Coffee Consumption and Blood Pressure: A Randomized, Crossover Clinical Trial PHILLIP C. ROSMARIN, MD, WILLIAM B. APPLEGATE, MD, MPH, GRANT W. SOMES, PhD Objective: To e x a m i n e the effect o f moderate coffee cons u m p t t o n o n blood p r e s s u r e o v e r a p r o l o n g e d p e r i o d o f time. P r e v i o u s w o r k in this a r e a h a s used p r i m a r i l y p u r i f l e d caffeine. Design: A prospective, r a n d o m i z e d , c r o s s o v e r clinical
trial Setting: A h y p e r t e n s i o n specialty o u t p a t i e n t clinic at the University o f Tennessee, Memphis. Patients: Healthy, young, white m e n w h o were m o d e r a t e coffee d r i n k e r s ( < 6 c u p s / d a y ) were recruited~ Twentyf o u r subjects were r a n d o m i z e d a n d 21 (average age 35.5 y e a r s ) completed the t r i a l Interventions: Subjects were r a n d o m i z e d to o n e o f two groups: Group A d r a n k three o r m o r e cups o f c o f f e e / d a y f o r two months, then c r o s s e d o v e r to a b s t a i n i n g f r o m coff e e f o r two months; g r o u p B a b s t a i n e d f r o m coffee first, then c r o s s e d o v e r to d r i n k i n g coffee. Only filter-brewed coffee was used. Subjects were seen a t m o n t h l y i ~ a l s for blood p r e s s u r e measurements. Measurements and main results: The average coffee cons u m p t i o n w a s 3.6 c u p s / d a y d u r i n g the coffee-drinking phases. There w a s n o difference between the coffee-drinki n g p h a s e a n d the abstention p h a s e i n either systolic blood pressure (110.1 m m H g vs. 108.0 m m H ~ respectively; 95% CI o f difference -- 7.3, 2.5) o r diastolic blood p r e s s u r e (67.2 m m H g vs. 69.6 m m H ~ respectively; 95% CI o f difference -2.2, 6.4). Conclusions: M o d e r a t e daily c o n s u m p t i o n o f coffee d o e s n o t elevate blood pressure. Key words: coffee; filtered coffee; blood pressure; hypertens/on. J GEN INTERNMEt) 1990; 5:211-213.
SINCE EARLYIN THIS CENTURY, t h e r e h a v e b e e n c o n f l i c t i n g reports on the effects of coffee on arterial b l o o d
pressure (BP). Early work b y Horst et al. found a slight increase in BP acutely following coffee consumption. 1 This pressor effect was shown to attenuate with time. 2 Other work by Freestone and Ramsay has shown that coffee can elevate b l o o d pressure in hypertensive subjects over a two-hour study period. 3 Cigarette smoking was shown to have an additive effect to coffee in the acute setting, but long-term effects w e r e not studied. Cross-sectional studies have shown positive, ~ negative, 5 or no correlation 6, 7 b e t w e e n coffee intake and b l o o d pressure. Received from the Departments of Medicine and Preventive Medicine (PCR, WBA) and the Department of Biostatistics and Epidemiology (GWS), University of Tennessee, Memphis, Tennessee. Supported in part by a grant from the University Physicians Foundation of the University of Tennessee, Memphis. Address correspondence and reprint requests to Dr. Applegate: Department of Preventive Medicine, University of Tennessee, 800 Madison Avenue, Memphis, TN 38163.
We p e r f o r m e d a prospective randomized crossover clinical trial to determine the long-term effect of moderate coffee intake on arterial b l o o d pressure in normal, healthy volunteers.
