Coffee Consumption in the Presence of CV Risk Factors
In nonhabitual coffee drinkers, diastolic and systolic BP rise after coffee consumption.[3] This effect on BP does not seem to be dose-dependent and exhibits large inter-individual differences. In subjects with regular, daily coffee consumption or habitual coffee drinkers, the effect of coffee on the BP is smaller or not detectable compared with nonhabitual coffee drinkers.[32] It is not clear whether resting BP differs between habitual and nonhabitual coffee drinkers. Age may also contribute to the effects of coffee consumption. Elderly individuals show pronounced BP increases after coffee ingestion.[32]
The pattern of coffee consumption is important. We have recently shown that in healthy subjects the CV effects of coffee differ according to drinking habits.[33] A rise in BP is not seen in habitual coffee drinkers after coffee consumption despite significant activation of sympathetic nerve activity. In nonhabitual coffee drinkers, intake of coffee is associated with a similar activation of the sympathetic nervous system and rise in BP. We also found that decaffeinated coffee increased BP and sympathetic nervous activity in nonhabitual drinkerssuggesting that ingredients other than caffeine may be responsible for the CV effects induced by coffee.[33]
The short-term risk of hypertensive emergencies was evaluated in healthy subjects with high coffee consumption. In a double-blind study, regular coffee intake (eight cups per day for 4 weeks, corresponding to a daily dose of 500 mg caffeine) was associated with increased risk for hypertensive emergencies.[34] The analysis of dietary risk factors for hypertension in a group of 12,000 men taking part in the Multiple Risk Factor Intervention Trial (MRFIT)[35] showed an inverse relationship between regular coffee consumption and BP. Due to the pronounced tendency for tolerance development, the Seventh Report of the Joint NationalCommittee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) recommendations for the treatment of hypertension do not include intake of coffee or beverages containing caffeine as a risk factor for hypertension.[36]
A significant causal relationship exists between coffee and increased plasma concentrations of cholesterol and apolipoprotein A and B.[37] These changes are also observed after intake of decaffeinated coffee.[38] The lipid effects of coffee are apparently not related to caffeine but rather to other ingredients in coffee. A double-blind, randomized study has shown that the lipid profile is unchanged after 9 weeks of coffee abstinence.[39] It is important, however, to consider the type of coffee consumed. For example, cooked coffee consumed for 9-10 weeks increased plasma levels of cholesterol by 5%-10%, while filtered coffee had no effect.[40] In another study conducted in 18 subjects, unfiltered boiled coffee induced a significant increase of plasma tryglicerides, apolipoprotein B, and LDL/high-density lipoprotein (HDL) ratio, while apolipoprotein A-I and HDL were not altered. In this study it was assumed that about 80% of the lipids contained in coffee were held back by the filter paper.[41]
In humans, acute administration of caffeine decreases insulin sensitivity and impairs glucose tolerance.[16] On the other hand, caffeine stimulates thermogenesis and increases energy expenditure, which may facilitate weight reduction and maintenance. Because of these complex physiologic effects of caffeine and because tolerance to the humoral and hemodynamic effects of caffeine typically develops with long-term use, it is difficult to extrapolate findings from short-term metabolic studies to long-term use of coffee and other caffeinated beverages.
In a recent study, a statistically significant inverse association was found between coffee consumption and risk for type 2 diabetes in a sample of Dutch participants.[42] After adjustment for potential confounders, the relative risk (RR) for type 2 diabetes among participants consuming at least seven cups of coffee per day as compared with those consuming two cups or less per day was 50%. However, regular coffee consumption could not be distinguished from decaffeinated coffee consumption, and the association with total caffeine intake was not evaluated in the study. In 2004, three new studies were published and all of them confirm that coffee consumption is associated with a reduced incidence of type 2 diabetes. Salazar-Martinez et al.[43] evaluated the effect of long-term intake of coffee and other caffeinated beverages and decaffeinated coffee in relation to the incidence of type 2 diabetes in two large prospective cohorts of men and women. The findings suggest that long-term coffee consumption is associated with a statistically significant lower risk for type 2 diabetes. Rosengren et al.[44] examined the long-term incidence of diabetes in relation to coffee consumption in a random population sample of Swedish women (n=1361, aged 39-65 years) and concluded that coffee consumption protects from the development of diabetes in women. Agardh et al.[45] conducted a population-based cross-sectional study in 7949 healthy Swedish subjects (aged 35-56 years) showing that high coffee consumption is associated with a reduced risk of both type 2 diabetes and impaired glucose tolerance. The author suggested that the beneficial effects may involve both improved insulin sensitivity and enhanced insulin response.
The interpretation of the effect of chronic coffee consumption on CV morbidity and mortality has always been difficult because of its strong association with other important CV risk factors such as smoking.[46] Smokers, and heavy smokers in particular, drink substantially more coffee than nonsmokers.[46,47] Interestingly, cigarette smoking (similar to coffee drinking) shows a more pronounced effect on the CV system (rise of heart rate and systolic BP) in nonsmokers or after a period of abstinence.[47]
A recent observational study showed a positive association between coffee intake and homocysteine concentrations.[48] In another recent study[49] the plasma concentrations of total homocysteine during consumption of paper-filtered coffee were studied. Forty-eight subjects (aged 19-65 years) were enrolled in a randomized crossover study with three treatments (six capsules providing 870 mg/d caffeine, paper-filtered coffee providing 870 mg/d caffeine, or six placebo capsules), each lasting 2 weeks. This study showed that caffeine may not be responsible for the homocysteine-raising effect of coffee. Coffee, but not caffeine, affects homocysteine metabolism within hours after intake, although the effect is still substantial after an overnight fast.
Prog Cardiovasc Nurs. 2005;20(2):65-69. © 2005 Le Jacq Communications, Inc.
© 2007 Prog Cardiovasc Nurs
Cite this: Cardiovascular Effects of Coffee: Is It a Risk Factor? - Medscape - May 01, 2005.
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