251

Atherosclerosis, 83 (1990) 257-261 Elsevier Scientific Publishers Ireland,

ATHERO

Ltd.

04513

Dose-dependent concentrations

effect on serum cholesterol and apoprotein B by consumption of boiled, non-filtered coffee

Antti Aro I, Juha Teirilti 2 and Carl-Gustav

Gref 1

’Department of Biochemistry

National Public Health Institute, Mannerhermintie 166, SF-00300 Helsinki (F&znd), .’Occupational Health Service of Finnish Co-operative Wholesale Society, Helsinki (Finland) (Received 27 December, 1989) (Revised, received 18 April, 1990) (Accepted 26 April, 1990)

Summary The effects of boiled coffee (BC) and filtered coffee (FC) on serum lipoproteins were compared in 41 healthy subjects whose serum cholesterol concentration was less than 7 mmol/l. The subjects consumed in random order BC and FC for 4-week periods in a crossover design. The individual daily consumption ranged from 2 to 14 cups (mean 5.7 cups per day) and was similar during both study periods. The serum total and LDL-cholesterol and apoprotein B concentrations were higher (P < 0.001) and HDL-cholesterol lower (P < 0.05) after BC than after FC. Bodyweight, apoprotein A-I and triglycerides remained unchanged. In the 16 subjects who consumed coffee < 5 cups per day the difference in serum total cholesterol between the BC and FC periods was non-significant (P = 0.16). The differences in serum total cholesterol and LDL-cholesterol between the periods showed significant linear correlations with the but no amount of coffee consumed daily (r = 0.52, P < 0.001and r = 0.33, P -c0.05, respectively) association was found between the difference in HDL-cholesterol and the amount of coffee (r = 0.14, P = 0.39). The results indicate a dose-dependent increasing effect on serum total and LDL-cholesterol and apoprotein B concentrations of boiled coffee.

Key words:

Coffee;

Serum apoproteins;

Serum cholesterol;

Introduction In several epidemiological studies a positive statistical association has been found between the consumption of coffee and serum cholesterol con-

Correspondence to: Antti Aro, MD, National Public Health Institute, Mannerheimintie 166, SF-00300 Helsinki, Finland. 0021-9150/90/$03.50

0 1990 Elsevier Scientific

Publishers

Ireland,

Serum lipoproteins

centration [l]. This association is probably the result of the combined effects of coffee itself and associated dietary factors like saturated fat intake [1,2]. In Norway and Finland it is confined to people who drink traditional boiled coffee [3,4] while the consumption of filtered coffee shows no association with serum cholesterol. Boiled coffee increases the serum cholesterol concentration of hypercholesterolaemic subjects [5,6], due to an Ltd.

258 effect on low-density lipoprotein (LDL) concentration [6]. The effect has also been confirmed recently in a group of normocholesterolaemic Dutch subjects [7]. The present study was conducted in order to evaluate the effects of boiled coffee in normocholesterolaemic people and to find out whether the effect is dependent on the amount of coffee ingested. Material and Methods Subjects The subjects were healthy people aged 23-61 years (median 45 years), employed by the Finnish Co-operative Wholesale Society in Helsinki. Subjects on drug therapy or with a serum cholesterol concentration of 7 mmol/l or greater were excluded. Forty-one subjects (13 men, 28 women) were selected from volunteers to participate in the study. They were regular coffee drinkers, and their habitual daily coffee consumption ranged from 2 to 14 cups (mean 5.7 cups per day). The majority consumed filtered coffee, only four subjects drank boiled coffee habitually. Study design The study included two 4-week periods separated by a 2-week “free” period. The subjects were randomly allocated into two groups. Group A (20 subjects) consumed boiled coffee only during the first period and filtered coffee only during the second period. Group B (21 subjects) consumed first filtered coffee and then boiled coffee.

The participants were told only to change the brewing method and to keep the amount of consumed coffee unchanged. During the intervening 2-week period habitual coffee consumption was allowed. The subjects were advised not to change their dietary habits during the study. The study protocol was approved by the Ethical Committee of the National Public Health Institute. During the study periods the subjects kept daily records on the amount and type of coffee consumed. The subjects visited the clinic at 2-week intervals for fasting venous blood samples and weighing and for filling out a questionnaire about the use of milk products and fat spreads during the previous 2-week period. Boiled coffee was prepared by mixing ground coffee with boiling water and reheating it to boiling. The coffee was then taken off the heat, and the grounds were allowed to settle for 5-10 min. Filtered coffee was prepared by pouring hot water over coffee and filtering it through paper. The coffee preparations, provided by the investigators, were of similar blend and roasting. The coffee for boiling was more coarsely ground than that for filtering. A standard spoonful (about 7 g) of ground coffee per cup was used for brewing during both periods. Assay methods Cholesterol and triglycerides were analyzed by automated enzymatic methods (kits from Boehringer-Mannheim GmbH, F.R.G.), HDL-cholesterol after precipitation with dextran sulphate and magnesium chloride [8]. LDL-cholesterol was

