Review: Exercise and the Brain: Something to Chew On

Exercise

The article reviewed here is ‘Exercise and the Brain: Something to Chew On’ by Henriette van Praag and freely available here.

The issue of exercise and the brain has been covered in some detail in the very interesting book Spark which was reviewed in an earlier post (see here). Given the mention of the role of exercise in the NIH  consensus statement on prevention of dementia and cognitive decline (see here) as well as the evidence supporting the Seattle exercise protocols the role of exercise in promoting healthy cognitive aging is becoming more apparent. Perhaps the story will be a little more complex than is suggested at the current time but it is an exciting area of research given the accessibility of exercise and the potential benefits. Finally this paper was published in the journal ‘Trends in Neurosciences’ which publishes concise reviews allowing the reader to gain a rapid and contemporary overview of a subject area.

Moving onto the contents, this is a brief article which focuses on the synergistic benefits of exercise and diet on cognition. The article gets off to a flying start with a lot of really useful pieces of information. Quoting from the introduction

There is also increasing evidence that dietary supplements enhance learning and memory. Of interest are the omega fatty acids, certain spices, teas and fruits

The author further points out that there is an interplay between the benefits of diet and exercise. The remainder of the article is divided up into the effects of exercise on cognition in humans and rodents, the effects of diet on cognition and the mechanisms of action for these effects. This latter point of exactly how exercise and diet contribute to cognition os obviously the key to developing therapeutic interventions. I thought the discussion around these mechanisms was extremely interesting and it was quite remarkable to hear of the evidence for so many different effects of diet and exercise on the biology of the brain, ranging from neurotransmitter levels, to the mechanism of Long Term Potentiation, dendritic spine density and neurogenesis.

There were a few of particular interest. A central theme which ran through the article was that of the benefits of flavonols. On the basis of this article these compounds are certainly worth a closer look in terms of cognitive health benefits.

Another thought I had while reading the article was that there is some scope for selection of articles which support a main argument, at least in this style of article. Perhaps these reviews can be used in conjunction with meta-analyses or even by articles where the author holds a diametrically opposed view. In any case, I think having a central argument is very useful in being able to manage the vast amount of research material out there.  In comparison with the NIH article referred to above, I find this article slightly easier to get to grips with. As well as citing the evidence, the author proposes a very concrete theoretical model for how these effects might be mediated. By providing these molecular and cellular mechanisms, van Praag is able to take a vast array of evidence and begin to piece it together. Without consideration of neurogenesis, neuronal structural changes and the posited intracellular pathways, how is it otherwise possible to integrate the effects of exercise and diet in a meaningful way?

The only difficulty is that the model is so finely detailed that at this level there are a large number of other factors which will influence the causal chain. These factors range from circadian rhythms all the way through to hormonal changes and genetics. Perhaps the model features very strong relationships which are maintained despite the background fluctuations (noise) in these other factors. At least it is a starting point and the interested reader could return to this article to test this model with other evidence and refine it as appropriate. For example, the relationship between BDNF, exercise and neurogenesis is certainly gaining traction and is just one part of the model described here. I would be interested to return to a similar model in say five years time and I suspect that it would be rather complicated. If that is the case, then it may even impact on the type of advice given to those wanting to use exercise and diet to prevent decline in cognition but we will have to wait and see.

Acknowledgements

Diagram of the flavonol: Author: Yikrazuul. Permission. This has been released into the public domain. http://en.wikipedia.org/wiki/File:Flavonol_num.svg

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