Nutrition and the Ageing Brain
It has been nearly 6 months since I started my first graduate job as a research assistant. The research I am working on revolves mainly around Alzheimer’s disease. I thought it would be great to write a bit about how nutrition may have an impact on how our brains function as we get older, and how diet may play a role in preventing the onset of this debilitating disease.
This blog post will focus on all things nutrition and the brain, the way we can best protect our brain and cognitive function as we age, and the evidence behind how nutrition may play a key role in the development and/or prevention of dementia.
Ageing and the brain
Ageing is a natural occurrence in which all our organs begin to slow down and may not function as well as they had at a younger age, this also includes the brain. Signs of aging of the brain include memory loss - something which we all experience from time to time. However, some individuals may experience a more rapid decline in brain function with more serious symptoms such as confusion, difficulty with language and mood swings. These are all symptoms of dementia.
As the average age of our population is increasing and people are living for longer, the rates of dementia are ever increasing, with now 1 in 14 people over the age of 65 suffering from a form of dementia, this increases to 1 in 6 over 80's .
There are many forms of dementia, however the most prevalent in our society is Alzheimer’s disease, it makes up 60 to 70% of all dementia cases diagnosed.
Alzheimer’s disease is caused by a complex interplay between both modifiable and non-modifiable risk factors. Modifiable risk factors include diet, lifestyle and whether you smoke or not. Age is a major non-modifiable risk factor, as well as our genetics – these are factors we can’t change.
On a cellular level, Alzheimer’s disease is caused by a build-up of a protein called amyloid-beta. This protein is present in healthy brains too, however individuals suffering from Alzheimer's disease will have an increased amount of this protein which is not folded properly and therefore cannot carry out its function. When lots of this protein builds up in the cells, it starts to form plaques. Additionally, there is a build-up of a protein called Tau, which causes tangles to form in brain cells.
The build-up of these plaques and tangles starts to affect the way our brain sends messages, there is a decrease in neurotransmitters (the chemicals that send messages around our brain) and therefore this affects our brain function.
Increased oxidative stress, which causes further damage to cells, , is one hypothesis to why in some individuals have an increased build-up of these misfolded proteins compare to others. Oxidative stress itself also causes an increase in the amount of amyloid-beta plaques in the brain cells, resulting in a further increase in cognitive decline.
Oxidative stress is a natural phenomenon; our cells have ways to protect themselves from damage caused by this mechanism known as our antioxidant defence systems. The brain is a particularly vulnerable organ to oxidative stress and has less antioxidants present than in other organs.
Nutrition and the ageing brain
As I mentioned above, diet and lifestyle are major modifiable risk factors in the development of Alzheimer’s disease. The brain uses 20% of our daily energy intake, therefore fuelling yourself and your brain correctly is actually very important!
There are many nutrients which are involved in protecting our brain cells from damage by oxidative stress, these nutrients are known as antioxidants. They protect our brain cells from being destroyed by chemicals that are produced as a result of normal brain functioning.
There are three specific dietary patterns which have been scientifically shown to decrease the risk of developing cancer; these are the Mediterranean diet, the DASH diet and the MIND diet.
The Mediterranean diet has hugely increased in popularity over the last few years owing to its cardioprotective effects, some of which I have already touched upon in my Intermittent fasting post.
The DASH diet is very similar to the Mediterranean diet but is specifically designed to control blood pressure and hence has a strong focus on lowering salt intake. This diet is mainly advised for those at risk of coronary heart disease. However high blood pressure is also a risk factor for developing dementia, therefore there is emerging evidence that owing to its efficacy at reducing blood pressure, the DASH diet may also help to prevent dementia and Alzheimer’s disease .
The MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) has been specifically designed to help reduce cognitive decline with ageing. This diet is a combination of both the Mediterranean and the DASH diet.
These diets emphasise the consumption of foods such as:
Fruit and vegetables
Wholegrains (brown pasta, rice & bread, quinoa, bulgur wheat, oats)
Nuts, seeds & legumes
Low fat diary
The MIND diet also specifies an increase in consumption of green leafy vegetables and berries. These foods have high levels of antioxidants and therefore may help protect our brains from oxidative damage and consequently slow the rate of cognitive decline and/or protect our brains and reduce the risk of developing Alzheimer’s disease.
Evidence for the protective effects of these dietary patterns
So how effective are these diets in preventing cognitive decline and the onset of dementia and specifically Alzheimer’s disease?
A review published in 2019 looked at a total of 56 published articles which examined the relationship between adherence to either the Mediterranean, MIND or DASH diet and cognitive health of patients. The review determined that the higher the adherence to these diets, the better the cognitive scores of the patients and thus lower cognitive decline observed. There was also an association between the adherence to these diets and a lower risk of developing Alzheimer’s disease .
