Drinking coffee and tea every day may actually benefit people with heart troubles.
New Australian research has linked caffeine consumption from the two popular drinks to decreased rates of arrhythmias, or abnormal heart rhythms.
The researchers, however, warn against the consumption of energy drinks that contain high levels of caffeine for anyone with a pre-existing heart condition.
Arrhythmias cause the heart to beat too fast, slow or unevenly.
Many clinicians advise patients with atrial or ventricular arrhythmias to avoid caffeinated beverages.
“There is a public perception, often based on anecdotal experience, that caffeine is a common acute trigger for heart rhythm problems,” said Dr Peter Kistler, director of electrophysiology at Alfred Hospital and Baker Heart and Diabetes Institute.
“Our extensive review of the medical literature suggests this is not the case,” he said.
Researchers conducted a review of 11 major international studies involving 360,000 people and found caffeine had no effect on ventricular arrhythmias (VAs).
The analysis suggests caffeine intake of up to 300 mg/day may be safe for patients with arrhythmias. This equate to roughly three cups of coffee per day.
However, there may be individual differences in susceptibility to the effects of caffeine on the factors which trigger arrhythmias in some, the researchers noted.
“Caffeinated beverages such as coffee and tea may have long term anti-arrhythmic properties mediated by antioxidant effects and antagonism of adenosine,” said Dr Kistler.
“In numerous population-based studies, patients who regularly consume coffee and tea at moderate levels have a lower lifetime risk of developing heart rhythm problems and possibly improved survival.”
The study is published in The Journal of the American College of Cardiology. You can access it here.
American scientists have unearthed fresh evidence that coffee exerts protective effects against heart failure and stroke.
According to the researchers, for every extra cup of coffee drunk per week, there was a 7% reduction in risk of heart failure and an 8% risk reduction for stroke.
So, is this more good news for coffee lovers, or a case of be careful what you read?
As the researchers explain in the media article:
We don’t know if it’s the coffee, compounds in the coffee or behaviour associated with drinking coffee.
The data comes from observational studies showing an association between coffee consumption, and heart failure and stroke. It does not prove causation. It shows that people who drank more coffee had lower rates of heart failure and stroke, not that drinking more coffee was responsible for reducing this risk.
There may be other reasons why people with heart failure and those who have had a stroke drink less coffee, for example, being on fluid restrictions for medical reasons, or not being able to move independently enough to make a cup of coffee.
That doesn’t mean you should avoid having another cup of coffee. A review of 20 observational studies from 2014 found those who drank the most coffee had longer life expectancies than those who drank the least or no coffee.
Again, these studies showed correlation not causation, but the evidence to suggest coffee is good for you is mounting.
The study used a powerful new statistical approach called random forest machine-learning methods. This uses all the individuals’ data to construct multiple decision trees and work out what the common patterns are when predicting their health outcomes. The researchers said this technique was a bit like the algorithms used in the marketing programs that predict our shopping behaviours.
The researchers confirmed that high blood pressure, high blood cholesterol and older age increased the risk of heart disease. They also identified that higher intakes of coffee predicted a lower risk of heart failure and stroke.
Lastly, the researchers created a statistical model that included the well-documented heart disease risk factors – age, sex, total and HDL (good) blood cholesterol levels, blood pressure, smoking and diabetes – that are used to calculate a person’s Framingham Risk Score. This is a person’s ten-year probability of developing cardiovascular disease, including stroke, heart failure and atherosclerosis (fatty deposits that clog arteries).
This analysis found that including coffee consumption in the equation improved the accuracy of the Framingham Risk Score in predicting heart failure and stroke by 4%.
The researchers reported finding similar trends – the 7% reduction in risk of heart failure and 8% risk reduction for stroke – in two separate studies.
What does this mean?
The study in the media headline was not about heart attack, it looked at heart failure and stroke, which are very different conditions:
Heart attack is triggered by short-term lack of blood and oxygen to the heart muscle causing some muscle cells to die
Heart failure means the heart can’t pump blood around the body adequately
Stroke is when the blood supply to the brain is interrupted by either a blockage or a burst blood vessel.
This difference is important because while something might be good for the heart muscle itself, it’s not necessarily good for the blood vessels in the heart and brain.
The data was from a conference abstract only. So it includes very limited details of the methods and results, and misses important information such as:
which variables were adjusted for in the statistical analyses (external factors that might skew the results)
how coffee intake was assessed
whether decaffeinated coffee was included, and
exactly how much was consumed each day or over the week.
While it’s great to hear about early research findings, the data has not gone through the full peer review publication process and so we will have to wait to eventually read the full paper.
Most importantly, this data comes from observational studies and shows an association between coffee consumption and heart health. It does not prove causation.
So is coffee good for your health?
If you are a smoker, it’s wise to avoid regular coffee. A review of the best evidence found a higher risk of lung cancer for smokers who drank regular coffee, although drinking decaffeinated coffee was suggestive of a lower risk.
Among those with high blood pressure, caffeine in coffeedoes lead to an immediate increase in blood pressure that can last a few hours. However, there is no evidence of an overall higher risk of heart disease.