Selenium interventions

Attempts to demonstrate disease-reduction benefit with respect to cardiovascular disease by selenium intervention have proven disappointing, despite the theoretical benefit of lipid peroxide removal by GPx and apparently beneficial changes in intermediate markers such as platelet aggregation, vasoconstriction, and thromboxane prostacyclin ratios following supplementation. Further studies of high-risk populations are needed, including a focus on the concerted action by combinations of selenium and vitamin E. 

E. H. Larsen, M. Hansen, H. Paulin, S. Moesgaard, M. Reid, M. Rayman, Speciation and bioavailability of selenium in yeast-based intervention agents used in cancer chemoprevention studies, J. AO AC lnt., 87 (2004), 225 D 232. 

Speciation and hioavailahility of selenium 149 in yeast-hased intervention agents the results revealed different SeMet contents, depending on the product source, hatch and age. Differences in intake, speciation or hioavailahility of selenium from the yeast-hased supplements could he responsible for different increases in Se in hlood plasma observed in the chnical trials... 

Larsen, E. H., Hansen, M., Paulin, H., Moesgaard, S., Reid, M., et al. Speciation and hioavailahility of selenium in yeast-hased intervention agents used in cancer chemoprevention studies. J AOAC lnt 2004, 87, 225-232. 

Additional intervention trials of various micronutrients, including selenium and folic acid, and other chemopreventive agents have been completed or are ongoing. - Because of their different mechanisms of action and sites of influence on the process of colorectal carcinogenesis, certain populations of individuals may benefit most from selected agents. 

Yu SY, Zhu YJ, Li WG, et al. 1991. A preliminary report on the intervention trials of primary liver cancer in high-risk populations with nutritional supplementation of selenium in China. Biol Trace Elem Res 29(3) 289-294. 

Human Intervention Trials In several human intervention trials, significant cancer-preventive effects of supplemental selenium have already been demonstrated, and several other studies are pres-... 

R = H) occurs smoothly in boiling xylene, in the presence of sulphur. The suggested mechanism involves formation of a spiro-compound (34) as an intermediate. When sulphur is replaced by selenium, the normal product, 2,5-diphenyl-6a-thiathiophthen, is accompanied by the 6a-selenathiophthen (35 R == Ph, R = H). The possible intervention of a... 

The Supplementation Vitamin, Minerals and Antioxidant Trial (SU. VI.M.AX) is testing, in 15,000 healthy French men and women, whether a combination of antioxidant vitamins and minerals, including vitamin E, p-carotene, vitamin C, selenium, and zinc, protects against CHD. In the United States, an intervention trial was started with 8000 women with recent CHD in order to test in a factorial design the effect of P-carotene, vitamin E, and vitamin C. 

Blot et al (1993) recently reported the results of a large clinical trial in Linxian, China, an area with a high incidence of esophageal cancer and cardia carcinoma of the stomach. After 5.25 years of supplementation no effect on disease risk was seen for vitamin C supplements combined with molybdenum. However, a decrease in total cancer mortality and mortality from stomach cancer was seen with supplementation of -carotene, vitamin E, and selenium. Also, an endoscopic survey at the end of the intervention period did not reveal an effect of vitamin C supplementation on the prevalence of esophageal and gastric dysplasia (Wang et al, 1994). 

Drug-combination studies The effectiveness of Coenzyme QIO, vitamin E, selenium, and methionine in the treatment of chronic recurrent viral mucocutaneous infections in two clinical trials including a total of 157 patients [90=]. Significantly increased rates of healing and reduced incidents of relapse were observed in the intervention group compared with controls (p < 0.05). No adverse effects were reported. 

See also Antioxidants Observational Studies Intervention Studies. Ascorbic Acid Physiology, Dietary Sources and Requirements. Carotenoids Chemistry, Sources and Physiology Epidemiology of Health Effects. Copper. Folic Acid. Riboflavin. Selenium. Vitamin E Physiology and Health Effects. Zinc Physiology. 

A few trials have suggested that selenium supplementation may have a protective effect on liver cancer in high-risk groups living in low-selenium areas. The provision of selenium-fortified salt to a town in Qidong, China, with high rates of primary liver cancer, reduced the incidence of this cancer by 35% compared with towns that did not receive this intervention (Table 3). Trials have also demonstrated the incidence of liver cancer to be... 

Selenoproteins seem to have a number of functions, comprising various catalytic roles (glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases), structural roles, detoxifying functions (e.g., selenoprotein P), and storage and transport activities. Many of these functions are incompletely understood, and advances in this area should help to clarify uncertainties about human requirements and the role of selenoproteins in disease, especially in multifactorial conditions such as cancers. Several controlled intervention trials involving selenium are under way, and these should provide evidence to underpin public health programs in the near future. 

As noted previously, neither Keshan disease nor Kashin-Beck disease are now thought to be simple dietary deficiency diseases. They probably also involve viral components and may be exacerbated by environmental toxins, including mycotoxins. Thus, they are probably multifactorial, but importantly, public health selenium supplementation interventions have had a dramatically beneficial effect on the prevalence of these diseases. The main clinical features of Keshan disease are cardiac insufficiency and enlargement, electrocardiographic changes, and fibrosis. Those of Kashin-Beck disease are osteoarthropathy and necrosis of the joints and epiphysial plate cartilage. Both diseases occur in school-age... 

The Linxian, China, intervention trial provided evidence that nutritional supplementation may lower the risk of certain cancers. A modest but significant reduction in cancer mortality was observed in a general population trial in those receiving daily (for 5.25 years) a combination of /3-carotene (15 mg), vitamin E (30 mg), and selenium (50 pg). The subjects who received this mixture had a 13% lower incidence of cancer and a 10% lower mortality from stomach and oesophageal cancer than did the subjects who did not receive the mixture. In the ATBC study, male smokers who took vitamin E supplements had a 34% lower incidence of prostate cancer and 41% lower mortality from prostate cancer than did those who did not take the supplements. In the United States, in a nested case-control study conducted to examine the association of a-tocopherol, 7-tocopherol, and selenium with the incidence of prostate cancer, a striking fivefold reduction in risk was observed for the men in the highest quintile of 7-tocopherol compared with those in the lowest. Overall, evidence for the protection from cancer by vitamin E is not compelling. 

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