Pregnancy support- Vitamin Treatment

Selenium - updated: 03 November 2008

The argument for increasing selenium intake

Proc Nutr Soc. 2002 May;61(2):203-15

Rayman MP, Rayman MP.

The essential trace mineral, Se, is of fundamental importance to human health. As a constituent of selenoproteins it plays both structural and enzymic roles, in the latter context being best known as an antioxidant and catalyst for the production of active thyroid hormone. While Se-deficiency diseases have been recognised for some time, evidence is mounting that less-overt deficiency can also cause adverse health effects and furthermore, that supra-nutritional levels of Se may give additional protection from disease. In the context of these effects, low or diminishing Se status in some parts of the world, notably in some European countries such as the UK, is giving cause for concern. While deficiency has an adverse effect on immunocompetence, Se supplementation appears to enhance the immune response. Se appears to be a key nutrient in counteracting certain viral infections; thus, in a Se-deficient host the benign coxsackie virus becomes virulent, causing heart damage, the influenza virus causes more serious lung pathology and HIV infection progresses more rapidly to AIDS. Long recognised as essential for successful animal reproduction, Se is required for human sperm maturation and sperm motility and may reduce the risk of miscarriage. Deficiency has been linked to adverse mood states. Findings have been equivocal in linking Se to cardiovascular disease risk, although other conditions involving oxidative stress and inflammation have shown some association with Se status. There is growing evidence that higher Se intakes are associated with reduced cancer risk. While persuasive evidence already exists to suggest that additional Se would be beneficial in some health conditions, results from intervention trials underway or planned have the potential to reinforce or refute the argument for increasing Se intake.

Publication Types:

• Review

The selenium status of women with a history of recurrent miscarriage

BJOG. 2001 Oct;108(10):1094-7

Al-Kunani AS, Knight R, Haswell SJ, Thompson JW, Lindow SW.

OBJECTIVE: To assess the relationship between selenium levels in human blood and hair, and the risk of recurrent miscarriages. DESIGN: Case-control study. PARTICIPANTS: Two groups of non-pregnant women: 18 women with one or more successful pregnancies and no history of miscarriage (control group); 26 women with a history of recurrent miscarriage (> or = 3) with no subsequent successful pregnancies (study group). METHODS: Samples of venous blood and scalp hair were collected and the selenium content analysed by inductively coupled plasma mass spectrometry. RESULTS: No significance difference was found between the level of selenium in the blood samples of the women in each group. There was a significant reduction in the mean hair selenium level in the recurrent miscarriage group compared with the control group (0.14 microg/g vs 0.34 microg/g). Further analysis of the recurrent miscarriage group revealed no relationship between levels of serum or hair selenium with parity. There was a significantly greater proportion of women in the control group who ate cereals, vitamin supplements, and liver or kidney. CONCLUSION: There was evidence of selenium deficiency in women with recurrent miscarriages compared with a control group of women with a good reproductive performance. This difference was seen in hair samples but not serum samples and therefore may not represent a simple nutritional deficiency. The importance of selenium deficiency in miscarriage has still not been determined.

Publication Types:

• CASE control Study

Effects of dietary selenium on sperm motility in healthy men

J Androl. 2001 Sep-Oct;22(5):764-72

Hawkes WC, Turek PJ.

A deficiency of dietary selenium leads to immotile, deformed sperm and infertility in rats, whereas supplementation of the diet with selenium compounds has been associated with both beneficial and deleterious effects on sperm function, depending on the chemical form of selenium. We conducted a randomized, controlled, and blinded intervention study on the effects of selenium in food on semen quality. Eleven healthy men were fed a controlled diet of foods naturally high or low in selenium for 120 days while confined in a metabolic research unit. Dietary selenium was 47 microg/d for the first 21 days, then either 13 microg/d or 297 microg/d for 99 days, resulting in significant changes in selenium concentrations in blood and semen. Seminal plasma selenium concentration increased 50% with high selenium and decreased 40% with low selenium. The fraction of motile sperm in the high-selenium group decreased by 32% by week 13 and ended 18% lower than baseline. Selenium concentrations changed in seminal plasma but not in sperm, and serum androgen concentrations were unchanged in both groups, indicating this effect was neither androgen dependent nor caused by a change in the selenium supply to the testes. Serum triiodothyronine decreased and thyroid-stimulating hormone increased in the high-selenium group, suggesting that altered thyroid hormone metabolism may have affected sperm motility. Although this decrease in sperm motility does not necessarily predict decreased fertility, the increasing frequency of selenium supplementation in the healthy population suggests the need for larger studies to more fully assess this potential side effect.

Publication Types:

• Randomized Controlled Trial

Selenium in mammalian spermiogenesis

Biol Chem. 2007 Oct;388(10):987-95

Flohé L.

The role of selenium in male fertility is reviewed with special emphasis on selenoprotein P and phospholipid hydroperoxide glutathione peroxidase (GPx4) in spermiogenesis. Inverse genetics reveal that selenoprotein P is required for selenium supply to the testis. GPx4 is abundantly synthesized in spermatids. As a moonlighting protein it is transformed in the later stages of spermiogenesis from an active selenoperoxidase into a structural protein that becomes a constituent of the mitochondrial sheath of spermatozoa. The transformation is paralleled by loss of glutathione. Mechanistically, the process is an alternate substrate inactivation of GPx4 resulting from reactions of its selenenic form with thiols of GPx4 itself and other proteins. Circumstantial evidence and ongoing experimental genetics indicate that the mitochondrially expressed form of the GPx4 gene is the most relevant one in spermiogenesis, with the nuclear form being dispensable for fertility and the role of cytosolic GPx4 remaining unclear. Clinical data reveal a strong association of low sperm GPx4 with infertility. Thus, impaired GPx4 biosynthesis, due to selenium deficiency or to genetic defects in gpx4 itself or in proteins involved in Se distribution and selenoprotein biosynthesis, causes male infertility, but can also be an epiphenomenon due to any perturbation of testicular function.

Publication Types:

• Review

Biofortification of UK food crops with selenium

Proc Nutr Soc. 2006 May;65(2):169-81.

Broadley MR, White PJ, Bryson RJ, Meacham MC, Bowen HC, Johnson SE, Hawkesford MJ, McGrath SP, Zhao FJ, Breward N, Harriman M, Tucker M.

Se is an essential element for animals. In man low dietary Se intakes are associated with health disorders including oxidative stress-related conditions, reduced fertility and immune functions and an increased risk of cancers. Although the reference nutrient intakes for adult females and males in the UK are 60 and 75 microg Se/d respectively, dietary Se intakes in the UK have declined from >60 microg Se/d in the 1970s to 35 microg Se/d in the 1990s, with a concomitant decline in human Se status. This decline in Se intake and status has been attributed primarily to the replacement of milling wheat having high levels of grain Se and grown on high-Se soils in North America with UK-sourced wheat having low levels of grain Se and grown on low-Se soils. An immediate solution to low dietary Se intake and status is to enrich UK-grown food crops using Se fertilisers (agronomic biofortification). Such a strategy has been adopted with success in Finland. It may also be possible to enrich food crops in the longer term by selecting or breeding crop varieties with enhanced Se-accumulation characteristics (genetic biofortification). The present paper will review the potential for biofortification of UK food crops with Se.

Publication Types:

• Review

Publication Types:

• Review