Cervical Cancer and Selenium
Selenium is a trace mineral that our bodies use to produce glutathione peroxidase. Glutathione peroxidase is part of the body's antioxidant defense system; it works with vitamin E to protect cell membranes from damage caused by dangerous, naturally occurring substances known as free radicals.
China has very low rates of colon cancer, presumably because of the nation's low-fat diet. However, in some parts of China where the soil is depleted of selenium, the incidence of various types of cancer is much higher than in the rest of the country. This fact has given rise to a theory that selenium deficiency is a common cause of many forms cancer, and that selenium supplements can reduce this risk. This is the reason that selenium is listed here as a treatment for cervical cancer.
Additionally, for the treatment of cervical or any other form of cancer, it is important to keep a well-rounded diet, perhaps take herbal supplements, and certainly determine if any of the medications you are taking are creating deficiencies of key nutrients in your body.
Effect of Selenium on Cervical Cancer
There is some preliminary evidence that selenium supplements might provide some protection against some types of cancer among people living in the US, but this evidence is far from definitive.
Research Evidence on Selenium
The most important double-blind study on selenium and cancer was conducted by researchers at the University of Arizona Cancer Center.37 In this trial, which began in 1983, 1,312 people were divided into two groups. One group received 200 mcg of yeast-based selenium daily; the other received placebo. Participants were not deficient in selenium, although their selenium levels fell toward the bottom of the normal range. The researchers were trying to determine whether selenium could lower the incidence of skin cancers.
As it happened, no benefits for skin cancer were seen. (In fact, careful analysis of the data suggests that selenium supplements actually marginally increased risk of certain forms of skin cancer.58) However, researchers saw dramatic declines in the incidence of several other cancers in the selenium group. For ethical reasons, researchers felt compelled to stop the study after several years and allow all participants to take selenium.
When all the results were tabulated, it became clear that the selenium-treated group developed almost 66% fewer prostate cancers, 50% fewer colorectal cancers, and about 40% fewer lung cancers as compared with the placebo group. (All these results were statistically significant.) Selenium-treated subjects also experienced a statistically significant (17%) decrease in overall mortality, a greater than 50% decrease in lung cancer deaths, and nearly a 50% decrease in total cancer deaths. A subsequent close look at the data showed that only study participants who were relatively low in selenium to begin with experienced protection from lung cancer or colon cancer; people with average or above average levels of selenium did not benefit significantly.55, 60 It has not yet been reported whether this limitation of benefit to low-selenium participants was true of the other forms of cancer as well.
While this evidence is promising, it has one major flaw. The laws of statistics tell us that when researchers start to deviate from the question their research was designed to answer, the results may not be trustworthy. Currently, other studies are underway in an attempt to validate the findings accidentally discovered in this trial.
Interestingly, combining the results of 12 recent placebo-controlled trials investigating the association between antioxidant supplementation and cancer, researchers found that men who took selenium experienced an overall reduction in the incidence of cancer. No similar effect, however, was observed in women.65 This difference cannot be explained without more research. In addition, selenium supplementation appeared to modestly lower cancer mortality in both men and women.
Other evidence for the possible anticancer benefits of selenium comes from large-scale Chinese studies showing that giving selenium supplements to people who live in selenium-deficient areas reduces the incidence of cancer.38 In addition, animal trials have found anticancer benefits.41,42
However, one study published in 2007 reported negative results in transplant patients.63 People who undergo organ transplants are at particularly high risk of skin cancer linked to the human papilloma virus (HPV). In this double-blind study, 184 organ transplant recipients were given either placebo or selenium at a dose of 200 mg daily. The results over two years failed to show benefit; both the placebo and the selenium group developed precancerous and cancerous lesions at the same rate.
Side Effects and Warnings
The US Institute of Medicine issues guidelines for the maximum total daily intake of various nutrients, based on estimations of what should be safe for virtually all healthy individuals. These tolerable upper intake levels (ULs) are, thus, conservative guidelines. For selenium, they have been set as follows: ^
- 0-6 months: 45 mcg
- 7-12 months: 60 mcg
- 1-3 years: 90 mcg
- 4-8 years: 150 mcg
- 9-13 years: 280 mcg
- Males and Females
- 14 years and older: 400 mcg
- Pregnant or Nursing Women: 400 mcg
Note that these dosages apply to combined dietary and supplemental intake of selenium. When deciding how much selenium it’s safe to take, keep in mind that most adults already receive about 100 mcg of selenium in the daily diet.
Maximum safe doses of selenium for individuals with severe liver or kidney disease have not been established. There is some evidence that supplementing selenium over the long-term in areas where selenium is already adequate in the diet may increase the risk of diabetes and perhaps hypercholesterolemia. ^ Highly excessive selenium intake, beginning at about 900 mcg daily, can cause selenium toxicity. ^ Signs include depression, nervousness, emotional instability, nausea, vomiting, and in some cases loss of hair and fingernails.
#Interactions You Should Know About
If you are taking medications that reduce stomach acid, such as H 2 blockers or proton pump inhibitors , you may need extra selenium.
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