Selenium and cancer

Selenium for cancer

High doses of selenium in the treatment of blood cancers have been tested all the way from 1915, but the enthusiasm that had come to seem justified was somewhat tempered by a subsequent report published in 1943, under which such doses induced cirrhosis and hepatic tumors in laboratory animals.

Fortunately, best and most extensive investigations demonstrate that selenium produced less, rather than more tumors. From 55 studies published since 1949, 49 of them would find that selenium inhibits cancer (15).

Cancer and Selenium

The plausibility of a link between this mineral and cancer was increased in 1973 when it was found that selenium is a component of glutathione peroxidase.

It is known that this enzyme macromolecules protects the body against oxidative stress. Early indications derived from epidemiological studies give us the Shamberger and Frost, who have shown that cancer mortality is inversely correlated with the concentration of selenium in forage crops (16). Confirmation is afforded both themselves and other researchers who have tested actual mineral dietary intakes against blood levels and found a strong inverse correlation of selenium with breast cancer and colon cancer.

In most of the case control studies, patients with cancer present in the blood and tissues lower concentrations of selenium. However, research based on blood concentrations are difficult to interpret. It may be possible that cancer is the origin of lower concentrations of mineral insulation: by reducing their uptake or impaired absorption or secretion (17). No doubt that selenium concentrations decline in cancer patients as the disease progresses (18) and patients in the later stages of the disease tend to have lower concentrations (19).

However, even in the earliest stages of tumor formation, were found in blood plasma selenium concentrations reduced in patients with skin cancer melanoma precursor characteristics (20).

In prospective studies, the potential of cancer for altering the concentrations of selenium has been minimized, since the samples are collected at baseline, and then analyzed only in cases in which cancer develops with a sample from the who do not develop. By applying this method, it was found that the mean concentrations of selenium in serum prediagnostic between sick people who developed cancer were significantly lower than those found between the corresponding controls (21).

Those with the lowest levels of the trace mineral were exposed to a cancer risk that was twice that of the higher levels. In two subsequent studies conducted in Finland, there was an increase between triple and sextuple in cancer risk for those with low levels of selenium in serum compared with others.

Although these prospective research seemed promising, further similar research produced no definite type of relationship between low selenium and cancer. Two independent investigations conducted in the United States and the Netherlands respectively, using the levels of selenium in cuts toenails as indicators of the mineral in the body.

In the American study (21), a group of 62,641 women between nurses health study (Nurses Health Study) levels cut the toenails during the period 1982-1983. During 53 months of follow-up, 434 cases were diagnosed with breast cancer. The average level of selenium in toenails of women turned out to be almost identical to the controls who did not develop breast cancer. These findings applied equally to pre-menopausal women and post-menopausal women.

In the Dutch trial (22), much smaller in number, carried out between 1985 and 1987, selenium dietary intake was assessed among 133 breast cancer cases and 238 population controls. Selenium levels in blood plasma, red blood cells and toenails were similar in cases and controls. There appeared no statistically significant trend in the proportions of any of the four selenium level indicators. Therefore, in the U.S. data, we found no suggestion any association between selenium levels and breast cancer research in the short and long term.

Other cancers may yield different results. For example, a 10-year study of Finnish men and women (39,268 individuals) indicated that selenium levels in blood serum in cancer cases in males (average 59.1 ug / l) were significantly different from those of the controls (average 62.5 ug / L) in women but levels were virtually identical (63.6 and 63.9 ug / l). The final conclusion points out that low selenium intake may increase the risk of developing stomach cancer and lung cancer among men (22).

Selenium and leukemia

Children with leukemia have significantly lower serum selenium levels than healthy controls (the minor surgery) but this difference depends on the type of malignancy. Sufferers of acute lymphatic leukemia and other malignant proliferative diseases have the lowest levels of selenium. Lymphoma affected by both Hodgkins and otherwise, have selenium levels similar to the controls (23).

Therefore, we can assume that, in the majority of cancer cases, in both adults and children, selenium level is low. What we do not know is whether this is the cause or consequence of cancer. There is no significant research to show that selenium can inhibit the development of an existing cancer, or invest in the intact organism, although it has been observed inhibition of cancer cells in vitro.

Source: Dr Leonard Mervyn

References
15. COOMBS. G.F. and COOMBS, S.B. The role of selenium in Nutrition. Orlando. Florida, Ac? Td, Entic Press, p413-6, 1986.
16. Shamberger, Pi. and Frost, D. V. Possible protective effect of selenium against! Turns bncer. Can.Mecl.Assoc.J., 100, p.682. 1969.
17. R1ZK, S.L. and others. Comparison Between Concentrations of trace elements in normal and tumor neoplastie btrast tissue. Cancer Res. 44, p.5390-I. 1984.
18. Sundstrom, H. and others. Serum selenium in patients with ovarian cancer therapy During and after. Carcinogenesis, 5, p.731-4, 1984.
19. MeCONNELL, K.P. and others. Selcnium Levels in Human Blood and tissties in Health and Disease. J.Ntar., 105. p.1026-31, 1975.
20. CLARK, C.I. and others. Plasma selenium asid skin neoplasms, a case control study. Nutr.Cancer, 6, p.13-2 I, 1984.
21 HUNTER, DI and others. A prospective study of seleniurn status and breast cancer risk. lAmer.Med.Assoc., 264, p.I128, 1990.
22. KNEKT, P. and others. Selenium Serunt sud subsequent risk of cancer among Finnish men and women. J.Nat.Cancer Inst. 82, p.864-68, 1990.
23. MIK AC-Devic, M. and others. Sclenium Serum Levels in Children with untreated acute lymphoblastic letikaemia I. J. Trace.

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