Food for Thought, Literally

by Cheong E Von 

At a Glance:

  • Food plays an important role in maintaining brain health and cognitive function.
  • At the molecular level, food affects the brain by altering the levels of brain-derived neurotrophic factor (BDNF), synaptic transmission as well as membrane fluidity of the brain.
  • Nutrients that may promote brain health include omega-3 fatty acids and antioxidants.
  • Lifestyles that may associate with healthy cognitive function are exercising, moderating calorie consumption, and adopting a Mediterranean diet.

“Food is like a pharmaceutical compound that affects the brain,” said Dr. Fernando Gómez-Pinilla, a professor of neurosurgery and physiological science at the University of California, Los Angeles (UCLA) [1]. He has analysed more than 160 studies on how food affects the brain. In July 2008, the results of his analyses were compiled and published in the journal Nature Reviews Neuroscience [2].

In this article, I attempt to explain the points raised by Dr. Gómez-Pinilla and at the same time, include information from other researches on this subject.

It was evident from Dr. Gómez-Pinilla’s review that over the years, an increasing number of studies have unravelled the significance of dietary factors on brain health and cognitive function. This raises the exciting possibility of nutrition being a simple yet powerful tool in enhancing brain power and shaping the landscape of neurological diseases prevention.

The mechanisms in which food affects brain processes are varied. Synaptic transmission, membrane fluidity and plasma levels of brain-derived neurotrophic factor (BDNF) are some of the notable pathways that mediate the effects of certain foods on brain health and cognitive ability [2].

Despite the increasing body of work highlighting the link between nutrition and brain health, the notion of food affecting the brain is yet to be readily accepted by the general public. A sustaining momentum of research elucidating the role of food in brain health is therefore needed.

Brain-derived neurotrophic factor (BDNF)

A key component in the molecular basis of food’s effects on the brain is a nerve growth factor known as BDNF. BDNF promotes the survival of nerve cells known as neurons through its role in neuronal growth, differentiation and maintenance [3]. This protein also plays a significant role in the regulation of synaptic plasticity – an important aspect of learning and memory. Decreased levels of BDNF were observed in patients with Alzheimer’s and Parkinson’s disease. This led researchers to believe that BDNF promotes the survival of all major neuronal types affected in Alzheimer’s and Parkinson’s disease such as the hippocampal and neocortical neurons [4].

BDNF is found in regions of the brain that control eating, drinking and body weight, hence conferring it its role in the management of these functions [3]. Studies have also shown that nutrition and exercise can significantly influence BDNF levels [2,5]. This provides an important insight into how we can manipulate our diet and lifestyle to enhance brain power.

Figure 1: Dietary omega-3 fatty acids can affect synaptic plasticity and cognition. Omega-3 fatty acids enhance synaptic transmission via the activation of energy-generating metabolic pathways and by maintaining membrane ionic permeability [2]. This subsequently affects brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF1) molecules which act at presynaptic and postsynaptic receptors to activate several signalling systems. These signalling systems facilitate synaptic transmission and support long-term potentiation that is associated with learning and memory. Figure adapted from [2]. Illustration by Charis Loke.
Figure 1: Dietary omega-3 fatty acids can affect synaptic plasticity and cognition. Omega-3 fatty acids enhance synaptic transmission via the activation of energy-generating metabolic pathways and by maintaining membrane ionic permeability [2]. This subsequently affects brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF1) molecules which act at presynaptic and postsynaptic receptors to activate several signalling systems. These signalling systems facilitate synaptic transmission and support long-term potentiation that is associated with learning and memory. Figure adapted from [2]. Illustration by Charis Loke.
The effect of omega-3 fatty acids on neuronal excitability and BDNF

Docosahexaenoic acid (DHA) is the most abundant omega-3 fatty acid in the mammalian brain, accounting for more than 30% of phospholipid composition of the brain’s plasma membrane [2]. The hydrophobicity of the membrane core confers a high degree of flexibility and enables direct interaction with membrane proteins, and hence, speeding neurotransmission [6]. This renders DHA a crucial role in neuronal excitability and synaptic function.

