Glucose

Note: See also Economical Alternatives.

Glucose is the most familiar of the essential sugars and the most ubiquitous (present everywhere at the same time). Glucose is a simple monosaccharide and one of the most important sources of energy for plants and animals. Photosynthesis converts carbon dioxide and water to glucose, which is then stored in leaves, stems, fruits, roots, pods, and seeds as glucose, starch, or other glucose units. Digestion converts the starch back to glucose in the body.

Glucose is often incorrectly referred to as “table sugar”. Sucrose is table sugar and a disaccharide composed of a glucose molecule and a fructose molecule — in roughly equal amounts. Both saccharides are abundant in many processed foods, soft drinks, and desserts, as well as bread, rice, pasta, vegetables, cereal, honey, corn syrup, and fruit – all of which can dramatically affect glucose levels in the blood.

Absorption
Glucose is readily aborbed and quickly distributed throughout the body via the bloodstream. Orally, it is absorbed in the intestines, reabsorbed in the kidneys, and crosses blood-tissue barriers using specific transporters called membrane proteins.

Obviously, there are two types of Glucose transporters. One is abundant in the plasma and comprised of blood-brain, blood-ocular (eyes), and placental barriers. It also participates in pancreatic and kidney transport and regulates Glucose levels in the liver. The other type is the sodium-dependent transporter which functions in the intestines and kidneys to carry Glucose against a concentration gradient. Glucose is easily metabolized by other nutritional sugars (essential sugars), but its transporters are shared with only some like Galactose, but not with Xylose, for instance. For some reason, Glucose transporters much prefer the D-form of Glucose to the L-form.

Glucose absorption from the intestines is influenced by many factors, including meal composition, rate of gastric emptying, intestinal hormones, and intestinal blood flow. There are several carbohydrate absorption disorders involving Glucose. These are generally recognized with such symptoms as diarrhea, gas, bloating, and other symptoms. This, in turn, affects digestive enzymes.

Excretion
Glucose is excreted via the kidneys. Normally, urine concentrations of Glucose are very low since about 98% of filtered glucose is reabsorbed in the proximal tubules of the kidney. However, excretion can increase 7-fold in diabetics since blood Glucose levels exceed the reabsorption capacity of the kidney transporters. In a newborn, Glucose can be excreted as a complex carbohydrate in the stools.

Functions

• Used by hospitals, sports enthusiasts, and everyone in between as a potent fast-energy source, Glucose is easily absorbed into the bloodstream. Glucose enhances memory, stimulates calcium absorption, and increases cellular communication. However, too much can raise insulin levels, leading to obesity and diabetes; but too little can cause hypoglycemia or worse, insulin shock (diabetic coma).
• Vital to brain function, Glucose metabolism is disturbed in depression, manic-depression, anorexia, and bulimia. In addition, Alzheimer patients, for instance, register much lower glucose levels than those with other forms of brain malfunction that resulted from stroke or other vascular disease. Researchers found that a dietary supplement of 75 grams of Glucose increased performance on a number of memory tests and reached across a broad range of cognitive tasks. Absorbed into liver cells, Glucose reduces the secretion of Glucagon, resulting in an increased uptake of Glucose by muscle and fat tissue cells. Excess blood Glucose levels is converted to fatty acids and triglycerides by the liver and fat tissues.
• Normal amounts of Glucose at a level that did not cause digestive symptoms has a beneficial effect on intestinal flora, especially that of bifidobacteria, vital for proper digestion and nutrient uptake. Researchers have also discovered a significant reduction in ratings of urges to smoke when smokers were given Glucose tablets to chew compared to groups who were given Sorbitol tablets. In preliminary work, scientists are finding the same theory holds true for alcoholics.

Safety
The safety of Glucose consumption is well known. North Americans consume far too much of this sugar, as much as 4-times the daily recommended limit. Consuming too much Glucose suppresses the immune system, resulting in a host of chronic diseases and disorders ranging from the common cold to malabsorption syndromes, diabetes, and obesity. How much Glucose is too much or what is the minimum requirement is an individual question. It depends on how much alcohol is consumed, antibiotics or antimicrobial foods taken, metabolic energy requirements, and so on. But it is safe to say, that very few people are even close to being deficient.

Dietary Sources
There is obviously no shortage of Glucose in the average diet, but the following list (mg. of Glucose per 100 grams of food) provides some better sources of dietary Glucose than that found in processed foods:

• Honey (33,900), Grapes (7,300), Bananas (7,000), Cherries (6,600), Strawberries (2,000), Mangoes, Cocoa, Aloe Vera, Licorice herb, Sarsaparilla, Hawthorn, Garlic, Kelp, and Echinacea.

References