1. Field of the Invention
This invention relates to the field of human dietary supplements, and more specifically to a novel yeast strain of the genus Saccharomyces boulardii sequela which has the ability to process certain metallic compounds into forms that are biologically active and useful in supplementing the human diet.
2. Background of the Invention
Metal supplementation of the human diet is generally recognized as an important area in the field of nutritional science. Although no "RDA" minimum daily intake requirements have been officially adopted, research has strongly suggested that absence of some minerals, particularly metallic minerals such as chromium, germanium, and selenium, can lead to improper functioning of the body's metabolic processes, and a host of diseases and disorders. For example, selenium has been implicated as a mineral that may affect a reduction in the incidence of certain cancers when ingested in amounts of about 50 .mu.g. [W. Blott et al., J. Natl. Cancer Institute, 85(18):1483-92 (1993); H. P. Leis, Int. Surg., 76:1-5 (1991)]. Chromium is believed to play a role in modulating the symptoms of diabetes. [G. Mahdi and D. Naismith, Ann. Nutr. Metab., 35:65-70 (1991)].
Nutritional supplementation of the human diet with metals, using inorganic or organometallic sources for the metals, has met with limited success. Safety and efficacy in the human metabolism of such metals has been questioned, since most inorganic forms of metals are know to have appreciable toxicity. For example, selenium is usually administered as selenium trioxide species--an agent which is extremely toxic. Trivalent chromium has been administered as inorganic chromium, typically chromium chloride or chromium acetate, or as organometallic species such as chromium picolinate or chromium nicotinate, but each of these forms of chromium has been shown to be toxic in one fashion or another, reflecting a major shortcoming in their use in nutritional supplements. In addition, inorganic forms of such metals generally have a low bioavailability, making their use in nutritional supplements questionable.
Supplementation of the human diet with metal-enriched yeast products has been sought as an alternative. Potential advantages of administering a metal derived from yeast as a nutritional supplement over non-yeast derived forms are that the toxicity of the metal will be lower in yeast-derived organometallic compounds, and that since yeast-derived organometallic compounds are more soluble, such compounds will be better metabolized by the human body. However, a drawback of using yeast-derived metallic material as a food supplement is that rather large amounts of yeast are usually needed in order to acquire the proper dosage, since the levels of metal ion produced in yeast typically range from about 500 to 2000 ppm (.mu.g/g)--levels which would require ingestion of large amounts of yeast if the nutritional benefit of the organometallic compounds is to be realized.