Alzheimer’s disease has long been a condition of catastrophic consequences; a condition affecting around 26 million people worldwide, a high number of fatalities and a severe financial burden upon healthcare throughout the Western world. But need this be the case?
Research is categorizing Alzheimer’s disease as being among the “diseases of civilisation” – meaning it is primarily caused by unhealthy modern Western diets and poor lifestyle choices, causative factors that are also relevant to the onset of many of today’s most prevalent chronic diseases, including Diabetes.
In fact, the link between Diabetes and Alzheimer’s disease actually goes far beyond this; in this week’s article we look at how many within this field of science are now suggesting that Alzheimer’s disease is a form of Diabetes known as ‘Type 3’, defined as such because of the role that insulin resistance and glucose metabolism plays in Alzheimer’s three main pathological features.
What is Alzheimer’s disease?
Alzheimer’s disease is the most common form of dementia that specifically affects the parts of the brain that control thought, memory and language. It is characterized and differentiated by the specific pathology of a build-up of oligomerized β-amyloid plaques in the spaces between the nerve cells, tau tangles that build-up inside the cells and brain tissue atrophy of the hippocampus.
Alzheimer’s disease is a condition that normally gets worse over time, although the symptoms vary greatly. The first noticeable sign of its onset is forgetfulness on a level that is severe enough to affect day to day functioning at home or at work. Or it might be noticed by a family member or a friend that a person is becoming increasingly forgetful. The disease may cause the person to become confused, lost in familiar places, to frequently misplace things, or to have trouble with language.
The initial changes that take place in the brain begin at a microscopic level, long before any symptoms actually appear. The brain has 100 billion nerve cells (neurons). Each nerve cell connects to many others via synapses to form communication networks. In addition to nerve cells, the brain includes cells specialised to nourish and support other cells.
Each group of nerve cells has specialised tasks – some of these are involved in thinking, learning and memory, whereas others help us to see, hear, smell and move. These brain cells operate like tiny factories; they receive supplies of nourishment, generate energy, construct new cells and get rid of waste. Cells also process and store information as well as communicating with other cells. The healthy function of these cells relies upon large amounts of oxygen and fuel in the form of phosphorylated glucose.
Alzheimer’s disease starts when the co-ordination of this dynamic process breaks down. Problems in one area cascade into problems in other areas and, as damage spreads, cells lose their ability to function correctly and die. This process eventually causes the whole network to break down.
The link between Diabetes and Alzheimer’s disease
Having type 2 diabetes could mean you are already on the path to Alzheimer’s disease, quite a startling claim, however, one which is gathering research.
Indeed, on the Diabetes Association website it states that “People that have insulin resistance, in particular those with type 2 diabetes have an increased risk of suffering from Alzheimer’s disease estimated to be between 50% and 65% higher”.
In Type 2 Diabetes your cells fail to retrieve glucose from the blood and this can be down to two main reasons; either because your pancreas is not producing an adequate amount of insulin or your cells are not responding to the insulin and using it efficiently; the latter is known as insulin resistance.
In the case of Alzheimer’s disease, it appears that something very similar is occurring, but in the brain as opposed to the entire body. Insulin is needed to help the neurons in the brain absorb glucose for efficient and healthy functioning, however if these cells become insulin resistant, it can lead to Alzheimer’s disease.
In fact, this link between the two conditions is now so strong that the latter is now frequently referred to as ‘Type 3 Diabetes’, so what role does insulin have to play in all of this?
The Role of Insulin in the body
Insulin is a hormone that we all require in adequate levels on a daily basis. In people that are non-diabetic, insulin is released to help cells take in the glucose that they need for energy – across all areas of the body. However these cells can only hold so much, any excess is first stored as glycogen and then fat.
Insulin is essential for keeping the blood vessels that supply the brain healthy and it also encourages the brain’s cells to absorb glucose, allowing them to become stronger and more efficient. Low insulin levels, as we will discuss shortly, is now associated with reduced brain function.
Insulin Resistance and Alzheimer’s disease
Only last week Dr David Morris provided a brilliant article for us on how to treat insulin resistance through dietary changes, and how we should now be concentrating on a non-pharmaceutical approach to this global problem.
