N-acetylneuraminic Acid

N-acetylneuraminic acid (sialic acid) is found in a wide variety of substances and tissues in animals and humans, occurring most abundantly in glycoproteins and glycolipids.

An acidic aminosugar was first isolated and named sialic acid by one scientist. Another isolated a similar crystallized form and called it neuraminic acid. When both were found to be the same molecule, the correct structure was proposed by a third scientist. All three finally agreed to use sialic acid as the family name covering all of the more than thirty derivatives of neuraminic acid, with N-acetylneuraminic acid and N-glycolylneuraminic acid forming the core structures.

Sialic acid is widely distributed throughout human tissues and found in several fluids, including serum, cerebrospinal fluid, saliva, urine, amniotic fluid, and mother's milk. In experimental mammals, it is found in high levels in the brain, adrenal glands, and the heart. In humans, concentrations are found in the brain and kidney as well as many other tissues.

Absorption
Although specific information is not yet known, it is assumed that sialic acid is readily absorbed when ingested. This is based on its appearance in numerous glycoconjugates (a molecule with one or more sugars attached to a protein or lipid) throughout the body and its excretion in the urine.

Enzymes involved in sialic acid metabolism also appear to be important in the metabolic regulation of other essential sugars and glycoconjugates. Sialic acid can be manufactured, by certain enzyme action in the body, from Glucosamine and N-acetylmannosamine.

Excretion
Sialic acid is rapidly eliminated via the kidneys. In lab animals, at least 98% of ingested sialic acid is found in the urine six hours after ingestion while about 90% appears in the urine within 10 minutes of an IV dose. During lactation, excretion of the sugar is markedly increased. When this data is applied to humans, most of the sugar would be expected to be excreted within 8 hours of ingestion. Therefore, it, or the other sugars, does not accumulate in body tissues.

Functions
Sialic acid is an immune moderator that affects the flow resistance of mucus which, in turn, repels bacteria, viruses, and other harmful microbes. In several in vitro and animal studies, the saccharide has been shown to inhibit strains of influenza A and B viruses more effectively than any prescription antivirals. In the April 2001 issue of Protein Science, scientists from Australia reported findings that showed sialic acid was an effective antiflu agent. Another study reported in a 1995 issue of Antimicrobial Agents and Chemotherapy, stated that a sialic acid mixture was up to 1000 times more effective in fighting influenza than potent antiviral drugs. Such viruses can also cause cold sores, hepatitis, viral pneumonia, as well as the common cold. Therefore, this helpful information is nothing to sneeze at!!

Since high levels are found in the human brain and kidney, it is speculated that sialic acid may play a key role in brain development and learning and in lessening the risk of kidney stone formation. Animal studies indicate that this essential saccharide does appear to improve both memory and cognitive performance.

Sialic acid is also found in such other tissues as the skin and testes leading to speculation that disruptions like skin diseases and reproductive problems could be reversed with supplementation of this essential sugar.

Sialic acid also influences blood coagulation and cholesterol levels, lowering LDL (bad cholesterol).

In alcoholics as well as those with Sjgren's syndrome, the levels of this saccharide are altered, suggesting that supplementation could reverse these disorders.

Abnormalities in sialic acid metabolism are seen in infants who fail to grow, who regress in development, who have enlarged livers and/or spleens, who show a coarsening of facial features, and who display a failure to produce pigmentation of the skin and hair.

Sialic acid, like the other essential sugars, appears to be important during pregnancy and lactation. The fact that levels are increased during these stages indicates the need for these sugars by the developing infant both for establishing immunity and for its physical and mental development.

In severely ill patients, sialic acid levels are markedly decreased in the upper airway cells, which is an important barrier for preventing opportunistic respiratory infections seen in many of these patients.

Sialic acid levels are markedly reduced in those with rheumatoid arthritis, confirming that this saccharide plays an important part in the immune system.

Researchers at Kumamoto University in Japan discovered that sialic acid blocked the release of histamine, thus decreasing the severity of allergic reactions as well as asthmatic bronchial spasms.

Safety
There does not appear to be any data that indicates any adverse reactions to a supplementation of sialic acid. On the contrary, researchers who, consistantly used high doses in experimental animals, found that the learning abilities of these animals increased. Nor did it seem to matter whether the dose was given orally or intravenously, the result was the same, indicating that the sugar is just as reactive using either route.

However, if there is a metabolic disorder that prevents the proper absorption of the sugar, disorders can be aggravated, causing a reversal in the positive effects seen in others. Malabsorption could result in mental retardation and ataxia (muscle coordination failure), as well as enlarged livers, developmental delays, and an excess excretion of sialic acid in the urine. Therefore, establishing whether this or other sugars are properly assimilated is very important. This is just one reason why taking all eight essential sugars together is much better than trying to take them individually and guessing the amounts. All work together to help each other, thereby drastically reducing the risk of problems when taking only one sugar.

It is suggested that the maximum safe dosage would be 140 mg. for a healthy 150-pound adult.

Dietary Sources
Whey protein isolate or concentrate - not the powder (even those allergic to dairy products are able to tolerate this substance. It appears that the concentrate has a higher amount of sialic acid than the isolate.) Hen's egg (organic, of course!)

References
1.Mondoa, Emil I. MD and Mindy Kitei. Sugars that Heal. Ballantine Publishing, 2001.
2.Elkins, Rita MH. Miracle Sugars. Woodland Publishing, 2003.
3.Glycoscience website (This site prohibits direct linkage.)
4.http://www.burnoutsolutions.com.au/glyconutrients.htm (A glyconutrient site by Dr David Bird MbChB, Dip Clinical Nutrition, FACNEM [Fellow of the Australian College of Nutritional and Environmental Medicine])
5.http://www.biochemicals.cn/N-Acetylneuraminic_Acid.html (a site by Shangyuchem, a biochemical company from China)
6.http://www.glycoforum.gr.jp/science/word/glycolipid/GL-A04E.html (an explanation of the saccharide by Akemi Suzuki (Tokyo Metropolitan Institute of Medical Science)


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