx.doi.org/10.1016/j.diabres.2014.07.007.

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