The Science behind the Headlines
6 November, 2009
This headline came from the November 3 Bangkok Post and similar articles appeared in Singapore, Australia and India. The article is based on work done in the UK by researchers studying a group of British civil servants. The study subjects were divided into two groups: one group who ate mainly “whole foods” (heavily loaded by vegetables, fruits and fish); and another group that ate mainly “processed foods” (heavily loaded by sweeteneddesserts, fried food, processed meat, refined grains and high-fatdairy products).
The authors reported that study participants who ate mainly processed foods were 58% more likely to report symptoms of depression than participants who ate mainly whole foods. The authors also claimed that a diet based on whole foods was protective against developing depression. The results were published in the British Journal of Psychiatry.
On the surface, this seems to argue against eating processed foods, but how strong is the “link”? There are at least three areas that should be examined more thoroughly before concluding that the science behind this finding is compelling. First, the participants in this study all reported their dietary habits over long periods of time by personal recollection. These recollections were not independently verified. Second, the symptoms of depression were all reported by the participants themselves and there was no clinical study of all participants. Third, while the difference in numbers of people reporting depression in the two groups was found to be statistically significant, the inherent unreliability of self reporting dietary habits and symptoms of depression call into question whether the difference is large enough to be meaningful.
Even if the difference between the two groups is real, it is not all clear that eating a processed food diet can be claimed to be a cause of depression or that eating a whole food diet protects against depression. Other possible explanations might be that people who become depressed seek out fatty foods rather than vice-versa. Or it could be that people who feel good about themselves report eating whole foods even if they do also indulge in processed foods. While the numbers reported in the study were sufficient to garner headlines around the world, the real story will have to wait for a more thorough investigation of the questions not answered by this study.
