PHILADELPHIA - Almost everyone knows someone – either a family member or a friend’s family member – whose life has been devastated by Alzheimer’s disease. The debilitating cognitive disease has no known cure, and steadily eats away at a person’s mind until she can’t even recognise the people she loves or take care of herself.
Alzheimer’s is on the rise. It currently affects almost 30m people around the world, and is expected to affect 1 in 85 people around the world by 2050, costing hundreds of billions of dollars and causing untold human suffering.
We typically think of Alzheimer’s as caused by a build-up of certain kinds of plaques in the brain that cause brain tissues to erode. In the last few years, however, scientists have been asking more and more questions about why those plaques start to build up in the first place. Obviously, there is a major genetic component to developing the condition, as there is with most chronic diseases. But some say that there’s even more to the story. In fact, according to some experts, Alzheimer’s disease is actually just a form of something much more familiar – diabetes.
The idea that Alzheimer’s is “Type 3 diabetes” first appeared in 2005, when Brown Medical School professor Suzanne de la Monte and her team, who were studying Alzheimer’s patients’ brain tissues, showed that the levels of insulin and insulin receptors in the brains they were studying were unusually low. The team also demonstrated that as Alzheimer’s developed insulin levels in the brain fell – in other words, low brain insulin and brain glucose problems were associated with the development and progress of Alzheimer’s. Other research found similar relationships (see, for example, here, here, and here).
Now, insulin resistance is the first stage in the development of Type-2 diabetes, and diabetes is a condition in which blood sugar (or glucose) levels are elevated because of problems in insulin metabolism. Insulin is the hormone your body uses to deal with sugar, not just the white stuff you put in your tea, but the final product of all carbohydrates once they’ve been digested and hit your bloodstream. Essentially, what insulin does is goes to your cells and instructs them to open up and take in sugar from the blood, which they can then use for energy.
The problem is that some people develop issues with insulin. In a grossly simplified way, what happens is that, perhaps when we eat too many carbs and have too much sugar floating around in our blood, insulin gets overworked. It instructs cells to pick up glucose too much, and the cells start to ignore it – they become insulin resistant. Or, perhaps because there’s so much sugar in the blood and the demand for insulin is so high, the pancreas, which produces the bulk of the hormone, gets overworked and reduces insulin production. Either way, there just isn’t enough insulin, or cellular receptivity to insulin, for all the sugar in the blood to be absorbed.
Unfortunately, that sugar still has to go somewhere, and that means that it crystallises in blood cells and tissues, causing blood vessel, heart and kidney damage, blindness, neuropathy in the hands and feet, and impotence.
Where Alzheimer’s fits into all this is as follows (you can see de la Monte’s explanation here). Like most organs, the brain needs glucose to function, as well as to make various neurotransmitters and even lay down memories. If your brain starts to get too little insulin, or becomes insulin resistant, it’s possible that certain plaques may start to develop in the brain (as they do in blood vessels), and that’s basically what Alzheimer’s is.
So what does this mean? Well, the use of diabetes drugs to treat Alzheimer’s has had mixed results. However, scientists have been able to induce Alzheimer’s (or something that looks just like it) in mice by feeding them high-carb, high-fat diets, and diets full of nitrates (something found in processed foods like hot dogs). You could therefore theoretically reduce your risk of developing Alzheimer’s by eating a diet focused on plant foods, complex carbs, low fat protein, and avoiding sugary drinks, processed foods, and fatty meals that are low in nutrients. Since that diet also has a host of other benefits – weight loss, lowered risk of heart disease and cancer, improved sleep and so on – there’s really no reason not to.