In his review, Dr. Gómez-Pinilla highlighted the trajectory of studies investigating the effects of omega-3 fatty acids on the brain. Some studies are based on evaluating the effects of omega-3 fatty acids in reducing cognitive deficit among patients with psychiatric disorders [2, 7-11]. On the other hand, some attempts have been made to determine how omega-3 fatty acid supplementation impact the performance of school children [2, 12-15].

A research involving 1,613 individuals ranging from 45 to 70 years old showed that the consumption of fatty fish and marine omega-3 polyunsaturated fatty acids was linked to the reduced risk of cognitive impairment in the middle-aged population [16]. Cognitive function was assessed in terms of memory function, higher order information processing and complex speed tasks.

Since the brain and the body are deficient in the machinery to make DHA, we must obtain the amount of DHA we need through our diet. Dietary sources of DHA include fatty fish like salmon and walnut.

The effect of oxidative stress and moderate caloric restriction on BDNF

Calories come from the energy derived from the electrical bonds between carbon atoms in food. Our body removes the remaining carbon atoms by inhaling a lung full of oxygen and exhaling carbon dioxide. Unfortunately, the leftover oxygen atoms eventually become free radicals that can cause cell injury and death in our body [17]. In a series of experiments investigating the relationship between oxidative stress and BDNF, it was found that rats maintained on a diet high in saturated fat for two months had reduced BDNF mRNA and protein levels and exhibited a decline in cognitive function relative to control rats on a regular diet [5].

Therefore, moderate caloric restriction could provide protection to the brain by reducing oxidative damage and elevating levels of BDNF – an important modulator of synaptic plasticity and cognitive function [2].

Antioxidants

An array of neurological conditions are associated with oxidative stress, as the brain is exposed throughout life to oxidative stress. It is therefore important to consume foods containing antioxidants. Blueberries, for example, are known for their strong antioxidant capacity. Examples of other micronutrients with an antioxidant capacity include vitamin E and curcumin. Vitamin E is abundant in fortified cereals and green leafy vegetables whereas curcumin is a prime ingredient in curry powder. The potent antioxidant properties of curcumin have been suggested to be the contributing factor to the low prevalence of Alzheimer’s disease in India [1].

Mediterranean Diet

Figure 2: An ideal Mediterranean food template. Illustration by Charis Loke.
Figure 2: An ideal Mediterranean food template. Illustration by Charis Loke.

In recent years, studies elucidating the benefits of Mediterranean diet in brain health have been gaining momentum. A Mediterranean diet comprises general characteristics of a diet and lifestyle as illustrated in Figure 2.

In a study aimed at assessing the effect of Mediterranean diet on plasma BDNF levels, it was shown that adherence to a Mediterranean diet supplemented with nuts was associated with significant increases in the plasma BDNF levels of participants with prevalent depression [18]. It is unclear why participants with prevalent depression showed significant improvement in plasma BDNF levels when assigned to a Mediterranean diet relative to other participants. However, this finding raises an exciting possibility for the incorporation of a Mediterranean diet in enhancing brain health.

Similarly, the Northern Manhattan Study unravelled the potential of a Mediterranean-style diet in conferring protection to the small blood vessels in the brain [19]. The researchers used magnetic resonance imaging (MRI) scans of the brain to measure white matter hyperintensity volume (WMHV). WMHV indicates damaged small blood vessels that can cause small silent strokes and affect cognitive performance over time. The study showed that people with the highest Mediterranean diet scores had the lowest white-matter volume burden. However, the same study also cautioned that randomised trials are needed to prove this association.

“…the classical perception that food merely functions to provide energy has been displaced by the increasing awareness of its ability to prevent diseases and shape our well-being.”

Conclusion

The knowledge that diet has the potential to enhance brain health and cognitive function provides a significant insight into the power of lifestyle factors in shaping our well-being. The growing body of research on this subject has enabled increased understanding on the mechanisms in which dietary factors can affect the brain and identification of specific benefits to the brain conferred by particular nutrients. These discoveries raise many exciting possibilities, paving a way for diet to be incorporated into treatment regimens in neurology. However, more work will have to be done to fill the existing loopholes and provide substantial evidence on certain associations proposed.

Over the years, the classical perception that food merely functions to provide energy has been displaced by the increasing awareness of its ability to prevent diseases and shape our well-being. Ironically, with the advent of research and development, we are travelling back to the era where Hippocrates said “Let food be thy medicine” – food for thought, literally, indeed.