METHODS Healthy young white men were recruited and interviewed to ascertain their coffee-drinking and smoking habits. After signed informed consent was obtained, baseline evaluations, including physical examination and laboratory studies, were performed. Exclusion criteria included: non-coffee drinkers, heavy coffee drinkers ( > 6 cups/day), NYHA class 2 or greater heart disease, hyperlipidemia (total cholesterol > 6.85 m m o l / L [265 mg/dl]), diabetes mellitus, p e p t i c ulcer disease, obstructive airways disease requiring or potentially requiring theophylline therapy, and hypertension (SBP > 140 mmHg, DBP > 95 mmHg). Also, subjects taking medications that contained methylxanthines w e r e excluded. Of 35 respondents to the recruiting efforts, 24 subjects meeting the inclusion criteria were enrolled and randomized. A computer-generated list of random numbers was used to randomize to one of two groups: G r o u p A drank three or more cups of coffee/day for two months, then crossed over to abstaining from coffee for two months; group B abstained from coffee the first two months, then crossed over to drinking three or more c u p s / d a y for the final two months. All other forms of caffeine were e x c l u d e d during the four months of the study. Subjects were instructed to use filter-brewed coffee only and w e r e supplied with drip-grind coffee and a one-cup drip coffee filter funnel and filters (Melitta, Inc.) to help meet this requirement. They were instructed to maintain their usual dietary and smoking patterns aside from the changes in caffeine and coffee intake. Subjects were seen at monthly intervals after randomization. At each visit b l o o d pressure was measured on a Hawksley random-zero m e r c u r y sphygmomanometer (Baum, Inc.). Three measurements of brachial BP were taken with the subject in the sitting position after 15 minutes of relaxation, resetting the machine after each reading. The final BP value was taken as the average of the last two measurements. The study protocol was approved by the Institutional Review Board of the University of Tennessee. Data w e r e analyzed by analysis of variance for reZll
212
Rosmarin el, aL, COFFEECONSUMPTIONAND BLOODPRESSURE
TABLE 1 Baseline Characteristicsof RandomizedSubJects,Mean ___SD Group A (n = 12) Age Weight Body mass index Systolic blood pressure Diastolic blood pressure Total cholesterol Daily coffee consumption, by recall Weekly alcohol consumption, by recall Regular aerobic exercisehabits
35.9 + 85.2 + 27.0 + 114.3 + 71.3 + 195.2 + 3.96 + 1.4 +
p e a t e d measures. This m o d e l included factors for treatm e n t effect as well as effects of time and g r o u p assignment. RESULTS
Following randomization, three subjects failed to return for follow-up, and the results presented here are for the 21 w h o successfully c o m p l e t e d the protocol. Their baseline characteristics are p r e s e n t e d in Table 1. The average coffee intake during the coffee phase was 3.6 c u p s / d a y (range 2.1 - 6.7). C o m p l i a n c e with protocol, based on subjects' self-reporting, was 95%. The adjusted results, given in Table 2, s h o w the effect of coffee with all other factors (i.e., g r o u p assignment, p e r i o d effect, dietary changes, and smoking) controlled. The m e a n b l o o d pressure did not change with the use of coffee.
DISCUSSION In healthy individuals, m o d e r a t e coffee c o n s u m p tion did not cause any sustained rise in arterial b l o o d pressure over a t w o - m o n t h period. The mean coffee intake during this study was at a level felt to b e representative of that of the average coffee consumer. There TABLE 2 Coffee vs. No Coffee Effects on Blood Pressure--All Subjects ( N : 21), Mean, ConfidenceInterval, and Detectable Difference
Systolic blood pressure Diastolic blood pressure
Coffee
No Coffee
CI*
DDt
110.1 mmHg
108.0 mmHg
(--7.3, 2.5)
7.3
67.2 mmHg
69.6 mmHg
(--2.2, 6.4)
6.3
*95% confidenceinterval of difference between effect on and off coffee. ~Size of the detectable difference with this sample size and the observed variance with a power of 0.80 and level of significanceof 0.05 (see discussion),
6.7 years 12.3 kg 3.6 kg/m z 14.7 mmHg 10.4 mmHg 29.0 mg/dl 1.66 cups/day 1.6 drinks/week 6
Group B (n = 12) 34.8 + 6.0 years 89.7 _+ 27.1 kg 28.5 + 7.3 kg/m 2 116.4 +_ 11.4 mmHg 72.3 _+ 13.3 mmHg 185.3 + 38.2 mg/dl 4.00 _+ 1.64 cups/day 2.0 + 4,1 drinks/week 3
