The daily dietary selenium intake of West German adults

The selenium content of food consumed in the Federal Republic of Germany (FRG) was determined for the estimation of the dietary selenium intake of West German adults. The daily dietary selenium intake of men is 47 micrograms (micrograms) and that of women 38 micrograms, corresponding to 0.67 microgram/kg body weight per day for both men and women. Animal protein is the main source of dietary selenium, accounting for 65.5% of the total selenium intake. Pork contributes 25.1% to the total Se intake, reflecting the current consumption and the selenium supplementation of feedstock rather than the availability of selenium from natural dietary sources. The selenium intake of adults in West Germany is only slightly higher than in New Zealand, Finland, and Italy, nearly equal to that in Belgium and France, and distinctly lower than in Great Britain, the USA, Canada, and Japan.     

Effect of dietary hempseed intake on cardiac ischemia-reperfusion injury

Polyunsaturated fatty acids (PUFAs) have significant, cardioprotective effects against ischemia. Hempseed contains a high proportion of the PUFAs linoleic acid (LA) and alpha-linolenic acid (ALA), which may have opposing effects on postischemic heart performance. There are no reported data concerning the cardiovascular effects of dietary hempseed intake. A group of 40 male Sprague-Dawley rats were distributed evenly into four groups that were fed for 12 wk a normal rat chow supplemented with hempseed (5% and 10%), palm oil (1%), or a 10% partially delipidated hempseed that served as a control. Plasma ALA and gamma-linolenic acid levels were significantly elevated in the rats that were fed a 5% or 10% hempseed-supplemented diet, but in heart tissue only ALA levels were significantly elevated in the rats fed these diets compared with control. After the dietary interventions were completed, postischemic heart performance was evaluated by measuring developed tension, resting tension, the rates of tension development and relaxation, and the number of extrasystoles. Hearts from rats fed a hempseed-supplemented diet exhibited significantly better postischemic recovery of maximal contractile function and enhanced rates of tension development and relaxation during reperfusion than hearts from the other groups. These hearts, however, were not protected from the occurrence of extrasystoles, nor were the increases in resting tension altered during ischemia or reperfusion as a function of any dietary intervention. Our data demonstrate that dietary hempseed can provide significant cardioprotective effects during postischemic reperfusion. This appears to be due to its highly enriched PUFA content.     

Effect of dietary selenium restriction on selected parameters of selenium status in men with high life-long intake

The influence of selenium (Se) restriction on disposition in plasma and urine fractions of infused (74)Se (selenite) was studied when adult males (Enshi City, Hubei Province, PRC) whose habitual daily Se intake is approximately 480 microg per day were transferred to Lichuan County, where the daily intake is approximately 30 microg. The subjects received an infusion (106 microg Se) on the day before consuming foods low in Se and a second infusion (113 microg Se) 63 days later. Blood and 24-hour urine samples were collected each day for 7 days after the first infusion and on days 22, 43, and 62 following the first infusion. Urine and blood were also collected daily for the next 7 days after the second infusion. Plasma total Se concentration increased for 7 days after each of the two infusions and urine Se decreased exponentially following both the first and second infusions. The excretion of trimethylselenonium followed the same pattern as the total urinary Se. Surprisingly, there was not a significant difference in selenite retention between the two infusion periods, and the data indicated that, regardless of the chemical form of Se present in various organs, its catabolism leading to excretion in urine followed the same pathway as that of selenite. Labeled Se was incorporated predominantly in the plasma selenoprotein P fraction and the half-life of Se in this fraction was determined to be 1.9 to 2.9 days. Thus, a longer depletion period is required in these subjects to obtain more significant changes.     

Determination of selenium in serum by FI-HG-AAS and calculation of dietary intake

A method was developed for the determination of selenium concentration in serum by flow injection-hydride generation-atomic absorption spectrometry (FI-HG-AAS) following microwave digestion of serum samples and reduction of selenate to selenite. The detection limit of the method was 0.3 μg Se/L and the characteristic concentration, corresponding to the 0.0044 absorbance signal, was 0.12 μg Se/L. The results from the analysis of two Seronorm standard reference materials showed good agreement with the certified values. The method was then used to analyze selenium in sera of Austrian and Slovenian people for the calculation of dietary intakes. The selenium concentrations in sera of mothers at delivery, their neonates, and the male and female adults were 71 ± 14, 42 ± 6, 75 ± 21, and 65 ± 16 μg/L for the Austrians and 62 ± 15, 34 ± 7, 70 ± 12, and 66 ± 15 μg/L for the Slovenians. The dietary intakes of selenium of the mothers and the male and the female adults were calculated as 52, 37, and 46 μg/d for the Austrians and 45, 38, and 32 μg/d for the Slovenians.     

