She says the evidence suggests that Alzheimer’s “is a metabolic disease with virtually all the features of diabetes mellitus but largely confined to the brain”.
People already suffering from Type 2 diabetes will be particularly at risk.
Type 2 is the most common variety and is linked with obesity and lack of exercise and increases the risk of strokes, CHD,blindness, nerve damage and amputation. Poor sensitivity to insulin is also associated with Type 2 diabetes in which liver, fat, and muscle cells fail to respond to the hormone.
Studies show that consuming a lot of food high in saturated fat and sugar or anything with a high glycaemic index (GI) keep your insulin levels high which is not good for the brain.
Experiments at the University of California showed that rats drinking water laced with high-fructose corn syrup – a cheap and common sweetener in soft drinks, processed food, and condiments – developed learning and memory problems after only 6 weeks and their brain tissue became less responsive to insulin.
However rats that drank the corn syrup water alongside omega-3 fatty acids from flax seed oil didn’t have those problems. Omega-3 acids are found in oily fish and alongside flavonoids (found in tea, red wine and dark chocolate) are thought reduce the risk of dementia.
A mediterranean diet is associated with less cognitive decline, dementia, and Alzheimer’s and is known to be rich in fish oil, low GI fruit, and a little wine.
Most people know enough about diabetes to understand that insulin is connected with blood sugar levels. Recently scientists have discovered that insulin not only regulates blood sugar but is also important for your brain as it helps neurons take up glucose for energy and regulates neurotransmitters which are crucial for memory and learning.
The hormone also encourages brain plasticity, the process in which the brain makes and changes connections, and is important for the function and growth of blood vessels by which the brain gets its fuel, oxygen and glucose.
Reducing insulin levels in the brain immediately impairs your thinking, your memory, and your spatial awareness, similar to taking morphine. Constantly high levels of insulin triggered by fat and sugar in western diets can overwhelm the brain which is on constant high alert. The brain might then turn down its insulin signalling thus impairing your ability to think and make memories before leading to permanent brain damage.
There are evolutionary reasons for these mechanisms. Scavenging for scarce food resources and then gorging when you found something would create a glucose spike followed by a dose of insulin which would help the brain create a memory of where you found the food.
What served us well on the savannah is no longer helpful if we eat a diet of sugary, fatty foods which create insulin spikes on a regular basis. There is a ratchet effect and the insulin sticks at a higher level so muscle, liver and fat cells stop responding to it and therefore don’t mop up the glucose and fat in the blood.
The pancreas then overworks to produce more insulin to try and control the glucose until eventually it stops doing it effectively. Hence the lower levels of insulin typically found in people with Type 2 diabetes.
And there is a link with obesity as 80% of people with Type 2 are either overweight or obese. Obesity seems to trigger the release of inflammatory and metabolic stress molecules inside liver and fat cells that disrupt insulin’s action leading to high blood glucose levels and then insulin resistance. With 36% of the population in the USA obese, you can see the risks they are facing.
There are many researchers working in this field and some have used insulin nasal sprays with promising results in terms of improved memory and renewed interest in hobbies.
So drugs used to treat diabetes might prove useful in treating or preventing Alzheimer’s. In the meantime a healthy diet and exercise won’t do any harm and will probably help, not just your body, but your brain.
FYI: Type 1 is juvenile onset diabetes which affects about 5% of people and is due to an auto-immune response destroying the insulin producing cells in the pancreas so the body van no longer regulate blood sugar levels.
Source: New Scientist 1 September 2012 & APA Monitor February 2013