- Dennis Lipton, MD
Importance of A1c and blood sugar
What is the A1c and why do we measure it? Our real concern is your blood sugar, and the A1c is one way of getting an idea of what your blood sugar is, on average. Having an elevated A1c is correlated with increased risk of heart and vascular disease, worse brain health, and overall decreased longevity.(https://www.nytimes.com/2019/03/21/well/eat/sugary-drinks-tied-to-shorter-life-span.html).
Glucose is your body’s energy currency. Every cell in your body can use it for energy. Your body keeps very tight control of how much free glucose is circulating in your bloodstream at any one time. In fact, there is only about 5 grams, or one teaspoon, of glucose dissolved in your blood at any one time. The rest of it is stored in cells mainly in your liver, muscles, and adipose tissue.
Glucose is very reactive and ‘sticky’. It inappropriately sticks to proteins and peptides that it touches in your bloodstream, which is a process called ‘glycation’. This can lead to ‘Advanced Glycation End Products’ (AGEs). Once a protein is glycated it acts abnormally, and impairs the function of the cell. This is a permanent change, for the life of the protein. Hemoglobin, the oxygen-carrying protein in your blood, is one of these proteins that glucose attaches to. So, the ‘hemoglobin A1c’ is the percentage of hemoglobin that is glycated. It’s not perfect, but it’s a pretty good proxy what your glucose levels have been ‘on average’ in the past 3 months or so (since the average life of a red blood cell is 3 months).
Another one of the screening tools for diabetes is the fasting blood sugar. If it’s over 126, you have diabetes. If it’s 100-126 you may have ‘prediabetes’. Under 100 is ‘normal’. A common scenario is that someone can have normal or only slightly high fasting blood sugar but have an A1c elevated into the prediabetes range of 5.6 to 6.4. This slight elevation increases risk of cardiovascular disease, stroke, dementia, cancer weight gain, and developing full blown diabetes.
Elevated glycated hemoglobin is certainly not good, as it can interfere with normal function of your red cells and oxygen carrying capacity. What really scares me, however, is all the other proteins that we are NOT measuring that are being glycated. For example, LDL cholesterol particles express a protein called apoB. LDL receptors on the liver recognize the apoB and are able clear the LDL from your bloodstream to prevent it from causing trouble (ie making atherosclerotic plaque). When apoB is glycated, the liver no longer recognizes it, so the LDL stays in the blood stream, leading to a rise in LDL and increased likelihood of plaque buildup in arteries (atherosclerosis). This is one of the reasons people with diabetes and prediabetes have such elevated risk of atherosclerotic disease, heart attack, and stroke. In addition, hormones and hormone receptors can become glycated, leading to impaired hormone activity and all its downstream adverse effects. I commonly see male patients with symptoms of ‘low T’ who think they need more testosterone. They may not need a testosterone prescription. Instead, they may need to optimize their hormone metabolism and signaling, which will make them feel better.
Hopefully now you can see why I harp on the A1c, even if it’s not in ‘diabetic’ range. A1c above normal range is correlated with heart disease, cognitive decline, and premature aging. In the next posts we’ll cover more about glucose, insulin, and the dangers of glycation and AGEs and what you can do about them.