One is made of fruit. The other is caffeinated. So a smoothie is a healthier option than a coffee, right? Don’t be so sure, says Michael Mosley, as he weighs the evidence.
Which is healthier – coffee or smoothies?
It seems obvious that the answer must be a smoothie. After all, drinking coffee is a necessary evil while having a smoothie, made from fruit, is part of your five-a-day. But when you look into the scientific studies they reveal something much more surprising. Let’s start with coffee.
There have been numerous claims down the years that drinking coffee will increase your risk of a whole range of terrible things from heart disease to cancer.
These claims have been largely based on case control studies, where you take a group of people who drink coffee and compare them with another matched group who don’t.
The problem with this approach is that coffee drinkers are more likely than non-coffee drinkers to have other “bad” habits, like drinking alcohol or smoking, so it is hard to tease apart what is really doing the harm.
A more reliable way to get at the truth is to do what is called a prospective cohort study. You take a group of disease-free individuals, collect data about them, then follow them for a large number of years to see what happens.
When scientists collected data on the coffee drinking habits of 130,000 men and women and then followed them for over 20 years they found that coffee is rather a good thing (The Relationship of Coffee Consumption with Mortality, Annals of Internal Medicine, June 2008).
They crunched the numbers and concluded that “regular coffee consumption was not associated with an increased mortality rate in either men or women”.
In fact, data from this study suggests that moderate coffee consumption is mildly protective, leading to slightly lower all-cause mortality in coffee drinkers than non-coffee drinkers. Based on this and other studies the most effective “dose” is two to five cups a day. More than that and any benefits drop off. There are hundreds of different substances in coffee, including many different flavonoids (compounds widely found in plants that have antioxidant effects). Which of these ingredients is beneficial, we simply don’t know.