Recent Developments
1. Selenium and Human Health - Summary
2. Selenium and Human Health - Latest Studies
3. Selenium in Food: Studies on Grains and Fish
4. Studies on Selenium in China
1. SELENIUM & HUMAN HEALTH - SUMMARY
Note that numbers correspond to individual studies in the Latest Studies section
1. Recommended intake and upper tolerable levels for selenium are about 50 and 300 micrograms/day respectively, a difference of only six-fold between the recommended intake level and the maximal safe level. Based on this small difference, better chemical characterization of selenium compounds in foods and in particular supplements is needed, as well as improved understanding of the apparent differences in biological activity between selenium compounds, both with respect to nutrition, disease protection and adverse effects. Supplementation studies should focus on possible adverse effects as well as potential beneficial effects.
2. A new study found no benefit of selenium supplementation on the incidence of type 2 diabetes, even when the analyses took into account differences in age, sex, body mass index, and smoking status. The study concluded that selenium supplementation does not seem to prevent, and may even increase, risk for type 2 diabetes.
3. A review article examined the association between each of the trace elements and the risk of cancers of the lung, breast, colorectum, prostate, urinary bladder, and stomach. Overall, the evidence currently available appears to support an inverse association between selenium exposure and prostate cancer risk, and possibly also a reduction in risk with respect to lung cancer, although additional prospective studies are needed. There is also limited evidence for an inverse association between zinc and breast cancer. Most studies have reported no association between selenium and risk of breast, colorectal, and stomach cancer and between zinc and prostate cancer risk. There is compelling evidence in support of positive associations between arsenic and risk of both lung and bladder cancers, and between cadmium and lung cancer risk.
4. When rabbits are simultaneously injected with arsenite and selenate, or with mercuric chloride and selenate , compounds with As- Se and Hg- Se bonds are formed in the bloodstream. The glutathione-driven formation of these compounds in the blood stream fundamentally links the metabolism of the environmental pollutants mercuric mercury and arsenite with that of the essential ultra-trace element selenium , establishes a feasible biological mechanism by which the chronic low-level exposure of various human populations to these toxic metals and metalloid compounds is linked to human diseases, including cancer and neurodegenerative diseases.
5. A health review concluded that the minimum requirement for selenium is that which prevents Keshan disease, a potentially fatal disease of the heart muscle caused by selenium deficiency . There is an urgent need for more large-scale data on which to base more reliable estimates for intakes and plasma selenium levels that are protective.
6. Blood or plasma levels of selenium are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail- Se values and the incidence of cancer. Even though the seleno proteins found in selenium accumulator plants such as broccoli and garlic were shown to be the most effective seleno -compounds in the reduction of mammary tumors, they may not be the most effective seleno -compound for reduction of colon tumors as reported by Oregon State University researchers.
7. The results of a study suggest that in populations exposed to arsenic, selenium intake may be correlated with urinary arsenic excretion, may alter arsenic methylation, and may increase excretion of arsenic.
8. Based on recent studies at the Mayo Clinic, the authors propose a novel explanation for the mechanism by which viruses cause heart muscle disease (cardiomyopathy). The model incorporates trace element (mercury and selenium ) imbalance and its interactions with the cellular physiology of viral-induced heart muscle dysfunction.
9. The Mercury Roundtable at the second meeting of the new International Society of Environmental Bioindicators gathered human health, wildlife, and molecularly focused researchers to evaluate the current status of mercury bioindicators. Recommendations include the evaluation of additional co-contaminated residues in tissues, such as selenium , as the toxicity is related to the mercury to selenium ratio.
10. Medical Geology, the study of the impacts of geological materials and processes on animal and human health, is a dynamic emerging discipline bringing together the geosciences, biomedical, and public health communities to solve a wide range of environmental health problems. Goiter is discussed, as is deficiency of selenium in the soil as the cause of juvenile cardiomyopathy and muscular abnormalities.