Plants,selenium and human health

Selenium is an essential nutrient for animals, microorganisms and some other eukaryotes. Although selenium has not been demonstrated to be essential in vascular plants, the ability of some plants to accumulate and transform selenium into bioactive compounds has important implications for human nutrition and health, and for the environment. Selenium-accumulating plants provide unique tools to help us understand selenium metabolism. They are also a source of genetic material that can be used to alter selenium metabolism and tolerance to help develop food crops that have enhanced levels of anticarcinogenic selenium compounds, as well as plants that are ideally suited for the phytoremediation of selenium-contaminated soils.     

N-6 fatty acids and cardiovascular health: dietary intake recommendations

Omega-6 polyunsaturated fatty acids (n-6 PUFA) are well known for their critical role in many physiological functions and reduce risks of cardiovascular disease (CVD). However, some argue that excessive consumption of n-6 PUFA may lead to adverse effects on health and therefore recommend reducing dietary n-6 PUFA intake or fixing an upper limit. Epidemiological studies show that n-6 PUFA dietary intake significantly lowers blood LDL-cholesterol levels. In addition, n-6 PUFA intake lower several cardiovascular risk factors such as blood pressure, inflammatory markers, haemostatic parameters and obesity. Data from prospective cohort and interventional studies converge towards a specific protective role of dietary n-6 PUFA intake, in particular linoleic acid, against CVD. In regards to studies examined in this narrative review, recommendation for n-6 PUFA intake above 5%, and ideally about 10% of total energy appears justified for the prevention of ischemic heart disease.     

Components of plastic: experimental studies in animals and relevance for human health

Components used in plastics, such as phthalates, bisphenol A (BPA), polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A (TBBPA), are detected in humans. In addition to their utility in plastics, an inadvertent characteristic of these chemicals is the ability to alter the endocrine system. Phthalates function as anti-androgens while the main action attributed to BPA is oestrogen-like activity. PBDE and TBBPA have been shown to disrupt thyroid hormone homeostasis while PBDEs also exhibit anti-androgen action. Experimental investigations in animals indicate a wide variety of effects associated with exposure to these compounds, causing concern regarding potential risk to human health. For example, the spectrum of effects following perinatal exposure of male rats to phthalates has remarkable similarities to the testicular dysgenesis syndrome in humans. Concentrations of BPA in the foetal mouse within the range of unconjugated BPA levels observed in human foetal blood have produced effects in animal experiments. Finally, thyroid hormones are essential for normal neurological development and reproductive function. Human body burdens of these chemicals are detected with high prevalence, and concentrations in young children, a group particularly sensitive to exogenous insults, are typically higher, indicating the need to decrease exposure to these compounds.     

Investigation of lipid peroxide and glutathione redox status of chicken concerning on high dietary selenium intake

This study was designed to investigate the effects of excess (24.5 mg Se/kg feed) inorganic and organic dietary selenium supplementation on 3-week-old broilers. The experiments lasted 4 days. Intensity of lipid peroxidation processes (malondialdehyde, MDA) and the amount (reduced glutathione, GSH) and activity (glutathione peroxidase activity, GSHPx) of gluathione redox system were measured in blood plasma, red blood cell hemolysate and liver. Voluntary feed intake in the selenium-treated groups reduced remarkably. Elevated GSH concentration and GSHPx activity were measured in plasma and liver of both selenium-treated groups compared to the untreated control and the 'pair-fed' controls. The lipid peroxidation processes in the liver showed higher intensity than the control due to both selenium treatment. The applied dose of selenite and selenomethionine does not inhibit, but even improves the activity of glutathione redox system in the liver during the early period of selenium exposure.     

Effects of dietary selenium on glutathione peroxidase and thioredoxin reductase activity and recovery from cardiac ischemia-reperfusion.

