One key factor in health, I believe, is the general level of sugar in the bloodstream. We don’t want blood sugar levels too low (this starves the cells of energy in certain circumstances and can even be fatal). We don’t want them too high either. Glucose can bind to proteins in the body and damage them. This process, known as ‘glycation’, is believed to be a major cause of the complications of diabetes including retinal disease (disease at the back of the eye that can lead to visual problems and blindness), kidney disease and nerve damage.
In addition, ‘spikes’ in blood sugar, can lead to other processes linked with disease including increased inflammation, increased ‘oxidative stress’ (free radical damage), and increased coagulation (making the blood ‘stickier’ and more likely to clot). You can read more about these issues here.
One standard test of assessing blood sugar levels is a ‘serum glucose’, which can be measured in the fasting or non-fasting state. The fundamental problem with this test, as I see it, is that it really provides only a snapshot of blood sugar levels. It doesn’t, therefore, tell us much about the medium and long-term blood sugar levels in an individual.
A better test, in this regard, might be what is known as the HbA1c (sometimes abbreviated to the ‘A1c’). This test measures levels of what is known as ‘glycated haemoglobin’. Haemoglobin is the substance in the red blood cells responsible for carrying oxygen around the body. It’s also a protein. When glucose reacts to it, it forms glycated haemoglobin. Now, red blood cells are constantly being broken down and then replenished from the bone marrow. We get a complete new set of red blood cells every 3 months or so. What this means is that the HbA1c test gives us a pretty good idea of overall blood sugar control over the last 3 months or so. HbA1c levels are measured as a percentage of total haemoglobin. Ideally, HbA1c levels should be less than 5 per cent.
I was interested to read about a study published on-line recently which looked at the relationship between HbA1c levels and overall risk of death in individuals over a seven and a half-year period [1].
Compared to individuals with HbA1c levels of 5.5-5.9 per cent (used as the reference value), those with HbA1c levels of 6.5-7.4 per cent were 39 per cent more likely to die. Those with values 7.5 per cent and above were more than twice as likely to die.
Even when fasting blood sugar levels were taken into account, these results stood. However, interestingly, the fasting blood sugar level was not a good predictor of death once HbA1c levels were taken into account. In other words, HbA1c levels were a much better predictor of risk of death than fasting blood sugar levels.
Now, studies of this nature do not prove that having a relatively high HbA1c level is going to kill us. However, we do know that high sugar levels predispose to disease-causing processes, so there is a good likelihood that there is a direct relationship between HbA1c levels and risk of death.
Should you be interested in reducing your HbA1c levels over time (which has particular relevance for diabetics) then you might consider a low-carbohydrate diet. Although, if you take this approach, I recommend you work with a practitioner who can give you guidance on how to do this and adjust your medication accordingly (diabetics who adopt a low-carb approach very often require less medication and, not uncommonly, none at all).
References:
1. Silbernagel G, et al. Glycated Hemoglobin Predicts All-Cause, Cardiovascular, and Cancer Mortality in People Without a History of Diabetes Undergoing Coronary Angiography. Diabetes Care 22 April 2011 [epub ahead of print]
