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  • Writer's pictureNicole Musuwo

How does food affect our brain?

Updated: Jul 19, 2023

You may know that what we eat and drink can affect our heart, liver and other organs. However, did you know that our diet can also influence our brain health?


A healthy diet can preserve brain function, improve brain performance and mood. On the other hand, poor diets have been linked to mental health conditions, such as depression and anxiety, and decline in cognitive function.


In this article, we outline the dietary components that are known to positively affect the brain, alongside emerging research on the communication between our brain and gut!


Carbs, carbs, carbs!


Our brain's preferred source of energy is carbohydrates. Carbohydrates (carbs) are broken down into glucose and the brain uses glucose as the main source of energy. However, the quality of carbs is important. A diet high in simple carbohydrates (including heavily processed carbs such as cakes, sweets, pizzas) is associated with poorer mood, alertness and tiredness. [1]


Complex carbohydrates are best for brain health as the vitamins, minerals and antioxidants found in these not only fuel the brain, but they also protect brain cells against damage from free radicals (molecules that can form from exposure to cigarette smoke, air pollution and sunlight). These type of carbs also take longer to digest than refined simple carbs, and provide a steadier source of energy.


Complex carbohydrates are found in:

  • fruits and vegetables

  • wholegrain cereals, such as wheat, barley, rye

  • Wholewheat pasta, bread

  • Legumes, such as beans and chickpeas


Protein and fats


You may know that protein is important for building and repairing muscle. However, proteins are also an important building block for neurotransmitters that send messages throughout the brain. Neurotransmitters help to regulate thoughts and feelings. Good sources of protein include:

  • lean meats and poultry

  • fish

  • eggs

  • milk

  • legumes (beans, lentils, peas)

Eggs are a rich source of choline, which is important for brain function and especially important during pregnancy. Choline is also found in peanuts, beans, cauliflower and spinach.

With 70% of our brain made of fat, dietary fats are essential for brain function. As with carbohydrates, the quality of fats is key, with unsaturated fats (i.e. omega 3 and omega 6) most beneficial compared to saturated fats. Omega 3-fatty acids are the essential building blocks of our brain and important for learning and memory. Omega-3 is found in:

  • oily fish such as salmon, sardines, mackerel

  • nuts and seeds such as ground flaxseeds, chia seeds and walnuts

Aim to limit saturated fats, such as butter, fatty meat, and coconut oil and partially hydrogenated fats like trans fats, which are found in some heavily processed foods.



Ultra-proccesed foods


Ultra-processed foods (UPFs) are heavily processed foods which typically have more than 5 ingredients and generally have a long shelf life. They include ingredients that you would not not usually find or use in home cooking, such as preservatives, emulsifiers, sweeteners, and artificial colours and flavours. Examples of UPFs include sweets. crisps, biscuits, some breakfast cereals, carbonated drinks, ice cream, fruit-flavoured yogurts and instant soups.


UPFs are typically high in sugar, saturated fat and salt and higher in calories than minimally processed or unprocessed foods. They are thought to stimulate a greater sense of reward than others and can lead you to wanting more. A diet high in UPFs has been linked to poorer health and health outcomes, including cognitive decline. [2] As we await further research, it is best to limit UPFs and to have them less often in small amounts.


Dietary patterns


No one food in isolation can protect or improve brain health. However, healthy dietary patterns, such as the Mediterranean dietary pattern, has been linked to improved brain health and a lower risk of mental health conditions, such as depression. [3] The Mediterranean diet is:

  • High in fruits and vegetables

  • Includes moderate intake of fish and plant sources of proteins

  • Moderate intake nuts and unsaturated oils (olive oil)

  • low-to-moderate intake of dairy products

  • low in red meat and saturated fats


Gut-brain axis


Ever heard of the phrase “go with your gut” or “feeling butterflies in your stomach”? Over recent years, research has emerged on the gut-brain axis - the two-way communication that happens between our gastrointestinal tract (GI) and the central nervous system. [4] Interesting fact - the GI produces approx 95% of all serotonin (the ‘happy’ hormone) in our body!