w e r e too f e w smokers in o u r cohort to address any potential interaction b e t w e e n smoking and coffee intake on b l o o d pressure. 3 Nevertheless, w e feel these results are applicable to the average m o d e r a t e coffee consumer. Some earlier studies have shown that the intake of coffee causes a modest acute rise of b l o o d pressure, w h i c h may b e attenuated over time. ~, 2 W o r k b y Freestone and Ramsay s h o w e d that coffee c o n s u m p t i o n elevated b l o o d pressure acutely in hypertensive smokers w h o w e r e habitual coffee drinkers. 3 Additionally, they n o t e d an additive effect with cigarette smoking. T h e y did not e x a m i n e any long-term effects on b l o o d pressure, though, and their use of hypertensive subjects limits the generalization o f their results to the p u b l i c at large. Cross-sectional studies have yielded conflicting results. Hadley r e p o r t e d a positive correlation b e t w e e n coffee and tea intake and elevated b l o o d pressure. 4 More recently, Periti et al. f o u n d a negative correlation b e t w e e n a m o u n t of coffee c o n s u m e d and b l o o d pressure in a large p o p u l a t i o n survey, s Finally, b o t h the Framingham 6 and the IBM7 studies have r e p o r t e d no correlation b e t w e e n coffee intake and b l o o d pressure. Unfortunately there have b e e n f e w well-designed studies of the effect of coffee c o n s u m p t i o n on b l o o d pressure over an e x t e n d e d p e r i o d of time. Our study has several limitations. The h o m o g e n e ity of the study p o p u l a t i o n m a y restrict the generalization o f o u r results, but the results are a p p l i c a b l e to y o u n g white males w h o are at risk for p r e m a t u r e coronary heart disease (CHD). O u r study l o o k e d at the sustained effects o v e r t w o months in a p o p u l a t i o n o f healthy subjects, so that effects in selected p o p u l a t i o n s such as hypertensive individuals cannot b e directly addressed. Neither w e r e the acute effects o f coffee cons u m p t i o n examined, since these have b e e n r e p o r t e d b y others.L 3, s O u r intent was to define coffee's role in p r o d u c i n g a sustained rise in BP from chronic ingestion. Heavy coffee c o n s u m p t i o n was not tested here, and any effect of heavy c o n s u m p t i o n on b l o o d pressure remains to be proven. However, our intake level of 3.6
JOURNALOFGENERALINTERNALMEDICINE.Volume 5 (May/June). 1990
c u p s / d a y was felt to b e r e p r e s e n t a t i v e o f m o d e r a t e coffee use a n d is a b o v e t h e l e v e l r e p o r t e d t o c a u s e a c u t e e l e v a t i o n s of BP. ~, s A l t h o u g h r e p o r t e d c o m p l i a n c e was h i g h i n this study, u s e o f s e l f - r e p o r t to r e c o r d coffee i n t a k e c o u l d have u n d e r e s t i m a t e d t h e a m o u n t o f n o n c o m p l i a n c e i n e i t h e r t h e c o n t r o l or t h e i n t e r v e n t i o n p e r i o d s . T h e b r e w i n g m e t h o d i n o u r s t u d y was also r e s t r i c t e d to filtered d r i p - b r e w e d coffee, a n d w e c a n n o t address w h e t h e r instant, b o i l e d , o r p e r c o l a t e d coffee m i g h t have d e l e t e r i o u s effects o n b l o o d p r e s s u r e . W e c a n n o t e x c l u d e t h e p o s s i b i l i t y o f a s m a l l t y p e II error. O u r v a r i a n c e s for b o t h systolic a n d d i a s t o l i c b l o o d p r e s s u r e s w e r e small, so that g i v e n o u r s a m p l e size w e c o u l d a c t u a l l y d e t e c t d i f f e r e n c e s o f < 1 0 % i n t h e m e a n b l o o d p r e s s u r e (see T a b l e 2). This d o e s n o t e x c l u d e t h e p o s s i b i l i t y that s m a l l s u s t a i n e d rises i n BP m a y have g o n e u n d e t e c t e d , g i v e n t h e p o w e r o f o u r study. I n c o n c l u s i o n , w e f o u n d n o a d v e r s e effect o f sust a i n e d m o d e r a t e coffee c o n s u m p t i o n o n b l o o d p r e s s u r e i n h e a l t h y i n d i v i d u a l s u s i n g f i l t e r - b r e w e d coffee. A n y
213
p o t e n t i a l CHD risk f r o m coffee u s e i n m e n m u s t b e r e l a t e d to factors o t h e r t h a n i n d u c t i o n o f h y p e r t e n s i o n .
