Despite concern that caffeine could raise blood pressure, provoke abnormal heart rhythms and put stress on the cardiovascular system, a new study shows it could do the opposite.Liudmila Chernetska/Getty Images
For years, people with certain heart conditions were often told to go easy on caffeinated coffee.
Because caffeine is a stimulant, there was concern that it could raise blood pressure, provoke abnormal heart rhythms and put stress on the cardiovascular system.
Now, after reviewing the latest evidence, the American Heart Association has concluded that consuming up to 400 milligrams of caffeine a day – equivalent to three to five eight-ounce cups of coffee – is safe for most adults.
What’s more, the evidence shows that regular coffee consumption is associated with several cardiovascular benefits.
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Here’s a breakdown of the association’s new scientific statement on caffeine and cardiovascular health.
How the AHA reached its conclusions
For the statement, published July 20 in the American Heart Association’s scientific journal Circulation, an expert panel reviewed evidence from decades of research on caffeine, coffee and cardiovascular disease.
The panel looked at a wide range of health outcomes including blood pressure, blood cholesterol, coronary heart disease, stroke, heart failure, atrial fibrillation and type 2 diabetes.
The evidence included large observational studies, clinical trials and genetic studies. It also incorporated findings from recent randomized controlled trials that examined coffee’s effect on atrial fibrillation and blood pressure responses.
Key findings
According to the statement, a moderate intake of caffeinated coffee (three to five eight-ounce cups a day) was tied to a lower risk of coronary heart disease, heart failure, stroke, atrial fibrillation, type 2 diabetes and hypertension.
The evidence showed that caffeine could temporarily raise blood pressure, but that with regular coffee drinking, tolerance develops and effects are decreased. Long-term studies of caffeinated coffee consumption generally showed no effect or a lower risk of hypertension with moderate intake.
Strong evidence also consistently linked habitual coffee consumption to protection against type 2 diabetes. A review of 28 observational studies found a 20-per-cent and 30-per-cent lower risk of developing the condition among people who consumed, on average, 3.5 and 5 cups of coffee a day, respectively.
As for atrial fibrillation, most studies found that drinking caffeinated coffee did not increase the risk. Several even suggested it lowered the risk. A recent randomized controlled trial, for example, found a 39-per-cent lower risk of recurring atrial fibrillation among patients assigned to drink one cup of caffeinated coffee a day compared with those who avoided coffee and caffeine.
However, data from clinical trials also consistently showed that cafestol – a compound found in caffeinated and decaffeinated unfiltered coffee – increased LDL (“bad”) cholesterol in the bloodstream. Unfiltered coffees include French press, Greek/Turkish coffee, Scandinavian boiled coffee and, to a lesser extent, espresso. Filtered and instant coffees contain little cafestol.
Not all caffeine sources affect the heart equally
The AHA panel cautioned against extrapolating the potential health benefits observed to energy drinks, which may contain three to four times more caffeine than coffee.
While studies on energy drinks are limited, the evidence suggests they may harm cardiovascular health by increasing blood pressure and triggering abnormal heart rhythms.
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Energy drinks and caffeine-based supplements may also contain other ingredients that alter how quickly caffeine is absorbed and how rapidly it affects the body.
The panel also mentioned that adding sugar, syrups, milk and/or cream to coffee likely reduces its potential health benefits, but more research is needed to understand the impact of these additions.
Coffee contains more than caffeine
The researchers don’t believe caffeine alone explains coffee’s apparent cardiovascular benefits.
Coffee contains hundreds of biologically active compounds, including polyphenols and chlorogenic acid, which may help reduce oxidative stress and inflammation and improve blood sugar.
Coffee also provides small amounts of magnesium and chromium, which play roles in glucose metabolism and insulin action.
What does Health Canada say?
The AHA scientific statement reinforces Health Canada’s recommendation that up to 400 milligrams of caffeine a day is safe for most adults.
What it adds, though, is growing evidence that moderate coffee consumption within this limit is associated with lower risks of cardiovascular disease, atrial fibrillation and type 2 diabetes.
Note: Health Canada advises women who are planning to become pregnant and who are pregnant or breastfeeding to limit daily caffeine intake to 300 milligrams.
Bottom line
While the research suggests that consuming three to five eight-ounce cups of caffeinated coffee each day has cardiovascular benefits, there is no one-size-fits-all recommendation for caffeine intake.
Caffeine tolerance is highly individual and is influenced by age, medications, underlying health conditions, habitual intake and genetics, which affect how quickly caffeine is cleared from the body.
The amount of caffeine that’s right for one person may be too much for someone else, leading to adverse effects such as sleep disturbances, palpitations, headache and anxiousness.
If you’re unsure how much caffeine is right for you, speak to your health care provider.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.
