There seems to be as much confusion about sugar as there is interest at the moment, and mainly because of the random use of the word ‘sugar’. It is popularly used to refer to fructose – but it may also be referring to glucose or sucrose (the sugar we put in our coffee).
It is also virtually impossible to fully understand sugar without understanding insulin function. In my last post I wrote about fructose vs glucose but here I describe glucose, how it gets into our diet, how it affects our bodies, and the role of insulin, from A to Z – all in under a thousand words. (But you’ll get it!) So let’s take it from the top:
The principle digestible constituents of plants include carbohydrate, protein (amino acids), fats, and micronutrients. The digestible carbohydrate in plants is called starch. Starch is made of complex chains of glucose molecules called ‘polysaccharides’ and is referred to as ‘complex carbohydrate’.
Refining starch breaks down the polysaccharides into individual molecules of glucose. A molecule of glucose is called a ‘monosaccharide’ and is commonly referred to as ‘simple carbohydrate’, or sugar.
Your body uses glucose to make energy, and each cell in your body has the ability to absorb and utilise glucose to produce the energy it needs. Glucose is also stored as glycogen in your liver and muscles for future energy needs. What isn’t used as energy or stored as glycogen remains in your blood stream until it is used or excreted. If it remains in your blood stream for an extended period of time, it becomes toxic. Glucose toxicity causes vascular inflammation, cell death, impacts heavily on kidney health, and causes metabolic disorders including diabetes.
It is important to understand that glucose is not converted to, or stored, as fat. If it was, it would be removed from the bloodstream and glucose toxicity and diabetes could not occur. The reason it is not stored as fat is because your brain is fuelled exclusively by glucose. If your body stored glucose as fat, your brain would be denied fuel and would be unable to function. The consequences of this would be unpleasant, to say the least.
Neither does your body convert fat into glucose. There is no need to because fat (as free fatty acids) is converted directly into energy within the cells of your body (notably your muscle cells). However these free fatty acids cannot pass through the blood-brain barrier to supply energy to the brain. To complicate it further, brain cells cannot store glucose and therefore require a constant supply. This is something of a dilemma for your body – your muscle cells prefer free fatty acids for energy (because they provide much more energy than pure glucose) but your brain can only use glucose.
This sets up something of a juggling act and makes insulin function (the juggler) extremely important. When you eat glucose it is absorbed through the intestinal wall resulting in the release of the hormone insulin. One of the functions of insulin is to facilitate the absorption of glucose into your cells. The other is to prioritise the storage of fat from your blood stream while inhibiting the release of fat from stores. This is to maintain the balance between keeping up the supply of glucose your brain needs, and the reduction of glucose in your bloodstream to prevent it from becoming toxic.
Complex carbohydrates (unrefined starch, for example in vegetables) generate a steady insulin response. Simple carbohydrates (refined starch, for example white wheat flour) over-stimulate insulin production and, to cut a long story short, this is what causes toxicity and chronic disease.
Insulin function changes with activity levels. Your body will produce lower levels of insulin during activity because your muscle cells are using up glucose from your blood. In order to ensure an adequate supply of glucose to your brain during activity, free fatty acids are allowed to remain in the blood stream to provide fuel for your muscle cells. This reduces fat storage.
By contrast, inactivity requires maximum insulin function. This is to prevent unused glucose from remaining in the blood for too long and inducing glucose toxicity. This is the reason people who are sedentary and consume glucose from refined starch are so prone to putting on weight – their bodies are producing more insulin, and as one of the functions of insulin is to prioritise fat storage, any fat they are eating (with the refined starch) is being stored.
This is how glucose consumption indirectly causes weight gain. However, it is also very important to know that excessive glucose consumption can lead to metabolic syndrome, Type 2 Diabetes and Cardiovascular disease without significant weight gain.
It’s worth noting that while your body does not break down fat into glucose it can break protein down into glucose. If there is not enough glucose or protein in your diet then your body will cannibalise protein from your muscles and convert that to glucose. This is why people who are starving have noticeable muscle wastage. The risk you run when dieting is that weight loss is actually the result of the loss of muscle mass due to this process.
Glucose is also the fuel for cancer cells. Malignant tumours produce energy anaerobically (without oxygen). Normal tissue produces energy aerobically (using oxygen) because it is much more efficient. Anaerobic energy production is sensitive to energy supply – glucose. An abundance of glucose (as a monosaccharide) in your diet means an abundance of fuel for tumour cells. By removing refined starch from the diet and consuming glucose only from complex starches (vegetables), tumour cells are denied their primary fuel and means of survival. In Europe, cancer treatments have been shown to be more effective when refined carbohydrates are removed from the diet.
The most highly consumed sugar, by far, is glucose. In the modern Western diet, the main source of glucose is the refined starch used to make bread, pasta, noodles, biscuits, cake and virtually all manufactured dry foods. Added sugar is a catalyst for chronic disease, but it does not compare to amount of sugar consumed from refined starches. The high proportion of these products consumed in the typical Western diet is a major contributor to chronic disease, obesity, and the evolving health crisis.
If you have questions please post them in comments and I’ll do my best to answer them.
This post is an excerpt from my book: Eat, Move & Thrive: the 5 secrets of very healthy people.