REFERENCES 1. Horst K, Willson RJ, Smith RG. The effect of coffee and decaffeinated coffee on oxygen consumption, pulse rate and blood pressure. J Pharmacol Exp Ther. 1936;58:294-304. 2. Horst K, Buxton RE, Robinson WD. The effect of the habitual use of coffee or decaffeinated coffee upon blood pressure and certain motor reactions of normal young men. J Pbarmacol Exp Tber. 1934;52:322-37. 3. Freestone S, RamsayLE. Effect of coffee and cigarette smoking on the blood pressure of untreated and diuretic-treated hypertensive patients. AmJ Med. 1982;73:348-53. 4. Hadley HG. The effects of tea and coffee. Med Rec. 1945; 158:158-9. 5. Periti M, SalvaggioA, Quaglia G, DiMarzioL. Coffee consumption and blood pressure: an Italian study. Clin Sci. 1987;72:443-7. 6. Dawber TR, Kannel WB, Gordon T. Coffee and cardiovascular disease: observations from the Framingham Study. N Engl J Med. 1974;291:871-4. 7. Bertrand CA, Pomper I, HillmanG, DuffyJC, Michell I. No relation between coffee and blood pressure (letter). N Engl J Med. 1978;299:315-6. 8. SmitsP, Pietters G, Thien T. The role of epinephrine in the circulatory effects of coffee. Clin Pharmacol Ther. 1986;40:431-7.
trial Setting: A h y p e r t e n s i o n specialty o u t p a t i e n t clinic at the University o f Tennessee, Memphis. Patients: Healthy, young, white m e n w h o were m o d e r a t e coffee d r i n k e r s ( < 6 c u p s / d a y ) were recruited~ Twentyf o u r subjects were r a n d o m i z e d a n d 21 (average age 35.5 y e a r s ) completed the t r i a l Interventions: Subjects were r a n d o m i z e d to o n e o f two groups: Group A d r a n k three o r m o r e cups o f c o f f e e / d a y f o r two months, then c r o s s e d o v e r to a b s t a i n i n g f r o m coff e e f o r two months; g r o u p B a b s t a i n e d f r o m coffee first, then c r o s s e d o v e r to d r i n k i n g coffee. Only filter-brewed coffee was used. Subjects were seen a t m o n t h l y i ~ a l s for blood p r e s s u r e measurements. Measurements and main results: The average coffee cons u m p t i o n w a s 3.6 c u p s / d a y d u r i n g the coffee-drinking phases. There w a s n o difference between the coffee-drinki n g p h a s e a n d the abstention p h a s e i n either systolic blood pressure (110.1 m m H g vs. 108.0 m m H ~ respectively; 95% CI o f difference -- 7.3, 2.5) o r diastolic blood p r e s s u r e (67.2 m m H g vs. 69.6 m m H ~ respectively; 95% CI o f difference -2.2, 6.4). Conclusions: M o d e r a t e daily c o n s u m p t i o n o f coffee d o e s n o t elevate blood pressure. Key words: coffee; filtered coffee; blood pressure; hypertens/on. J GEN INTERNMEt) 1990; 5:211-213.
