Selenium and human health

Selenium is incorporated into selenoproteins that have a wide range of pleiotropic effects, ranging from antioxidant and anti-inflammatory effects to the production of active thyroid hormone. In the past 10 years, the discovery of disease-associated polymorphisms in selenoprotein genes has drawn attention to the relevance of selenoproteins to health. Low selenium status has been associated with increased risk of mortality, poor immune function, and cognitive decline. Higher selenium status or selenium supplementation has antiviral effects, is essential for successful male and female reproduction, and reduces the risk of autoimmune thyroid disease. Prospective studies have generally shown some benefit of higher selenium status on the risk of prostate, lung, colorectal, and bladder cancers, but findings from trials have been mixed, which probably emphasises the fact that supplementation will confer benefit only if intake of a nutrient is inadequate. Supplementation of people who already have adequate intake with additional selenium might increase their risk of type-2 diabetes. The crucial factor that needs to be emphasised with regard to the health effects of selenium is the inextricable U-shaped link with status; whereas additional selenium intake may benefit people with low status, those with adequate-to-high status might be affected adversely and should not take selenium supplements.     

Selenium status and cardiometabolic health: state of the evidence

Use of selenium enriched foods, supplements and fertilizers has increased markedly in recent years in the US and other Western countries because of the perception that the anti-oxidant properties of selenium could potentially reduce the risk of cancer and other chronic diseases. However, concern has been raised recently about possible adverse cardiometabolic effects of high selenium exposure, including an increased risk of diabetes and hyperlipidemia with high selenium intake. Hence, from a public health perspective, the relationship between selenium status and cardiometabolic health should be clarified in order to help guide consumers in their choices of nutritional supplements and enriched food products. Additional experimental evidence is needed to provide new insights into the role of selenium and of specific selenoproteins in human biology, especially to clarify the underlying mechanisms linking selenium to chronic disease endpoints. Further epidemiological studies and randomized clinical trials across populations with different selenium status should be conducted to determine the causal effect of selenium on cardiovascular disease and risk factors. Nevertheless, at the present time the widespread use of selenium supplements or other strategies that artificially increase selenium status above the level required for optimal selenoprotein activity is not justified and should not be encouraged.     

Serum selenium and risk of large size colorectal adenomas in a geographical area with a low selenium status

OBJECTIVE: Selenium is a fundamental nutrient to human health that might have anticarcinogenic effects. Previous studies have assessed the possible relationship of selenium status to colorectal adenomas with controversial results. We primarily aimed to assess the relationship of serum selenium status with the presence of large size colorectal adenomas in subjects living in a poor selenium region. The serum selenium status in colorectal cancer was also evaluated. METHODS: Serum selenium levels were measured in 28 patients with large size sporadic adenomatous polyps, 24 patients with colorectal adenocarcinomas, and 35 age-matched healthy individuals. A logistic regression analysis was performed to assess the relationship of serum selenium to colorectal adenomatous polyps after adjusting for confounding variables (age, sex, smoking habit, and alcohol drinking). RESULTS: Among subjects aged < or = 60 yr, mean serum selenium levels were significantly lower in both patient groups (adenoma, 57.9 +/- 4.3 microg/L; cancer, 43.7 +/- 6.6 microg/L) than in healthy controls (88.9 +/- 8 microg/L) (p = 0.0001). There were no difference among subjects > 60 yr old. A significant inverse association between selenium status and the diagnosis of large size adenomatous polyps after adjusting for confounding variables was found (adjusted p = 0.029). Subjects with higher selenium status (> or = 75th percentile value of 82.11 microg/L) had a lower probability (OR = 0.17, 95% CI = 0.03-0.84) to be in the adenoma group than subjects with lower selenium status (< 82.11 microg/L). This association was more marked in subjects aged < or = 60 yr (adjusted p value = 0.04, OR = 0.08, 95% CI = 0.007-0.91), and was not significant in older subjects. CONCLUSIONS: Results suggest that high selenium status may decrease the risk of large size adenomas in a low selenium region, and that this preventive effect seems to be exclusive to subjects < or = 60 yr. These results will need to be confirmed in additional epidemiological studies before recommending selenium supplementation in patients with colon adenomas.     

