A recent headline in The Australian newspaper claimed :
"American scientists have unearthed fresh evidence that coffee exerts protective effects against heart failure and stroke."
, for every extra cup of coffee drunk per week, there was a 7 per cent reduction in risk of heart failure and an 8 per cent 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 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.
How was the research conducted?
This story came from 2017 Scientific Sessions on November 14. The researchers used data from more than 12,000 adults in the to look for eating and drinking habits associated with .
The study used a powerful new statistical approach called . 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 and .
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 . This is a person’s ten-year probability of developing cardiovascular disease, including stroke, heart failure and (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 per cent.
The researchers reported finding similar trends – the 7 per cent reduction in risk of heart failure and 8 per cent risk reduction for stroke – in two separate studies.
What does this mean?
The study in the media headline was not about , 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 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 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 for smokers who drank regular coffee, although drinking decaffeinated coffee was suggestive of a lower risk.
Among those with does 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.
For a host of other reasons including a lower risk of type 2 diabetes, prostate cancer, liver cancer, and a longer life expectancy, to improve your overall health.
– Clare Collins
Blind peer review
This article was originally published on . Read the . is Professor in Nutrition and Dietetics, . Reviewed by Senior lecturer in Pharmacology, .