Insulin resistance arises from a diet high in simple sugar (i.e. sugary drinks, biscuits, cakes, sweet snacks) over a long period of time. As we will see it is a significant part of the pathology of Alzheimer’s disease.
The digestive tract breaks down carbohydrates – sugars and starches found in many foods – into glucose. Glucose is a form of sugar that enters the blood stream. With the help of insulin, cells through the body absorb glucose and use it for energy.
Insulin resistance is a condition in which the body produces insulin but does not use it effectively. When people have insulin resistance, glucose builds up in the blood instead of being absorbed into the cells, leading to type 2 diabetes.
The role of Insulin in the brain
Insulin is responsible for stimulating brain cells to take up glucose and metabolise it to make energy. It is also essential for making brain chemicals known as neurotransmitters which are necessary for efficient communication in the brain.
Research undertaken by Dr. Craft and cited on the HBO Website has also suggested that insulin is a stimulant for numerous functions that are responsible for tasks that require memory and learning:
“”We noticed that the people with higher insulin levels showed the most memory benefit. We wondered if the insulin was enhancing memory, not just the glucose.” In a follow-up study, they raised glucose levels, but gave a medication that stopped insulin from being secreted. They found that without insulin, the memory improvement did not occur.”
We have always known that Alzheimer’s disease is typically associated with plaques and tangles in the brain, however exactly how these abnormalities come about in the brain has not always been understood. What is now clear however is that insulin resistance plays a key role in the cause of the three main pathological features associated with Alzheimer’s disease; Beta-amyloid plaques, tau tangles and brain atrophy of the hippocampus.
These are deposits of protein that build up in the spaces between the nerve cells. β-amyloid is made from amyloid precursor protein and can have a beneficial or neurotoxic outcome. When functioning correctly as a soluble protein, its job is to help produce new nerve cells. However in certain instances it is produced as an insoluble substance which is neurotoxic and is considered to be possibly the most prominent feature in the pathology of Alzheimer’s disease.
A greater volume of β-amyloid is noteworthy because lower levels tend to stay soluble, however high levels are more likely to form plaques in the brain. Insulin is key here because both β-amyloid and insulin are degraded by the same enzyme, and they are consequentially in competition with each other. So therefore too much or too little insulin in the brain could reduce β-amyloid clearance and promote its accumulation.
The research cited on HBO Website has backed up the above claim:
“Dr. Craft asked one group of research volunteers to follow the high- fat/high-sugar diet for four weeks, and another group to follow a low-fat/low-sugar diet. The preliminary results show that, in just a month, the participants on the high-fat/high- sugar diet had changes in beta-amyloid in the spinal fluid that may adversely impact its clearance from the brain and significant increases in LDL cholesterol.
Those on the low-fat/low-sugar diet had improved beta-amyloid, insulin, and cholesterol profiles. Dr.Craft speculated that the temporary insulin resistance induced by the high fat/high sugar diet interfered with the clearance of beta-amyloid, perhaps by affecting the enzyme in the liver that normally clears beta-amyloid from the bloodstream.”
These are twisted fibres of proteins called ‘tau’ that build up inside the cells and promote the stability of the cell’s internal structure. However when tau tangles become hyperphosphorylated they begin to tangle within themselves and leave unwanted debris inside the cell. Most people develop some tangles as they age however people with Alzheimer’s disease develop far more.
The plaques and tangles block cell communication and disrupt the processes the cells need to survive. This destruction and death of nerve cells causes memory failure, personality changes and difficulty in carrying out normal daily activities.
Research is now frequently suggesting that insulin dysfunction or resistance is heavily linked to the over production of tau tangles. This is because the phosphorylation of tau tangles are regulated by the enzyme glycogen synthase kinase, and insulin inhibits this enzyme. However clearly if the brain has become insulin resistant then this process cannot be inhibited.
Brain Atrophy in the Hippocampus
The build-up of plaques and tangles is followed by brain tissue atrophy which usually starts in the hippocampus; this is the area of the brain involved in short term memory and for the transfer of short term to long term memory. Most brain tissue atrophy in cases of Alzheimer’s disease starts in the hippocampus.
