Diabetes can be a devastating disease, doubling our risk of heart disease and being the single most common cause of kidney failure and amputations, amongst other things. These potential consequences of diabetes are largely due to the presence of high levels of glucose in our blood.
What is glucose?
Glucose is the sugar that makes up carbohydrates, which is why carbs can cause problems for people with diabetes. Nonetheless, we do need some glucose in our circulation; the problem is when we have too much glucose. In fact, a healthy person should only have about 4 grams or a teaspoon of glucose in their circulation at any point – about a quarter of the amount of carbs that can be found in a single slice of bread.
What does glucose do to the body, and why do glucose levels matter?
Excess blood glucose actually binds to and damages proteins it comes in contact with. This is called glycation, resulting in advanced glycation end products (AGEs) – essentially proteins damaged by sugar. While this process does occur normally, it is vastly accelerated in diabetes. Amongst other things, levels of AGEs correlate with heart disease, stroke, cancer, dementia, arthritis and even aging of the skin. There is no doubt AGEs make healthy aging difficult, if not impossible.
In patients with type 2 diabetes where the normal method of removing glucose from the blood is impaired, the glucose from carbohydrate foods such as bread, pasta and potatoes can lead to massive rises in blood glucose levels. The question is, how much glucose is too much?
What are normal glucose levels?
We measure glucose levels by counting the number of glucose molecules per litre in the blood (mmol/L). Most of the time, blood glucose levels are measured in the early morning, before any food. This is known as a fasting level. A fasting glucose level of 7.0mmol/L or more is consistent with diabetes. Even fasting glucose levels of less than 7.0mmol/L can be problematic, however. A level of 5.6mmol or more is considered pre-diabetes, while research indicates the lowest chance of dying occurs with fasting glucose levels between 4.4 and 5.2 mmol/L.
Glucose levels can also be measured with an oral glucose tolerance test, where blood glucose levels are measured over two hours following a drink containing 75 grams of glucose. A two-hour glucose level of over 11.1 mmol/L, consistent with diabetes, is associated with more than double the chance of dying compared with someone with a two-hour glucose level of less than 6.1 mmol/L.
What is the HbA1c test?
Average blood glucose levels can also be estimated with a measurement known as haemoglobin A1c, or HbA1c. Your red blood cells circulate in your blood’s fluid containing glucose molecules. These glucose molecules, over time, will attach to your red blood cells: the more glucose that is present, the more which will attach to your blood cells.
Therefore, measuring the number of glucose molecules on each red blood cell shows your average glucose level. Of course, many factors can interfere with this measurement, including other factors in your blood that inhibit the binding of glucose to red blood cells (glycation inhibitors), as well as variations in the lifespan of your red blood cells.
Ironically, conditions in which red blood cells are being excessively destroyed will lead to an overall population of younger red blood cells with an artificially low reading. The reverse is true for people with longer-lived red blood cells, with their HbA1c overestimating their average glucose level. These limitations aside, HbA1c can be used to diagnose and monitor diabetes. A HbA1c of 6.5% or more may indicate you have diabetes, while reductions over time indicate improved glucose management.
What’s a ‘normal’ HbA1c result?
It’s interesting that traditionally, doctors do not recommend patients with type 2 diabetes aim for a ‘normal’ HbA1c between 4.0 – 5.6% while under standard medical care. This is because combining a high carbohydrate diet, as the dietary guidelines recommend, with diabetes medications usually results in significant fluctuations in blood glucose levels. To obtain normal HbA1c could mean periods when the blood glucose level is low, a state known as potentially dangerous hypoglycemia.
Of course, this is quite different from managing your blood glucose level with diet, and many people with type 2 diabetes can achieve a normal HbA1c (less than 6.5%) by following a low-carbohydrate diet.
Risk factors of high glucose levels
High blood glucose levels do not only have long-term consequences. If the levels are high enough, problems can arise rapidly. One of the most obvious problems with high glucose levels is when our kidneys can no longer prevent glucose from entering our urine. This is known as glycosuria and can lead to several issues, including dehydration due to excessive urination and an increased risk of bladder infection.
Symptoms of high glucose levels
- Increased urination: One potential indication of glucose in the urine and kidney damage is increased urination, especially overnight. The dehydration that results often leads to prominent thirst. Be sure to consult with your doctor if you notice these symptoms. It is generally considered that this leaking of glucose into the urine occurs whenever blood glucose levels exceed approximately 10 mmol/L. Note that this level is almost certainly being exceeded regularly in people with type 2 diabetes following the dietary guidelines. Perhaps even more of a problem is that this threshold is likely lower when the kidneys are damaged, as is common in diabetes.
- Infections: Consistent high levels of glucose will allow bacteria to happily feed and multiply. This impairs the functioning of the immune system, and persistent infections (including urinary tract infections, skin infections and coughs and colds) occur.
- Memory: The brain is especially vulnerable to metabolic disease. Anything impacting metabolic health – such as high blood glucose levels – can impact your brain health. So much so that dementia is now referred to as type 3 diabetes.
These are just three of the more common symptoms of having high blood glucose. However, there are many more physical signs of high blood glucose. If you notice any of these symptoms, it’s time to see your doctor.
What about fructose?
Fructose is the other half that, together with glucose, makes up sucrose, or table sugar. And fructose can be even more of a problem than glucose. For example, fructose damages proteins about seven times more than the same amount of glucose and is a much more potent cause of fatty liver disease. The thing is, fructose is not glucose. And that means it is overlooked when measuring your blood glucose. This is why 100 grams of table sugar (sucrose) won’t have the same impact on your blood glucose levels as 100 grams of pure glucose, but it is clearly worse for your health.
Dr David Unwin from the UK famously developed an infographic adopted by the UK National Health Service (NHS) demonstrating the sugar content of various foods in teaspoon amounts. For simplicity, he presented all sugar as glucose when, technically, he should also have included fructose. His critics used this to denigrate this valuable educational tool solely because some foods didn’t contain the specific amount of glucose indicated. While technically correct, the fructose contained in some foods is even more damaging to health than glucose. So yes, certain foods didn’t contain as much glucose as suggested, but the truth was even worse. The ‘missing’ glucose was fructose, a much more damaging sugar.
Treatment of high glucose levels
The solution to addressing high blood glucose levels essentially comes in two parts. First, there is the problem of reducing the source of glucose. If one understands that carbohydrates are made from glucose, then it is only common sense that they should be avoided.
The other half of the problem is the metabolic damage present in people with type 2 diabetes, which limits their capacity to process dietary carbohydrates. In addition to carbohydrates, dietary fructose (found in sugar) and vegetable oils are major contributors to this metabolic damage. The Defeat Diabetes Low Carb Program focuses on these principles to assist you in managing and potentially even putting your type 2 diabetes into remission.
