Potential intake of selenium by the inhabitants of different regions in Jordan M.S.Y. Haddadin S. Khattari Daniela Caretto and R.K. Robinson Selenium is widely, if somewhat unevenly, distributed in soils around the world, and higher than average concentrations are often associated with industrial pollution, e.g. coal- fired burners. It is present in soils mainly as selenium (Se), selenite (SeO 3 ) or selenate (SeO 4 ), and it becomes increasingly mobile and available for plant uptake with increasing state of oxidation. On average, the total selenium levels in soils range from 0.1- 2.0mg kg –1 (Swaine, 1955; Lakin, 1961) but, in the USA, values can reach 80mg kg -1 , with soluble fractions as high as 19.0mg kg -1 (Olson et al., 1942; Trelease, 1945). In the Middle East, Ravikovitch and Margolin (1957) detected soluble fractions of 0.6mg kg -1 , and they reported that this level was sufficient to cause selenium poisoning in cattle grazing in the area; Abuereish and Lahham (1987) found soluble fractions of 0.12mg kg -1 in the Jordan Valley. Equally important is the fact that plants may be selenium accumulators, and Olson et al. (1942) found that wheat growing on selenium-rich soils replaced the sulphur in cysteine and methionine with selenium, to give total levels in the grain of 31mg kg -1 . Brazil nuts (53mg kg -1 ) as well as meat and fish have been reported to introduce selenium into the diet (Thorn et al., 1978), but citrus fruits appear to be non-accumulators (0.01mg kg –1 ). These reported levels are, of course, acceptable to humans, for the American Food and Nutrition Board recommends a daily intake of 0.05-0.200mg day –1 for normal functioning of the human body. According to Thomson and Robinson (1993), selenium is a constituent of the enzyme, glutathione peroxidase, which is a major agent in the protection of cellular components from the deleterious effects of hydroperoxides. However, the margin between an adequate and toxic intake is quite narrow, and selenosis can arise following the routine consumption of high-selenium foods grown in seleniferous soils. In one extreme incident in China, average intakes of ~5.0mg day –1 induced severe hair and nail loss, skin and neurological problems and even death (Yang et al., 1983), and the American Food and Nutrition Board suggests that toxicity can arise from routine intakes of 2.4-3.0mg day –1 . Given that soluble forms of selenium as low as 0.6mg kg –1 in soils have caused problems for grazing cattle, and that little information is available about the levels of soil selenium in The authors M.S.Y. Haddadin, S. Khattari and Daniela Caretto are based at the Faculty of Graduate Studies, University of Jordan, Amman, Jordan. R.K. Robinson is at the School of Food Biosciences, University of Reading, Reading, Berkshire, UK. Keywords Jordan, Fruit, Health, Minerals Abstract The margin between a deficient (~0.02mg day -1 ), an adequate (~0.2mg day -1 ) and toxic (~2.4mg day -1 ) intake of selenium is quite narrow, and this study sought to establish whether fruits grown in the Jordan Valley were safe for consumers, and yet capable of supplying a likely dietary requirement for the mineral. The mean levels of soil selenium were 0.64, 0.74 and 0.63mg kg –1 in three different growing regions of the Valley, while the highest levels in citrus fruits were 2.5mg kg –1 in clementines (Citrus mitis) and 3.31mg kg –1 in the bomali (Citrus paradisi). As the latter values were on a dry weight basis, the risk of selenosis would appear to be minimal but, equally important, deficiency diseases should not be manifest either. Electronic access The current issue and full text archive of this journal is available at http://www.emerald-library.com/ft 230 Nutrition & Food Science Volume 31 . Number 5 . 2001 . pp. 230–233 # MCB University Press . ISSN 0034-6659