The Monosaccharide, Fructose

Christine L. Foutch Naturopathic Physician Rock Island, Illinois

Christine Foutch is a practicing Holistic Physician in Rock Island, Illinois, specializing in Holistic Nutrition and Biomechanics. Holistic medicine is the art and the science of healing that addresses the whole person – body, mind, and spirit. The practice of holistic medicine integrates conventional and alternative therapies... more

Early within the 1900s, the average individual took in about 15 grams of monosaccharide, otherwise known as fructose, daily.

So fructose, which can also be called fruit sugar, was once a much smaller part of our human diet; with the majority of the fructose coming from the consumption of whole foods, such as fruits and vegetables.

Glucose is the principal circulating simple sugar within us while sucrose is a disaccharide formed by the bonding of equal parts of the more simpler sugars. Glucose and fructose come together to form sucrose, which is the predominant circulating sugar in plants. And, plants obviously form the basic foundation of the food chain.

The herbivores, which are animals that feed off plants, and the omnivores, which are the animals that feed off both plants and animals, are all highly adapted to sucrose,which is  broken down and used for all of their energetic-purposes. Sucrose will then translate into the bio-synthetic abilities and then, of course, the bodily needs.

The major natural sources of fructose in human diet are fruits, honey, and sucrose, which is also known as table sugar.

Under what is considered to be the normal dietary intake, the majority of our ingested fructose becomes absorbed and metabolized by the enterocytes.

These enterocytes, which are the absorptive-cells within the small intestine, absorb the simplified nutrients, being referred to as chemicals after their chemical breakdown from the enzymatic activity that is taking place within the intestinal lumen, the hollow tubular-passageway, the Alimentary Canal. Within the enterocyte, fructose is primarily converted, or, maybe I should say metabolized, into glucose, with the rearrangement of the atoms within the molecule through enzymatic functions. This is then delivered as glucose out of the enterocyte and into systemic-circulation for utilization by the bodily cells for physiologic needs.

However, added in with the converted substrate to product ability, for the forming of glucose, you will find that fructose’s remaining molecules are also converted.

Those carbon-atoms from the consumed dietary-fructose molecules become rearranged, going onto being metabolized. Converted, as well, through the enzymatic activity within the intestinal enterocytes, which are the absorptive cells, into many other products. This will now include glycerate, glutamate, glutamine, alanine, ornithine, and citrulline.

Diets that contain the larger amounts of sucrose, the high fructose corn syrup, or even just fructose alone, overwhelm this ability to reform the simplified chemicals within the small intestine enterocyte, altering the metabolism of fructose. Then, it goes on and enters the systemic circulation.

Under these circumstances, the fructose metabolism becomes part of the liver’s responsibility, and to a lesser extent, the skeletal muscle and some of the other tissues of the body.

The simple sugars, otherwise known as monosaccharides, are by far the predominant carbohydrates absorbed in the digestive tract. In animals, they are the most important sources of energy.

However, the monosaccharides are rarely found in our normal diets.

Rather, they are derived from the enzymatic activity that is described, coming from the digestion of those more complex carbohydrates within the lumen of the small intestine, the hollow home for digestion.

Particularly, the important dietary carbohydrates will include starch and disaccharides, such as lactose and sucrose, however, none of these larger molecules can be absorbed into the enterocyte. For the very simple reason that they cannot cross the cellular membranes. This is unlike the situation for the monosaccharides, as they have the help from the GLUTs, which are transporters to carry them across.

Fructose does not circulate at the higher levels in animals; so, the ingested fructose is believed to be uniquely positioned to convey signals related to our sugar consumption.

Therefore, understanding the mechanisms by which fructose is used may help with the understanding of our many adaptive physiological responses to sucrose metabolism, as well as any potential consequences to any excessive sugar consumption.

For Your Health & Wellness

Educational Purposes

Christine Foutch


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