Tag: Selenium status

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Selenium and Human Health

What is the importance of selenium to human health? Selenium is an essential trace element. That selenium is essential to our health means two things:

  • Our bodies cannot synthesize selenium for us. We must get it from our diets.
  • Our bodies need selenium for physiological functions such as growth, metabolism, and reproduction.
Younger woman with elderly woman
Good health in our senior years depends in part on sufficient selenium intake and status. Selenium is an essential trace element.

How does selenium work in the body? Primarily, elemental selenium works as a component of selenoproteins – proteins that contain selenium. These selenoproteins have important biological functions in the human body, e.g., antioxidant defense, immune function, thyroid hormone metabolism, etc [Alexander & Olsen 2023].

What are the Recommended Daily Intake Levels for Adults?

The 2023 Nordic Nutrition Recommendations established Adequate Intake levels as follows [Blomhoff et al 2023]:

  • Women: 75 mcg/day
  • Men: 90 mcg/day
Who is Likely to Have Low Selenium Intakes?

The human intake of selenium varies considerably from region to region in the world. The selenium intake depends upon the selenium content of the soil and the crops in the region. For example, soil selenium is low in most area in the Nordic and the Baltic countries. The average intake of selenium in these countries, except Finland, is likely to be below recommended intake levels [Blomhoff et al 2023]. read more

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Selenium Intake and Status Related to Health

The quantity of selenium in foodstuffs may be inadequate in many parts of the world.  Sub-optimal selenium status is reported to be widespread throughout Europe, the UK, and the Middle East [Stoffaneller & Morse]. Coastal regions in the US tend to have selenium-poor soil. Vast regions in China, Korea, Siberia, Tibet, and New Zealand are low selenium regions. Low selenium status is associated with increased risk of cancer and cardiovascular disease and thyroid disorders [Tolonen].
The research evidence to date suggests that there is a U-shaped relationship between selenium intake and health.  According to a recent report by the long-time selenium researcher Professor Dr. Margaret P. Rayman, University of Surrey, UK, both selenium deficiency and selenium excess have been associated with adverse health effects.

Conditions Indicating a Need for Selenium Supplementation

Professor Rayman lists a number of conditions that have been associated in the research literature with selenium deficiency:

  • Keshan disease (a heart muscle disease caused by a selenium deficiency together with a strain of Coxsackie virus)
  • Kashin-Beck disease (a bone disease for which selenium deficiency is a factor)
  • Increased viral virulence
  • Increased mortality
  • Poorer immune function
  • Problematic fertility/reproduction
  • Thyroid autoimmune disease
  • Cognitive decline/dementia
  • Type-2 diabetes
  • Prostate cancer risk
  • Colo-rectal cancer risk (in women)
  • Increased risk of tuberculosis in HIV patients

Professor Rayman does not specify a plasma/serum selenium level for selenium deficiency. 

She does mention a US National Health and Nutrition Examination Survey that measured the serum selenium levels in 13,887 adult participants and then followed up for mortality for up to 18 years.  The mortality in that study showed a U-shaped association between serum selenium and death, with a serum selenium concentration of 135 micrograms per liter at the bottom of the U [Rayman 2019]. read more

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Low serum selenium status and increased mortality

Too few studies have investigated the relationship between low serum selenium status and negative health effects. Professor Urban Alehagen from Linköping University in Sweden has published the results of a study showing that low serum selenium status is significantly associated with increased cardiovascular and all-cause mortality.

During an almost seven-year follow-up period, elderly healthy Swedish citizens with low serum selenium concentrations had significantly increased cardiovascular mortality and total mortality rates compared to contemporaries with higher serum selenium concentrations.  Specifically, there was a 56% increased risk for cardiovascular mortality and a 43% increased risk for all-cause mortality.  Accordingly, the Swedish researchers suggested that selenium supplementation should be recommended to all Swedish citizens with a serum selenium concentration below 57 micrograms per liter [Alehagen 2016].

In fact, Professor Urban Alehagen and his team of researchers at Linköping University pointed out that the average serum selenium concentrations observed in the study of elderly Swedish citizens – 67.1 micrograms per liter – is not sufficient to achieve optimal function of the important selenoproteins that require selenium as a component [Alehagen 2016]: read more

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Serum/plasma selenium status and protection against cancer

In cancer prevention, there seems to be a U-shaped response to selenium supplementation. The threat of adversity is greater at the lower and higher levels of serum/plasma selenium. For example, Emily Chiang and her colleagues posit that the optimal serum selenium level for the reduction of prostate cancer risk is between 119 and 137 micrograms per liter. (Graph for illustration purposes only)

The documentation in various systematic reviews and meta-analyses of selenium and cancer studies shows a significant inverse association between selenium intake and/or plasma/serum selenium status and cancer [Lee; Hurst; Cai].

There is some evidence of a U-shaped relationship between plasma/serum selenium status and protection against cancer [Hurst; Rayman].  Low plasma/serum selenium status clearly correlates with higher risk of cancer.  High plasma/serum selenium status correlates with no increased protective effect against cancer.  The key is to find the supplement doses and subsequent plasma/serum status that give the best protection in between the two extremes.

Evaluating the evidence from published studies is complicated.  We need to remember that the following factors affect the relationship between selenium status and/or intake and cancer risk: read more