Glutathione peroxidase and thioredoxin reductase are selenocysteine-dependent enzymes that protect against oxidative injury. This study examined the effects of dietary selenium on the activity of these two enzymes in rats, and investigated the ability of selenium to modulate myocardial function post ischemia-reperfusion. Male wistar rats were fed diets containing 0, 50, 240 and 1000 microg/kg sodium selenite for 5 weeks. Langendorff perfused hearts isolated from these rats were subjected to 22.5 min global ischemia and 45 min reperfusion, with functional recovery assessed. Liver samples were collected at the time of sacrifice, and heart and liver tissues assayed for thioredoxin reductase and glutathione peroxidase activity. Selenium deficiency reduced the activity of both glutathione peroxidase and thioredoxin reductase systemically. Hearts from selenium deficient animals were more susceptible to ischemia-reperfusion injury when compared to normal controls (38% recovery of rate pressure product (RPP) vs. 47% recovery of RPP). Selenium supplementation increased the endogenous activity of thioredoxin reductase and glutathione peroxidase and resulted in improved recovery of cardiac function post ischemia reperfusion (57% recovery of RPP). Endogenous activity of glutathione peroxidase and thioredoxin reductase is dependent on an adequate supply of the micronutrient selenium. Reduced activity of these antioxidant enzymes is associated with significant reductions in myocardial function post ischemia-reperfusion.     

Impact of the training program on lipid profile and cardiac health

The aim of this study was to investigate the effects of training programs on serum lipid profile and myocardial oxidative stress. Male Wistar rats (2 mo-old) were divided into three groups (n = 8): sedentary (S), loadless trained (T) and trained-overload 2% body weight (TL). T and TL were trained through swimming for 9 weeks. T and TL rats had increased myocardial lipoperoxide (TBA) and lipid hydroperoxide (HP), whereas HP was higher in TL than in T animals. Superoxide dismutase (SOD) activities were lowest in TL. Myocardial glutathione peroxidase (GSH-Px) was lower in TL than in T and S rats. TL decreased HDL-cholesterol and increased LDL-cholesterol. The serum lactate dehydrogenase and TBA were increased, while SOD and GSH-Px activities were decreased in TL rats. Loadless training was able to improve HDL-cholesterol and to reduce LDL-cholesterol. In conclusion, the loadless training program induced beneficial effects on lipid profile, while overload training induced dyslipidemic profile that was associated with serum oxidative stress. The overload training program was deleterious relative to loadless training program, increasing myocardial oxidative stress.     

Biogeochemistry of selenium and its impact on food chain quality and human health

In areas where soils are low in bioavailable selenium (Se), potential Se deficiencies cause health risks for humans. Though higher plants have been considered not to require this element, the experience with low-Se soils in Finland has provided evidence that the supplementation of commercial fertilizers with sodium selenate affects positively not only the nutritive value of the whole food chain from soil to plants, animals and humans but also the quantity of plant yields. The level of Se addition has been optimal, and no abnormally high concentrations in plants or in foods of animal origin have been observed. Se levels in serum and human milk indicate that the average daily intake has been within limits considered to be safe and adequate. In fact, plants act as effective buffers, because their growth is reduced at high Se levels. They also tend to synthesize volatile compounds in order to reduce excess Se. On the other hand, when added at low concentrations, Se exerts a beneficial effect on plant growth via several mechanisms. As in humans and animals, Se strengthens the capacity of plants to counteract oxidative stress caused by oxygen radicals produced by internal metabolic or external factors. At proper levels it also delays some of the effects of senescence and may improve the utilization of short-wavelength light by plants. High additions are toxic and may trigger pro-oxidative reactions. Thus, the present supplementation of fertilizers with Se can be considered a very effective and readily controlled way to increase the average daily Se intake nationwide.     

Biogeochemistry of selenium and its impact on food chain quality and human health

In areas where soils are low in bioavailable selenium (Se), potential Se deficiencies cause health risks for humans. Though higher plants have been considered not to require this element, the experience with low-Se soils in Finland has provided evidence that the supplementation of commercial fertilizers with sodium selenate affects positively not only the nutritive value of the whole food chain from soil to plants, animals and humans but also the quantity of plant yields. The level of Se addition has been optimal, and no abnormally high concentrations in plants or in foods of animal origin have been observed. Se levels in serum and human milk indicate that the average daily intake has been within limits considered to be safe and adequate. In fact, plants act as effective buffers, because their growth is reduced at high Se levels. They also tend to synthesize volatile compounds in order to reduce excess Se. On the other hand, when added at low concentrations, Se exerts a beneficial effect on plant growth via several mechanisms. As in humans and animals, Se strengthens the capacity of plants to counteract oxidative stress caused by oxygen radicals produced by internal metabolic or external factors. At proper levels it also delays some of the effects of senescence and may improve the utilization of short-wavelength light by plants. High additions are toxic and may trigger pro-oxidative reactions. Thus, the present supplementation of fertilizers with Se can be considered a very effective and readily controlled way to increase the average daily Se intake nationwide.     

