Can blueberries boost brainpower? Our junior EinSTein myth-busters put health claims to the test.
The Daily Mail headline: “A bowl of blueberries keeps the brain active in the afternoon” sounds promising. Our class interrogates the article, noting that while blueberries are delicious, blueberry ‘companies’ have a vested interest in selling them, so it’s not clear how much we can trust what they have to say. First risk of bias successfully identified. Tick. The students are also well aware of the tricks and tools of marketing, commenting on the ‘pretty’ packaging and ‘pretty’ lady being used to sell the health message. Later we talk about the research behind the headlines and whether similar issues of ‘competing interest’ can affect researchers and universities. We also consider the problem of fidelity between what actually happened in the study with what later gets reported in the media. Even going so far as to read a press release from Tufts University, where we discover that much of the original research in this area was done in rats, using blueberry extract, with primary outcomes relating to motor behaviour and short-term memory loss. Not quite what the Daily Mail article would have us believe.
This is not, as you might expect, a first-year university tutorial on science communication. Instead, I’m in the junior school at Lingfield Notre Dame School in Surrey, having invited myself along to watch Dr. Sarah Pannell deliver a lesson in EBM through their junior scholars program. We have enthusiastic group of budding scientists from across Years 4-6, who have devoted Thursday afternoon to conducting their own experiment on the influence of blueberries on memory. After a quick primer on health claims and an explanation of the experimental design, we’re off. The first part of the experiment sees the whole class tested on their capacity to memorise and then accurately recall a list of ten assorted household items presented for 60 seconds on a covered tray. This puts me in mind of a favourite childhood party game, where the guest who could remember the most items correctly, won the biggest prize. I’m pleased to see that the intensity of competition amongst our scholars is no less fierce than my own friends at the same age! While the scholars are memorising the first set of items, we randomise them into two groups ‘A’ and ‘B’ handing a coloured card to each. Children in group B have been assigned to eat ‘a large handful’ of blueberries, while children in group A must wait patiently until the end of the session to receive their share. Admittedly we made provision in the allocation process for children who may have been allergic (none reported) or who did not enjoy blueberries (n=2). We also checked to see if any had already consumed blueberries that day. According to their self-report, none had.
While group B ate their blueberries, and allowing for a little digestion time, we counted up the results from the first memory test, calculated the mean number of items recalled, and worked our way through the press release. Scholars accurately identified confounders in our study and in the press release: differences in ‘dose’ between individuals in Group B, recruitment of rats rather than humans, and interestingly, the use of ‘lab’ rats versus ‘wild’ rats, which it was suggested, may skew their capacity to learn new things. The group got somewhat stuck on the concept of ‘reversing’ memory loss, but had no problem pointing out that the rats were ‘old’ (equivalent to 70-75 year old humans) and that their diet had included extract of strawberries, spinach and blueberries, not just berries alone. So when I asked them if we could use the results of the reported study and apply it to our experiment, it was an emphatic ‘NO’. After 10 minutes, we repeated the memory test with a new set of objects. The mean number of items recalled went down in both groups, creating the perfect stimulus for discussion on ‘effect’ and what we would need to see, in order to know that the groups had a real difference between them. It also intrigued our scholars – was the second test harder somehow? Had the blueberries helped or hindered those who ate them? Could we have improved our scores with practice?
While we didn’t get time to follow up the concepts of randomisation or blinding in more detail, we did touch on the uneven split in group numbers and between male and female participants. Throughout the afternoon, there was an encouraging, collaborative environment in the classroom, and all scholars offered an opinion and engaged in critical reflection at least once during the session. Personally, it was an absolute joy to see the students engaging so enthusiastically with the material and with the complexities of EBM. The session also gave both Dr Pannell and I confidence that it would be possible to extend much of the good work on teaching EBM in schools (read more here) to a younger audience. Our final conclusions? While blueberries look good on paper, and may help to reduce memory loss in geriatric rats, for junior scholars at Lingfield Notre Dame, they were but a tasty treat on the road to working critically and scientifically.
Sarah McNeill is a visiting student at the Centre for Evidence-Based Medicine and a postgraduate at the Australian National University, Canberra.