pistonpump; said:
care to share why zinc oxide is the worst? ....
It has to do with a combination of bioavailability and possible harsh impact on stomach lining (reduced by ingesting zinc oxide or zinc sulfate with food).
As you are aware, the cellular utilization of minerals in food is a fairly complicated process. First, the minerals must be extracted from food; then transported through the intestinal membranes and blood stream; and finally through the cell membrane into the cell interiors. This process is problematic. The most difficult chain is the intestinal wall. The cellular lining of the intestinal wall holds a negative charge on the surface of the membrane, whereas minerals already dissolved in digestive fluid have lost their neutral charge and gained a positive charge. These minerals will consequently be attracted to the cell membrane and be bound tightly there. Unable to pass through, these minerals will remain on the membrane until they are flushed away by secretion.
Chelation changes all this dramatically for some of the minerals. Chelators, organic molecules with electrical charges arranged such that they attract the positively charged minerals, are able to absorb these minerals into a larger complex. With the minerals' positive charge protected by the larger chelator mloecule, the complex appears neutral or negatively charged, and will consequently not be held by the membrane as it passes through. This assures a dramatic increase in bioavailability, an outcome that cannot be matched by inorganic forms of given minerals.
Zinc is available in two broad forms: as inorganic substance or as chelated substance. Inorganic zinc is usually in the form of zinc oxide or zinc sulfate. These inorganic forms are generally regarded as relatively inferior to the chelated forms, as they are less bioavailable. Chelated zinc is significantly more bioavailable. To be fair, zinc methionine is an exception, as studies show that it has low bioavailability comparable to inorganic forms. The hypothesis here is that the bond is not strong enough to survive the upper GI tract.
Now, as you know, for zinc to be absorbed into the body, it needs to be linked first to other substances. This is the motivation for supplement manufacturers to produce supplements containing zinc in a "chelated" form, where chelated simply means connected with another molecule.
There are two categories of chelates for zinc: organic acids and amino acids.
Organic acid chelates include picolinic acid, orotic acid, citric acid and gluconic acid. Correspondingly, the zinc forms here will be zinc picolinate, zinc orotate, zinc citrate, and zinc gluconate. Amino acid chelates include methionine, monomethionine, and aspartic acid. The corresponding zinc forms here are zinc methionine, zinc monomethionine, or zinc aspartate.
Chelated zinc is fundamentally superior to inorganic zinc.
Picolinic acid, produced from the amino acid tryptophan in the liver and kidneys and transported to the pancreas, is the body's prime natural chelator. The body constructs this molecule because it is the most efficient chelator for minerals such as chromium, zinc, manganese, copper, iron, and perhaps molybdenum. Consequently, some researchers consider zinc picolinate the most bioavailable form of zinc.