So, following these dietary patterns seem to have positive effects on our brain function as we age.
There has been much research on specific nutrients which could exert neuroprotective effects and reduce the risk of developing Alzheimer’s and/or slow the rate of cognitive decline in Alzheimer’s patients.
Specific nutrients include natural antioxidants such as vitamin A, B, C and E, in addition to plant compounds known as polyphenols which have shown to protect cells against neurotoxins which may cause cellular damage .
Vitamin E is an important antioxidant which is found in our cells and plays major roles in protecting our cells from oxidative stress. Our bodies cannot produce vitamin E, so we therefore need to include it in our diet.
There has been ample research in the effects of vitamin E supplementation and its effect on cognitive decline in Alzheimer’s patients. There have been many epidemiological studies looking at the relationship between vitamin E intake and cognitive decline which clearly show a positive correlation, increasing vitamin E intake decreases the rate of cognitive decline. There have also been several randomised control trials which also show that vitamin E supplementation slows down the rate of cognitive decline in Alzheimer’s patients .
Vitamin E is the only vitamin taken as a supplement to be proven to exert beneficial effects on cognitive function and reduce oxidative stress in Alzheimer’s patents. Studying specific nutrients in clinical outcomes is notoriously hard and therefore there is limited robust evidence to support the beneficial effects for Alzheimer’s patients for the other nutrients stated above.
It is also important to remember that we should be aiming to get these specific nutrients from our diet rather than in the supplement form. This is because of all the other nutrients which we will also get when consuming the foods and the effects that these combined nutrients may have together – also known as the effect of the food matrix.
There is still much research to be undertaken…
Like much of the research undertaken in the nutrition field, the evidence is mainly extracted from observational studies. Observational studies usually comprise of asking a group of individuals specific questions or filling in a questionnaire on their diets and lifestyle. These studies often have several limitations making it challenging to expel concrete evidence.
The strongest evidence relating to the effects of nutrition or specific nutrients in disease and/or health outcomes are obtained from randomised controlled trials. These studies allow us to determine whether a dietary pattern or specific nutrition CAUSE a slower rate in cognitive decline and/or prevent the development of AD, whereas observational studies only allow a relationship to between the dietary patterns and nutrients and cognitive health to be defined.
However, designing a randomised control trial looking at effects of nutrition on cognitive function and our brains as we age is unethical, as well as extremely hard to design owing to the copious amounts of confounding data (other factors which may also contribute to the observed outcome). In addition, the effects of specific nutrients on cognitive decline may be tiny and the beneficial effects may add up slowly over a long period of time, as well as there being differing rates of cognitive decline between individuals – we are all unique after all!
Therefore, there are still many questions which need to be answered.
So, what can we do to help protect our brain and slow the rate of cognitive decline as we age?
The best way to support our brains and decrease our risk of declining cognitive function (more severe than what naturally occurs when we age) is to eat a varied diet, high in fruits, vegetables and fibre and include foods containing omega 3 fatty acids such as oily fish. Dietary patterns which include these foods, whilst reducing our intake of processed foods and foods high in saturated fat, has been shown to potentially have positive effects on our brain function.
Let’s not forget that we can’t go through life obsessing over the little things, let’s focus on our overall healthy balanced dietary patterns and we can EAT HAPPY and LIVE WELL.
P.S. Despite having a job in biochemistry, my passion for nutrition is 100% still here. Now more than ever I am excited by the opportunities that having a career in nutrition can bring. Helping others to lead a happy, healthy life through nutrition education is my number 1 passion...so watch this space! For now, I am continuing with focusing on writing blog posts and with some more yummy recipes to come too!
Annelien C van den Brink, Elske M Brouwer-Brolsma, Agnes A M Berendsen, Ondine van de Rest, The Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) Diets Are Associated with Less Cognitive Decline and a Lower Risk of Alzheimer's Disease—A Review, Advances in Nutrition, Volume 10, Issue 6, November 2019, Pages 1040–1065, https://doi.org/10.1093/advances/nmz054
Chiara Colizzi, The protective effects of polyphenols on Alzheimer's disease: A systematic review, Alzheimer's & Dementia: Translational Research & Clinical Interventions, Volume 5, 2019, Pages 184-196. https://www.sciencedirect.com/science/article/pii/S2352873718300544
La Fata G, Weber P, Mohajeri MH. Effects of vitamin E on cognitive performance during ageing and in Alzheimer's disease. Nutrients. 2014;6(12):5453-5472. Published 2014 Nov 28. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276978/