Knowing All About Sugar: ­Essential for Life but Potentially Unhealthy: Part 1 of the Diabetic Story

Sugar is the familiar and common name for sucrose, a naturally occurring substance in nature that is formed in plants from the combination of water absorbed from soil and carbon dioxide absorbed from the air. Yes, sugar is composed simply of water and carbon dioxide. 

Sucrose is a complex sugar composed of the union of two smaller, simpler sugar molecules: glucose and fructose. Glucose and fructose and sucrose are each composed in nature as unique and independent compounds of carbon dioxide and water, and each exists as essential energy supplier compounds when ingested by animals of all kinds.  

Focusing on us humans, the compound “sucrose” is not absorbable as the double sugar. It must be cleaved into its two component parts: fructose and glucose. These are then separately absorbable by our intestinal tissues. The breakdown of sucrose into its components of fructose and glucose occurs within our digestive tracts as ingested carbohydrate foods move through. 

Once absorbed, glucose serves as our basic and essential energy molecule for each tissue cell - of all types and ages in our body. The journey of glucose is to travel in our bloodstream which bathes all of our tissues until each glucose molecule is transported into our myriad tissue cells. Within a tissue cell, the glucose molecule binds to other molecules and travels along pathways for the liberation of essential energy molecules. 

And, it is most amazing that the glucose molecule becomes split into water and carbon dioxide, just as it commenced its existence in plant leaves.  Thus, from carbon dioxide and water in plant leaves, the glucose molecule is formed, eventually eaten, enters the human body, travels throughout our bloodstream, is transported into numerous varying widely differentiated tissue cells, and then is changed back into carbon dioxide and water, while energy molecules (such as ATP) are generated for the essential support of the tissue cell life.  

The other component of sucrose is “fructose.” The journey of fructose, however, differs from the journey of glucose. Fructose is absorbable across our intestinal lining similar to glucose, and fructose does enter and circulate within our bloodstream. However, fructose does not have entry into other tissue cells (with one exception, the sperm cell). Thus, fructose cannot supply immediate energy for all other tissue cells. Rather, the fructose molecules are joined into chains within our liver and stored there as “starch” and “fat”, existing in those forms as “energy reserves” that may be released over several hours back into our bloodstream as needed and when needed after ingested circulating glucose molecules are “used up.” Once again, this is an amazing energy economy from consumed plant foods: immediate energy plus stored energy reserves.

An essential regulator of energy availability is the hormone insulin, which is manufactured within our pancreas gland. Insulin exists to “drive” glucose into our vital organ cells. Our pancreas “detects” glucose molecules directly after absorption from the intestine and then secretes insulin, which travels in the bloodstream to direct the uptake of glucose into our vital organ cells. Insulin is essential. Glucose uptake into our critical tissues will not occur without insulin. This insulin response is sensitive, predictable, and highly regulated and governed, such that just enough insulin is produced and secreted to match the glucose surge from eaten foods. Thus, any large surge of glucose from plant food ingestion is minimized because newly-absorbed and now circulating glucose is rapidly transported into tissues. Glucose concentrations in our blood are thus controlled. 

While fasting, our plasma glucose concentration will reside between 70 mg/dL and 99 mg/dL. With a snack or meal, our glucose surge should not rise above 125 mg/dL, no matter how much sucrose or simple glucose, or other complex sugars we have eaten. Our pancreas' response with insulin output is set to match the glucose entry. AND, very importantly, the entering glucose into our bloodstream will NOT circulate in the bloodstream for more than 90 minutes. New glucose will be transported into tissues that rapidly. 

Insulin secretion thus declines as glucose concentrations decline to levels below 100 mg/dL, and this response allows glucose concentrations to settle in the range of 70­ to 99 mg/dL. BUT, our tissue energy supplies will not disappear. Our blood glucose is renewed in a strategic way. As insulin declines, new glucose molecules are released into the bloodstream from the stored starch compounds residing in our liver.

Remember that starch formation is one fate of ingested fructose as well as ingested glucose, and these storage deposits in our liver exist just for the purpose of slow release of fresh glucose when we are not eating. In this way, glucose in our bloodstream is maintained at life-sustaining concentrations, always available for entry into vital organ cells for energy generation within the cells. Glucose is essential for life. Glucose is life-sustaining and energy supplying. 

However, these same life-sustaining glucose molecules can damage cell membranes if the molecules remain in our bloodstream too long! Glucose circulates until it is transported across a cell wall into the tissue and insulin is the governor and mediator of this cellular transfer. If glucose molecules are not transferred into cells within 90-120 minutes, then the glucose molecule will undergo a chemical change in the bloodstream and become stuck, or attached, to a nearby protein molecule.

Such a reaction is random, is not controlled by any enzyme, will happen if any single glucose molecule circulates too long in the bloodstream, and is called "glycation." “Glycation” is a toxic reaction. Glucose becomes stuck and cannot be released. This adhesion of glucose changes the structure and function of the molecule to which it attaches, and this then perpetrates permanent tissue alterations that result in a disease state. Thus, glucose can be a “toxic” molecule if it is not transported into tissues promptly.

Unfortunately, delayed transport of glucose into needy tissues is a common problem for millions of people worldwide. This circumstance prevails in Diabetes Mellitus as well as in those individuals living in a clear Prediabetic state. Diabetes Mellitus is defined by either an insufficient provision of insulin OR by a resistance to insulin action. Either of these abnormalities results in the delayed transfer of eaten glucose into vital tissue cells and thus elevated blood glucose concentrations and prolonged circulation of any ingested glucose. Vital cell structure injuries result.  

Knowing these details will help any reader who may be living with a Prediabetic State or an Actual Diabetes Mellitus diagnosis. Precise and regular diet adjustments plus thoughtfully-prescribed medications become essential for wellness and health. These shall be the subject matter of the second and third parts of this informational series.