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The effect of coffee and caffeine consumption on serum lipids in rats.N. Rakicioglu, G.
Pekcan and A. Cevik. International Journal of Food Sciences and Nutrition
1998): p441(1). (3575 words)
Coronary heart disease research confirms that coffee alone is not a significant risk factor. Laboratory rats were fed controlled diets with varying levels of coffee, caffeine and cholesterol. Findings revealed no correlation between cholesterol levels and coffee on blood lipids; however, the addition of coffee to a diet already high in cholesterol had a marked effect on serum total cholesterol.
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This study was carried out on the male adult Wistar-Albino rats in order to investigate the effects of coffee and caffeine consumption on serum lipids in atherogenic and normal diets. Fifty rats were divided into five groups and each group was fed with the following diets: first group was a control group and fed with the standard chow diet, coffee, caffeine, cholesterol and cholesterol plus coffee were added to second, third, fourth, and fifth groups, respectively. The results indicated that the consumption of coffee alone had no effect on serum lipids. However the addition of coffee to a hypercholesterolemic diet significantly increased the effect on serum total cholesterol (P [is less than] 0.01), triglycerides (P [is less than] 0.05), VLDL-cholesterol (P [is less than] 0.05), LDL-cholesterol (P [is less than] 0.01), and HDL-cholesterol (P [is less than] 0.01) levels. Adding caffeine to normal diet resulted in an increase in serum total cholesterol (P [is less than] 0.01). Despite these increases, the ratio of HDL-cholesterol to total cholesterol and LDL-cholesterol remained unchanged. The results indicated that coffee could not be considered alone as a risk factor for coronary heart disease.
Coffee is a widely consumed and socially accepted drink all over the world. In recent years, in Turkey, the consumption of instant coffee has increased to the level of traditional Turkish Coffee. Caffeine, which is one of the active substances in coffee, is found not only in tea but also in cacao, chocolate, carbonated beverages and in medical drugs (Gilbert et al., 1976; Anon. 1988; Schreiber et al., 1988). Coffee enhances urine production and gastric secretion. Coffee and its main constituent, caffeine, is perhaps best known as a stimulant of the central nervous system (CNS); certain aspects of this action include the abatement of drowsiness and fatigue, and changes in appetite (Curatolo & Robertson, 1983). In recent years the studies have focused on the effect of coffee and caffeine on cardiovascular diseases. Many researchers have studied the effect of various dietary components on the levels and distribution of plasma lipids. Alcohol, high fat consumption, and heavy smoking are conflicting factors complicating the interpretation of the results of the studies (Klatsky et al., 1990; Trompson et al., 1992). Although many factors take part in the etiology of coronary heart disease (CHD), no factor had an effect alone. The present study was therefore intended to assess the effect of dietary coffee and caffeine consumption on serum lipids, including total cholesterol, triglycerides, VLDL-cholesterol, LDL-cholesterol, and HDL-cholesterol, in the male Wistar-Albino rats.
Adult male Wistar-Albino 10-week-old rats were housed in wire cages under identical conditions at constant temperature (21 [degrees] C [+ or -] 1). All diets and water were given ad libitum every
day. The body weights and food intake of the animals were recorded daily, and the mean food intake was assessed during the study. At the end of the fourth week, the animals were anesthetised with ether after overnight fasting. Blood was collected from the heart for the analysis.
Fifty male Wistar-Albino rats were divided into five groups as described below.
Group 1 (Control Group) The animals consumed only commercial standard rat chow. The standard rat chow (g/100g) included protein, sugar, fat, and cellulose, 15.5, 8.3, 2.5 and 7.7%, respectively. The diet (100g) also contained [Beta]-carotene (0.01 mg), vitamin A (1785 IU), vitamin E (11.2mg) vitamin [B.sub.6] (0.8mg), selenium (0.01 mg) and zinc (11.4 mg).
Group 2 (Coffee) Coffee was added to the standard chow in the amount of 5 g/100 g diet. The amount of coffee added to the chow diet was estimated as equivalent to about 12 cups for a 70 kg man and based on an intake of 15-16 g of diet/day by a 220 g rat (mean weight after 30 days on diet). Metabolic weight ([kilogram.sup.0.75]) was calculated from the formula directly in proportion to body weight (Akinyanju & Yudkin, 1967; Naismith et al., 1969; Spiller, 1984). One cup (200-250 mL) of beverage contained 4.5-5 g coffee solids.
