So of course I had to buy it given my current interest on anything to do with nutrition science. I also had an inkling about what the article may be about so I wanted to see if I was right.
The main premise of the article is that some experts have made a link between elevated levels in insulin and the on set of dementia. This is what I suspected the article was about as I hadn’t long read about it in Gary Taubes book The Diet Delusion. What interested me was the scientists in the NewScientist article were starting to think of Dementia as Type-3 diabetes.
The link between diet and dementia is a fairly recent one. It was only back in the 90s that researchers started reporting that dementia and heart disease share common risk factors. So if you’re at risk of heart disease, then you’re also at risk of developing dementia.
Insulin has been shown to affect brain activity. In the short term, a boost of insulin actually increases brain activity and tests have been performed on patients suffering with Alzheimer’s where insulin is delivered deep into the nose. These patients receiving this treatment had a greater attention span and could remember more than they could previously. However, according to one theory, if the brain becomes insulin resistant as a result of chronic hyperinsulinaemia, then the effects of insulin on the brain are lost and it can no longer function as it once did.
Another theory linking insulin to dementia is to do with amyloid-plaque build up. People with Alzheimers are found to have this plaque build up in their brains and this plaque build up is though to result in the degeneration and death of the neurons in the brain. The amyloid-plaque is made up of a protein known as beta-amyloid, and this protein is what is left over after a larger precursor protein is split into two. The amyloid precursor protein appears naturally in the brain and the splitting process appears to part of normal cell function. A healthy brain clears up the amyloid after the split occurs, but in Alzheimers this doesn’t happen, and this may be down to insulin. In laboratory tests insulin has been shown to monopolise the attention of the insulin degrading enzyme (IDE) which normally clears and degrades both the amyloid protein and insulin from around the neurons. So the more insulin in the brain, then fewer amyloids get cleared up resulting in a build up of the amyloid plaques. Mice that lack the gene to produce IDE develop both Alzheimers and type-2 diabetes.
If all of this is true then it places the finger of blame for the rising number of dementia cases squarely at our diet, and specifically at foods that raise our blood sugar excessively. Sugar, refined carbohydrates and starches.
What frustrated me about the NewScientist article though was the instance of linking increased levels of insulin with a diet high in sugar AND fat. For instance, here’s a quote from the article
Recent studies have revealed that consuming a lot of foods high in saturated fat and sugar or anything with a high glycaemic index are bad for your brain because they keep your insulin levels high
This is inaccurate as foods high in fat but low in sugar keep your insulin levels low. Here’s how the University of Sydney describes the GI rating of food
The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger. Low GI diets also reduce insulin levels and insulin resistance
Notice that the GI is a ranking of carbohydrates. Nothing is mentioned about the fat content of food. In fact, in most GI charts foods like cheese aren’t rated because they have such a small effect on blood sugar. So there is no basis for the reporters in NewScientist to blame high insulin levels on fatty foods. This is frustrating given that our diets are generally a balancing act between fat and carbohydrates. If we eat more fat we eat less carbohydrates, and if we reduce our fat intake then we will increase our carb intake (and increase our insulin production) as we need to get our calories from somewhere.
What gets me angry about all this, the advice given to us by our experts and TV shows and magazines etc, eat less fat and more healthy wholegrains (only healthy in relation to refined grains by the way), is the exact opposite of what we should be doing. Eating less fat and more starches and grains raises our blood sugar, which raises our insulin, which makes us fatter and also raises our risk of heart disease and now it seems our risk of Alzheimers. If we want to reduce our insulin production and so reduce our risk of these diseases, then we should be eating less (or none!) grains and more saturated fat.
A friend of mine, who is a dementia nurse working for the NHS, said over the weekend that her boss keeps talking about a coming wave that the NHS won’t be able to deal with. This wave is an expected increase in the number of dementia cases in the UK which is a scary prospect. I can only hope that this new research will result in the correct dietary advice being given, this is the only way this “oncoming wave” can be averted.