Selenium intakes

Johansen, P., Pars, T. and Bjerregaard, P. (2000). Lead, cadmium, mercury and selenium intake by Greenlanders from local marine food, Sci. Total Environ., 245, 1-3, 187-194. 

Excess selenium intake can occur in both animals and humans living in areas with elevated selenium in the soil. Most grass and grains do not accumulate selenium, but when an animal consumes plants that do accumulate selenium (some up to 10,000 mg/kg) they can develop a condition called the blind staggers . Symptoms include depressed appetite, impaired vision, and staggering in circles and can ultimately lead to paralysis and death. Humans are susceptible to similar effects as well as additional neurological effects. Selenium deficiency results in heart disorders, skeletal muscle effects, and liver damage. 

Two types of epidemiological relationships have been found in two different populations. Both relationships were inverse to selenium bioavailability and paralleled the results from animal studies. In one type of study, selenium bioavailability has been inversely related to human cancer mortality in American cities and states (14-15). Schrauzer et.al. correlated the age-adjusted mortality from cancer at 17 major body sites with the apparent dietary selenium intakes estimated from food consumption data in 27 countries (16). Significant inverse correlations were observed for cancers of the large intestine, rectum, prostate, breast, ovary, lung, and leukemia. In addition, weaker inverse associations were found for cancers of the pancreas, skin, and bladder. 

Thomson, C.D., Burton, C.E., and Robinson, M.F. 1978. On supplementing the selenium intake of New Zealanders. I. Short experiments with large doses of selenite or selenomethionine. Br. 

Yang, G. and Zhou, R. 1994. Further observations on the human maximum safe dietary selenium intake in a seleniferous region of China. J. Trace Elem. Electrol. Health Dis. 8, 159-165. 

The estimated mean and 5th percentile intake of Se in the 1998-2003 period were 43 and 23 pg day-1, respectively, and the Se intake have shown only small changes with a decreasing tendency over that past 20 years (Table 9.4). Selenium intake is in good agreement with the recommended level of 40 and 50 pg day-1 for women and men, respectively. Few individuals have an intake below the lower intake of 20 pg day-1 [13]. The recommendations do not, however, take into consideration the possible cancer-preventive effect of Se at higher doses [14]. 

F. Li, E. Rossipal, K. J. Irgolic, Determination of selenium in human milk by hydride cold-trapping atomic absorption spectrometry and calculation of daily selenium intake, J. Agric. Food Chem., 47 (1999), 3265-3268. 

T. W. Westermarck, Consequences from low selenium intake for man, in P. Bratter, P. Schramel (eds), Trace Element Analytical Chemistry in Medicine and Biology, Vol. 3, Walter de Gruyter, Berlin, 1984, pp. 49-70. 

Kazuko, H., Katsuhiko, N., and Hiroshi, D. 1996. Selenium intake based on representative diets in Japan, 1957 to 19S9. Nutrition Research, 16(9) 1471-7. 

Yin, X.B. and Wang, Q.X. In press. Selenium toxicity and daily selenium intake in Enshi, China. Selenium Deficiency, Toxicity, and Biofortification for Human health. USTC Press. 

Selenium has been recognized as an essential trace element in the diets of man and animals for many years (1) Another strong indication of its essentiality is the fact that it is an essential component of the enzyme glutathione peroxidase (2) Recently, scientists from the People s Republic of China demonstrated that Keshan disease (a cardiomyopathy in children) was correlated with low dietary selenium Intakes ( ) and could largely be prevented with supplementation Similarly, poor selenium nutrition in patients receiving total parenteral nutrition has been linked to muscular discomfort (4) and cardiomyopathy ( ) ... 

There are two interesting paradoxes concerning selenium. The first is that excess selenium is toxic however, at lower levels it is a protective agent against the toxicity of cadmium, methylmercury, arsenic, copper, and thalium. The second paradox involves carcinogenicity. The US National Cancer Institute found selenium monosulfide (administered orally) to be carcinogenic in rodents however, many epidemiological studies associate selenium intake with lower cancer rates in humans. Moreover, in... 

The reference interval for selenium in whole blood, plasma or serum, hair, and nails should be established locally, since these indices are affected by dietary selenium intake. Plasma selenium adult values lie in the interval 63 to 160pg/L (0.8 to 2.0pmol/L). Values of less than 40 pg Se per L (0.5pmoI/L) indicate probable selenium depletion. 

Selenium toxicity may occur when patients receive doses exceeding 200 mcg/kg per day for prolonged periods. Selenium status may be assessed by measuring plasma selenium concentrations, which will reflect recent selenium intake. Decreased concentrations may indicate selenium deficiency, but reductions also have been observed in patients with malignancies, liver failure, and pregnancy. Assays that... 

Various estimates of the selenium intake for Americans have ranged from 0.071 to 0.152 mg selenium/day. The greatest portion of dietary selenium intake occurs from the ingestion of grains and cereals. Selenium is excreted in breast milk, and levels vary with maternal nutritional status. 

Selenium is known to be an essential micronutrient for humans and other animals both inadequate and excessive selenium intake can cause adverse health effects. However, most people in the United States are unlikely to suffer from selenium deficiency. The current recommended dietary allowance (RDA) for selenium established by the Food and Nutrition Board of the National Research Council is 55 pg/day for adults. Adverse health effects due to selenium are generally observed at doses at least 5 times greater than the RDA. 

An examination of thyroid hormone levels in lactating women residing in areas of Venezuela with high levels of selenium in the soil (selenium intake ranged from 250 to 980 pg per day as estimated from selenium content of breast milk) revealed a significant decrease in serum T3 levels, as compared with... 

No significant alterations in serum T4 or TSH levels or correlations with selenium intake were found. 

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