SINCE EARLYIN THIS CENTURY, t h e r e h a v e b e e n c o n f l i c t i n g reports on the effects of coffee on arterial b l o o d
pressure (BP). Early work b y Horst et al. found a slight increase in BP acutely following coffee consumption. 1 This pressor effect was shown to attenuate with time. 2 Other work by Freestone and Ramsay has shown that coffee can elevate b l o o d pressure in hypertensive subjects over a two-hour study period. 3 Cigarette smoking was shown to have an additive effect to coffee in the acute setting, but long-term effects w e r e not studied. Cross-sectional studies have shown positive, ~ negative, 5 or no correlation 6, 7 b e t w e e n coffee intake and b l o o d pressure. Received from the Departments of Medicine and Preventive Medicine (PCR, WBA) and the Department of Biostatistics and Epidemiology (GWS), University of Tennessee, Memphis, Tennessee. Supported in part by a grant from the University Physicians Foundation of the University of Tennessee, Memphis. Address correspondence and reprint requests to Dr. Applegate: Department of Preventive Medicine, University of Tennessee, 800 Madison Avenue, Memphis, TN 38163.
We p e r f o r m e d a prospective randomized crossover clinical trial to determine the long-term effect of moderate coffee intake on arterial b l o o d pressure in normal, healthy volunteers.
METHODS Healthy young white men were recruited and interviewed to ascertain their coffee-drinking and smoking habits. After signed informed consent was obtained, baseline evaluations, including physical examination and laboratory studies, were performed. Exclusion criteria included: non-coffee drinkers, heavy coffee drinkers ( > 6 cups/day), NYHA class 2 or greater heart disease, hyperlipidemia (total cholesterol > 6.85 m m o l / L [265 mg/dl]), diabetes mellitus, p e p t i c ulcer disease, obstructive airways disease requiring or potentially requiring theophylline therapy, and hypertension (SBP > 140 mmHg, DBP > 95 mmHg). Also, subjects taking medications that contained methylxanthines w e r e excluded. Of 35 respondents to the recruiting efforts, 24 subjects meeting the inclusion criteria were enrolled and randomized. A computer-generated list of random numbers was used to randomize to one of two groups: G r o u p A drank three or more cups of coffee/day for two months, then crossed over to abstaining from coffee for two months; group B abstained from coffee the first two months, then crossed over to drinking three or more c u p s / d a y for the final two months. All other forms of caffeine were e x c l u d e d during the four months of the study. Subjects were instructed to use filter-brewed coffee only and w e r e supplied with drip-grind coffee and a one-cup drip coffee filter funnel and filters (Melitta, Inc.) to help meet this requirement. They were instructed to maintain their usual dietary and smoking patterns aside from the changes in caffeine and coffee intake. Subjects were seen at monthly intervals after randomization. At each visit b l o o d pressure was measured on a Hawksley random-zero m e r c u r y sphygmomanometer (Baum, Inc.). Three measurements of brachial BP were taken with the subject in the sitting position after 15 minutes of relaxation, resetting the machine after each reading. The final BP value was taken as the average of the last two measurements. The study protocol was approved by the Institutional Review Board of the University of Tennessee. Data w e r e analyzed by analysis of variance for reZll
212
Rosmarin el, aL, COFFEECONSUMPTIONAND BLOODPRESSURE
TABLE 1 Baseline Characteristicsof RandomizedSubJects,Mean ___SD Group A (n = 12) Age Weight Body mass index Systolic blood pressure Diastolic blood pressure Total cholesterol Daily coffee consumption, by recall Weekly alcohol consumption, by recall Regular aerobic exercisehabits
35.9 + 85.2 + 27.0 + 114.3 + 71.3 + 195.2 + 3.96 + 1.4 +
p e a t e d measures. This m o d e l included factors for treatm e n t effect as well as effects of time and g r o u p assignment. RESULTS
Following randomization, three subjects failed to return for follow-up, and the results presented here are for the 21 w h o successfully c o m p l e t e d the protocol. Their baseline characteristics are p r e s e n t e d in Table 1. The average coffee intake during the coffee phase was 3.6 c u p s / d a y (range 2.1 - 6.7). C o m p l i a n c e with protocol, based on subjects' self-reporting, was 95%. The adjusted results, given in Table 2, s h o w the effect of coffee with all other factors (i.e., g r o u p assignment, p e r i o d effect, dietary changes, and smoking) controlled. The m e a n b l o o d pressure did not change with the use of coffee.