Group 3 (Caffeine) Caffeine was added as 120 mg/100 g diet. The amount of caffeine added to the diet was equivalent to about 12 cups of coffee content. Nescafe soluble coffee as the caffeine source in the synthetic diet was used in the present study. Caffeine analysis revealed that the caffeine content of the coffee was found to be 2.4g/100g coffee.
Group 4 (Cholesterol) To have a hypercholesterolemic diet, cholesterol (1 g/100g diet) and cholic acid (0.2 g/100 g diet) were added to the synthetic diet.
Group 5 (Cholesterol plus coffee) Coffee (5 g coffee/100g hypercholesterolemic diet) was added to the diet of Group 4.
The experimental stock diet was prepared for each group. The additions were made to standard rat chow diet (Group 1). All synthetic diets were prepared daily and were given to rats on the next day.
At the end of four weeks, blood was collected and centrifuged at 3500 rpm at 20 [degrees] C for 15 min and the serums were separated. Serum lipid concentrations were determined by a spectrophotometric method using a commercially available Randox Kit (Sannenwirth & Jarett, 1980).
Data for serum lipids and food consumptions were analysed using Student's t-test (Sumbuloglu & Sumbuloglu, 1994). All data was given as mean [+ or -] standard error of the mean (SEM). A significant level (P value) of 5% was used unless stated otherwise.
Table 1 summarizes the mean food intake of rats according to weeks. It appeared that the mean food intakes were significantly different in all groups with the exception of coffee (Group 2) and cholesterol plus coffee groups (Group 5) (P [is less than] 0.01). Differences in food consumption were also observed within the groups (Table 1). At the end of the feeding period the food intake was found to be the highest in Group 4. Caffeine consumption appeared to be less in Group 2 than in Group 3. At the end of the study, animals in Group 2 and Group 3 consumed 6052g food/30d (24.2mg caffeine/d) and 6922 g food/30d (27.7 mg caffeine/d), respectively. The caffeine intake was also found to be 24.8 mg/d in the Group 5.
Table 1. Mean food consumption in rats (g/day)(1, 2)
Weeks (g/day) Groups First Second Group 1 17.89 [+ or -] 0.52 19.96 [+ or -] 0.36 Group 2 19.44 [+ or -] 1.73 22.14 [+ or -] 0.56 Group 3 22.56 [+ or -] 0.72 25.11 [+ or -] 1.20 Group 4 24.07 [+ or -] 0.49 27.94 [+ or -] 0.43 Group 5 21.69 [+ or -] 0.90 22.07 [+ or -] 0.73 Weeks (g/day) Groups Third Fourth Group 1 18.85 [+ or -] 0.64 19.64 [+ or -] 0.30 Group 2 20.92 [+ or -] 0.63 19.63 [+ or -] 0.72 Group 3 23.74 [+ or -] 0.82 24.35 [+ or -] 0.61 Group 4 26.20 [+ or -] 0.36 24.71 [+ or -] 0.61 Group 5 21.07 [+ or -] 0.38 20.58 [+ or -] 0.51 Mead food consumption Groups (g/day) Group 1 19.01 [+ or -] [0.24.sup.a] Group 2 20.22 [+ or -] [0.34.sup.be] Group 3 23.57 [+ or -] [0.44.sup.c] Group 4 25.19 [+ or -] [0.37.sup.d] Group 5 20.86 [+ or -] [0.38.sup.e]
(2) Values on the same row not sharing the same superscript letters were significantly different (P < 0.05).
The animals were of similar weights, in a range between 160-164g at the beginning of the feeding period (Table 2). Animals grew well on all the synthetic diets over the period of 4 weeks. The food consumption and body weights were found to be less in Group 5 than Groups 3 and 4 (P [is less than] 0.01 for both) (Tables 1 and 2). It should be noted that the weight gain appeared to be affected by the diet. Coffee (Group 2) and cholesterol plus coffee (Group 5) lowered the final body weight, and consequently the total weight gain (g) and weight gain (%). In spite of more food consumption, the weight gain was found to be less in Group 5 than Group 1 (Tables 1 and 2).