硒与心脏疾病

硒被认为是与人类健康息息相关的一种微量元素。越来越多的证据表明,硒与包括心血管疾病在内的多种疾病的发生、发展有关。在临床上,硒具有促进冠心病及心力衰竭恢复的特性,在发生心血管疾病的患者中常常可发现硒缺乏。研究表明,硒缺乏可通过破坏体内氧化-还原平衡、影响某些重要硒化物的含量及某些硒蛋白（如谷胱甘肽过氧化物酶）的合成、修饰与活性等参与心血管疾病的发生发展。补充硒可以重建体内氧化-还原平衡,降低体内氧化反应造成的心肌应激损伤。另外,硒在心律失常、心肌病以及心肌炎的发病过程中也起着重要的作用,但机制还尚不清楚。相信对于硒和心脏疾病研究的不断深入可最终在促进心血管疾病基础研究、药物开发以及患者营养治疗等方面起到重要作用。     

The global epidemiological situation of schistosomiasis and new approaches to control and research

While the distribution of schistosomiasis has changed over the last 50 years and there have been successful control programmes, the number of people estimated to be infected or at risk of infection has not been reduced. Today, 85% of the number of infected people are estimated to be on the African continent where few control efforts are made. In terms of disease burden, there is therefore a growing discrepancy between sub-Saharan Africa and the rest of the world. WHO has now developed a dual strategy for the control of schistosomiasis: a strategy for morbidity control adapted to the public health context in high burden areas, and a strategy to consolidate control in areas where a low endemic level has been reached and elimination may be feasible. Related to this new vision, some research needs are pointed out.     

Omega-3 Fatty Acids,Mercury, and Selenium in Fish and the Risk of Cardiovascular Diseases

Fish consumption is associated with lower risk of cardiovascular disease. Some fish species also contain methylmercury, which may increase cardiovascular risk, as well as selenium, a trace element that could counter the effects of methylmercury or have beneficial effects itself. These potentially conflicting effects have created public confusion about the risks and benefits of fish consumption in adults. We examined the evidence for cardiovascular effects of fish consumption, particularly effects of marine omega-3 fatty acids, methylmercury, and selenium. Compelling evidence indicates that modest fish consumption substantially reduces cardiovascular risk, in particular cardiac mortality, related at least partly to benefits of omega-3 fatty acids. In contrast, observational studies and (for selenium) clinical trials demonstrate mixed and inconclusive results for cardiovascular effects of methylmercury and selenium. Net health benefits of overall fish consumption in adults are clear. Quantitative risk-benefit analyses of cardiovascular effects of consuming specific fish species, based on joint contents of fatty acids, methylmercury, and selenium, cannot currently be performed until the cardiovascular effects of methylmercury and selenium are established.     

Women and War

Most of today's 1.7 million women veterans obtain all or most of their medical care outside the VA health care system, where their veteran status is rarely recognized or acknowledged. Several aspects of women's military service have been associated with adverse psychologic and physical outcomes, and failure to assess women's veteran status, their deployment status, and military trauma history could delay identifying or treating such conditions. Yet few clinicians know of women's military history—or of military service's impact on women's subsequent health and well being. Because an individual's military service may be best understood within the historical context in which it occurred, we provide a focused historical overview of women's military contributions and their steady integration into the Armed Forces since the War for Independence. We then describe some of the medical and psychiatric conditions associated with military service.     

