|Scrutinizing the evidence for breast
cancer procedures and treatments
|Supplement Strategies - Selenium
The mineral, selenium, is a powerful antioxidant. Additionally,
research has found other mechanisms of action of interest to
breast cancer patients.
Linking Selenium Deficiency to Breast Cancer
- In 80 breast cancer patients who had a mastectomy, their blood
levels of selenium were lower than in healthy patients. In the
patients, there was a significantly higher concentration of selenium
in cancerous tissue, as opposed to adjacent healthy tissue. The
higher concentration of selenium in cancerous tissue may be
attributable in part to selenium's defense mechanism (selenium
activates the antioxidant glutathione) against the carcinogenic
process. (See Charalabopoulos K et al., Selenium in Serum and
Neoplastic Tissue in Breast Cancer: Correlation with CEA, bjcancer
- Selenium helps to convert T(4) - thyroxine, the prohormone with 4
molecules of iodine into T(3) - triiodothyrone, the cellularly active
thyroid hormone, with three molecules of iodine. Thyroid hormones
help the entire body - raising the metabolic rate and balancing
- Selenium is an antioxidant, a part of glutathione peroxidase, which
prevents fats from being oxidized. During the production of thyroid
hormones, selenium helps to degrade excess hydrogen peroxide
that can damage the cells.
Selenium Reverses Chromosome Breaks
UPDATE: Selenium has several anticancer properties, including
protection against oxidation and enhancing nucleotide excision repair.
Women who carry a mutation of the BRCA1 gene were found to have
more chromosome breaks (which can lead to breast cancer)than women
who did not carry the mutation. When women with the BRCA1 mutation
were given selenium for three months, the number of their chromosome
breaks were reduced to normal.
(See Kowalska E et al., Increased Rates of Chromosomes Breakage in
BRCA1 Carriers are Normalized by Oral Selenium Supplementation,
Cancer Epidemiology Biomarkers and Prevention 2005. See also
Alternative Medicine Magazine, March 2006.)
Double-Blind, Placebo-Controlled Cancer Study
Although there have been many studies on selenium, we include it on the
list of beneficial supplements for cancer principally because of the
following double-blind, placebo-controlled study published in JAMA.
Editor's note: the usual recommended selenium dose is
200 mcg. Selenium works synergistically with iodine and Vitamin E.
Selenium supplements can reduce cancer rates, new study shows
Jan. 7, 1997 Press release
ITHACA, N.Y. -- Men and women taking selenium supplements for 10
years had 41 percent less total cancer than those taking a placebo, a new
study by Cornell University and the University of Arizona shows. "Although
more than a hundred of animal and dozens of epidemiological studies
have linked high selenium status and cancer risk, this is the first double-
blind, placebo-controlled cancer prevention study with humans that
directly supports the thesis that a nutritional supplement of selenium, as a
single agent, can reduce the risk of cancer," said Gerald F. Combs Jr., a
nutritional biochemist and Cornell professor of nutritional sciences.
Combs and a group of co-authors reported their findings in the Jan. 1,
1997 issue of The Journal of the American Medical Association. The
senior author is epidemiologist Larry Clark, who was at Cornell at the
onset of the study and is now at the Department of Family and Community
Medicine at the University of Arizona School of Medicine.
In 1983, the researchers recruited 1,312 randomized patients with
histories of skin cancer at seven dermatology clinics located in low-
selenium areas of the United States (Augusta and Macon, Ga., Columbia,
S.C., Wilson and Greenville, S.C., Miami, and Newington, Conn., where
consumers ingest an average of about 100 micrograms of selenium a
day). The patients were given either a placebo or a 200-microgram daily
supplement of selenium (twice the average amount these Americans
consume in their diet, thereby tripling their selenium intake).
Skin cancer patients were chosen because they have a 25 percent
annual chance of a recurrence, and skin cancer is easy to diagnose and
can be quickly treated. The researchers set out to determine whether
they could reduce the average recurrence rate with selenium
Ironically, 10 years later, the results were not significant for skin cancer.
However, they were "compelling" for overall cancer incidence and
mortality rates, Combs stressed. Of the selenium group, 69 developed
some type of cancer compared with 116 of the placebo group; 28 of the
selenium patients died of cancer compared with 58 from the placebo
"Overall, the selenium group experienced 18 percent less mortality than
the placebo group, and almost all of that difference was due to some form
of cancer," said Combs, who credits Cornell with having the longest
history of research in selenium nutrition research in the world. "This is the
first time anyone has shown that any single nutrient can result in such a
reduction in cancer risk. The fact that we saw a pattern in lower incidence
and mortality rates across all the clinics gives us even greater confidence
in these findings."
Prostate, esophageal, colorectal and lung cancer rates were among the
most dramatic: patients in the selenium group had 71 percent, 67 percent,
62 and 46 percent reductions in cancer rates, respectively, than the
Selenium blood levels vary widely in populations. Even Americans with the
lowest selenium intake of 60 to 80 micrograms per day -- those living
along the Southeastern seaboard and in the Pacific Northwest -- ingest
two to five times more than citizens of New Zealand and 10 to 20 times
more than people living in some areas of China. Selenium blood levels
vary among populations largely because of wide differences in soil,
agronomic practices, food availability and preferences and methods of
The University of Arizona-Cornell research team reported in 1991 that low
selenium levels in the blood were linked to increased risk of neoplastic
polyps in the colon, a precursor to colorectal cancer. And in other studies
at Cornell, colleagues of Combs' reported in 1995 that animals fed diets
high in selenium had 50 percent fewer tumors than those fed diets of
average selenium content.
Of the 40 nutrients currently recognized as essential for human nutrition,
selenium was the last to be recognized in 1957. A key component for at
least two essential enzymes, selenium provides the body with antioxidant
protection in concert with vitamin E and is required for normal thyroid
The study was funded in part by grants from the American Institute of
Cancer Research, the American Cancer Society and the National
Institutes of Health.
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Web page updated January 1, 2019
proposed as a way of
detecting breast cancer risk
Breast Cancer Res Treat.
Selenium in serum as a
possible parameter for
assessment of breast disease.
Krsnjavi H, Beker D.
Institute for Medical Research
and Occupational Health,
The level of selenium in blood
serum was determined in 33
patients with breast cancer, 13
women with verified
mastopathy, and 43 healthy
subjects from the Zagreb area.
In the second and third
quartiles the values of
selenium obtained from sick
subjects (41-58 micrograms/L)
and healthy subjects (73-89
significantly (P less than
0.001). In the group of subjects
with mastopathy, serum
selenium in the same way
ranged from 67-76
micrograms/L and did not differ
significantly from the group of
healthy women, but differed
significantly from the patients
with breast cancer (P less than
Such a result leads to the
determination of selenium
in the blood could be used
as a non-invasive
diagnostic parameter in
clinical assessment of
malignant breast disease.
How to take Selenium