January 12, 2010
Intensive research is going on in utilization of selenium against cancer.
The public in Denmark do not hear much of it, but here is a selection of recent news.
The lack of television and newspaper information may give the impression that there is quiet on the antioxidant front concerning disease control. This is not the case. The news shortage is chiefly due to the censorship that has been introduced. Regarding selenium alone, being one of the major antioxidants, there were in 2009 published more than 900 scientific articles. Here we will mention a selection of recent articles about selenium in the fight against cancer.
A famous attempt to demonstrate whether antioxidants protect against cancer were performed in the years 1985-91 in the Chinese Linxian province. Nearly 30.000 participated in the study, which showed a strong decrease in cancer risk among those who received a supplement of selenium (50 micrograms) and Vitamin E and Beta Carotene (respectively 30 and 15 mg). Now it has been determined, what had happened to the participants 10 years later (2001). Even after so long a time, there were relatively more survivors in this group than among those who received other supplements (eg. Vitamin A + zinc, was of no benefit). In particular, the group had reduced incidence of cancer of the stomach, but it was the participants under 55 years of age who experienced the greatest gain – you must avoid lacking vital nutrients already from the youth.
Apparently this result is contradicted by another famous study, the SELECT trial conducted in the U.S. Here it appeared that you could not prevent prostate cancer using selenium, vitamin E or a combination of both. This study was in large scale and the result a huge disappointment.
One of the world’s leading selenium specialists, Margaret Rayman, did point out however, a few months ago what really is obvious: Supplementation with selenium is of no benefit if you already get enough! As a general rule you get enough in the U.S., where you typically get 3-4 times as much selenium in the diet as in Denmark. Sufficient selenium is essential for the body to form enough of the enzymes which we presume protects against cancer. Amongst others Rayman refer to another U.S. cancer trial where you just saw a massive impact in those who received the least amount of selenium, but no effect in those who got the most.
Heavy metals neutralized
One of the veterans in selenium research is Gerhard Schrauzer from San Diego University of California. He has been involved more than 20 years. Now he points out that selenium is able to detoxify numerous toxic metals that somehow during our civilized environment ends up in our bodies. This applies to lead, mercury, copper, cadmium, arsenic, etc. Selenium inactivates these metals by forming insoluble compounds with them. But, says Schrauzer, one must remember that at the same time selenium is used up, so we for that reason are less protected against cancer. In Europe we already get too little selenium, but heavy metals etc. increases the demand.
Taylor and associates have written an article on new advances in selenium research. They write that the renewed interest in selenium is linked to the fact that the anti-cancer effect is now very well documented in animal studies. This is worth noticing.
And precisely on animals a research team from San Diego University have demonstrated that the effect of chemotherapy (cisplatin) against cancer of the colon is reinforced considerably by large supplements of antioxidants (A and vitamin E and selenium) combined with fish oil. The group believes their achievement justifies that research is made with people. The result is very exciting because cancer doctors in this country often discourages in strong terms their patients from combining antioxidants with chemotherapy. The reason for this warning has hitherto been unclear.
Selenium and chemotherapy
Researchers from The Karolinska Hospital in Stockholm state without hesitation that it is well documented that selenium prevents cancer. They describe several experiments which have shown that selenium has strong anti cancer effects – especially against cancer, which no longer responds to chemotherapy. Normal cells will not be harmed by the selenium doses needed for this!
Italian researchers, however, stresses that people can get too much selenium (but living in Denmark you have take approx. two selenium tablets a day in order to get the same amount as a typical American). They argue that high doses may increase the risk of diabetes, an assertion, however, that is controversial.
In the Netherlands, like in China there has been an interest in selenium and cancer of the esophagus. More than 120,000 persons who was 55-69 years old in 1968, delivered at that time, a portion nail clips from their big toes. 16 years later it was found who and how many have got cancer of the esophagus or stomach in the meantime. Then the selenium levels in their nails was measured and compared with the levels in healthy subjects. It was found that the risk of both cancers was significantly higher among those who only had small amounts of selenium in their nails, and hence their body.
A curious study has been conducted in Japan. Here researchers cultivated broccoli-sprouts in a selenium-rich environment, so the sprouts got an extra high content of selenium. In a laboratory study the sprouts was investigated for their impact on prostate cancer tissue. The enriched sprouts inhibited cancer growth clearly better than normal sprouts. Now the Japanese suggests, that men eat that kind of sprouts to prevent cancer of the prostate.
Finally other Japanese mention, that it is well known that selenium can kill cancer cells from humans, but but precisely how this happens is still unclear. They have reached the conclusion that at least part of the effect is due to selenium starts off a cancer cell death process using the same mechanism (apoptosis) as when normal cells must be replaced and die. Such a mechanism is of course necessary, since almost all normal cells divide continuously. There would soon be twice as many, and we would grow indefinitely, if not worn-out cells were put out.
As you can see, the research is really alive. Much of our understanding of selenium is achieved in very recent years. More will undoubtly follow.
By: Niels Hertz, M.D.
1. Qiao YL et al. Total and cancer mortality after supplementation with vitamins and minerals: follow-up of the Linxian General Population Nutrition Intervention Trial. J Natl Cancer Inst. 2009 Apr 1;101(7):507-18. Epub 2009 Mar 24.
2. Lippman SM et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009 Jan 7;301(1):39-51. Epub 2008 Dec 9.
3. Rayman MP. Selenoproteins and human health: insights from epidemiological data.
Biochim Biophys Acta. 2009 Nov;1790(11):1533-40. Epub 2009 Mar 25.
4. Schrauzer GN Selenium and selenium-antagonistic elements in nutritional cancer prevention.
Crit Rev Biotechnol. 2009;29(1):10-7.
5. Taylor D. Recent developments in selenium research. Br J Biomed Sci. 2009;66(2):107-16; quiz 129.
6. Ma H. Bi Efficacy of dietary antioxidants combined with a chemotherapeutic agent on human colon cancer progression in a fluorescent orthotopic mouse model. Anticancer Res. 2009 Jul;29(7):2421-6.
7. Selenius M. Selenium and selenoproteins in the treatment and diagnostics of cancer.
Antioxid Redox Signal. 2009 Sep 21. [Epub ahead of print]
8. Vinceti M. Risk of chronic low-dose selenium overexposure in humans: insights from epidemiology and biochemistry Rev Environ Health. 2009 Jul-Sep;24(3):231-48.
9. Steevens J. Selenium status and the risk of esophageal and gastric cancer subtypes: the Netherlands cohort study. Gastroenterology.. [Epub ahead of print]
10. Abdulah R. Selenium enrichment of broccoli sprout extract increases chemosensitivity and apoptosis of LNCaP prostate cancer cells. BMC Cancer. 2009 Nov 30;9:414.