DISCUSSION In healthy individuals, m o d e r a t e coffee c o n s u m p tion did not cause any sustained rise in arterial b l o o d pressure over a t w o - m o n t h period. The mean coffee intake during this study was at a level felt to b e representative of that of the average coffee consumer. There TABLE 2 Coffee vs. No Coffee Effects on Blood Pressure--All Subjects ( N : 21), Mean, ConfidenceInterval, and Detectable Difference
Systolic blood pressure Diastolic blood pressure
Coffee
No Coffee
CI*
DDt
110.1 mmHg
108.0 mmHg
(--7.3, 2.5)
7.3
67.2 mmHg
69.6 mmHg
(--2.2, 6.4)
6.3
*95% confidenceinterval of difference between effect on and off coffee. ~Size of the detectable difference with this sample size and the observed variance with a power of 0.80 and level of significanceof 0.05 (see discussion),
6.7 years 12.3 kg 3.6 kg/m z 14.7 mmHg 10.4 mmHg 29.0 mg/dl 1.66 cups/day 1.6 drinks/week 6
Group B (n = 12) 34.8 + 6.0 years 89.7 _+ 27.1 kg 28.5 + 7.3 kg/m 2 116.4 +_ 11.4 mmHg 72.3 _+ 13.3 mmHg 185.3 + 38.2 mg/dl 4.00 _+ 1.64 cups/day 2.0 + 4,1 drinks/week 3
w e r e too f e w smokers in o u r cohort to address any potential interaction b e t w e e n smoking and coffee intake on b l o o d pressure. 3 Nevertheless, w e feel these results are applicable to the average m o d e r a t e coffee consumer. Some earlier studies have shown that the intake of coffee causes a modest acute rise of b l o o d pressure, w h i c h may b e attenuated over time. ~, 2 W o r k b y Freestone and Ramsay s h o w e d that coffee c o n s u m p t i o n elevated b l o o d pressure acutely in hypertensive smokers w h o w e r e habitual coffee drinkers. 3 Additionally, they n o t e d an additive effect with cigarette smoking. T h e y did not e x a m i n e any long-term effects on b l o o d pressure, though, and their use of hypertensive subjects limits the generalization o f their results to the p u b l i c at large. Cross-sectional studies have yielded conflicting results. Hadley r e p o r t e d a positive correlation b e t w e e n coffee and tea intake and elevated b l o o d pressure. 4 More recently, Periti et al. f o u n d a negative correlation b e t w e e n a m o u n t of coffee c o n s u m e d and b l o o d pressure in a large p o p u l a t i o n survey, s Finally, b o t h the Framingham 6 and the IBM7 studies have r e p o r t e d no correlation b e t w e e n coffee intake and b l o o d pressure. Unfortunately there have b e e n f e w well-designed studies of the effect of coffee c o n s u m p t i o n on b l o o d pressure over an e x t e n d e d p e r i o d of time. Our study has several limitations. The h o m o g e n e ity of the study p o p u l a t i o n m a y restrict the generalization o f o u r results, but the results are a p p l i c a b l e to y o u n g white males w h o are at risk for p r e m a t u r e coronary heart disease (CHD). O u r study l o o k e d at the sustained effects o v e r t w o months in a p o p u l a t i o n o f healthy subjects, so that effects in selected p o p u l a t i o n s such as hypertensive individuals cannot b e directly addressed. Neither w e r e the acute effects o f coffee cons u m p t i o n examined, since these have b e e n r e p o r t e d b y others.L 3, s O u r intent was to define coffee's role in p r o d u c i n g a sustained rise in BP from chronic ingestion. Heavy coffee c o n s u m p t i o n was not tested here, and any effect of heavy c o n s u m p t i o n on b l o o d pressure remains to be proven. However, our intake level of 3.6
