Dr. Gerhard N. Schrauzer – renowned selenium researcher

Dr. Gerhard N. Schrauzer was the first scientist to study the biological functions of selenium systematically. He was known internationally for his pioneering work in the cancer-protective properties of selenium. (Picture: Cancer Research, vol. 49 no. 23, Dec. 1, 1989)

Dr. Gerhard N. Schrauzer was the grand old man of selenium science.  Actually, he was the grand old man of trace element research in the United States for 30 years or more.  He was one of the pioneers and one of the major figures in selenium research.   Let’s take a look at the useful contributions of information to the selenium supplementation knowledge base that Dr. Schrauzer made.

First, who was Dr. Schrauzer in the context of selenium research?
Dr. Schrauzer did his graduate study in chemistry at the University in Munich, Germany. He was awarded his Ph.D. summa cum laude.  From 1966 to 1994, he was a chemistry and biochemistry professor at the University of California in San Diego (UCSD). After his retirement, he was a professor emeritus at UCSD.

Dr. Schrauzer was one of the first scientists to investigate seriously the biological functions of dietary and supplemental selenium and to investigate the cancer-protective properties of selenium supplementation.  In his Cancer Mortality Correlation Studies, Dr. Schrauzer showed that, in 27 countries surveyed, there was an inverse relationship between cancer mortality and the amount of selenium in the national diet. Low dietary selenium correlated with higher cancer mortality.  Dr. Schrauzer  was a leading expert on the subject of selenium supplementation.  He died in 2014.

Secondly, what are trace elements?
In the field of nutrition science, trace elements (sometimes called micronutrients) are defined as chemical elements necessary for the health of humans in minute quantities; frequently, they are a component of a protein. In this case, “minute” is defined as fewer than one element per 1000 elements. The following trace elements are needed by humans:

  • boron
  • copper
  • manganese
  • molybdenum
  • selenium
  • zinc

Thirdly, what did Dr. Schrauzer know about selenium supplementation?
In this article, we want to summarize the considered opinions of Dr. Schrauzer on the following issues:

  • Dietary and supplemental intakes of selenium
  • Formulation of the selenium supplement
  • Selenium’s biological functions
  • Selenium and oxidative stress
  • Selenium and cancer
  • Safety of selenium

Selenium intakes
Dr. Schrauzer’s selenium studies led him to believe that the recommended daily intake of 55 micrograms was inadequate for most adults, and he doubted that 75 micrograms per day would be sufficient for most adults to replace the amount of selenium that is eliminated every day and to build up the body’s reserves to a level that would prevent the development of cancer.

Dr. Schrauzer recognized early on that the question of recommended daily intakes is complicated by the considerable variation in the content of selenium in the soil from region to region and that, consequently, the selenium content in plant foods, and, by extension, in animal foods, also varies.

He was also aware that the amount of daily selenium intake to support the activity of the very important selenium-dependent glutathione peroxidase antioxidant enzymes might not be enough selenium intake to support the beneficial health activities of other selenoproteins such as selenoprotein P.  He thought that it would be wrong to limit estimates of required daily selenium intakes to the effect of selenium on the glutathione peroxidase enzymes.

Accordingly, Dr. Schrauzer thought that the appropriate level of selenium supplementation in humans for the purpose of cancer risk reduction lies in the 200-300 micrograms per day range.

Formulation of the selenium supplement
Dr. Schrauzer thought that the supplemental selenium should resemble dietary selenium as much as possible.  The selenomethionine form is the most common form of selenium in food, and it is the most common form of selenium found in organic selenium yeast supplements.  In addition, the high selenium yeast supplements contain as many as 30 other species of selenium, with, notably, small amounts of methylselenocysteine that may be most effective in cancer prevention.

The best cancer-preventative study results have been achieved with high selenium yeast supplements.

Selenium’s biological functions
In a 2010 interview with Dr. Richard A. Passwater, Dr. Schrauzer discussed biological functions of selenium.  In addition to a cancer-protective function, Dr. Schrauzer mentioned the following biological functions:

  • maintenance of immune system functions
  • maintenance of male reproductive function
  • protection against the toxic effects of heavy metals
  • protection of the skin against UV light radiation
  • protection against ionizing radiation
  • protection against harmful viruses
  • regulation of thyroid hormone function

He also warned that the body’s necessary use of selenium to de-toxify heavy metals can deplete the body’s reserves of selenium and diminish the extent of the protection against cancer that selenium provides.