A study conducted by Dr Nick Bryan from the University of Pennsylvania has shown that patients with Type 2 Diabetes are far more prone to severe brain atrophy – and the longer a patient had the condition, the more brain atrophy occurred.
He was quoted on the ‘University Herald’ Website as saying, “Diabetes duration correlated primarily with brain atrophy, stated another way, our results suggested that, for every 10 years of diabetes duration, the brain of a patient with diabetes looks approximately two years older than that of a non-diabetic person, in terms of grey matter volume.”
Treating ‘Type 3 Diabetes’ and Insulin Resistance
So with this information to hand, and knowing that insulin resistance plays such a key role in the pathology of Alzheimer’s disease, how can we avoid it?
Knowledge is key when it comes to a condition such as Alzheimer’s disease – the condition itself carries weight similar to cancers and heart conditions, it instils the ‘fear factor’ in us all and a feeling of complete loss of hope. But when you consider that Alzheimer’s disease can be prevented through lifestyle and dietary changes, you can become ‘self empowered’ and take charge of your own health.
Becca Levy, Associate Professor of Public Health at Yale School, conducted research stating that negative thoughts about ageing in general could be a leading cause of the pathological brain changes associated with Alzheimer’s.
Science Daily provided an article dedicated to this particular piece of research which stated that “participants [in the study] holding more negative beliefs about ageing had a significantly greater number of plaques and tangles.” – That as we now know, are two of the main pathological features of Alzheimer’s disease.
This indicates the importance of ‘self-empowerment’ when it comes to your own health, understanding that ageing is not in itself a disease and that Alzheimer’s disease can be prevented through deep lifestyle and dietary changes is key to preventing and reversing this condition.
It goes without saying that diet is incredibly important – as it is for the prevention of any condition. Most people that are insulin resistant develop it from eating a large quantity of highly refined and processed carbohydrates. The key is to concentrate on a healthy diet rich in nutrient dense foods; such as the paleo diet – follow the link to our blog find out more.
Low sugar and moderate starchy carbohydrates: Avoid fizzy drinks, fruit juices, biscuits, cakes, white rice. Starchy carbohydrates which are encouraged are sweet potatoes, carrots and beetroot.
Healthy fats: Fats to enjoy include extra virgin olive oil, coconut oil, avocado, seeds, nuts and small amounts of butter. Fats to avoid are corn oil, sunflower oil, fried foods, pastries and processed meats.
LOTS of vegetables: Vegetables should comprise at least half the plate at both lunch and supper and ideally include some at breakfast too. Aim to eat between 6-8 portions each day.
Low GI fruits: These include apples, pears, berries and plums.
Medium Chain Triglycerides (MCT’s): These are a naturally occurring source of dietary fat and are abundantly present in coconut oil and palm oil. It is considered that MCT’s such as coconut oil may provide nourishment for the brain if you are insulin resistant, and therefore your brain doesn’t have access to an adequate level of glucose.
If things do not change quickly, it looks ever more likely that Alzheimer’s disease, or type 3 diabetes, may fast become the world’s next epidemic with numbers of sufferers consistently on the increase and healthcare in the Western world becoming unable to cope.
However this does not need to be the case, we can take a proactive stance on our own health; eat a healthier diet consisting of nutrient dense foods and promote a healthier lifestyle.
Alzheimer’s disease is a condition that is impossible to exhaust in one blog post and today we have looked at just one causative factor of a condition with a multitude of causes. However, insulin resistance and glucose metabolism perfectly demonstrate just two causative factors of Alzheimer’s disease that can be prevented and reversed through dietary and lifestyle changes. Indeed, Alzheimer’s disease could in fact be a wholly preventable condition.
In future blogs we will be exploring other factors and mechanisms that contribute to the development of Alzheimer’s disease pathology and how to address them through diet and lifestyle.
If you have any questions regarding the health topics that have been raised, then please do get in touch with me (Amanda) via phone (01684 310099) or e-mail ([email protected])
Amanda Williams and The Cytoplan Editorial Team; Clare Daley and Joseph Forsyth