TABLE 1 SERUM LIPID AND APOLIPOPROTEIN

LEVELS AT THE END OF THE 4-WEEK STUDY

PERIODS

Values are means f SEM All subjects (n = 41) Coffee: Serum cholesterol (mmol/l) LDL cholesterol HDL cholesterol Serum triglycerides (mrnol/l) Serum apo B (g/l) Serum apo A-I (g/l)

Boiled 5.80 +0.15 3.78 f 0.14 1.45+0.05 1.24+0.12 1.17*0.05 1.81 f 0.04

*** *** * ***

> 5 cups/d

(n = 25)

< 5 cups/d (n = 16)

Filtered

Boiled

Filtered

Boiled

Filtered

5.48kO.12 3.46 * 0.12 1.52 + 0.05 1.08 + 0.09 1.04 + 0.04 1.82 5 0.04

5.87kO.19 *** 3.8950.18 ** 1.40 f 0.06 1.27 * 0.18 1.21+0.06 ** 1.77 + 0.05

5.43+0.14 3.50+0.13 1.45 * 0.05 1.05 kO.10 1.06 + 0.05 1.78 k 0.05

5.70 + 0.26 3.62 + 0.24 * 1.53 * 0.08 * 1.19io.14 l.lOkO.08 * 1.86 f 0.07

5.54+0.22 3.40 + 0.32 1.64+0.10 1.11 kO.16 1.00*0.08 1.90 f 0.07

* * * P < 0.001; * * P < 0.01; * P c 0.05 boiled vs. filtered coffee (paired f-test).

259 calculated by the formula of Friedewald et al. [9]. Apoproteins A-I and B were determined by immunoturbidometric methods (kits of Orion Diagnostica, Espoo, Finland) as described previously

(mmol/l) 6.5 TOTAL

CHOLESTEROL

6-

VI. Student’s t-test for paired samples and linear regression analysis were used for the statistical analysis of the results by SAS software. The results are given as the mean + SEM. Results When comparing the results recorded at the end of the study periods serum total cholesterol, LDL-cholesterol and apoprotein B concentrations were significantly higher when boiled coffee was consumed (Table 1). Serum HDL-cholesterol was lower during the boiled coffee period than during the filtered coffee period. When the subjects were allocated into two groups according to the level of coffee consumption, those who consumed less than 5 cups of coffee daily showed less significant differences, and the difference in serum total cholesterol remained statistically non-significant. However, the difference in HDL-cholesterol was statistically significant only for the subjects with low coffee consumption whereas the subjects who consumed > 5 cups per day showed no significant difference (Table 1). Serum triglyceride and apoprotein A-I concentrations remained unchanged during the study. The serum total cholesterol and LDLcholesterol values are given separately for the two groups in Fig. 1. There was a tendency to increased values during consumption of boiled coffee independently of the order of the periods. As most subjects habitually consumed filtered coffee there seemed to be no difference between the filtered coffee periods and the background on habitual coffee consumption. The difference in serum total cholesterol concentrations between the boiled coffee and filtered coffee periods showed a highly significant linear correlation with the number of cups consumed daily (r = 0.52, P < 0.001, Fig. 2). Also the difference in LDL-cholesterol was associated with the amount of coffee (Y = 0.33, P -c 0.05). The association between the difference in serum apoprotein B and the amount of coffee consumed

5.5 -

5-

4.5 LDL-CHOLESTEROL 4-

3.5 -

3PERIOD

1

PERIOD

2

?

I

0

2

4 Time (reeks)

6

6

10

Fig. 1. Serum total cholesterol and LDL-cholesterol values (mean and SEM) during the study periods. 0, o = group A, A, A = group B. Closed symbols represent boiled coffee and open symbols filtered coffee.

during the boiled coffee period was less evident (r = 0.27, P = 0.09), and no apparent association was found between the difference in HDLcholesterol and the amount of coffee (r = 0.14, P = 0.39). No associations were found between (cups/d) 16 . 14

r - 0.52

a

.

6

.

4

.

.

?? :

0.

.

se ..,:

‘.*1

?? m

‘0 ??

-0.6

0

CHOLESTEROL

.

.

?? e I

0’

-1

.

??

0.5

I

I

,

1

1.6

2

DIFFERENCE

(mmol/l)

Fig. 2. The correlation between the difference in serum total cholesterol concentrations at the end of the study periods (boiled/filtered coffee) and the amount of coffee consumed.