Table 2. Mean weight and weight gain in rats(1, 2) Initial body Final body Groups weight (g) weight (g) Group 1 160.5 [+ or -] 1.71 220.0 [+ or -] 4.73 Group 2 163.8 [+ or -] 2.25 204.0 [+ or -] 8.45 Group 3 160.5 [+ or -] 3.00 225.4 [+ or -] 7.74 Group 4 162.4 [+ or -] 3.49 223.5 [+ or -] 8.47 Group 5 162.4 [+ or -] 3.32 191.6 [+ or -] 7.6 Total weight Groups gain (g) Weight gain (%) Group 1 59.5 [+ or -] [4.84.sup.ab] 37.18 [+ or -] [3.15.sup.ab] Group 2 40.2 [+ or -] [8.68.sup.ac] 24.74 [+ or -] [5.39.sup.ac] Group 3 64.9 [+ or -] [6.24.sup.ab] 40.34 [+ or -] [3.79.sup.ab] Group 4 61.7 [+ or -] [7.05.sup.ab] 37.89 [+ or -] [4.15.sup.ab] Group 5 29.2 [+ or -] [6.05.sup.c] 17.87 [+ or -] [3.64.sup.c]
(2) Values on the same row not sharing the same superscript letters were significantly different (P
The serum lipid levels of rats are given in Table 3. Serum total cholesterol levels were found to be higher in Group 3 (P [is less than] 0.05), Group 4 (P [is less than] 0.05), and Group 5 (P [is less than] 0.01) than the control group (Group 1). The addition of coffee plus cholesterol to the diet increased the serum total cholesterol level compared to Group 2 (P [is less than] 0.01), Group 3 (P [is less than] 0.05), and Group 4 (P [is less than] 0.01). Addition of coffee to the hypercholesterolemic diet increased the levels of serum triglycerides and VLDL-cholesterol (P [is less than] 0.05 for both). The triglycerides and VLDL-cholesterol levels were 63.44 [+ or -] 6.73 mg/dL and 12.69 [+ or -] 1.34 mg/dL in Group 1, 85.82 [+ or -] 7.87 mg/dL and 17.17 [+ or -] 1.57 mg/dL in Group 5, respectively. LDL-cholesterol was found to be significantly higher in Group 5 than Group 1 (P [is less than] 0.01), and Group 2 (P [is less than] 0.05). HDL-cholesterol level in Group 5 was higher than all of the other groups (P [is less than] 0.01). There were no statistically significant differences in the ratios of HDL-cholesterol to total cholesterol or HDL-cholesterol to LDL-cholesterol.
[TABULAR DATA 3 NOT REPRODUCIBLE IN ASCII]
In the present study, the addition of 12 cups of coffee to the control diet had no significant effect on serum lipids. However, it should be noted that the addition of coffee to hypercholesterolemic diet (Group 5) resulted in an increase in serum total cholesterol (P [is less than] 0.01), triglycerides (P [is less than] 0.05), VLDL-cholesterol (P [is less than] 0.05), LDL-cholesterol (P [is less than] 0.01), and HDL-cholesterol (P [is less than] 0.01) levels (Table 3). Addition of cholesterol (Group 4) to the standard chow diet increased serum total cholesterol and HDL-cholesterol levels (P [is less than] 0.05 for both), but no significant change was observed in triglycerides, VLDL-cholesterol and LDL-cholesterol levels. The addition of cholesterol to the diet (Group 4) had a lower effect on serum total cholesterol than the cholesterol plus coffee added diet (Group 5) (P [is less than] 0.01). Similar results have been observed in other animal and human studies. Adding coffee (equivalent to 9-12 cups of coffee per person) to the animals fed on an atherogenic diet resulted in an increase in serum cholesterol and triglycerides (Akinyanju & Yudkin, 1967; Heyden et al., 1969). Coffee, tea, and caffeine addition to the standard rat chow diet, not including any atherogenic substances such as cholesterol and cholic acid as used in the present study, had an effect on the serum lipid parameters. It was also noted that increases in serum lipids were found to be related to the concentration of caffeine in the diet. As tea contains half the caffeine compared to the same amount of coffee, it is tempting to think that tea and decaffeinated coffee may cause very little or no changes in the level of plasma cholesterol (Naismith et al., 1969). This notion can also support the findings of the present study with regard to the effect of caffeine addition to the diet on the levels of plasma cholesterol. In another study, high level intake of cholesterol with 10mg/kg caffeine enhanced serum cholesterol and LDL-cholesterol levels in Albino rats (Lin et al., 1986). Also, addition of 2.5 g caffeine to each kg of the rats' standard diet caused a lower and temporary increase in the serum cholesterol (Fears, 1978). In the present study, adding caffeine to the standard chow diet increased only serum total cholesterol level compared to the control group (P [is less than] 0.01). Animals in Group 5 consumed less caffeine (relating to less food intake) than Group 3. Despite this, a significant increase in the serum total cholesterol level was found in the coffee-added Group 5 than Group 3 (P [is less than] 0.05) (Table 2). It should be considered, however, that studies with regard to the interaction of caffeine and serum lipids have conflicted. A group of researchers worked on the possibility of hypocholesterolemic effect of caffeine. It was concluded that caffeine may have a suppressing effect on the release of VLDL-cholesterol and sterols from liver and cause accumulation in tissues (Hostmark et al., 1986, 1988). It may be drawn from the results available that the amount of caffeine, and the composition of diet are the important factors for the effects of caffeine.