Selenium and oxidative stress
Dr. Schrauzer knew that one of the inevitable consequences of producing cellular energy using oxygen is the by-product called free radicals. Free radicals are highly reactive atoms that can set off chain reactions that can cause damage to cells and to cell DNA. This sort of damage, called oxidative damage, can eventually lead to cancer and ageing and other degenerative diseases.

One of the major health benefits of selenium is that it is a necessary component of selenoproteins that are, themselves, powerful antioxidant enzymes that help to neutralize harmful free radicals and prevent damage to the cells.

Selenium and cancer prevention
Selenium as a component of selenium-dependent antioxidant enzymes helps to neutralize free radicals and thus prevent cellular damage.  One theory of cancer holds that free radical damage to cell DNA may lead to the development of certain cancers.

Dr. Schrauzer was aware of the significant cancer-protective results of supplementation with selenium and other antioxidants in the Linxian and Su.Vi.Max clinical trials and in the National Prevention of Cancer study (more about these research studies in future articles on this website).

Dr. Schrauzer did not think that the inconclusive outcomes of the SELECT study suggest any general ineffectiveness of selenium supplementation against cancer risk; he explained the results of the SELECT study by reference to the following factors:

  • the relatively high baseline selenium status of the participants
  • the use of a synthetic selenomethionine form of selenium as the intervention (instead of a high selenium yeast preparation previously shown to have cancer-protective properties)
  • the use of selenomethionine in its pure form instead of in its protein-bound form (it is protein-bound in the high selenium yeast preparations)

N. B. We will discuss the selenium and cancer research studies in greater detail in future articles.

Safety of selenium supplementation
Dr. Schrauzer regarded a supplement of 100 to 200 micrograms of selenium daily as perfectly safe. He noted that the safe maximal intake for selenium is set at 400 micrograms per day. He pointed out that individuals whose diets contain adequate amounts of protein can more easily tolerate higher levels of selenium intake.

Selenium does not accumulate in the body.  It leaves the body relatively quickly. If we reduce or stop our dietary and supplemental intakes of selenium, we will not continue to have the body reserves needed to prevent cancer.

Moreover, the early signs of any selenium toxicity in the event of an accidental overdose — discolored and brittle fingernails and toenails and foul garlic breath –are easily recognized, and any dangerous results can be avoided.

Without the research and publications of Dr. Schrauzer and  his colleagues, the development of the science of selenium supplementation and the scientific study of selenium as a cancer-protective agent would have been much delayed.



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.

Larsen, E. H., Hansen, M., Paulin, H., Moesgaard, S., Reid, M., & Rayman, M. (2004). Speciation and bioavailability of selenium in yeast-based intervention agents used in cancer chemoprevention studies. Journal Of AOAC International, 87(1), 225-232.

McCann, J. C., & Ames, B. N. (2011). Adaptive dysfunction of selenoproteins from the perspective of the triage theory: why modest selenium deficiency may increase risk of diseases of aging. FASEB Journal, 25(6), 1793-1814.

Olmsted, L., Schrauzer, G. N., Flores-Arce, M., & Dowd, J. (1989). Selenium supplementation of symptomatic human immunodeficiency virus infected patients. Biological Trace Element Research, 20(1-2), 59-65.

Passwater, R. (2013, June). Selenium and human health: an interview with Gerhard Schrauzer, Ph.D. Whole Foods Magazine. Retrieved from http://www.drpasswater.com/nutrition_library/SeleniumHumanHealth.html.

Schrauzer, G. N. (2000). Anticarcinogenic effects of selenium. Cellular And Molecular Life Sciences: CMLS, 57(13-14), 1864-1873.

Schrauzer, G. N. (2009). Selenium and selenium-antagonistic elements in nutritional cancer prevention. Critical Reviews In Biotechnology, 29(1), 10-17.

Schrauzer, G. N., & White, D. A. (1978). Selenium in human nutrition: dietary intakes and effects of supplementation. Bioinorganic Chemistry, 8(4), 303-318.


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