At this time of year the word ‘diet’ is exclusively used to refer to the new 4, 8 or 12 week plan that will help you ‘drop a dress size’ or ‘blast belly fat’. In fact, when people think about the functions of food they will usually think about its role in fuelling or reshaping the body; it’s unusual for us to think about the influence of diet on brain structure and function. Even though we have an understanding that nutrients from food are important for the health of our organs, e.g. ‘eat carrots for better night vision’ and might even go as far as taking supplements to improve the condition of our skin or hair, we neglect the brain, forgetting that it too is an organ and relies on nutrients from the diet for optimal function. In fact, though your brain makes up only about 2% of your total body weight it accounts for nearly 25% of the body’s energy requirements; it has a huge nutritional demand. So, this January how about making a resolution to take better care of your brain?
A Quick Note on Omega 3s
If we took your brain out of your head, removed all the water, 60% of what was left would be fats, and especially omega 3s. Omega 3 fats are essential fats, ‘essential’ meaning they are crucial to brain function but the body is unable to synthesise them; they must be taken in through the diet. These fats are critical for the normal development of the brain.
There are three forms of omega-3: ALA, EPA and DHA. ALA is the version found in plants, things like chia seed (although they are also relative high in phytates that can reduce the absorption of important minerals) and flaxseeds. EPA and DHA are found in marine sources; oily fish and other seafood. The NHS recommends that we eat two portions of fish per week, of which one should be oily but barely anyone is achieving that intake. DHA is the most abundant essential fat in the brain and is understood to be particularly important for brain development so it is critical during pregnancy, infancy and childhood. As we age EPA comes in to its own providing a protective, anti-inflammatory action as well as supporting neurochemical synthesis and transmission. It’s actually very difficult for the body to make use of ALA; it can use it to synthesis EPA and DHA but not very efficiently and only in tiny amounts so people who avoid animal products and are unwilling to take a fish oil supplement are likely to be deficient.
Supplementation with EPA + DHA has been shown to improve memory performance(2), vocabulary and non-verbal reasoning (3) and may prevent age-related brain shrinkage (4). It may also play a preventative role in the disease course of Alzheimer’s Disease, now the leading cause of death in England and Wales (5). Older people with mild cognitive impairment who were supplemented with DHA and EPA improved their depression scores (6). Omega 3s may also play a preventative role in post-partum depression (7).
A number of studies have shown a positive effect of a healthy diet on brain health and mood. Polyphenols are the anti-oxidant compounds found in berries, green tea, vegetables, spices and cocoa and they have been shown to have a protective effect on brain cells and can even promote the growth of new ones. Flavanols (a type of polyphenol) in cocoa can increase the flow of blood to the brain and as a result may improve cognitive functions such as attention, learning and memory (8). Consuming polyphenols can promote the production of BDNF, a protein that stimulates the growth of new brain cells (9). Low levels of BDNF in the brain have also be implicated in the development of brain disorders such as Alzheimer’s Disease, Parkinson’s, depression, bipolar disorder and schizophrenia (10). Though there is some question about exactly how polyphenols themselves may act on the brain it is a consistent and robust finding that people who consume diets high in polyphenol rich foods (leafy green and brightly coloured vegetables, berries, spices) are less likely to develop depression and age-related decline in brain function. In 2008 a plant- and omega-3-rich diet was suggested as a preventative strategy for Alzheimer’s Disease (11). More recently a large American trial tested a modified Mediterranean Diet and found that it was linked to a lowered likelihood of developing Alzheimer’s (12). A large Spanish studied that followed 15,000 people over 10 years found that, after controlling for other factors such as smoking, activity levels and BMI, those who ate the healthiest diets were up to 30% less likely to become depressed (13).
So, when we’re talking about a diet that protects the brain the evidence suggests that 500g of vegetables and fruit, 10g of dark chocolate, a small glass of red wine and four cups of green tea per day is effective, and supplemental omega-3s may also be beneficial.
Next week I’ll be talking about how exercise can change the structure and function of your brain. Until then, eat your greens!
1. Hamazaki, K., Harauma, A., Otaka, Y., Moriguchi, T. & Inadera, H. (2016). Serum n-3 polyunsaturated fatty acids and psychological distress in early pregnancy: Adjunct Study of Japan Environment and Children Study. Translational Psychiatry, 6, e737. doi: 10.1038/tp.2016.2
2. Yurko-Mauro K., Alexander D.D., van Elswyk M.E. (2015). Docosahexaenoic acid and adult memory: A systematic review and meta-analysis. PLoS ONE. 10:99
3. Muldoon M.F., Ryan C.M., Sheu L., Yao J.K., Conklin S.M., Manuck S.B. (2010). Serum phospholipid docosahexaenonic acid is associated with cognitive functioning during middle adulthood. Journal of Nutrition,140, 848–853. doi: 10.3945/jn.109.119578
4. Conklin S.M., Gianaros P.J., Brown S.M., Yao J.K., Hariri A.R., Manuck S.B., Muldoon M.F. Long-chain omega-3 fatty acid intake is associated positively with corticolimbic gray matter volume in healthy adults. Neurosci. Lett. 2007;421:209–212. doi: 10.1016/j.neulet.2007.04.086.
6. Sinn, N., Milte, CM., Street, S. J., Buckley, J. D., Coates, A. M., Petkov, J. & Howe, P. R. (2012). Effects of n-3 fatty acid, EPA and DHA, on depressive symptoms, quality of life, memory and executive function in older adults with mild cognitive impairment: a 6 month randomised control trial. British Journal of Nutrition, 107, 1682-1693.
7. De Vriese, S. R., Christope, A. B. & Maes, M. (2003). Lowered serum n-3 polyunsaturated fatty acid (PUFA) levels predict the occurance of post-partum depression: further evidence that lowered n-PUFAs are related to major depression. Life Science, 73, 3181-3187.
8. Lamport, D., Pal, D., Moutsiana, C., Field, D., Williams, C., Spencer, J. and Butler, L. (2015) The effect of flavanol-rich cocoa on cerebral perfusion in healthy older adults during conscious resting state: a placebo controlled, crossover, acute trial. Psychopharmacology, 232, 3227-3234.
9. Murphy, T., Dias, G. P. & Thuret, S. (2014). Effects of diet on brain plasticity in animal and human studies: Mind the gap. Neural Plasticity, doi: 10.1155/2014/563160
10. Gomez-Pinilla, F. & Nguyen, T. T. J. (2012). Natural mood foods: The actions of polyphenols against psychiatric and cognitive disorders. Nutritional Neuroscience, 15, 127-133.
11. Kidd, P. M. (2008). Alzheimer's disease, amnestic mild cognitive impairment, and age-associated memory impairment: current understanding and progress toward integrative prevention. Alternative Medicine Review, 13, 85-115.
12. Morris, M. C., Tangney, C. C., Wang, Y., Sacks, F. M., Bennett, D. A. & Aggarwal, N. T. (2015). MIND diet associated with reduced incidence of Alzheimer’s Disease. Alzheimer’s & Dementia, 11, 1007-1014.
13. Sánchez-Villegas, A., Henríquez-Sánchez, P., Ruiz-Canela, M., Lahortiga, F., Molero, P., Toledo, E., & Martínez-González, M. (2015). A longitudinal analysis of diet quality scores and the risk of incident depression in the SUN Project. BMC Medicine, 13, 197-197.