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Updated November 10, 2014.
In the past, the consumption of coffee was generally regarded as being detrimental to heart health. Coffee was said to increase blood pressure, increase cholesterol levels, and increase the risk of heart attack and cardiac arrhythmias. However, more recent and more careful studies have suggested that coffee might not increase the risk of heart disease, and in fact might actually reduce that risk.
Why the discrepancy?
In many cases, earlier studies did not take into account other risk factors for heart disease, such as lack of exercise and smoking. These risk factors may be more common in dedicated coffee drinkers. More recent studies have taken care to control for these confounding risk factors. These more recent studies have suggested that, when consumed in moderation, coffee does not increase cardiac risk, and may often be beneficial.
Coffee and Blood Pressure
The effect of coffee on blood pressure appears to be mixed. In non-coffee drinkers, acute exposure to caffeine can increase the blood pressure by up to 10 mm Hg. However, in chronic coffee drinkers, the acute ingestion of caffeine does not appear to raise the blood pressure. Several large studies have now failed to show a correlation between chronic coffee drinking and hypertension.
While these large population studies are reassuring, it appears likely that some individuals probably do have an increase in blood pressure when caffeine is ingested.
So if you are diagnosed with hypertension, it still makes sense to try abstaining from coffee for a month or so, to see whether eliminating coffee benefits your blood pressure.
Coffee and Arrhythmias
The belief that coffee causes cardiac arrhythmias is quite widespread, even among medical professionals. And indeed, it seems undeniable that some individuals will experience an increase in palpitations when they drink coffee.
However, neither large population studies nor studies in the laboratory have demonstrated that moderate amounts of coffee increase the risk of cardiac arrhythmias. Indeed, a recent study from Kaiser Permanente suggested that people who drank four cups of coffee per day had significantly fewer cardiac arrhythmias, including less atrial fibrillation and fewer PVCs.
At the very least, unless you are one of those individuals who notices a clear increase in palpitations after drinking coffee, there appears to be no reason to avoid moderate amounts of coffee because of a concern about cardiac arrhythmias.
Coffee and Diabetes
Several studies have now shown a correlation between coffee consumption and a reduced risk of type 2 diabetes. At least one study showed that the same reduction in risk is seen with decaffeinated coffee, suggesting that the protective effect of coffee, with regard to diabetes, may not be due to its caffeine content.Coffee and Stroke
A large meta-analysis involving almost 500,000 participants failed to show any increase in the risk of stroke among coffee drinkers. In fact, in individuals who drank 1 to 3 cups of coffee per day, the risk of stroke was significantly reduced.
And in a more recent study from Japan, people who drank at least 1 cup of coffee per day (or 4 cups of green tea, which is a more common practice in Japan) had a 20% reduction in their risk of stroke over a 13-year period.
Coffee and Coronary Artery Disease
Several large population studies have failed to show any increase in the risk of coronary artery disease among coffee drinkers. And in women, coffee drinking may even have a protective effect.However, as is nearly always the case, in any large population there are many individuals who do not display "average" behavior. It turns out that there is a fairly common genetic mutation that causes individuals to metabolize caffeine slowly. It appears that in these individuals, the risk of coronary artery disease may be increased with coffee consumption. When genetic testing becomes more routine, it will be easy to identify these slow caffeine metabolizers.
Coffee and Cholesterol
Coffee contains compounds - particularly a substance called cafestol - that can increase LDL cholesterol. However, paper filters reliably remove these lipid-active substances. So coffee brewed with paper filters does not increase blood cholesterol levels. On the other hand, the chronic ingestion of unfiltered coffee can increase LDL cholesterol levels by as much as 15 mg/dl. So, while drinking filter-brewed coffee seems prudent, frequently drinking unfiltered coffee may not be.Coffee and Heart Failure
A recent meta-analysis suggests that people who drink 1 to 4 cups of coffee per day have a reduced risk of developing heart failure. This apparent benefit of drinking coffee is lost when five or more cups of coffee are consumed per day.Summary
In general, the widespread concerns many people have about the potentially deleterious effects of coffee on the heart have not been supported by recent scientific studies. It appears that, in the large majority of people, moderate coffee drinking is not detrimental to cardiac health, and in many cases may even be beneficial.
As with everything else, moderation is the key. In most people, one to four cups of coffee per day appears safe for cardiac health. Just keep in mind that loading up your cup of coffee with cream, sugar, syrup or whipped cream may more than cancel out any benefit you might otherwise gain from it.
Sources:
Hasan AS, Morton C, Armstrong MA, et al. Coffee, caffeine, and risk of hospitalization for arrhythmias. EPI|NPAM 2010; March 2-5, 2010, San Francisco, CA. Abstract P461.
Pereira MA, Parker ED, and Folsom AR. Coffee consumption and risk of type 2 diabetes mellitus. An 11-year prospective study of 28 812 postmenopausal women. Arch Intern Med 2006; 166:1311-1316
D'Elia L, Cairella G, Garbagnati F, et al. Moderate coffee consumption is associated with lower risk of stroke: meta-analysis of prospective studies. J Hypertension 2012; 30 (e-Supplement A):e107
Mostofsky E, Rice MS, Levitan EB, Mittleman MA. Habitual coffee consumption and risk of heart failure: a dose-response meta-analysis. Circ Heart Fail 2012; DOI:10.1161/CIRCHEARTFAILURE.112.967299.
Kokubo Y, Iso H, Saito I, et al. The impact of green tea and coffee consumption on the reduced risk of stroke incidence in Japanese population: The Japan public health center-based study cohort. Stroke 2013; DOI:10.1161/STROKEAHA.111.677500.
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