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

Selenium and antioxidants in combination against cancer

Nothing is clear-cut, it seems.  Yes, we want to eat fruits and berries for their antioxidant content.  But, fruits and berries are full of the sugar called fructose.  So, like everything else, we need to eat fruits and berries in moderation.  In this report, I focus on studies of selenium and antioxidant combinations to prevent cancer.

On the topic of cancer and selenium as a cancer chemo-preventive agent, we know some basic facts from published research:

  • selenium prevents or delays tumor development in animals [Schrauzer]
  • regions with low selenium intakes are regions with higher incidence of cancer [Schrauzer]
  • greater exposure to selenium is associated with lower incidence of cancer [Cai]
  • single interventions with high-selenium yeast preparations reduce the incidence of cancer [Clark; Yu; Li]

What do randomized controlled studies reveal about the efficacy of selenium and antioxidant combinations against the development of cancerous tumors, I wondered.

The first studies to come to mind were the Linxian Nutritional Intervention Studies, which are probably just as important in the history of selenium and cancer research as Professor Larry Clark’s Nutritional Prevention of Cancer study is.

Professor Blot’s Linxian Nutrition Intervention Studies in China

The Linxian studies were a very big research undertaking.  The researchers enrolled 29,584 study participants aged 40 to 69 years from four Linxian County municipalities.  The study participants lived in a region of China characterized by constantly low intakes of selenium and by high cancer mortality rates. read more