There is no single laboratory test that adequately measures zinc nutritional status.
The best method of accurately determining zinc status is through measuring white blood cell levels. Since this test is not readily available and may be more expensive, serum zinc is routinely used as a screening tool.
Hair levels may show deficiencies or excesses but are generally not considered as reliable as other tests of zinc status. While low hair zinc is likely to be indicative of poor zinc status, elevated hair zinc may be indicative of low zinc in the cells or contamination from the use of zinc-containing shampoos.
The zinc taste test appears to be of some value in determining general zinc status. The test is based on the knowledge that the functions of taste and smell are dependent upon there being sufficient zinc available in the body. Thus, if zinc is deficient then taste function will be diminished. This principle is utilized in the taste test by offering a standard test solution of zinc sulfate for tasting. The response is then compared with a series of defined standards and the zinc status thus determined.
This simple, non-toxic zinc taste test uses a test solution of zinc sulfate in purified water, at a concentration of 1gm/liter. Once prepared, the solution should be stored in a refrigerator and discarded after six months. The solution should be removed from storage and left at room temperature for about two hours before carrying out the test. The test involves taking a sip of the solution (approximately 5-10ml) and holding it in the mouth exactly ten seconds. Due to the possible influence of recently consumed food or drink on the taste experienced, it is essential that neither be taken for approximately one hour before the test.
For the zinc taste test, the defined standards are:
It is clear that brain zinc content changes during disease states and that brain zinc deficiency is possibly dynamically related to alcoholism. McLardy (1973) observed a 30% deficit in brain zinc levels amongst chronic alcoholics.
Zinc is concentrated in ejaculate, and important for prostate health. Zinc stores can be reduced by frequent ejaculation. Marginal zinc status is associated with poor sperm count and motility (especially if testosterone levels are low).
Zinc levels amongst patients with rheumatoid arthritis are usually reduced. Results from zinc supplementation trials amongst rheumatoid arthritis patients have been mixed, though most find some improvement.