Review
Exercise and the brain: something to chew on

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Evidence is accumulating that exercise has profound benefits for brain function. Physical activity improves learning and memory in humans and animals. Moreover, an active lifestyle might prevent or delay loss of cognitive function with aging or neurodegenerative disease. Recent research indicates that the effects of exercise on the brain can be enhanced by concurrent consumption of natural products such as omega fatty acids or plant polyphenols. The potential synergy between diet and exercise could involve common cellular pathways important for neurogenesis, cell survival, synaptic plasticity and vascular function. Optimal maintenance of brain health might depend on exercise and intake of natural products.

Introduction

‘To get back my youth I would do anything in the world, except take exercise, get up early, or be respectable’ (Oscar Wilde, The Picture of Dorian Gray, 1891).

Unfortunately for those of us who subscribe to this outlook, physical activity is the most effective way to maintain a healthy body and mind. This might seem obvious; however, the evidence that exercise is beneficial for general health (i.e. prevention of hypertension, heart disease, type II diabetes, osteoporosis and depression) began to be taken seriously in western society only towards the end of the previous century. Indeed, in 1975 it was observed that ‘physical fitness and physical education have no respected place in the American public health movement. Their practitioners have been labeled by at least one elder statesman of public health as “the big-muscle boys”, and this contemptuous attitude has persisted to this day’ [1]. However, a decade later, in view of the increasing evidence for the health benefits of exercise ‘the Public Health Service specified “Physical Fitness and Exercise” as 1 of the 15 areas of greatest importance for improving the health of the public’ [2].

Study after study has now shown that the risk of contracting cardiovascular, metabolic and metastatic diseases is mitigated by exercise and a diet containing fruits and vegetables 3, 4. However, it is not as well appreciated that exercise and a healthy diet also provide substantial benefits for brain function. Physical activity improves cognition and might delay age-related memory decline 5, 6. In addition, exercise protects against brain damage caused by stroke [7], promotes recovery after injury [8] and is an antidepressant [9].

Similar to exercise, nutrition affects brain function. Consumption of food high in saturated fats and cholesterol increases the risk of cognitive decline, whereas dietary restriction benefits learning and protects the brain from oxidative stress [10]. There is also increasing evidence that dietary supplements enhance learning and memory. Of interest are the omega fatty acids, certain spices, teas and fruits [11]. Interestingly, these supplements enhance the benefits of exercise for brain function 11, 12, 13. Possible common mechanisms of action for exercise and diet on cognition are discussed.

Section snippets

Young and aged humans

Few studies pertaining to exercise and cognition have been carried out in children and young adults [6]. However, a positive correlation between physical activity and learning and intelligence scores was reported in a meta-analysis of school-age children [14]. In addition, in college students reaction time [15] and vocabulary learning were faster immediately after intense running [16]. Similar results were obtained in young adults after 12 weeks of aerobic training (average age 33) [17]. This

Diet and cognition

In recent years there is increasing evidence that changes in diet can benefit cognition. The most rigorous alterations are intermittent fasting and caloric restriction. Research in animals has shown these regimens enhance learning, neurogenesis and neurotrophin levels. In humans limited calorie intake correlates with a reduced risk for AD [10]. However, dietary restriction regimens are difficult to maintain. In fact, the search for caloric restriction mimetics is a focus of intense research [41]

Mechanisms that mediate the effects of exercise and nutrition on the brain

Research pertaining to mechanisms underlying the effects of exercise on brain function has focused on changes in neurotransmitters, neurotrophins and vasculature [5]. Specific to the hippocampus, a brain area important for learning and memory, is the robust increase in new neurons with exercise [30]. The beneficial effects of running on cognition could be mediated, at least in part, by enhanced hippocampal neurogenesis 30, 47. Elucidation of effects of nutrition on the brain, by contrast, has

Acknowledgements

This review was supported by the Intramural Research Program of the National Institutes of Health, National Institute on Aging (www.nia.nih.gov). I thank Mark Mattson for comments on the manuscript, David J. Creer for editorial assistance and K.C. Alexander for figure preparation.

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