The Imperial College news release states:
A large analysis of current research shows that people who eat at least 20g of nuts a day have a lower risk of heart disease, cancer and other diseases.
The analysis of all current studies on nut consumption and disease risk has revealed that 20g a day – equivalent to a handful – can cut people’s risk of coronary heart disease by nearly 30 percent, their risk of cancer by 15 percent, and their risk of premature death by 22 percent.
An average of at least 20g of nut consumption was also associated with a reduced risk of dying from respiratory disease by about a half, and diabetes by nearly 40 percent, although the researchers note that there is less data about these diseases in relation to nut consumption.
I added the bold, italicized, underlined emphasis. The “can cut risk” statement is causal and should not be used. The “was associated with” statement is accurate, because all that was found was a statistical association found by analysis of 29 studies of more than 800,000 people. It wasn’t a true experiment. There was no intervention. It was an observation of what happened to people over time. The study can be found online.
The news release didn’t have one word about the limitations of the evidence – nothing such as this reminder in the published journal manuscript:
“results from observational studies alone cannot be used to draw conclusions with regards to whether the observed associations are causal”
Let me emphasize: there is a growing body of evidence about the potential benefits of people eating nuts and this large meta-analysis adds to that body of evidence.
But that is no reason to inflate the findings as if they showed something they did not – that nut consumption caused fewer cases of heart disease.
We’ve written about observational studies about nut consumption before. Examples:
Our longstanding primer on the language used to describe observational studies may be helpful for broader understanding.
It’s too late to help these already-published news stories:
New York Times: A Handful of Nuts Is Good For Your Health
Voice of America: Daily Handful of Nuts Reduces Disease Risk: Study
Medical News Today:Daily handful of nuts slashes the risk of disease and death