ZINC YEAST

A summary

The physiological importance of the element Zinc is well known. With a total amount of 1.5 to 2.3 g in the body of an adult it is next to iron the quantitatively most important trace element (KIRCHGESSNER, 1990). It occurs in particular high concentrations in certain parts of the organism, namely in the skin, in the insular cells of the pancreas (100 - 1000 ppm), in the retina (500 - 1000 ppm) and in the iris (5000 ppm), in the latter as a Zinc melanin complex. Its function in the pancreas is probably to increase the storage capacity for insulin by forming complexes with it. In the eye its role is said to be in vision at reduced light intensity. Zinc is also a constituent of many enzymes (LANG, 1979).

In correspondence with the multiple functions of Zinc an insufficient Zinc status shows numerous symptons, ranging from an affection of the sense of taste and smell, of hearing and of vision (poor adaptation to reduced light intensity) to growth disturbances, dermatological problems, infertility, a weak immune reaction, and cerebral disturbances (behavioural disturbances) (GRÜNGREIFF, 1992). Slow growth of infants may be caused by insufficient Zinc supply (WALRAVENS, 1992).

The average Zinc intake of the (German as well as US American) population is known to be suboptimal (BAYER, 1988).

The German Society for Nutrition recommends the intake of the following amounts of Zinc: Babies 5 mg, children 7 to 15 mg, adults 12 to 15 mg, nursing mothers 22 mg, in each case per day and person (DGE, 1991).

To obtain a sufficient Zinc supply a Zinc containing yeast can be usefull. Yeast is considered to be legally a food. Therefore it is generally assumed that Zinc yeast can be offered as a supplementary food (that is "over the counter", as non-prescription item) as long as the Zinc is not merely added to the yeast but is organically bound to it.

Yeast is capable to absorb Zinc if the growing yeast is exposed to high - potentially damaging - concentrations of Zinc ions. By a lengthy adaptation process KNEER (1993) succeeded to prepare yeast with a Zinc concentration of 4.65% on a laboratory scale. The Zinc absorption is probably caused by a formation of binding sites (carboxy and amino groups) in the cell walls which bind Zinc ions in a chelate complex. By the formation of these binding sites the yeast succeeds to lower the concentration of dissolved Zinc ions in the environment by the sequestering of Zinc in the cell walls thus reducing the concentration gradient towards the interior of the cell and preventing thus an excessive influx of Zinc.

On a production scale it is possible to produce yeast with a concentration of organically bound Zinc of at least 1% in the dry matter.

References

BAYER, W., SCHMIDT, K., 1988: Zur biomedizinischen Bedeutung von Zink. VitaMinSpur 3,3 (1988) 113-124

DGE, 1991: Deutsche Gesellschaft für Ernährung. Empfehlungen für die Nährstoffzufuhr, S. 72, Umschau-Verlag Frankfurt

GRÜNGREIFF, K., 1992: Zink - Bedeutung in der Inneren Medizin. VitaMinSpur 2, 92, 7. Jg, Juni 1992, S. 65-72

KIRCHGESSNER, W., 1990: Spurenelemente und Ernährung, S. 101 f., Wissenschaftliche Verlagsgesellschaft Stuttgart.

KNEER, R. et al., 1993: Unpublished.

LANG, K., 1979: Biochemie der Ernährung, S. 347 f., Steinkopff-Verlag Darmstadt.

WALRAVENS, P.A.; CHAKAR, A. et al., 1992: Zinc supplementation in breastfed infants. The Lancet, 1992, vol.340, 683-685

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