About the Author

Cheong E Von is a medical undergraduate at University College Cork, Ireland. She can be contacted at [email protected] Find out more about E Von by visiting her Scientific Malaysian profile at http://www.scientificmalaysian.com/members/cheongevon/.

References

[1] Wolpert, S. Scientists learn how what you eat affects your brain  and those of your kids. UCLA; Newsroom [July 9, 2008]. http://newsroom.ucla.edu/portal/ucla/scientists-learn-how-food-affects-52668.aspx

[2]. Gómez-Pinilla, F. (2008) Brain foods: the effects of nutrients on brain function. Nature Reviews Neuroscience, 9: 568-578.

[3] U.S. National Library Medicine. BDNF. Genetics Home Reference: Genes. [reviewed Mar 2013; published Aug 12, 2013]. http://ghr.nlm.nih.gov/gene/BDNF

[4] Murer, M.G., Yan, Q. & Raisman-Vozari, R. (2001) Brain-derived neurotrophic factor in the control human brain, and in Alzheimer’s disease and Parkinson’s disease. Progress in Neurobiology, 63: 71-124.

[5] Vaynman, S. & Gomez-Pinilla, F. (2006) Revenge of the “Sit”: How lifestyle impacts neuronal and cognitive health through molecular systems that interface energy metabolism with neuronal plasticity. Journal of Neuroscience Research, 84: 699-715.

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[7] Adams, P.B., Lawson S., Sanigorski, A., Sinclair, A.J. (1996) Arachidonic acid to eicosapentaenoic acid ratio in blood correlates positively with clinical symptoms of depression. Lipids, 31 (Suppl): 157–161.

[8] Peet, M., Laugharne, J.D., Mellor, J., Ramchand, C.N. (1996) Essential fatty acid deficiency in erythrocyte membranes from chronic schizophrenic patients, and the clinical effects of dietary supplementation. Prostaglandins Leukot Essent Fatty Acids, 55: 71–75.

[9] Hibbeln, J.R. (1998) Fish consumption and major depression. Lancet, 351: 1213.

[10] Horrobin, D.F. (1998) Schizophrenia: the illness that made us human. Med Hypotheses, 50: 269–288.

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[12] Portwood, M.M. (2006) The role of dietary fatty acids in children’s behaviour and learning. Nutr Health, 18: 233–247.

[13] Richardson, A.J., Montgomery, P. (2005) The Oxford-Durham study: a randomized, controlled trial of dietary supplementation with fatty acids in children with developmental coordination disorder. Pediatrics, 115: 1360–1366.

[14] Osendarp, S.J., et al. (2007) Effect of a 12-mo micronutrient intervention on learning and memory in well-nourished and marginally nourished school-aged children: 2 parallel, randomized, placebo-controlled studies in Australia and Indonesia. Am J Clin Nutr, 86: 1082–1093.

[15] Innis, S.M. (2007) Dietary (n-3) fatty acids and brain development. J Nutr, 137: 855–859.

[16] Kalmijn, S., van Boxtel, M.P., Ocke, M., Verschuren, W.M., Kromhout, D. & Launer, L.J. (2004) Dietary intake of fatty acids and fish in relation to cognitive performance at middle age.; Neurology, 62: 275-280.

[17]. Wenk, G.L. For a healthy life: fewer calories and marijuana. Psychology Today [updated Oct 23, 2012; cited Apr 5, 2013]. http://www.psychologytoday.com/blog/your-brain-food/201210/healthy-life-fewer-calories-and-marijuana

[18] Sánchez-Villegas, A., Galbete, C;., Martinez-González, M.A., Martinez J.A., Razquin, C;., Salas-Salvadó, J., Ramon, Estruch, Buil Cosiales, P. & Marti, A. (2011) The effect of the Mediterranean diet on plasma brain-derived neurotrophic factor (BDNF) levels: the PREDIMED-NAVARRA randomized trial. Nutritional Neuroscience, 14: 195-201.

[19] Gardener, H., Scarmeas, N., Gu, Y., Boden-Albala, B., Elkind, M.S.V., Sacco, R.L., DeCarli, C. & Wright., C.B (2012) Mediterranean diet and white matter hyperintensity volume in the Northern Manhattan Study. Archives of Neurology, 69: 251-256.



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