Selenium requirements/recommendations

XI. Selenium Requirements and Recommended Dietary Intakes XII. Summary and Conclusions References... 

Selenium is an essential trace element. As an important constituent of glutathion peroxydase and thioredoxin reductase, it must be considered an extremely valuable antioxidant. The daily requirement of 75 gg is very often not achieved, especially by tumour patients, so that substitution is necessary. In addition, malignant diseases generally show a reduction in the serum value of selenium. Moreover, it intensifies the cytotoxicity of T lymphocytes and natural killer cells, leading to a corresponding effect on tumour cells. This effect can be enhanced through the stimulation of IFNy. The application of cytostatics thus becomes more favourable in every respect. A daily dose of 200 qg (-1,000 qg) selenium is recommended. Even in acute infections, i.v. administration of selenite has proved extremely useful, (s. p. 304)... 

Human Selenium Requirements and Recommended Dietary Intakes All intake recommendations depend on the definitions used to derive them and the available scientific information. Accordingly, they are not to be considered final as they are periodically re-evaluated and revised. 

These are classified as those with a requirement below one pg (microgram) per day. Elements in this class include boron, chromium, fluoride, iodine, molybdenum, nickel, selenium, cobalt and manganese. Cobalt is part of vitamin (see above). However, there appear to be no recommended dietary intakes for any of these except molybdenum. 

Supplementation with the antioxidant vitamins ascorbic acid (250 mg) and mixed natural tocopherols (50 IU on alternate days) may be beneficial. Higher doses may vitiate the impact of lipid lowering therapy. Other naturally occurring antioxidants such as resveratrol, 3-catechin, selenium, and various carotenoids found in a variety of fruits and vegetables may provide additional antioxidant defense. Homocysteine, which initiates proatherogenic changes in endothelium, can be reduced in many patients by restriction of total protein intake to the amount required for amino acid replacement. Daily supplementation with up to 2 mg of folic acid plus other B vitamins is also recommended. 

The recommended procedure is readily adaptable to any laboratory with atomic absorption capabilities. However, considerable experience with the procedure is required before valid results can be obtained. It is recommended that a sample of known selenium concentration be analyzed until the necessary skills are developed, before attempting to analyze samples of unknown selenium concentration. 

The required daily selenium intake of women was found to be 20 pg. In case of a lower selenium intake, the women s selenium balances proved negative, and their f Tj-levels in blood serum were too low (Anke etal. 2003a). Men require 25 pg Se per day, while both genders require 0.4 pg Se kg body weight and a dietary selenium concentration of 70 pgkg consumed DM. The recommended daily selenium intake is 30-50 pg, which is far from the toxic limit of 400 mg per day (Drobner 1997, Anke etal. 2002, 2003a). 

Due to the effect of sulfur on copper and selenium metabolism, and reports of polio-encephalomalacia in beef cattle at dietary sulfur dosages > 5 g kg the National Research Council recommends a maximal tolerable level of sulfur of 4 g kg feed DM, vhereas 2 g kg feed DM is regarded as the sulfur requirement for cattle (National Research Council 2001). 

Previous studies investigating dietary intake of micronutrients have reported that the dupficate portion technique offers the most accurate estimation. A study comparing dietary assessment methods to measure selenium intake concluded that diet record assessment was not adequate for predicting selenium intakes of individuals, and that duplicate diet analysis remains the recommended measure for research purposes (Duffield and Thomson, 1999). Furthermore, Koutras et al. (1970) state that if iodine intake is to be measured, the best method is the dupficate portion technique. However, the dupficate portion technique is labor intensive and requires a significant amount of subject commitment therefore, its use is usually restricted to small groups and data are usually collected over a short period of time. 

Recommended dietary allowances for a male adult (daily intake, in foods and food supplements) of some nutrients, usually the amounts estimated as needed to prevent overt manifestation of deficiency disease in most persons. For the substances listed in smaller amounts the optimum intake, leading to the best of health, may be somewhat greater. Not shown, but probably or possibly required, are the essential fatty acids, />aminobenzoic acid, choline, vitamin D, vitamin K, chromium, manganese, cobalt, nickel, zinc, selenium, molybdenum, vanadium, tin, and silicon. 

Selenium (Se) is essential to most organisms including human beings. It is required in very small quantities. The recommended maximum daUy intake is 450 microgram. Se becomes toxic when present in excess. The average human adult contains about 15 milligram of selenium. [milli=one thousandth micro=one millionth]. 

LRNI, Lower Reference Nutrient Intake RNI, Reference Nutrient Intake Al, Adequate Intake RDA, Recommended Dietary Allowance. Sources UK Department of Health (1991) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom, Report on Health and Social Subjects No. 41. London HMSO. USA Food and Nutrition Board, Institute of Medicine (2000) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids. Washington, DC National Academy Press. WHO/FAO WHO/FAO (2002) Human Vitamin and Mineral Requirements. Report of a Joint FAO/WHO Expert Consultation, Bangkok, Thailand. Rome WHO/ FAO. 

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