In the past, 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 probably does not increase the risk of heart disease; and in some cases may even be beneficial.
Why the discrepancy?
Some earlier studies did not take other heart disease risk factors into sufficient account, such as lack of exercise and smoking. 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.
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 blood pressure by up to 10 mm Hg. However, in people who regularly drink coffee, 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 they drink a lot of coffee.
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 people 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 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 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 percent 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 some people to metabolize caffeine slowly. It appears that in these people 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 blood levels. However, paper filters reliably remove these lipid-active substances. So coffee brewed with paper filters does not increase blood cholesterol levels.1 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.
Be Aware of Differences in Caffeine Sensitivity
While all this information is comforting to people who enjoy caffeinated beverages, we need to be aware that caffeine affects different people in very different ways. In particular, some are very sensitive to even small amounts of caffeine.
People who are caffeine-sensitive can indeed experience the jitters, palpitations, insomnia and other symptoms when they ingest caffeine. These individuals should limit their caffeine intake
Sensitivity to caffeine is largely determined by the activity of the CYP1A2 enzyme in the liver. The more active the CYP1A2, the less sensitive we are to caffeine. Several factors affect CYP1A2 activity:
- Age: CYP1A2 activity tends to decrease with age, so older people tend to be more sensitive to caffeine
- Sex: women tend to have lower CYP1A2 activity than men.
- Oral contraceptive use and pregnancy: estrogens inhibit CYP1A2 activity and caffeine sensitivity increases. In general, pregnant women should try to limit or avoid caffeine.
- Genetic makeup: Several gene variants have now been identified that affect CYP1A2 activity. While genetic testing can categorize your level of caffeine sensitivity, having formal testing is generally not necessary for you to know—at least generally speaking—whether or not you are very sensitive to caffeine. And if you are, it is likely that nobody needs to tell you to cut back.
Black Coffee or Cream and Sugar?
Almost all of these studies looked at coffee drinking without regard to whether the coffee was consumed with cream, sugar, other ingredients—or just black. This makes sense because whether you drink your coffee black or not, odds are that you often consume it with other foods. And it really doesn’t make any difference to your digestive system whether the “other foods” are mixed into the coffee itself, or consumed separately with a fork or spoon. 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, just as eating other unhealthy foods would do.
A Word From Verywell
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 some cases may even be beneficial.
As with everything else, moderation is the key. In most people, however, 1 to 4 cups of coffee per day appears safe for cardiac health.
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