JOURNALOFGENERALINTERNALMEDICINE.Volume 5 (May/June). 1990
c u p s / d a y was felt to b e r e p r e s e n t a t i v e o f m o d e r a t e coffee use a n d is a b o v e t h e l e v e l r e p o r t e d t o c a u s e a c u t e e l e v a t i o n s of BP. ~, s A l t h o u g h r e p o r t e d c o m p l i a n c e was h i g h i n this study, u s e o f s e l f - r e p o r t to r e c o r d coffee i n t a k e c o u l d have u n d e r e s t i m a t e d t h e a m o u n t o f n o n c o m p l i a n c e i n e i t h e r t h e c o n t r o l or t h e i n t e r v e n t i o n p e r i o d s . T h e b r e w i n g m e t h o d i n o u r s t u d y was also r e s t r i c t e d to filtered d r i p - b r e w e d coffee, a n d w e c a n n o t address w h e t h e r instant, b o i l e d , o r p e r c o l a t e d coffee m i g h t have d e l e t e r i o u s effects o n b l o o d p r e s s u r e . W e c a n n o t e x c l u d e t h e p o s s i b i l i t y o f a s m a l l t y p e II error. O u r v a r i a n c e s for b o t h systolic a n d d i a s t o l i c b l o o d p r e s s u r e s w e r e small, so that g i v e n o u r s a m p l e size w e c o u l d a c t u a l l y d e t e c t d i f f e r e n c e s o f < 1 0 % i n t h e m e a n b l o o d p r e s s u r e (see T a b l e 2). This d o e s n o t e x c l u d e t h e p o s s i b i l i t y that s m a l l s u s t a i n e d rises i n BP m a y have g o n e u n d e t e c t e d , g i v e n t h e p o w e r o f o u r study. I n c o n c l u s i o n , w e f o u n d n o a d v e r s e effect o f sust a i n e d m o d e r a t e coffee c o n s u m p t i o n o n b l o o d p r e s s u r e i n h e a l t h y i n d i v i d u a l s u s i n g f i l t e r - b r e w e d coffee. A n y
213
p o t e n t i a l CHD risk f r o m coffee u s e i n m e n m u s t b e r e l a t e d to factors o t h e r t h a n i n d u c t i o n o f h y p e r t e n s i o n .
REFERENCES 1. Horst K, Willson RJ, Smith RG. The effect of coffee and decaffeinated coffee on oxygen consumption, pulse rate and blood pressure. J Pharmacol Exp Ther. 1936;58:294-304. 2. Horst K, Buxton RE, Robinson WD. The effect of the habitual use of coffee or decaffeinated coffee upon blood pressure and certain motor reactions of normal young men. J Pbarmacol Exp Tber. 1934;52:322-37. 3. Freestone S, RamsayLE. Effect of coffee and cigarette smoking on the blood pressure of untreated and diuretic-treated hypertensive patients. AmJ Med. 1982;73:348-53. 4. Hadley HG. The effects of tea and coffee. Med Rec. 1945; 158:158-9. 5. Periti M, SalvaggioA, Quaglia G, DiMarzioL. Coffee consumption and blood pressure: an Italian study. Clin Sci. 1987;72:443-7. 6. Dawber TR, Kannel WB, Gordon T. Coffee and cardiovascular disease: observations from the Framingham Study. N Engl J Med. 1974;291:871-4. 7. Bertrand CA, Pomper I, HillmanG, DuffyJC, Michell I. No relation between coffee and blood pressure (letter). N Engl J Med. 1978;299:315-6. 8. SmitsP, Pietters G, Thien T. The role of epinephrine in the circulatory effects of coffee. Clin Pharmacol Ther. 1986;40:431-7.
