Archive for category Selenium'

Selenium: Practice Points – Patient Counselling. FAQ

Selenium is a trace element that is essential for health. • Low selenium states have been associated with a variety of conditions, such as cardiovascular disease, cancer, asthma, atopy, male subfertility, rheumatoid arthritis, depression and anxiety and compromised immune function. • Studies have identified selenium deficiency in a significant number of people with the HIV infection and suggested a link between selenium levels and mortality rate. • It is also involved in the detoxification of some heavy metals and xenobiotics. • Selenium-enriched yeast is the safest way to supplement the diet, but other forms are also used. Answers to Patients’ Frequently Asked Questions What will this supplement do for me? Selenium supplementation may reduce the risk of developing certain cancers and heart disease and help to improve a range of conditions such as rheumatoid arthritis, asthma, autoimmune thyroiditis, male subfertility, depression and anxiety. When will it start to work? If a protective effect is to occur with selenium against cancer or cardiovascular disease, the effect appears to develop slowly over several years’ consistent intake. Are there any safety issues? High intakes Read more […]

Selenium: Adverse Reactions. Interactions. Pregnancy Use.

Toxicity Long-term ingestion of excessive levels of selenium (> 1000 µg/day) may produce fatigue, depression, arthritis, hair or fingernail loss, garlicky breath or body odour and gastrointestinal disorders or irritability. Adverse Reactions Nausea, vomiting, nail changes, irritability and fatigue have been reported. The organic form of selenium found in high-selenium yeast is often preferred because it is less toxic. The National Health and Medical Research Council of Australia states that selenium intake should not exceed 600 µg/day. Significant Interactions CISPLATIN Selenium may reduce associated nephrotoxicity, myeloid suppression and weight loss, according to in vitro and in vivo tests — beneficial interaction. HEAVY METALS (E.G. MERCURY, LEAD, ARSENIC, SILVER AND CADMIUM) Selenium reduces toxicity of heavy metals such as mercury, lead, arsenic, silver and cadmium by forming inert complexes — beneficial interaction. Contraindications and Precautions Sensitivity to selenium. Pregnancy Use Considered safe in usual dietary doses; safety at higher levels is unknown.

Selenium: Clinical Use. Dosage

DEFICIENCY STATES: PREVENTION AND TREATMENT Traditionally, selenium supplementation has been used to treat deficiency or prevent deficiency in conditions such as malabsorption syndromes. CANCER: PREVENTION AND POSSIBLE ADJUNCT TO TREATMENT Selenium supplementation is used to reduce total cancer incidence and mortality. Chemoprevention Collectively, geographical studies, epidemiological data, laboratory bioassays, studies in over 12 different animal models and human intervention trials generally support a protective role for selenium against the development of cancer. Populations who live in low selenium environments and have low selenium intakes tend to have higher cancer mortality rates. However, the results from epidemiological studies have been less consistent and show the effect is strongest in males. Total cancer incidence and mortality The Nutritional Prevention of Cancer Trial was a large multicentre, double-blind, randomised, placebo-controlled trial conducted with 1312 patients with a history of basal cell or squamous cell carcinomas of the skin, which investigated the effects of 200 µg selenium daily (as 500 mg brewer’s yeast) as a cancer protective agent. Selenium supplementation in this population Read more […]

Selenium: Actions

ANTIOXIDANT Selenium is an integral part of thioredoxin reductase and the glutathione peroxidases and therefore is intimately involved in the body’s antioxidant systems. These enzymes are involved in controlling tissue levels of free radical molecules and maintain cell-mediated immunity. CHEMOPREVENTATIVE Chemoprotective effects of selenium have been indicated by an epidemiological relationship, RCTs and by experimental studies of selenium and known carcinogens in the development of specific cell lines. Overall, it appears that selenium works by inhibiting important early steps in carcinogenesis. Several mechanisms have been postulated to explain the chemopreventative effect of selenium, including protection against oxidative damage, alterations to immune and metabolic systems, alterations to carcinogen metabolism, production of cytotoxic selenium metabolites, inhibition of protein synthesis, stabilisation of genetic material and stimulation of apoptosis. One study demonstrated that combining vitamin E succinate and methylselenic acid produces a synergistic effect on cell growth suppression, primarily mediated by augmenting apoptosis. In humans, the chemopreventative effect is strongest for individuals with Read more […]

Selenium: Background. Deficiency Signs and Symptoms

Background and Relevant Pharmacokinetics Selenium is an essential trace element that enters the food chain through incorporation into plants from the soil. Selenium is mainly present in the form of selenite in acid soils, which is poorly assimilated by crops, whereas for alkaline soils, it is in the form of selenate, which is more soluble and assimilated by crops. When taken in supplement form, animal and human trials demonstrate that bioavailability of organic forms of selenium (Se-methionine and Se-cysteine) is higher than that obtained for inorganic forms (selenite and selenate). The variation in selenium content of adult humans living in different parts of the world is testimony to the influence of the natural environment on the selenium content of soils, crops and human tissues. According to a WHO report, adults in New Zealand have approximately 3 mg selenium in their bodies compared with 14 mg in some Americans (WHO 2002). Selenium is readily absorbed, especially in the duodenum but also in the caecum and colon. Vitamins A, E, and C can modulate selenium absorption, and there is a complex relationship between selenium and vitamin E that has not been entirely elucidated for humans. Selenium enters the body Read more […]