Previous research suggests that people who break down caffeine more slowly have a greater risk of heart disease. It does not come out. Kris Atomic
There is only one thing better than a hot cup of coffee in the morning: a new research paper that tells you that your daily habits are good for your health. The July 2018 headlines featured good news from the journal JAMA Internal Medicine.
As with most previous studies, the role of JAMA found that people who drink coffee have a lower risk of death of any cause - and in particular, from death from heart disease and cancer - in the course of study.
But this study only shows a correlation between drinking coffee and a lower risk of early death. It does not show coffee is the cause of lower risk.
Research is important, however, because it reverses the theory that people who drink six or more cups of coffee a day have a higher risk of early death. This issue has not been effectively addressed in previous studies.
How was the research conducted?
This is an expected test, which has tracked nearly half a million British residents over ten years as part of the UK Biobank Study.
In a prospective trial, subjects are recruited, then their health and illness are observed over time. We have a great idea of how healthy they are to start with. We also have a good idea of other factors that may affect their health from the start, rather than trying to regenerate them after they get sick.
In a baseline questionnaire, the subjects provided detailed responses to coffee consumption (how often, how often, what type of coffee and whether it was caffeinated or decaffeinated), as well as other factors such as alcohol, tea, race, education, physical activity, body mass index (BMI) and smoking (including intensity, type of tobacco and time of departure).
All volunteers were genotyped to determine their genetic variations of the major caffeine metabolizing enzymes.
The health status of the participants was monitored during the study and, if they died, their cause of death was determined by the National Health Service using internationally recognized standards.
What did they do?
After considering factors such as smoking and alcohol use, the researchers found that fewer coffee drinkers died than those who did not drink coffee during the ten-year study period.
Depending on the amount consumed, coffee drinkers are around 5-10% more likely to die from heart disease, cancer and other causes during the study than non-coffee drinkers.
Compared to those who do not drink coffee, those who ate one cup of coffee a day had an 8% lower risk of premature death; it increased to a lower risk of 16 for people who drank six cups a day. People who drink up to eight cups of coffee a day are 14 times less likely to die prematurely than those who do not drink coffee.
This pattern is seen for all types of coffee, including instant and decaffeinated coffee.
The researchers found drinking six or more cups of coffee a day was no longer associated with an increased risk of death. While some previous studies have hinted that this (see here and here) the relationship is not yet certain. The current study is the most comprehensive discovery of high coffee consumption to date.
They also found people with a history of cancer, diabetes, heart attack or stroke were not at an increased risk of death from drinking moderate amounts of coffee.
Finally, and most importantly, the researchers found that people who do not break down caffeine are not at higher risk of death.
We do not know exactly why coffee is linked to longevity but there are rational explanations. Rawpixel
Initially, researchers thought that people who break down caffeine are more likely to have a higher risk of heart disease because caffeine levels in the blood are higher than the average person. It turns out not so.
What does this mean?
As with previous studies, this is a correlation study. Thus, while there has been a correlation between coffee consumption and a lower risk of death, we cannot say that coffee is the cause of the lower risk of death.
There may be some other variables in the environment that are not relevant. Consumption of coffee may contain more walks, for example, missed in lifestyle questionnaires.
But it still looks like coffee because of the reduced risk of death. While coffee is best known for its caffeine content, it also contains a host of antioxidants such as a caffeic acid and cholorogenic acid, which can have health benefits.
This may be the reason why the JAMA study has a lower risk of death for people who drink decaffeinated coffee. Decaf has also been effective in reducing the risk of heart disease in other studies.
Despite a recent U.S. court decision California coffee companies should carry cancer warning labels, this study supports previous research that coffee consumption is protective against cancer , especially of the colon and liver.
Drinking coffee is also thought to be protective against type two diabetes, Parkinson's and Alzheimer's Disease. However, the effect of coffee consumption is moderate, and should not be replaced by other factors such as diet and exercise.
On the other hand, women who drink coffee may have an increased risk of fracture, and may request to reduce coffee consumption during pregnancy.
This week’s JAMA study isn’t a good reason to be able to drink coffee, but if you love the drink, you don’t have to worry about having another cup. - Ian Musgrave
This is a fair and accurate analysis. Although a surveillance study, this is still good news for coffee drinkers. We are unlikely to have a large, randomized controlled trial that can truly answer this practice question.
One limitation of the study, described in the paper, was that the researchers only asked participants to mark what type of coffee they drank predominately. So there may be some misrepresentation of people who regularly drink more than one type of coffee. - Clare Collins
Research Reviews ask newly published studies and how they are reported in the media. The study was conducted by an academic who was not involved in the study, and reviewed by another, to ensure that it was accurate.