Women and war. What physicians should know

Most of today's 1.7 million women veterans obtain all or most of their medical care outside the VA health care system, where their veteran status is rarely recognized or acknowledged. Several aspects of women's military service have been associated with adverse psychologic and physical outcomes, and failure to assess women's veteran status, their deployment status, and military trauma history could delay identifying or treating such conditions. Yet few clinicians know of women's military history--or of military service's impact on women's subsequent health and well being. Because an individual's military service may be best understood within the historical context in which it occurred, we provide a focused historical overview of women's military contributions and their steady integration into the Armed Forces since the War for Independence. We then describe some of the medical and psychiatric conditions associated with military service.     

Use of probiotics and yogurts in maintenance of health

The role of probiotics in treating or preventing diarrheal diseases is well known. Less understood is the impact probiotics may have on maintaining health. Although it can be a challenge to demonstrate improved health of an already healthy population, some recent studies provide evidence that probiotics may reduce the risk of getting sick in populations that are at risk by nature of environmental exposure (eg, children in day care centers), physical status (eg, premature infants or people taking antibiotics), or family history of disease (eg, infants with a primary relative with atopic disease). These benefits may be the result of improved immune status, fewer intestinal infections, or improved intestinal integrity. The live microorganisms mediating these effects may be delivered in different formats, but the role of yogurt as a delivery vehicle for efficacious probiotics is specifically discussed.     

Selenium, selenoproteins and the thyroid gland: interactions in health and disease

The trace element selenium is an essential micronutrient that is required for the biosynthesis of selenocysteine-containing selenoproteins. Most of the known selenoproteins are expressed in the thyroid gland, including some with still unknown functions. Among the well-characterized selenoproteins are the iodothyronine deiodinases, glutathione peroxidases and thioredoxin reductases, enzymes involved in thyroid hormone metabolism, regulation of redox state and protection from oxidative damage. Selenium content in selenium-sensitive tissues such as the liver, kidney or muscle and expression of nonessential selenoproteins, such as the glutathione peroxidases GPx1 and GPx3, is controlled by nutritional supply. The thyroid gland is, however, largely independent from dietary selenium intake and thyroid selenoproteins are preferentially expressed. As a consequence, no explicit effects on thyroid hormone profiles are observed in healthy individuals undergoing selenium supplementation. However, low selenium status correlates with risk of goiter and multiple nodules in European women. Some clinical studies have demonstrated that selenium-deficient patients with autoimmune thyroid disease benefit from selenium supplementation, although the data are conflicting and many parameters must still be defined. The baseline selenium status of an individual could constitute the most important parameter modifying the outcome of selenium supplementation, which might primarily disrupt self-amplifying cycles of the endocrine-immune system interface rectifying the interaction of lymphocytes with thyroid autoantigens. Selenium deficiency is likely to constitute a risk factor for a feedforward derangement of the immune system-thyroid interaction, while selenium supplementation appears to dampen the self-amplifying nature of this derailed interaction.     

Selenium is depleted in Crohn's disease on enteral nutrition

BACKGROUD/AIMS: Selenium is an important trace element and its deficiency has been reported to be associated with cardiomyopathy or gastrointestinal cancer. The aim of this study is to clarify the selenium status in Crohn's disease (CD) on enteral nutrition. METHODS: We measured serum selenium concentrations in 53 patients with CD and compared them with those in 21 healthy controls. Twenty-nine patients were under the treatment by enteral nutrition (EN group), and the remaining 24 patients were free from formulated enteral nutrition (non-EN group). RESULTS: While the serum selenium concentration in the non-EN group was not decreased when compared to controls, the value in the EN group was significantly lower than those in the non-EN group and in controls. Clinical manifestations of selenium deficiency were found in a patient on exclusive enteral nutrition. In the EN group, the serum selenium concentration showed an inverse correlation with the duration and the daily dose of enteral nutrition. In the non-EN group, the serum selenium concentrations were inversely correlated with the Crohn's disease activity index. CONCLUSION: These findings suggest that patients with CD on enteral nutrition are at risk for selenium deficiency and that even patients without enteral nutrition may develop selenium deficiency at the active phase of the disease.     

