The mineral zinc performs widely varied functions in the body, largely as a co-enzyme. In fact, zinc plays the role of co-enzyme in more processes than all of the other minerals combined. The physiological functions of zinc include cell and tissue growth, immunity, bone formation and skin integrity. Dietary zinc is found in foods that contain protein -- animal products, grains and vegetables.
Hydrolyzation
Before zinc can be absorbed into the blood stream to be transported for use and storage, it must first be separated, or hydrolyzed, from the amino acids it is attached to at the time of consumption. Hydrolysis takes place in the stomach, and stomach acid plays an important role in breaking zinc molecules away from their amino acid carriers. As a result, you will absorb less zinc when you are taking antacids.
Absorption
Once zinc molecules are separate from the protein they rode in on, they are ready for absorption. Absorption occurs all along the path of the small intestine, with the majority of absorption at the beginning of the small intestine and decreasing absorption as the small intestine nears the large intestine. The absorptive process is not entirely clear, but zinc seems to pass into the intestinal absorptive cells, or enterocytes, primarily by means of a carrier. At very high intestinal concentrations, zinc may pass to the enterocytes by passive diffusion.
Absorption Enhancers
The presence of substances that bind with zinc and help carry it across to the enterocytes enhance zinc absorption. Some of these substances are citric acid and picolinic acid and the amino acids histidine, cysteine, lysine and glycine. Low zinc status also enhances absorption as your body attempts to correct its zinc shortfall.
Absorption Inhibitors
There are a large number of potential inhibitors of zinc that either bind to zinc molecules to prevent their absorption, or competitively bind with the substances that help carry zinc into the enterocytes and other inhibitory interactions. Some of the substances that have the potential to inhibit zinc absorption include fiber, phytate, oxalate, polyphenols, folic acid, calcium, copper and iron.
Transport and Storage
After zinc has been successfully absorbed into the enterocytes, it is carried through the bloodstream bound to albumin. Zinc that is not needed immediately is stored throughout the body. At any given time, you can find zinc in all of your organs, including your skin and bones, because zinc is required in small amounts by every cell in the body. However, the zinc stored in your organs and tissue is released slowly, if at all, and cells draw primarily from the pool of zinc in your bloodstream to fulfill their needs.
References
- "Advanced Nutrition and Human Metabolism: Third Edition"; James L. Groff and Sareen S. Gropper; 2000
- "Anatomy & Physiology: Understanding the Human Body"; Robert K. Clark; 2004
- "Microbiology: A Human Perspective, Third Edition"; Eugene Nester, et al.; 2001
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