New research into the relationship between the consumption of flavonoids (a naturally occuring substance in plants), and cognitive decline has been reported in a number of news outlets.
The Daily Express incorrectly extrapolated the findings to talk about Alzheimer’s, claiming “a cherry a day keeps Alzheimer’s away”, and that “eating plenty of colourful foods could slash the risk of Alzheimer’s by more than a third according to research”.
But the study looked at subjective cognitive decline in general, not specifically Alzheimer’s. Subjective cognitive decline is a term used to describe self reported difficulties with cognitive function, which are not detected by objective testing. While most, if not all, people who are diagnosed with Alzheimer’s (a type of dementia) will experience cognitive decline, not everyone with cognitive decline will go on to develop dementia.
The study claims: “Higher intake of total flavonoids was associated with lower odds of subjective cognitive decline”, and that the findings support “a benefit of higher flavonoid intakes for maintaining cognitive function in US men and women”.
In addition, the design of this study means that it shows a correlation between increased flavonoid consumption and reduced cognitive decline, rather than demonstrating causation.
Dr Sara Imarisio at Alzheimer’s Research UK told Full Fact that understanding the risk factors around dementia is vital, but said of the study that “while the researchers found that those eating a diet with high levels of flavonoids were less likely to report memory and thinking problems, we should treat these results with caution.”
She explained that the study relied on participants self reporting their food intake, rather than having it monitored. In addition, as the study didn’t look at dementia, she cautioned that we can’t use it to determine whether a diet high in flavonoids would have any effect in either preventing or delaying the onset of the condition.
Dr Imarisio added: “Dementia is caused by a complex mix of age, genetics and lifestyle factors. From this study alone we are unable to untangle diet or a specific food component from other lifestyle factors which contribute to dementia risk.
“While a balanced diet is one way we can help to maintain a healthy brain, the best current evidence points to a number of other lifestyle factors that can also play a role. These include not smoking, staying mentally and physically active, drinking within the recommended guidelines and keeping blood pressure and cholesterol in check.”