Women and war

Most of today’s 1.7 million women veterans obtain all or most of their medical care outside the VA health care system, where their veteran status is rarely recognized or acknowledged. Several aspects of women’s military service have been associated with adverse psychologic and physical outcomes, and failure to assess women’s veteran status, their deployment status, and military trauma history could delay identifying or treating such conditions. Yet few clinicians know of women’s military history—or of military service’s impact on women’s subsequent health and well being. Because an individual’s military service may be best understood within the historical context in which it occurred, we provide a focused historical overview of women’s military contributions and their steady integration into the Armed Forces since the War for Independence. We then describe some of the medical and psychiatric conditions associated with military service.     

Relationship of homocysteine with cardiovascular disease and blood pressure

Elevated plasma homocysteine (Hcy) concentration is considered a risk factor for cardiovascular disease and may also be associated with hypertension. Although links have been established between hyperhomocysteinemia and elevated risk for cardiovascular events, the precise role of plasma Hcy in cardiovascular disease is unclear. Plasma Hcy increases with aging and is associated with other health-related behaviors, including smoking and diet patterns. Both epidemiologic and longitudinal clinical investigations have investigated the possible contribution of plasma Hcy to cardiovascular disease, and most report an association of plasma Hcy with the risk for cardiovascular and cerebral events. Some reports describe a significant relationship between Hcy and blood pressure levels, as well as higher Hcy in hypertensives compared to normotensives. Other studies find that the effect of Hcy disappears following adjustment for other risk factors. Because Hcy cosegregates with other risk factors, it has been difficult to identify an independent effect of Hcy on cardiovascular disease or hypertension. Hcy can be modified to some extent by vitamin supplementation. Hcy reduction may have some benefit in reducing cardiovascular risk in some patients, particularly the elderly. Because the question of an independent role of Hcy on risk for cardiovascular disease has not been determined, the assessment and treatment of Hcy should be approached in the context of other modifiable risk factors.     

Soziale Ungleichheit und Diabetes

In Germany, the most important risk factors for type 2 diabetes have been shown to be more prevalent in lower status groups, and accordingly the incidence and prevalence of type 2 diabetes increase with decreasing socioeconomic status. For type 1 diabetes, the association between disease and social status has been scarcely investigated. Nevertheless, there are indications to suggest an inverse relationship between social status and the incidence of type 1 diabetes as well. Social status also has an impact on the health status of diabetic patients; for example, diabetic patients with a low social status suffer more often from complications. Factors at least partly explaining these relationships range from the health behavior and health literacy of patients to access to the health system and on to characteristics of the treatment process. On the basis of these factors, some recommendations for health politicians and practice-based physicians are specified.     

Food intake and serum selenium concentration in elderly people

BACKGROUND/AIMS: It is becoming apparent that the essential trace element selenium plays a critical role in the maintenance of optimal health status. The objective of this study was to identify the food groups that most contributed to selenium intake and its serum levels in elderly people. METHODS: Dietary intake was assessed in 205 institutionalized elderly by means of a 1-year food frequency questionnaire (FFQ). Intake of macronutrients and minerals of the diet were estimated. Selenium was determined in serum and analyzed by graphite-furnace atomic absorption spectrometry. RESULTS: Selenium intake and serum concentration were both within the normal range. The major contributors to selenium intake were cereals and bakery, fish and shellfish, meat and meat products and dairy products. All of them except cereals were also associated to serum selenium. Intake of animal protein, but not the vegetable one, contributed to serum selenium. CONCLUSION: An adequate intake of fish and meat would be of importance to improve selenium status and health principally in elderly people who are at high risk of mineral deficiency.     

