The trace element selenium is an essential component of the selenium-dependent enzymes called selenoproteins. We need these selenoproteins for the optimal biological functioning of our cells. Specifically, we need adequate daily intakes of selenium for the protection of cellular DNA, for successful reproduction, for proper thyroid gland function, for protection against infections, for anti-oxidative protection against the damage caused by free radicals, and for the prevention of cancer and heart disease.
What form of selenium is best?
Many of us cannot get enough selenium in our diets, especially if we do not regularly eat Brazil nuts (very high in selenium) or if we eat relatively little meat and fish. However, there are various supplemental forms of selenium available to us as consumers.
There are both organic and inorganic forms available. Organic forms are chemical compounds that contain carbon atoms; for example, the selenomethionine molecule, C5H11NO2Se, contains five carbon atoms.
The high selenium yeast supplement contains organic forms of selenium. High selenium yeast is the best form of selenium supplement available. It is a natural form (not a synthetic form). It is a form that contains several different species of selenium, each of which may have different influences on biological functions.
Organic forms of selenium preferred
Generally, organic forms of selenium supplements give better absorption, better retention, and better health benefits than inorganic forms do.
In particular, among the organic forms of selenium supplements, the high selenium yeast preparations (also known as selenium-enriched yeast preparations) have been shown to give the best health benefits (more about this later in this article).
Inorganic selenium forms can be recognized by their names
The inorganic forms of selenium, which also have a good absorption but have not been shown to have as good health effects as organic forms, are recognizable by the form of their names.
The inorganic selenium supplements are salts: ionic compounds formed by the reaction of an acid and a base. Thus, the mostly commonly available inorganic selenium supplements have names such as sodium selenite and sodium selenate.
These inorganic selenium salts are being replaced in human supplements and in animal feedstuffs by the organic forms: selenomethionine and high selenium yeast.
High selenium yeast preparations
High selenium yeast preparations are supplements that have been produced by growing a strain of yeast – Saccharomyces cerevisiae, the same species of yeast that is used in baking and for brewing beer – in a selenium-rich medium.
The selenium enrichment of the yeast cells comes from the addition of inorganic selenium, most commonly sodium selenite, to the medium in which the yeast cells are being grown.
The selenium atoms in the medium are incorporated into the proteins in the yeast and thus become organically bound to the yeast.
Selenium yeast cells are dead and inactive in the high selenium yeast supplements
At the end of the yeast growing process, the yeast cells are carefully dried, and the yeast itself is rendered inactive. In high-quality high selenium yeast supplements, the yeast cells are are sterilized by heating. The yeast cells are broken up into cell fragments. The cell fragments are made into a protein-rich, selenium-rich powder that is then pressed into tablet form.
No worries about selenium yeast and yeast infections
There is thus no reason to worry about getting a yeast infection, e.g. a Candida albicans infection. However as yeast allergens are still present in this powder, some individuals who already have a Candida infection might experience some allergy-related worsening of the symptoms.
Several species of selenium in the high selenium yeast supplements
For the most part, the resulting high selenium yeast tablets contain between 60 and 80 percent selenomethionine, but, in a well formulated selenium-enriched yeast preparation, there will be as many as 30 other species of selenium. In the high selenium yeast preparations, for example, there will most likely be small amounts of such species as gamma-glutamyl Se-methylselenocysteine and methylselenocysteine, the species of selenium that are found in broccoli, cabbage, garlic, and onions.
The reason for preferring a high selenium yeast preparation over a purely selenomethionine preparation is twofold:
- The high selenium yeast preparation provides additional species of selenium to the body, species that may well have important biological functions.
- The high selenium yeast preparations have performed better in cancer prevention studies than the pure selenomethionine preparation has.
High selenium yeast and cancer
We know from observational studies that low selenium status is associated with increased risk of cancer [Vinceti]. Furthermore, we know from a meta-analysis of 69 studies that high selenium exposure has a protective effect on cancer risk [Cai].
Three randomized controlled studies using high selenium yeast supplements have shown significantly lower risk of cancer:
- The Linxian study in China showed significantly reduced cancer mortality rates [Blot].
- The Nutritional Prevention of Cancer study showed significant reductions of the risk of colon cancer, lung cancer, and prostate cancer [Clark].
- The SU.VI.MAX study showed significantly reduced cancer incidence and cancer deaths [Hercberg].
Selenomethionine and cancer
A big cancer prevention study using a synthetic selenomethionine supplement was halted early because no anti-cancer health benefits were seen [Klein, Lippman].
High selenium yeast and heart disease
The development and progression of heart disease — whether ischemic heart disease or chronic heart failure — may well be influenced by the patients’ deficient anti-oxidative capacity. A randomized controlled study using both a high selenium yeast preparation and a well-formulated Coenzyme Q10 preparation with elderly study participants showed a significant reduction in heart disease mortality, improved heart function, and lower heart muscle wall tension as compared to placebo [Alehagen].
The evidence from randomized controlled trials is clearly on the side of preferring a high selenium yeast preparation over a selenomethionine or sodium selenite preparation.
Alehagen, U., Johansson, P., Björnstedt, M., Rosén, A., & Dahlström, U. (2013). Cardiovascular mortality and N-terminal-proBNP reduced after combined selenium and coenzyme Q10 supplementation: a 5-year prospective randomized double-blind placebo-controlled trial among elderly Swedish citizens. International Journal of Cardiology, 167(5), 1860-1866.
Alehagen, U., & Aaseth, J. (2015). Selenium and coenzyme Q10 interrelationship in cardiovascular diseases–A clinician’s point of view. Journal of Trace Elements in Medicine and Biology, 31157-162.
Blot, W. J., Li, J. Y., Taylor, P. R., Guo, W., Dawsey, S., Wang, G. Q., & Li, B. (1993). Nutrition intervention trials in Linxian, China: supplementation with specific vitamin/mineral combinations, cancer incidence, and disease-specific mortality in the general population. Journal of The National Cancer Institute, 85(18), 1483- 1492.
Cai, X., Wang, C., Yu, W., Fan, W., Wang, S., Shen, N., & Wang, F. (2016). Selenium exposure and cancer risk: an updated meta-analysis and meta-regression. Scientific Reports, 619213.
Clark, L. C., Combs, G. J., Turnbull, B. W., Slate, E. H., Chalker, D. K., Chow, J., & … Taylor, J. R. (1996). Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA, 276(24), 1957-1963.
Clark, L. C., Combs, G. J., Turnbull, B. W., Slate, E. H., Chalker, D. K., Chow, J., & Taylor, J. R. (1996). Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA, 276(24), 1957-1963.
Hercberg, S., Galan, P., Preziosi, P., Bertrais, S., Mennen, L., Malvy, D., & Briançon, S. (2004). The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals. Archives of Internal Medicine, 164(21), 2335-2342.
Klein, E. A., Thompson, I. J., Tangen, C. M., Crowley, J. J., Lucia, M. S., Goodman, P. J., & Baker, L. H. (2011). Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA, 306(14), 1549-1556.
Lippman, S. M., Klein, E. A., Goodman, P. J., Lucia, M. S., Thompson, I. M., Ford, L. G., & Coltman, C. J. (2009). Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). Jama, 301(1), 39-51.
Vinceti, M., Dennert, G., & Crespi, C.M. (2014). Selenium for preventing cancer. Cochrane Database Syst Rev., 3:CD005195.