Carbohydrates in Food and Medicine

Carbohydrates and Cartilage Joints and cartilage are a complex matrix of various combinations of carbohydrates, called glycoaminoglycans (GAG’s) and proteins and carbohydrates on a backbone structure called a proteoglycan. Repeating sequence of the glycoaminoglycan chain, hyaluronic acid. Note the presence of glucosamine

Carbohydrates and Cartilage These GAGs and proteoglycans can associate to form huge polymeric complexes in the extracellular matrix. Molecules of aggrecan, for example, the major proteoglycan in cartilage assemble with hyaluronan in the extracellular space to form aggregates that are as big as a bacterium.

Blood Types The cell surface of blood cells is covered with glycoproteins and the carbohydrate chains project out into the blood stream where they can easily be recognized by antibodies. We make antibodies to all sorts of things but the ones that attack our own cells are removed before they can do any harm. This anti-self screening of antibodies is one of the things that goes wrong in auto-immune diseases.

Blood Types The proteins on the erythrocyte cell surface contain a wide variety of different oligosaccharides that are attached in various ways to the protein. However, in spite of this variation, there are a few structures that are very common. One of the most common “core” structures is something called H- antigen. It is composed of many different sugars but the outside end of the H-antigen structure always consists of a fucose (Fuc) residue, a galactose residue (Gal), and an N-acetylglucosamine (GlcNAc) residue.

Blood Types Normal red blood cells are recognized as “self” so we don’t have antibodies against our own cells. However, we will have antibodies against the red blood cells of other people’s blood if their cell surface carbohydrates are different from ours. This is the basis of ABO blood group and it’s why we have to match blood types in a blood transfusion.

Sweetness The global cost for sugar from cane sugar is far too unpredictable and high for the food industry. As a result, several changes have been made. First, was taking advantage of the low cost corn that became available after deregulation. Enter, the chemist Japan chemists had pioneered ways to efficiently engineer high-fructose corn syrup, HFCS, from the corn. This sweetener is nearly twice as sweet as regular sugar and very low cost. The result is a mono-saccharide of glucose and fructose with a slightly higher fructose content. Almost immediately, the soft drink industry switched over, making a sweeter product at a lower cost. Currently, HFCS is the predominant sweetener in the food industry.

The result… Fructose, a common sugar is not metabolized in the body as are other sugars. It is sent directly to the liver. The high use of fructose (high fructose corn syrup) as a sweetener has been associated with numerous health effects, among them: Elevation of blood triglycerides as the liver uses fructose as building blocks for the synthesis of these fats. Increased uric acid levels, blood pressure and a reduction of HDL cholesterol.* A 10-fold likelihood of leading to the formation of Advanced Glycosidic End Products (AGE’s) than glucose or sucrose.** Increased insulin resistance, hyperinsulinemia, impaired glucose tolerance and a resulting increase in adiposity. Interestingly, vegetarians that have higher intakes of fruits and, therefore, fructose, demonstrate higher levels of AGE products The items in yellow are not added back in “enriched bread”. *Hallfrisch H. “Metabolic Effects of Dietary Fructose” The FASEB Journal 4 2652 (1990), Starc T.J. Am. J. clin. Nutr. 67 1147 (1998), and Bantle J.P. et. al. Am. J. Clin. Nut. 72 1128 (2000) ** Levi B. et. al. J. Nutrition 128 1442 (1998) and Krajcovivova-Kudlackova M. Physiol. Res. 51 313 (2002)

Alternative Sweeteners Medical researchers recognized that the high insulin caused by chronically high blood sugar was a factor in the development of insulin resistance, a precursor to glucose intolerance and diabetes. The increasing numbers of diabetics (now growing to epidemic levels in young adults) lead the public to begin looking for sweeteners that did not produce the insulin response of sucrose. (We’re not to the reduction of calories yet) The food industry responded by utilizing parts of the sugar molecule that gives the sweet sensation. Enter the synthesis chemist and the development of the “sugar alcohol”

Reduced Sugars

Calories still count The sugar alcohols, although not raising blood insulin levels, do have a caloric content of about 5-7 Cal/gram as compared to 4 Cal/gram for regular sugar. A corresponding cause for a number of diseases in addition to diabetes led many to become more calorie conscious. Enter the food chemist again with the artificial sweetener. The challenge has been to produce a sweetener that tastes like sugar, but does not have the calorie content. Recently, interest has been in the development of non-caloric sweeteners made from sugar, but not digestible.

Sucralose Sucralose is made from sucrose by exchanging some oxygen and hydrogen atoms for chlorine atoms

Fat Substitute Although the introduction of hydrogenated oils improved aspects of the food products, the calorie conscious and those wishing to reduce their fat intake needed a substitute. Enter the synthesis chemist…

Olestra Similar to the idea of Sucralose, Olestra is intended to be a natural substance, altered so that the body can’t absorb it. The solution was in the sugar molecule, again. This time, the sugar was combined with the long carbon chains of the fats to produce a combination molecule. The result was a substance that had a fatty mouth feel, but was too large to pass through the gut into the blood stream. The body does not have the necessary enzymes in which to break the molecule down and digest it. As a result, it passes through the gut largely intact.

Olestra

The Result: Olestra is a fatty molecule that travels through the gut. As it passes through, it collects and carries fat-soluble vitamins out of the body. The gathering of fats produces a large molecule that is digested by bacteria in the gut leading to gas production and diarrhea.