Selenium and the thyroid gland: more good news for clinicians

The thyroid is the organ with the highest selenium content per gram of tissue because it expresses specific selenoproteins. Since the discovery of myxoedematous cretinism and thyroid destruction following selenium repletion in iodine‐ and selenium‐deficient children, data on links between thyroid metabolism and selenium have multiplied. Although very minor amounts of selenium appear sufficient for adequate activity of deiodinases, thus limiting the impact of its potential deficiency on synthesis of thyroid hormones, selenium status appears to have an impact on the development of thyroid pathologies. The value of selenium supplementation in autoimmune thyroid disorders has been emphasized. Most authors attribute the effect of supplementation on the immune system to the regulation of the production of reactive oxygen species and their metabolites. In patients with Hashimoto's disease and in pregnant women with anti‐TPO antibodies, selenium supplementation decreases anti‐thyroid antibody levels and improves the ultrasound structure of the thyroid gland. Although clinical applications still need to be defined for Hashimoto's disease, they are very interesting for pregnant women given that supplementation significantly decreases the percentage of postpartum thyroiditis and definitive hypothyroidism. In Graves' disease, selenium supplementation results in euthyroidism being achieved more rapidly and appears to have a beneficial effect on mild inflammatory orbitopathy. A risk of diabetes has been reported following long‐term selenium supplementation, but few data are available on the side effects associated with such supplementation and further studies are required.     

Promoting vitamin A status in low-income countries

Adequate vitamin A status decreases mortality among children under age 5 years by an average of 23%. The benefits of such status for maternal mortality are also now being recognized. Health benefits likely accrue through the effects of retinol upon the maintenance of epithelial integrity and the promotion of immune functions, and in the case of maternal mortality in Nepal, possibly also through the antioxidant activity of provitamin A carotenoids, the form of vitamin A in plants. The clear importance of vitamin A for health has led to the implementation in many countries of programs to improve the vitamin A status of women and children. The main strategies for improving micronutrient status among populations are supplementation, food fortification, and dietary diversification. All of these approaches have been investigated for vitamin A and, at least in some populations, have been shown to be effective in improving vitamin A status and child health or survival. The choice of strategy must be context specific and take into account climate, the agricultural potential of the region, local infrastructure, food beliefs and practices, and the population's socioeconomic status.     

Moderate Alcohol Consumption and Breast Cancer in Women: From Epidemiology to Mechanisms and Interventions

Epidemiologic studies indicate that moderate alcohol consumption increases breast cancer risk in women. Understanding the mechanistic basis of this relationship has important implications for women's health and breast cancer prevention. In this commentary, we focus on some recent epidemiologic studies linking moderate alcohol consumption to breast cancer risk and place the results of those studies within the framework of our current understanding of the temporal and mechanistic basis of human carcinogenesis. This analysis supports the hypothesis that alcohol acts as a weak cumulative breast carcinogen and may also be a tumor promoter. We discuss the implications of these mechanisms for the prevention and treatment of alcohol‐related breast cancer and present some considerations for future studies. Moderate alcohol consumption has been shown to benefit cardiovascular health and recently been associated with healthy aging. Therefore, a better understanding of how moderate alcohol consumption impacts breast cancer risk will allow women to make better informed decisions about the risks and benefits of alcohol consumption in the context of their overall health and at different stages of their life. Such mechanistic information is also important for the development of rational clinical interventions to reduce ethanol‐related breast cancer mortality.     

Long-term selenium exposure.

Metabolic pathways and toxic effects of long-term selenium exposure in animal models and humans have both similarities and significant differences. In animal models the target organ is the liver, in which chronic cirrhosis develops. In man the target organ appears to be the lung, which manifests acute "rose cold," or, as in our patient, a chronic granulomatous hypersensitivity. Our data indicate not only a different target organ than would have been predicted from animal models, but also a difference in the distribution of selenium in human tissues. Long-term use of selenium favors production of dimethylselenide, which is excreted by the lungs and should be considered a pulmonary toxin. The ramifications of these findings may require a change in the monitoring techniques of long-term industrial exposure and mandate a close follow-up of selenium as a health fad.