Relationship of dietary intake of fish and non-fish selenium to serum lipids in Japanese rural coastal community.

Several studies have suggested that dietary selenium deficiency may be associated with an increased risk of coronary heart disease (CHD). In the present study, 55 men and 71 women were selected from participants in a health examination in a rural coastal community in Japan. The mean dietary selenium intake calculated from the simple food frequency questionnaire (SFFQ) was 127.5 micrograms/day. Fish was the major source of dietary selenium and it contributed to 68.7% of the daily total. HDL cholesterol was higher in the middle selenium intake group and in the high selenium intake group than in the low selenium intake group in all subjects and for males, and a significant difference was found between the middle selenium intake group and the low selenium intake group. The atherogenic index was significantly higher in the low selenium intake group than in the middle selenium intake group and in the high selenium intake group in males. GPx activity, total cholesterol and triacylglycerols did not show any significant differences among the three different selenium intake groups. Dietary intake of non-fish Se had a positive correlation with HDL cholesterol, and an inverse correlation with the atherogenic index in all subjects and for females. On the other hand, dietary intake of fish-Se had no relationship with any serum lipids. Non-fish Se is an important factor in selenium status for the prevention of CHD.     

Influence of dietary intake and physical activity on annual rhythm of human blood cholesterol concentrations

Seasonal variation in the plasma total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) have been repeatedly reported, with contradictory results regarding the pattern of seasonal variation of these parameters. Furthermore, it is still not well established whether the variation is due to changes in the nutrition or changes in physical activity depending on the season. The aim of this study was therefore to determine plasma TC and HDL-C in different groups of healthy participants: 19 vegetarians with a constant diet independent of the season, 14 athletes with almost constant physical activity over the year, and 114 controls in the age groups 20-26 years (mean age 24 + 1.5 years) and 40-48 years (mean age 44.3 + 2.1 years). Over 2 years, blood samples were collected every 2-3 months and were analyzed for plasma TC and HDL-C. At all visits, body mass index (BMI) and waist-to-hip ratio (WHR) were calculated, and nutrition and physical activity profiles were obtained. The seasonal model was calculated using object-oriented software for the analysis of longitudinal data in S (OSWALD); multiple regression analysis was used to determine the influence of age, gender, diet, and physical activity on seasonal changes of the lipid parameters. In all groups, we found an annual rhythm of the plasma TC and HDL-C concentrations, which can be mathematically described by a sine curve with a maximum in winter and a minimum in summer. This rhythm was independent of the age, gender, BMI, diet, or physical activity. The observed seasonal differences between the maximum and the minimum were about 5%-10% for TC and about 5%-8% for HDL-C concentration. These differences were greater than the determined circadian (TC 3.5%, HDL-C 4%) and day-to-day changes for TC and HDL-C (coefficient of variation <5% for both). In conclusion, annual rhythm of TC and HDL-C is not primarily induced by seasonal differences in dietary intake or physical activity. Therefore, the annual rhythm in cholesterol levels is most likely determined by endogenous factors or factors directly related to seasonal changes in the environment.     

Cadmium-induced alterations in the antioxidant defense system of the rat eye in relation to dietary selenium intake

Cytosolic activity of glutathione peroxidase (GSH-Px), selenium-independent GSH-Px, and catalase, thiobarbituric acid reactive substances (TBARS), and glutathione and selenium (Se) concentration were measured in ocular tissues of rats maintained on a low (0.05 ppm) or adequate (0.10 ppm) Se diet and treated with 0 or 25 ppm cadmium (Cd) in their drinking water for fourteen weeks. Feeding rats a low Se diet resulted in a significant decrease in GSH-Px activity when compared to rats maintained on adequate dietary Se, irrespective of Cd treatment. Se-independent GSH-Px activity of rats maintained at 0.05 ppm Se decreased 27% when compared to Se-adequate controls, whereas activity increased 38% in the Cd-treated low-Se group. When comparisons were made between ocular TBARS in rats maintained at either level of dietary Se and treated with 0 or 25 ppm Cd, a trend toward decreased amounts of TBARS in Cd-treated groups was observed. A significant decrease in ocular Se concentration occurred in rats fed 0.05 ppm Se when compared to the Se-adequate group. Administering Cd to the low-Se group increased ocular Se levels 100%. A negative correlation between ocular Se concentration and TBARS was observed, suggesting a possible alternate role for Se as an antioxidant in the eye.