Selenium
is a mineral that naturally occurs in foods such as whole grains, seafood,
garlic, eggs and mushrooms. It is believed that selenium helps fight diseases
including cancer by neutralizing harmful elements called "free radicals,"
the unstable molecules that damage tissue. Most individuals receive some
selenium in their diet, but dietary supplements are available at many
grocery and health food stores.
Selenium and Overall Cancer In a longitudinal study of 39,268 men and women, a 10-year follow up
revealed 1,096 new cases of cancer. The mean serum selenium level for
male cancer cases was lower by a statistically significant level than
that of male controls who were matched for age and municipality. Low serum
selenium levels were associated with an increased risk of developing cancer
at several sites, especially cancers of the stomach and lung among men.
Knekt P, et al., "Serum selenium and subsequent risk of
cancer among Finish men and women," Journal of the National Cancer Institute,
1990; 82: 864-868.
A case of 8,113 people found that in the 128 cases of overall cancer
cases, serum selenium levels in cases were significantly lower than matched
controls.
Salonen JT, et al., "Association between serum selenium
and the risk of cancer," American Journal of Epidemiology, 1984; Vol.
120, No. 3: 342-349.
In a 10-year study consisting of 8,271 person years, the group taking
200 mcg/day of organically bound selenium yeast showed a significant (50%)
reduction in total cancer mortality and in total cancer incidence (37%).
Clark LC, et al.," Effects of selenium supplementation
for cancer prevention in patients with carcinoma of the skin," The Journal
of the American Medical Association, December 25, 1996; Vol. 276, No.
24: 1957-1963.
In a multiple logistic analysis, serum selenium levels remained a significant
predictor of cancer risk when the effects of serum retinol, vitamin E,
and lipid levels as well as age, sex, and race were taken into account.
Willett W, et al., " Prediagnostic serum selenium and
risk of cancer," The Lancet, July 16, 1983: 130-134.
From a random sampling of some 12,000 people aged 30-64 years living
in Eastern Finland, 51 patients with cancer were paired with a control
matched for age, sex, and smoking. Patients who died of cancer during
the follow-up period had a 12% lower mean serum selenium concentration
than the controls.
Salomen JT, etal., "Risk of cancer in relation to serum
concentrations of selenium and vitamins A and E: matched case-control
analysis of prospective data," British Medical Journal, February. 9, 1985;
Vol. 290: 417-420.
From a sampling of 10,532 persons, 86 died of cancer since the baseline
examination. 164 cohort members were matched for age, sex, and smoking.
The mean serum selenium level of 116.7 + /-4 mcg/liter among all cancer
deaths was significantly different (p=0.04) from that in the control subjects
(126.4+/-31ug/le).
Kok FJ, et al., "Is serum selenium a risk factor for cancer
in men only?" American Journal of Epidemiology, 1987; 125: 12-16.
In a nested case control study, the stored, frozen sera from 22 cases
of cancer of the pancreas and 44 matched control subjects were assayed.
The association between cancer of the pancreas and serum Se was significant
when the data were analyzed as a whole, but its effect was seen principally
in men.
Burney PGJ, et al., "Serologic precursors of cancer: serum
micronutrients and the subsequent risk of pancreatic cancer," American
Journal of Clinical Nutrition 1989; 49: 895-900.
From 29,584 adults who received daily vitamin and mineral supplementation
during a 6-year period, a total of 2,127 deaths occurred. Cancer was the
leading cause of death, with 32% of all deaths due to esophageal or stomach
cancer. Significantly (P=0.03) lower total mortality occurred among those
receiving a supplement with beta-carotene, Vitamin E and Selenium. This
reduction was mainly due to lower cancer rates (RR=0.87%)
Blot MJ, et al., "Nutrition Intervention Trials in Linxian,
China: Supplementation with specific vitamin / mineral combinations, cancer
incidence and disease specific mortality in the general population," JNCI,
September 15, 1993; Vol.85, No.18: 1483-1491.
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Selenium's Effect on Prostate Cancer
A 10-year trial following 974 men showed that the group receiving 200
mcg/day of selenium yeast had a 63% reduction in prostate cancer incidence
compared to the group receiving placebo yeast.
Clark LC, et al., "Effects of selenium supplementation
for cancer prevention in patients with carcinoma of the skin," The Journal
of the American Medical Association, December 25, 1996; Vol. 276, No.
24: 1957-1963.
By use of a nested case-control design within a prospective study, i.e.
The Health Professionals Follow-Up Study, the association between risk
of prostate cancer and prediagnostic levels of selenium in toenails was
studied. When case vs control data were analyzed, higher selenium levels
were associated with a 50% reduced risk of advanced prostate cancer.
Yoshizawa K, et al., "Study of prediagnostic selenium
level in toenails and the risk of advanced prostate cancer," JNCI, Vol.90,
No.16, August 19, 1998; 1219-1224.
In a 10-year trial, when results are restricted to the 843 patients with
initially normal levels of prostate specific antigen (<4ng/ml), only 4
cases of prostate cancer were reported in the group receiving 200 mcg/day
of High Selenium Yeast; as compared to 16 cases of prostate cancer in
the placebo yeast group after a two year lag (RR=0.26 P=0.009).
Clark LC, et al., "Decreased incidence of prostate cancer
with selenium supplementation; results of a double-blind cancer prevention
trial," British Journal of Urology, 1998; 81: 730-734.
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Selenium and Lung Cancer
Between 1968 1976 serum samples from 9,101 cancer free individuals
were collected and stored. During a follow up that ended in 1991, 95 cases
of lung cancer were diagnosed. Serum selenium for cases were compared
to 190 controls matched for sex, age, and place of residence. A relative
risk of 0.41 existed between the groups with highest and lowest serum
selenium levels.
Knekt P, et al., "Is low selenium status a risk factor
for lung cancer?" American Journal of Epidemiology, November 15, 1998;
148(10): 975-982.
A 10-year trial involving 1,312 people reveals that the group who consumed
200 mcg/day tablet of high selenium yeast has 46% fewer incidences of
lung cancer when compared to the group receiving a placebo yeast tablet.
Clark LC, et al., "Effects of selenium supplementation
for cancer prevention in patients with carcinoma of the skin," The Journal
of the American Medical Association, December 25, 1996; Vol. 276, No.
24: 1957-1963.
In a study of 37 lung cancer patients, their sons & daughters, and age-rates
matched controls. Family members of lung cancer patients showed a trend
towards lower levels of serum selenium levels than the controls (0.05
< P < 0.10), but this difference was not significant. However, lung cancer
patients had significantly lower serum selenium levels (0.099 +/- 0.016
mcg/?) than the controls and lung cancer patient family members (P < 0.0l).
Miyamoto Hiroshi, et al, "Serum Selenium and Vitamin E
Concentrations in Families of Lung Cancer Patients," Cancer, March 10,
1987, Vol 60: 1159-1162.
back to top Selenium and Colon Cancer
According to a recent report in the journal Cancer Epidemiology Biomarkers
and prevention, low dietary selenium intake seems to increase the risk
of developing adenomatous colon polyps.
Skerret PJ, "Low selenium linked to precancerous colon
polyps," Medical World News, April 1993; 34(4): 16.
Double-blind, placebo controlled trial has results of 58% fewer colorectal
cancer incidences in participants taking 200 mcg/day of selenium yeast
as compared to participants taking a placebo yeast.
Clark LC, et al., "Effects of selenium supplementation
for cancer prevention in patients with carcinoma of the skin," The Journal
of the American Medical Association, December 25, 1996; Vol. 276, No.
24: 1957-1963.
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