The Sugar in our Blood

In simple terms, Blood sugar (aka. Blood Glucose) is the body’s principal form of energy, readily used by our brains, muscles and other organs to function

The Sugar in our Blood
Photo by Erol Ahmed / Unsplash

What is Blood Sugar?

In simple terms, Blood sugar (aka. Blood Glucose) is the body’s principal form of energy, readily used by our brains, muscles and other organs to function. It is the preferred fuel source for our brains and a healthy level of blood glucose is required for a healthy metabolism and overall health.

How does the body get Glucose? How is it used?

Glucose is obtained mainly from the breakdown of ingested carbohydrates like bread, pasta, sugars, fruits, etc. Carbohydrates are quickly broken down into glucose, starting in your mouth and absorbed into the bloodstream by our bowels.

Once in the bloodstream, glucose can either be used directly to power organs, or  stored in muscles and in our liver for future use, in the form of glycogen.

The body's stores of glycogen can be readily converted to glucose in muscles, and can also be released by the liver, in the form of blood glucose, to maintain a steady level of blood glucose, supporting healthy metabolic processes.

Ok! But what about fat & protein?

Blood glucose is not the only fuel source used by our bodies. Our bodies can convert glucose, protein & fat into energy, but glucose is the most readily metabolised, and therefore the first form of fuel to be used.

Body fat contains a highly concentrated form of energy that takes longer to metabolise than glucose, so is used for endurance and for low to moderate intensity activity. But even metabolising fat requires some glucose consumption.

Protein use as an energy source on the other hand only happens when the body is unable to access glucose directly or indirectly (through glycogen), unable to access fat storage, or due to malnutrition or imbalances in the body (e.g.: hormonal).  As clever as our body is, it will try its hardest to avoid using protein as a fuel source as it leads to muscle breakdown.

It is important to note that these forms of fuel are not used in isolation, the body is an incredibly complex and flexible system and will, at certain times, use a mixture of glucose & fat for energy. But the body will naturally consume glucose first, and at a faster rate as it is easier to metabolise. The graph below gives you an idea of how the body uses Glucose & fat in the context of physical activity:

Interesting… Why should I care?

In healthy individuals the concentration of glucose in the bloodstream is carefully balanced via the hormones insulin and glucagon.

Insulin is responsible for reducing blood glucose by instructing its storage as glycogen in liver and muscles, or as fat. Glucagon, on the other hand, is responsible for raising blood glucose by instructing the liver to stop storing glucose and release its storage of glycogen as glucose into the bloodstream (in times of starvation it instructs the breakdown of amino-acids into glucose).

The Insulin/Glucagon balancing act is crucial as high concentration of glucose in the bloodstream (hyperglycaemia) is toxic to human tissues, leading to tissue death.

Actually, the inability to control blood glucose is the signature of Diabetes which, left untreated, can lead to blindness, nerve damage, heart & kidney damage, etc.

Diabetes is obviously a very serious condition, and unfortunately it is a condition that is becoming increasingly common. The vast majority of people with Diabetes suffer from what is known as Type II diabetes, a condition which although very serious, is preventable, and even reversible.

Unlike Type I diabetes, Type II diabetes is not caused by the body’s inability to create insulin (which lowers blood glucose as we have seen), but is caused by the body’s inability to respond to healthy levels of insulin, a condition named Insulin Resistance.

Insulin resistance means the body is less sensitive to insulin, meaning that more and more insulin is required to lower blood glucose, leading to a “catch 22” situation where the body ends up being unable to produce enough insulin to control blood glucose, and other important metabolic processes.

It may sound like insulin resistance is a malignant mechanism, but, on the contrary, it is a natural adaptation, and a desired one in certain situations (e.g.: pregnancy).

The problem occurs when insulin resistance becomes an adaptation to frequent exposure to insulin due to lifestyle factors.

Sedentary lifestyles, diets high in simple carbohydrates and sugars, and unlimited access to food means the average human is now frequently and heavily relying on insulin to lower their blood glucose, which means frequent and heavy exposure to insulin, and, as we have learnt, our body adapts to this exposure by becoming more resistant to insulin

Insulin Resistance is rapidly proving to be the underlying cause of obesity^[10]^ and many of the conditions and chronic diseases that plague our modern society: from high blood pressure, to type II diabetes, to cardiovascular disease. Alarmingly, it also is being linked to many forms of the most common cancers, Alzheimer's and even erectile dysfunction.

The silver lining is that what often causes Insulin resistance, and the cascading conditions and diseases it leads to, is often the solution: lifestyle choices.

Ok, so what can I do?

If you are insulin sensitive, great! Keep at it!

Otherwise, the quick and simplistic answer is ensuring your blood glucose is within healthy levels, and that you don’t overtax your body to the point of becoming insulin resistant.

If you are overweight, have high blood pressure or high level of blood triglycerides, you most likely are Insulin Resistant, if you suffer from type II diabetes you are almost guaranteed to be Insulin Resistant.

If you find yourself reading these words you likely fell into the last group. You probably also know, and painfully so, that there are no quick and simple solutions to lifestyle change.

…but what if the solution was not quick but actually quite simple?

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Sources:

  1. Physiology, Glucose Metabolism | link
  2. What Is The Aerobic Threshold: A Beginners Guide| link
  3. Hyperglycemia in diabetes | link
  4. Preventing Type 2 Diabetes | link
  5. Reversing Type 2 Diabetes: A Narrative Review of the Evidence | link
  6. Insulin Resistance and Diabetes | link
  7. Insulin Resistance & Prediabetes| link
  8. Insulin Resistance [Cleveland Clinic] | link
  9. Normal Pregnancy- A State of Insulin Resistance | link
  10. Obesity and insulin resistance | link
  11. Insulin resistance. A multifaceted syndrome responsible for NIDDM, obesity, hypertension, dyslipidemia, and atherosclerotic cardiovascular disease | link
  12. Plasma aldosterone, plasma lipoproteins, obesity and insulin resistance in humans | link
  13. Insulin resistance and cardiovascular disease | link
  14. Association between insulin resistance and the development of cardiovascular disease | link
  15. Obesity, Insulin Resistance and Cancer Risk | link
  16. Insulin resistance and cancer: the role of insulin and IGFs | link
  17. Prostate cancer: another aspect of the insulin-resistance syndrome? | link
  18. Insulin Resistance in Alzheimer's Disease | link
  19. Insulin Resistance Is an Independent Determinate of ED in Young Adult Men | link