260 the age of the subjects and coffee consumption or the differences in serum lipoprotein lipids between the periods. The mean body weight of the subjects was the same, 69.9 kg, during both study periods. According to the daily records the coffee consumption was 5.5 f 0.3 cups during the boiled coffee period and 5.8 & 0.3 cups during the filtered coffee period (difference n.s.). None of the subjects reported changes in the quality of milk products and fat spreads consumed during the study. No detailed food records were obtained. Discussion The results confirm the findings of previous studies in hypercholesterolaemic subjects [5,6] and show that the effects of boiled coffee on serum LDL are evident even in persons with normal serum cholesterol levels. As our previous study showed no significant effects on serum lipids by filtered coffee [6] we used filtered coffee as the reference preparation in the present study. The effects of boiled coffee on serum total cholesterol and LDL-cholesterol concentrations were clearly dose-dependent. A statistically highly significant linear correlation was found between the amount of coffee consumed and the change in serum total cholesterol. Accordingly, the effect was most marked in those with the highest coffee consumption. The small but statistically significant difference in serum HDL-cholesterol concentration between the study periods was probably not related to the quality of coffee, since the difference showed no correlation with the amount of coffee consumed. On the contrary, the difference was most marked in the subjects who consumed least coffee. One woman consumed between 14 and 15 cups of coffee daily during both study periods. Her serum total cholesterol concentration was 1.8 mmol/l higher after the boiled coffee period as compared with the filtered coffee period (Fig. 2) whereas the difference in apoprotein B concentration was considerably smaller, 0.29 g/l. If her results are excluded from the statistical analysis, the correlations between the amount of coffee and the lipid values become less marked: r = 0.34 (P = 0.03) for total cholesterol, r = 0.16 (P = 0.31)

for LDL-cholesterol, and r = 0.23 (P = 0.15) for apoprotein B. Thus the results of this subject with particularly high coffee consumption have important effects on the observed correlations, but the correlation between the amount of coffee and the difference in serum total cholesterol concentration remained statistically significant even after exclusion of this one outlier. Either the higher temperature used for the preparation of boiled coffee or the filtering through paper remain possible factors which may explain the difference between filtered coffee and coffee made by boiling [5,6]. Bak et al. [7] recently reported that coffee which was prepared by mixing boiling water and coffee and which was consumed without filtering also increased the serum cholesterol concentration. As this type of coffee is not boiled in the same way as it is done in Scandinavia [5,6] and as it was done in the present study, it is possible that boiling is not essential for the hypercholesterolaemic effect but rather that the hypercholesterolaemic factor is retained by the paper filter. The effect of boiled coffee on serum cholesterol concentration was 0.3-0.4 mmol/l at the level of mean consumption which is exactly in accordance with the results of a recent epidemiological survey in Finland [4]. It has been estimated that substituting filtered coffee for the traditional boiled coffee has probably made an important contribution to the decline of mean serum cholesterol concentration which has occurred in the Finnish population since the 1960s [lo]. In conclusion, the present results together with earlier observations confirm that boiled coffee which is prepared without filtering contains a factor which has a dose-dependent increasing effect on serum low-density lipoprotein concentration. Acknowledgement Supported Foundation,

by a grant from the Food Helsinki (Finland).

Research

References 1 Thelle, D.S., Heyden, S. and Fodor, J.G., Coffee and cholesterol in epidemiological and experimental studies. Atherosclerosis, 67 (1987) 97.

261 2 Aro.

3

4

5

6

A., Pietinen, P., Uusitalo, U. and Tuomilehto, J., Coffee and tea consumption, dietary fat intake and serum cholesterol concentration of Finnish men and women. Arch. Intern. Med.. 226 (1989) 127. Bonaa. K., Amesen, E., Thelle, D.S. and Forde, O.H.. Coffee and cholesterol: is it all in the brewing? The Tromso Study. Br. Med. J., 297 (1988) 1103. Pietinen, P., Aro, A., Tuomilehto, J., Uusitalo, U. and Korhonen, H.. Consumption of boiled coffee is correlated with serum cholesterol in Finland. Int. J. Epidemiol., (1990) in press. Forde, O.H., Knutsen, SF., Amesen, E. and Thelle, D.S.. The Tromso Heart Study. Coffee consumption and serum lipid concentration in men with hypercholesterolaemia. A randomized intervention study. Br. Med. J., 290 (1985) 893. Aro, A., Tuomilehto, J., Kostiainen, E., Uusitalo, U. and Pietinen, P., Boiled coffee increases serum low density lipoprotein concentration. Metabolism, 36 (1987) 1027.

7 Bak, A.A.A. and Grobbee, D.E., The effect on serum cholesterol levels of coffee brewed by filtering or boiling. N. Engl. J. Med., (1989) 1432. 8 Kostner, G.M., Enzymatic determination of cholesterol in high density lipoprotein fractions prepared by polyanion precipitation. Clin. Chem., 22 (1976) 695. 9 Friedewald, F.T.. Levy, R.I. and Fredrickson, D.S.. Estimation of the concentration of low density lipoprotein cholesterol in plasma without use of the preparative ultracentrifuge. Clin. Chem., 18 (1972) 499. 10 Aro. A.. Serum cholesterol levels in Finland and their relationship to coffee brewing methods. In: D. Thelle (Ed.), Workshop on coffee and coronary heart disease with special emphasis on the coffee - blood lipids relationship. Proceedings, Nordic School of Pubhc Health. Gliteborg. 1990, in press.

Dose-dependent effect on serum cholesterol and apoprotein B concentrations by consumption of boiled, non-filtered coffee.

The effects of boiled coffee (BC) and filtered coffee (FC) on serum lipoproteins were compared in 41 healthy subjects whose serum cholesterol concentr...
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