The trillions of bacteria that live in our guts, called the gut microbiome, can influence the gut-brain relationship, influencing mental state and emotional regulation, for example. Greater diversity and number of beneficial bacteria in our guts can support the gut-brain relationship. The following foods have been shown to be beneficial for our gut:

  • Fibre-rich foods from a variety of fruit, vegetables, wholegrains, beans, pulses and legumes.

  • Prebiotics - these are plant-fibres found in fruit and veg such as onions, leeks, garlic, asparagus, artichoke [5]

  • Probiotics - live bacteria found in yoghurts and fermented foods such as kefir and sauerkraut [5]

  • Omega-3 fats found in oily fish, nuts and seeds

  • Polyphenol-rich foods found in plant foods such cocoa olive oil and coffee

  • Tryptophan-rich foods such as turkey, cheese and eggs. Tryptophan is an amino acid that is converted into the neurotransmitter serotonin - a neurotransmitter that helps to regulate sleep, appetite and mediate moods.


Diet and the ageing brain


Changes in brain and mental function are common with increasing age. However, alongside factors that can help to slow or prevent cognitive decline, such as physical activity, maintaining good social networks, adequate sleep and mental stimulation; a healthy diet can also help. Studies show that healthy dietary patterns, such as the Mediterranean diet, positively alter the gut microbiome in the elderly, reduce the risk of cognitive impairment, dementia and Alzheimer’s disease. [6]


Nutrients such as omega-3 fatty acids, flavonoids, vitamins B, D and E, and choline - have been associated with improved cognitive function and maintenance of thinking skills among older adults.


Summary

  • A diet rich in a variety of fruits, vegetables, oily fish, nuts and seeds can positively impact our brain health.

  • The benefits won't come from eating these foods once in while or certain foods in isolation - aim to adopt a healthy eating pattern for the long term.

  • Speak to your GP or health professional before making sudden changes to your diet!


References

  1. Clemente-Suárez, V.J.; Mielgo-Ayuso, J.; Martín-Rodríguez, A.; Ramos-Campo, D.J.; Redondo-Flórez, L.; Tornero-Aguilera, J.F. The Burden of Carbohydrates in Health and Disease. Nutrients. 2022, 14, 3809. https://doi.org/10.3390/nu14183809

  2. Gomes Gonçalves N, Vidal Ferreira N, Khandpur N, et al. Association Between Consumption of Ultraprocessed Foods and Cognitive Decline. JAMA Neurol. 2023;80(2):142–150. doi:10.1001/jamaneurol.2022.4397

  3. Molendijk M, Molero P, Ortuno Sanchez-Pedreno F, Van der Does W, Angel Martinez-Gonzalez M. Diet quality and depression risk: a systematic review and dose-response meta-analysis of prospective studies. J Affect Disord. (2018) 226:346–54. https://doi.org/10.1016/j.jad.2017.09022

  4. Skonieczna-Żydecka, K.; Marlicz, W.; Misera, A.; Koulaouzidis, A.; Łoniewski, I. Microbiome—The Missing Link in the Gut-Brain Axis: Focus on Its Role in Gastrointestinal and Mental Health. J. Clin. Med. 2018, 7, 521. https://doi.org/10.3390/jcm7120521

  5. Liu RT, Walsh RFL, Sheehan AE. Prebiotics and probiotics for depression and anxiety: a systematic review and meta-analysis of controlled clinical trials. Neurosci Biobehav Rev2019;102:13-23. 10.1016/j.neubiorev.2019.03.023

  6. Fu J, Tan LJ, Lee JE, Shin S. Association between the mediterranean diet and cognitive health among healthy adults: A systematic review and meta-analysis. Front Nutr. 2022 Jul 28;9:946361. doi: 10.3389/fnut.2022.946361

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