I suspect many individuals dread the idea of losing their mental faculties as they age. I think nutrition probably plays a very important role in how well the brain ages and how well its functioning is preserved. This week saw the on-line publication of a study that suggests that a key factor here may be good ‘glycaemic’ control.
While we do not want blood sugar levels to be too low, we do not want them too high, either. Abnormally elevated blood sugar levels is a hallmark feature of diabetes. One of the risks here is that glucose can bind to and damage tissues through the process ‘glycation’, and this can lead to a variety of complications for diabetics including nerve, kidney, blood vessel and eye damage.
One of the ways doctors can assess broad blood sugar control is through a test known as the ‘HbA1c’ (also known as the ‘A1c’, or ‘glycated haemoglobin’ or ‘glycosylated haemoglobin’). This test measures the amount of the protein haemoglobin in the red blood cells that is bound up with glucose. Basically, higher levels of HbA1c signal poorer blood sugar control.
In this week’s study, the relationship between brain structure and function and HbA1c levels was assessed in a group of non-diabetics. Higher HbA1c scores were found to be associated with smaller regions in the brain known as the ‘hippocampus’ (a part of the brain involved in memory). Those with higher HbA1c levels performed generally worse in tests of memory and learning.
In recent years, there has been growing interest in the relationship between blood sugar control and Alzheimer’s disease. Some researchers have suggested that at least some cases of this condition are due to what is being terms ‘type 3 diabetes’ – essentially, a mix of insufficient insulin (a feature of type 1 diabetes) with poorly functioning insulin (a common feature of type 2 diabetes).
Raised blood glucose levels might perhaps damage the brain through several mechanisms. Glycation is one. Also, though, raised blood sugar is inflammatory in nature, and inflammation in a potential underlying factor in deteriorating brain function over time.
Another mechanism that may be relevant here concerns cholesterol. Cholesterol is highly concentrated in the brain, where it performs several functions. It’s critical, for instance, to the function of the synapse (the ‘gap’ where one cell can communicate with another), and also has a role as an electrical insulator and as a structural ‘scaffold’ in the brain. Cholesterol is also a functional component of all cell membranes in the brain . Higher levels of glycation (through higher blood sugar levels) can impair cholesterol uptake into the brain, potentially starving this organ of a component critical for its proper functioning.
What is perhaps interesting about this week’s study is that the relationship between improved blood sugar control and better brain function was found in non-diabetics. This throws up the possibility that scaling back on blood sugar disruptive carbohydrates such as those rich in sugar and starch could well be a good tactic for those of us wishing to preserve their mental functioning as they age, whether we have diabetes or not.
1. Kerti L, et al. Higher glucose levels associated with lower memory and reduced hippocampal microstructure. Neurology, 23 October 2013
2. Seneff A, et al. Nutrition and Alzheimer’s disease: The detrimental role of a high carbohydrate diet Eur J Int Med 2011;22:134-140
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