Recent clinical trials have shown that the unnecessary use of certain dietary supplements can lead to far more serious problems then known before. Such a study conducted in the US has shown that the high levels of the mineral Selenium can lead to a 91% increased risk for high grade cancer.
According to the the study leader Dr. Alan Kristal (Fred Hutchinson Cancer Research Centre, Seattle)"These supplements are popular – especially vitamin E – although so far no large, well-designed and well-conducted study has shown any benefits for preventing major chronic disease.
"Men using these supplements should stop, period. Neither selenium nor vitamin E supplementation confers any known benefits, only risks."
This adverse effect appeared only when men with already high levels took the selenium supplement and not in men who originally had low levels. It was also noted that Vitamin E also increased the risk of cancer almost doubling it in men who had low level of selenium.
This study was a follow-up of Select (selenium and vitamin E cancer prevention trial), which originally recruited more than 35,000 men to see if the supplements could help prevent prostate cancer. The main goal of the trial was to prove whether selenium and vitamin E supplements actually prevented prostrate cancer. It was concluded "SELECT was initially planned for a minimum of seven years and a maximum of 12 years of participants taking supplements, plus follow-up observation after the men finished taking their supplements. However, the independent Data and Safety Monitoring Committee (DSMC) for the trial met on September 15, 2008, to review SELECT study data and found that selenium and vitamin E, taken alone or together did not prevent prostate cancer. The committee also determined that it was unlikely selenium and vitamin E supplementation would ever produce a 25 percent reduction in prostate cancer incidence, as the study was designed to show. Based on their recommendation, with SWOG and NCI agreement, SELECT participants were told in October 2008 to stop taking their study supplements." (National Cancer Institute)
The Select trial suggested that Vitamin E intake may have more detrimental effects then initially thought, whereas the outcome of overuse of selenium was still disputed hence the follow up study. "In 2011, data showed that men taking vitamin E alone had a significantly increased risk of prostate cancer, but men taking vitamin E plus selenium did not. If men had low selenium levels at the start of the trial, the selenium supplement may have counteracted a negative effect of the vitamin E supplement." (Select study - NCI)
The results of this follow-up study have shown a clear relation between selenium and vitamin E supplements and the increased risk of prostrate cancer.
"In an analysis published in 2014, men who had high levels of selenium at the start of the trial, as assessed by measures of selenium in their toenail clippings, had almost double the chance of developing a high-grade prostate cancer if they took the selenium supplement compared to men with low levels of selenium at the start of the trial. This finding was unexpected, as previous studies had shown that men with low levels of selenium had an increased risk of prostate cancer that was reduced with supplements (11, 12). Additionally, men with low levels of selenium at the start of the trial had double the chance of developing a high-grade prostate cancer if they took the vitamin E supplement."
(National Cancer Institute)
A detailed article on the latest results was published on February 21st 2014 in The Guardian, titled
Some vitamin supplements raise risk of cancer in men, research shows.
P.S:
References:
Selenium and Vitamin E Cancer Prevention Trial (SELECT) (National Cancer Institute) Some vitamin supplements raise risk of cancer in men, research shows. (The Guardian)
