Source/Physicians Committee for Responsible Medicine

Thursday, April 16, 2015

Review: Power Foods for the Brain

By: David O. Kennedy, Ph.D.

Editor's Note: Can a plant-based diet help stave off dementia and Alzheimer’s disease? Neal Barnard, M.D., president of the Physicians Committee for Responsible Medicine, who was featured in the popular documentary, Forks over Knives, makes a case for it in his best-selling book, Power Foods for the Brain (Hachette). In his review, David O. Kennedy leans on his own research on plants, nutrition, and human brain function to discuss the merits of the author’s claims.

T he complex interaction between numerous components of our diets and the functioning of our brains is a fascinating topic. The physiological and biomolecular effects of consuming a range of nutrients, including but not restricted to vitamins, minerals, omega-3 fatty acids, amino acids, and numerous polyphenols and other phytochemicals, are receiving unprecedented attention by researchers. Equally, the detrimental effect of the typical contemporary high-energy and low-nutrient diet is becoming better understood.

The emerging pattern of findings suggests that potential benefits of consuming specific nutrients and adopting a healthier diet can range from almost immediate boosts in cardiovascular and brain function to neuroprotective effects that may be able to extend good brain function deeper into very old age. If you are interested in arriving at a better understanding of this wide, complex, and fascinating topic, then Power Foods for the Brain is probably not really the book for you. If, on the other hand, you fall into the book’s apparent intended demographic—aging, nonexercising, possibly overweight, or prediabetic with a poor diet, who worry that their mental faculties are deserting them—then this book may well be what you are looking for.

Neal Barnard’s self-help book certainly seems aimed firmly at anybody who checks a few of those boxes, and for this group it certainly provides a practical guide to a lifestyle change that almost certainly will pay dividends, in terms of both general health and long-term brain function. In essence, Barnard argues for a strict vegan diet composed entirely of plant-derived foods, a bit of physical exercise, avoiding potentially toxic metals, and engaging in mental exercise. The first two of these will undoubtedly prove beneficial, and the latter two, while unsupported by any clear evidence at present, should do no harm beyond the costs of purchasing new cooking pots and brain-training computer software.

My only reservation regarding the book’s intentions involves research showing that, for public-health messages, anxiety is only an effective driver of change if the proposed remedy is achievable by the audience. If it isn’t, individuals will engage in an entirely internal process of anxiety-reducing psychological self-defense, typified by denial that the fear-inducing outcomes apply to them at all. The message in Power Foods for the Brain is delivered by increasing the reader’s anxiety about the prospect of their imminent descent into cognitive dysfunction and dementia. However, I wonder whether if Barnard’s all-or-nothing, hardcore vegan remedy, which disallows all meat, fish, and dairy products, may simply be seen by the typical intended reader as being unachievable. It may be difficult to follow for anyone who feeds a family or partner, and it will inevitably involve a major life-changing modification of eating habits, including avoiding the processed, ready-made foods in the typical diet in favor of cooking and preparing all foods from healthy, plant-derived ingredients. The diet may be well worth following, but if the remedy being proposed doesn’t seem achievable (and for many it might not), it isn’t likely to be adopted.  

In reality, it isn’t necessary to become a vegan to benefit from improving your diet. Simply shifting your dietary habits so that you avoid the bad aspects of our contemporary diets—energy-dense foods, "bad" fats, and refined sugars—while increasing your consumption of fruits, vegetables, and other plant-derived foods will pay dividends in terms of potential improvements to cardiovascular and metabolic health and improved or preserved brain function, particularly if coupled with increased exercise. So, maybe proposing a slightly softer remedy—one that acknowledges simply that the farther you travel down the road toward replacing the unhealthy elements of your diet with healthy plant-derived foods, the better—might be a more effective message at the end of the day.

Throughout, Barnard seasons his advice with a smattering of relevant science, and the scientific rationale for his dietary recommendations is written in an accessible, interesting style. He certainly has a knack for describing complex biology in understandable language. But where the science content falls down is in the very limited scope of the information; the book provides only a brief scientific rationale for reducing the consumption of “bad” saturated fats and trans fats and increasing consumption of “good” omega-3 fats. It also espouses building a “vitamin shield” by increasing consumption of foods high in vitamins E, B6, B9, and B12. The stated rationale for boosting the three B vitamins is their contribution to breaking down a naturally occurring, potentially neurotoxic amino acid called homocysteine, thus preventing its buildup and reducing its toxicity. However, it is unclear to date whether homocysteine is a causal factor in cognitive decline and dementia or merely a coincidental phenomenon related to less than optimal intake of these vitamins. Surprisingly, the book gives no consideration to the potential benefits of increased consumption of vitamins A, B1, B2, B3, B5, B7, C, or D, all of which have an equally strong claim in terms of potential benefits to brain function.

Even more surprisingly, there is no mention at all of the other bioactive phytochemicals richly expressed in the diet of plant-derived foods that the book espouses. For instance, the words "flavonoid" and "polyphenol" are not mentioned once, despite good evidence that these (and their other phenolic stablemates) are the classes of plant-food-derived compounds that may do the heavy lifting in terms of improved cardiovascular function and neuroprotection. Similarly absent are the obesity-inducing scourge of refined sugars and high-fructose corn syrup, and the complex interplay between brain function and the diet-induced deterioration in multiple cardiovascular and metabolic parameters. Simplification may be a necessary property of a self-help book aimed at a nonscientific audience—the message has to be understandable and clear, and not fogged by too much complexity—but while the proposed diet probably will work, it won’t necessarily succeed for the stated reasons.

Another good argument Barnard doesn’t touch is that your current brain function is, in part, a reflection of your lifelong diet to date, an argument that can be translated into clear societal advice to improve diets and the delivery of key nutrients from cradle to grave. While his book provides a potentially effective method of soothing some of the damage of a misspent life in dietary terms, it doesn’t address this wider point at all. To me, this can only reduce the potential audience and therefore the impact of the book’s message.

The recipes at the end of the book do look tasty. I didn’t spend long hours in the kitchen trying them out, but I suspect my children might be on the receiving end of some of the healthy, sweeter options this summer (they’ll definitely be trying the banana ice cream). But here, too, I would have liked to see more information on how to plan a sustainable vegan diet that contains adequate levels of all essential nutrients. All in all, the book is a useful guide to preserving brain function by modifying the diet (and getting that equally important exercise), but a little more of the fascinating science around this subject would have been appreciated.


About Cerebrum

Bill Glovin, editor
Carolyn Asbury, Ph.D., consultant

Scientific Advisory Board
Joseph T. Coyle, M.D., Harvard Medical School
Kay Redfield Jamison, Ph.D., The Johns Hopkins University School of Medicine
Pierre J. Magistretti, M.D., Ph.D., University of Lausanne Medical School and Hospital
Robert Malenka, M.D., Ph.D., Stanford University School of Medicine
Bruce S. McEwen, Ph.D., The Rockefeller University
Donald Price, M.D., The Johns Hopkins University School of Medicine
Charles Zorumski, M.D., Washington University School of Medicine

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