Zinc is a very important trace mineral in human nutrition. Zinc is incorporated into a number of metalloproteins in cells, some of which are enzymes. Zinc is known to be an essential part of over 100 enzymes covering every enzyme class, and is used to either catalyse reactions or give structure to the enzyme. Zinc also has a role in the stabilisation of cell membranes and in the immune system response. Zinc intakes have been found to be low in a number of studies based on Western populations. In other research, nutritional supplements have been shown to be effective at reversing low plasma and cellular levels of zinc. A number of conditions necessitate higher zinc intakes including heavy alcohol consumption, absorption problems (such as Crohn’s disease and celiac disease) as well as those who undertake intense physical activity.
Zinc is available in supplemental form as both inorganic mineral supplements or in an organic mineral complex. Inorganic mineral supplements are metal ions bound to inorganic components and include zinc oxide or zinc sulfate. These compounds of zinc are found in rocks, which is where they naturally originate. Inorganic minerals are taken up by plant roots after the rocks are pulverised to form soils. Zinc can also be bound to organic components such as amino acids such as histidine or methionine; or organic acids such gluconate or succinate. These organic complexes more closely resemble the forms of zinc stored in plant and animal tissue and evidence suggest that they are better absorbed than their inorganic counterparts. The absorption characteristics are likely due to the change in chemical and physical properties seen between organic and inorganic versions of zinc.
For example in research published in the Journal of Nutrition in 19871, zinc histidine was shown to increase serum zinc concentration in 10 healthy volunteers 25 % more than ingestion of the same amount of zinc sulfate. The researchers found that application of 15 mg of zinc histidine produced an identical serum zinc concentration as 45 mg of zinc sulfate. However, the researchers noted that the zinc histidine complex did not show increase plasma concentrations because of more rapid absorption, because peak values of all supplements were identical. The researchers also noted that increasing the number of histidine residues in the organic complex did not increase plasma levels, but did cause a rebound of levels below the initial value after 6 hours. This, they surmised, was due to increased uptake of the zinc into tissues in the presence of more histidine.
RdB
