rs79.vrx.palo-alto.ca.us

Haug 2007

Long 2015

joy 2015

usgs

joy 2015 Dietary mineral supplies in Africa Dietary micronutrient deficiencies (MNDs) are widespread, yet their prevalence can be difficult to assess. Here, we estimate MND risks due to inadequate intakes for seven minerals in Africa using food supply and composition data, and consider the potential of food-based and agricultural interventions. Food Balance Sheets (FBSs) for 46 countries were integrated with food composition data to estimate per capita supply of calcium (Ca), copper (Cu), iron (Fe), iodine (I), magnesium (Mg), selenium (Se) and zinc (Zn), and also phytate. Deficiency risks were quantified using an estimated average requirement (EAR) ‘cut-point’ approach. Deficiency risks are highest for Ca (54% of the population), followed by Zn (40%), Se (28%) and I (19%, after accounting for iodized salt consumption). The risk of Cu (1%) and Mg (<1%) deficiency are low. Deficiency risks are generally lower in the north and west of Africa. Multiple MND risks are high in many countries. The population-weighted mean phytate supply is 2770 mg capita−1 day−1. Deficiency risks for Fe are lower than expected (5%). However, ‘cut-point’ approaches for Fe are sensitive to assumptions regarding requirements; e.g. estimates of Fe deficiency risks are 43% under very low bioavailability scenarios consistent with high-phytate, low-animal protein diets. Fertilization and breeding strategies could greatly reduce certain MNDs. For example, meeting harvestplus breeding targets for Zn would reduce dietary Zn deficiency risk by 90% based on supply data. Dietary diversification or direct fortification is likely to be needed to address Ca deficiency risks. See full size Dietary Map of African mineral deficiencies usgs Linking Selenium Sources to Ecosystems: Local and Global Perspectives Given the geographic patterns, Se emerges as a contaminant within specific regions of the globe that may limit phosphate mining, oil refining, and drainage of agricultural lands because of potential ecological risks to vulnerable food webs. Selenium also may serve as a geochemical exploration tool that signals an ancient productive biological environment.

Haug 2007 How to use the world's scarce selenium resources efficiently to increase the selenium concentration in food. The world's rare selenium resources need to be managed carefully. Selenium is extracted as a by-product of copper mining and there are no deposits that can be mined for selenium alone. Selenium has unique properties as a semi-conductor, making it of special value to industry, but it is also an essential nutrient for humans and animals and may promote plant growth and quality. Selenium deficiency is regarded as a major health problem for 0.5 to 1 billion people worldwide, while an even larger number may consume less selenium than required for optimal protection against cancer, cardiovascular diseases and severe infectious diseases including HIV disease. Efficient recycling of selenium is difficult. Selenium is added in some commercial fertilizers, but only a small proportion is taken up by plants and much of the remainder is lost for future utilization. Large biofortification programmes with selenium added to commercial fertilizers may therefore be a fortification method that is too wasteful to be applied to large areas of our planet. Direct addition of selenium compounds to food (process fortification) can be undertaken by the food industry. If selenomethionine is added directly to food, however, oxidation due to heat processing needs to be avoided. New ways to biofortify food products are needed, and it is generally observed that there is less wastage if selenium is added late in the production chain rather than early. On these bases we have proposed adding selenium-enriched, sprouted cereal grain during food processing as an efficient way to introduce this nutrient into deficient diets. Selenium is a non-renewable resource. There is now an enormous wastage of selenium associated with large-scale mining and industrial processing. We recommend that this must be changed and that much of the selenium that is extracted should be stockpiled for use as a nutrient by future generations. Long 2015 Severe selenium depletion in the Phanerozoic oceans as a factor in three global mass extinction events Highlights Sustained severe Se depletion in the past oceans correlates closely with three major mass extinction events. These represent periods of Se depletion > 1.5-2 orders of magnitude lower than current ocean levels. Se depletion may have thus been one of several factors in these complex extinction scenarios. Abstract Selenium (Se) is one of the key trace elements required by all animal and most plant life, and Se deficiencies in the food chain cause pathologies or death. Here we show from new geochemical analyses of trace elements in Phanerozoic marine pyrite that sustained periods of severe Se depletion in the past oceans correlate closely with three major mass extinction events, at the end of the Ordovician, Devonian and Triassic periods. These represent periods of Se depletion > 1.5–2 orders of magnitude lower than current ocean abundances, being within the range to cause severe pathological damage in extant Se-reliant organisms. Se depletion may have been one of several factors in these complex extinction scenarios. Recovery from the depletion/extinction events is likely part of a natural marine cycle, although rapid rises in global oxygen from sudden major increases in marine productivity and plant biomass after each extinction event may also have played a crucial role.