In healthy people, consumption of instant coffee had no effect on serum lipids in a balanced diet without smoking (Bellet et al., 1965; Aro et al., 1985; Donahue et al., 1987). It was found that caffeine (75 mg/d) did not cause any changes in serum lipids (Bakk & Grobbee, 1991). A number of recent studies indicated that there may be unknown substances in coffee besides caffeine causing the increases in serum lipids (Superko et al., 1991). Brewed coffee caused an increase in plasma cholesterol correlated to the consumption amount, but this effect was not observed in filtered coffee (Bakk & Grobbee, 1989; Aro et al., 1990). Lipid materials on the surface of the
centrifuged brewed and filtered coffee appeared to be in the range of 0.1-0.2 g/dL and 0.001 g/dL, respectively. Therefore brewed coffee raised cholesterol more than filtered coffee, because lipid material was not filtered during coffee preparation (Zock et al., 1990).
In the present study, it was found that the addition of coffee to the diet containing cholesterol resulted in an increase in HDL-cholesterol levels more than the other groups (P [is less than] 0.01) (Table 3). It was shown that coffee consumption with high fat and cholesterol diet caused an increase in plasma HDL-cholesterol concentrations in animals (Sanders & Sandaradura, 1992) and in non-smoking humans (Salonen et al., 1987; Fried et al., 1992). Although heart-protective [HDL.sub.2] and [HDL.sub.3] sub-fractions of HDL-cholesterol were not measured in the present study, it is widely accepted that an increase in LDL-cholesterol levels, but not HDL-cholesterol, increase the risk of coronary heart disease (Kannel et al., 1979; Anon., 1984). Furthermore, HDL-cholesterol reduces the risk and has a preventative effect (Miller et al., 1977; Grundy, 1990). In the present study no changes were observed in the ratio of HDL-cholesterol to total cholesterol and LDL-cholesterol in the animals fed on the caffeine-added diet and the cholesterol plus coffee-added diet.
As a result of the present study, it may be concluded that coffee was not the only factor effecting serum lipids, the composition of diet may have an effect on serum cholesterol levels. There is no need to limit the consumption of coffee without sugar in healthy people who have normal serum lipid levels. Limitation of coffee consumption should be recommended in people who have hyperlipidemia and consume high cholesterol diets. The type of coffee consumed is another important factor which may affect the lipid parameters, due to caffeine and other substances present. There is therefore a need for comprehensive epidemiologic and experimental research to identify the effect of the coffee type and brewing methods on human health.
Acknowledgements--We express our appreciation to Dr A.S. Buyukdevrim and Dr T. Altug for their help in providing the rats, and performing laboratory work. Also the entire staff of Istanbul University, Institute of Medical Research Application are sincerely appreciated.
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Correspondence to: N. Rakicioglu, Hacettepe University, Department of Nutrition and Dietetics, 06100, Ankara, Turkey.
N. Rakicioglu,(1) G. Pekcan(1) and A. Cevik(2)
(1) Department of Nutrition and Dietetics, Hacettepe University, Ankara and (2) Institute of Medical Research Application, Istanbul University, Istanbul, Turkey
Rakicioglu, N., G. Pekcan, and A. Cevik. "The effect of coffee and caffeine consumption
on serum lipids in rats." International Journal of Food Sciences and Nutrition 49.6 (Nov 1998): 441
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