You are what you eat, or so the saying goes, but can we really prevent disease through what we ingest? There are numerous studies now suggesting that our brain health can indeed be affected by our diet, and therefore that neurological conditions like Alzheimer’s disease may be preventable, to a degree.
Alzheimer’s Disease is the most common cause of dementia in the UK, yet the exact cause of it is not entirely understood. It seems to be related to a complex interplay between a number of mechanisms, but we believe it to be related to the abnormal buildup of proteins called amyloid and tau, which cause plaques and tangles in the brain cells. This causes damage to the cells and to the messengers between the cells, eventually leading to different areas in the brain shrinking. In Alzheimer’s the first areas to shrink tend to be those related to memory, which is why this can be one of the most noticeable first symptoms, but it can also affect other areas for example those that govern language and vision.
There are a number of factors that we know can increase your risk of developing Alzheimer’s, and these include increasing age, a family history of the disease, a history of head injuries and social isolation. Another area that research has supported in being an underlying risk factor includes lifestyle factors and cardiovascular disease. The studies suggest that a sedentary lifestyle, smoking, obesity, diabetes, high blood pressure and high cholesterol may all play a part.
It is of course difficult to control for the two biggest risk factors for Alzheimer’s which are age and genetics, but there are many other risk factors that can be optimised through lifestyle modifications including diet, exercise and “brain training”.
How can diet affect our brain?
For many years there was skepticism surrounding the concept of diet affecting Alzheimer’s risk. A study in 2013 was a changing point for many, when they found that in a group of 500 people aged 55-80, the half that were allocated the Mediterranean Diet scored better on their cognitive tests 6.5 years later than those that followed the low-fat diet. Since this study, many others have followed suit, confirming the findings with MRI scans that also showed changes to the brain depending on diet followed.
We believe that diet affects our brain due to its influence on inflammation and oxidative stress (which is a process that occurs when our body’s defence system is exceeded). It is these factors that promote the formation of the protein plaques and tangles that cause brain cell damage in Alzheimer’s.
One theory is that the gut microbiome may contribute to the development of Alzheimer’s. These are the community of trillions of bacteria, fungi and other microorganisms that colonise our gut and it is thought they communicate with our central nervous system via what is termed the ‘gut-brain axis’. Alterations in the composition of these microorganisms have been found to increase the leakiness of the intestines, which allows bacteria to travel across the intestines and access the nervous system, resulting in inflammation and cell damage within the brain, potentially leading to neurodegenerative conditions like Alzheimer’s.
Our gut microbiome feeds off prebiotics, and is boosted by probiotics. There have been several studies confirming the benefits of probiotic supplementation in reducing the inflammation and damage in the brain. However, one of the best ways of improving your gut flora is through the simple dietary measures of eating plenty of plant-based, fermented foods, and foods rich in omega 3 and antioxidants, and limiting saturated fats and refined sugars.
There are so many fad diets out there, and they all claim a one size fits all, but which should you follow if you have specific concerns about Alzheimer’s disease? The Mediterrannean-DASH Intervention for Neurodegenerative Delay (aptly named the MIND) diet, combines the elements of 2 diets- the Mediterranean Diet and the DASH diet, both of which have been found to reduce the risk of cardiovascular conditions, like high blood pressure, heart attacks and strokes.
The Mediterranean diet is based on the traditional foods of Greece, Italy and other Mediterranean countries and is composed of lots of fruits and vegetables, cereals, olive oil, nuts and seeds, a moderate intake of fish, a low to moderate consumption of dairy and wine, and a low intake of red and processed meats. The DASH (Dietary Approaches to Stop Hypertension ) diet was first developed to manage blood pressure through diet, and is high in fruits, vegetables, nuts, whole-cereal, low-fat dairy, fish, and poultry. DASH also discourages the intake of foods like red and processed meats, full-fat dairy foods, and tropical oils (like coconut and palm oil), as well as sugary drinks and sweets.
The combination MIND diet is based on the following 10 “brain foods” -leafy green vegetables, other vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil, and wine, and also calls on the reduction of red meats, butter/margarines, cheese, pastries, sweets, and fried or fast food. These are all foods and nutrients that have been shown through the scientific literature to be associated specifically with a reduced dementia risk. It differs from DASH and Mediterranen diet by specifically encouraging a diet high in berries and green leafy vegetables, and does not specially include any other fruit, dairy, potatoes or >1 fish dish a week.
Studies have shown that the MIND diet is superior in slowing down the rates of cognitive decline and in the risk of developing Alzheimer’s disease when compared to both the Mediterranean and the DASH diets. However there have been no randomised controlled trials (the gold standard in trials) to date, to robustly study the effect of the MIND diet on the prevention of Alzheimer’s disease. The studies thus far are “observational” studies which means that they cannot prove that the diet is the cause of the reduced risk of Alzheimer’s disease, but only infer. The researchers have done their best to exclude any other factors that could affect the risk of getting the disease but we cannot say from these studies that this diet definitely protects from it.
With what was observed to be a success from the MIND diet studies, researchers have attempted to fine tune which specific foods and nutrients in the diet are considered “super” for brain health. Studies have researched fish, omega 3, antioxidants, vitamins. Whilst there has been rationale behind all of these, the results have been conflicting and the data is limited. As we don’t know which of the foods in the diet might make a difference, and it is unlikely that it is one single food or supplement that is reducing the risk of Alzheimer’s, for now the best advice is to simply eat a healthy well-balanced diet, as opposed to solely consuming any individual food.