September 2010 Issue
Coffee and Heart Health — The Answers to Many Common Questions Are Still Brewing
By Jenna A. Bell, PhD, RD, CSSD
Today’s Dietitian
Vol. 12 No. 9 P. 16
Perhaps you enjoy a cup of coffee after dinner or maybe you take a travel mug to work every morning. Truth is, coffee has become a drink of choice for many, and according to the 2010 edition of the Coffee Statistics Report, people consume 400 billion cups worldwide each year.
Throughout history, coffee has been touted as an aid for digestion and for relieving headaches and cough as well as a beverage to benefit overall health.1 However, news of its possible health attributes has also been peppered with concerns about potential risks. As with most frequently consumed foods and beverages, scientists are compelled to investigate coffee’s short- and long-term health consequences, especially in regard to matters of the heart. Whether drinking coffee is hazardous to heart health is a common concern among clients and patients, and answering this question remains a challenge since the science is controversial.
Read on to find out why the answers to heart health and coffee questions continue to evade us. Note that this article will focus only on cardiovascular health; it will not address the evidence for coffee consumption and other potential positive effects concerning Parkinson’s disease, liver disease, cancer, etc or negative health effects regarding bone health, pregnancy, drug interactions, etc.
The Questions
Because of its unique composition of caffeine, potassium, magnesium, niacin, and vitamin E along with chlorogenic acid and the diterpene alcohols cafestol and kahweol, scientists have scrutinized coffee’s effect on the heart. In a study published in Pharmacology & Therapeutics, Riksen et al reviewed the acute and long-term cardiovascular effects of coffee.2 The authors outlined the impact of chronic coffee consumption and a single-dose effect on cardiovascular parameters. While tolerance and genotype appear to influence short- and long-term responses, the overall consequences of coffee consumption and its constituents are summarized in the accompanying table.
Blood Pressure
For decades, drinking about two cups of coffee has been known to acutely increase systolic and diastolic blood pressure in healthy subjects.3 Caffeinated coffee also appears to affect vascular tone through vasoconstriction, an increase in (nor)epinephrine, and arterial stiffness. These seemingly negative results appear to exist only temporarily; after three days of coffee consumption, the pressor effects and (nor)epinephrine response subside.3
Additionally, Riksen et al described results from studies of caffeinated coffee showing that after five days, blood pressure was normal.2 Long-term investigations have not confirmed a link between coffee consumption and hypertension.
Cholesterol
Studies using nonfiltered, boiled coffee have shown a relationship between coffee consumption and elevated cholesterol levels.4 Because boiled coffee is a significant source of diterpene alcohols, scientists believed the link to increased cholesterol levels was isolated to unfiltered coffee. However, more recent studies have revealed that filtered coffee may also slightly increase cholesterol levels.2
On the flipside, a 2004 issue of Biochemistry published results from Yukawa et al showing that coffee may favorably affect endothelial atherosclerotic plaques by reducing the susceptibility to LDL oxidation. Although the study was small in size (n = 11) and lasted only one week, it is possible that the antioxidant properties of chlorogenic acid may help protect from oxidation.5
Plasma Homocysteine
Coffee consumption has been associated with an independent risk factor for cardiovascular disease: elevated plasma homocysteine levels.1 Studies have identified a dose-dependent response on plasma homocysteine levels2 that appears to be partly due to the caffeine or a response to the chlorogenic acid. The jury is still out and questions remain about whether a moderate consumption has any impact.2
Inflammation
Research has yielded the beneficial effects of coffee consumption on inflammation and endothelial function, especially in individuals with type 2 diabetes. An inverse association was detected between caffeinated coffee consumption and biomarkers of inflammation (surface leukocyte adhesion molecules and C-reactive protein) in women with diabetes.5 However, a cross-sectional study found that moderate to high coffee intake increased C-reactive protein and other biomarkers of inflammation in individuals without diabetes.1
Type 2 Diabetes
The protective effect of coffee consumption on type 2 diabetes appears to be solid despite the results of short-term studies showing that caffeine impairs insulin sensitivity. Prospective cohort studies have confirmed that consuming coffee lowers the risk of type 2 diabetes, but the mechanism for its beneficial effect is unclear.1,2 Because decaffeinated coffee beverages are also linked to a reduced risk, Campos et al suggest the effects may be attributed to the chlorogenic acid’s antioxidant potency in inhibiting glucose absorption in the intestine or its beneficial impact on insulin sensitivity.1 Another hypothesis is that coffee exerts a thermogenic effect that increases metabolic rate.
Coronary Heart Disease or Stroke
Notwithstanding coffee’s potential influence on cardiovascular function, epidemiological studies conclude that there is no association between coffee consumption and coronary heart disease or stroke. In fact, prospective studies have identified a positive association between coffee and coronary heart disease.2 Similarly, a study published in the June issue of Arteriosclerosis, Thrombosis, and Vascular Biology, a journal of the American Heart Association, reported that consuming two to four cups of coffee per day reduced the risk of coronary heart disease, although the finding was not statistically significant. A 2009 study by Lopez-Garcia et al revealed a modest reduction in stroke risk in women from the Nurses’ Health Study.
Mortality
To determine the overall relationship between coffee and mortality, Lopez-Garcia et al reviewed the coffee consumption of 41,736 men and 86,214 women from the Health Professionals Follow-Up Study and the Nurses’ Health Study.5 After controlling for age, smoking, and other cardiovascular disease and cancer risk factors, regular coffee consumption was not found to be associated with an increased risk of mortality rate.
Is Coffee OK for Heart Health?
Based on the research, there does not appear to be a simple answer to this question. The effects of coffee appear to depend on the length of use, brewing techniques, and interindividual variations. Because the aforementioned studies vary in end-point measures, size, and design, drawing any conclusions is impossible at this time. While the American Heart Association lumps all caffeine-containing foods and beverages together on its consumer educational website, it states that the link between high caffeine intake and coronary heart disease is still under investigation but that moderate coffee consumption does not appear to be harmful.
— Jenna A. Bell, PhD, RD, CSSD, is a nutrition writer, blogger, and communications consultant living in Chicago.
References
1. Campos H, Bailing A. Coffee consumption and risk for type 2 diabetes and heart disease. Nutr Rev. 2007;65(4):173-179.
2. Riksen NP, Rongen GA, Smits P. Acute and long-term cardiovascular effects of coffee: Implications for coronary heart disease. Pharmacol Ther. 2009;121(2):185-191.
3. Robertson D, Frolich JC, Carr RK, et al. Effects of caffeine on plasma renin activity, catecholamines and blood pressure. N Engl J Med. 1978;298(4):181-186.
4. Nystad T, Melhus M, Brustad M, Lund E. The effect of coffee consumption on serum total cholesterol in the Sami and Norwegian populations. Public Health Nutr. 2010;26:1-8.
5. Lopez-Garcia E, van Dam RM, Li TY, Rodriguez-Artalejo F, Hu FB. The relationship of coffee consumption with mortality. Ann Intern Med. 2008;148(12):904-914.