Hidden hunger and hidden danger: regional gradients in rice grain nutrient elements, vitamins B and E and toxicants arsenic and cadmium along a north–south transect of Western Bangladesh

Here is presented a study to investigate the geographic variation in rice grain nutrients (trace and macro-elements and vitamins) and toxicants (arsenic species and cadmium) across a contiguous strip of 36 districts that constitute western Bangladesh. The survey collected ~ 500 market rice samples, averaging 15 samples and 10.7 cultivars per district. New LC-MS methods were developed for rice relevant, B and E complex compounds. Cadmium and zinc decreased southward, while copper, DMA, inorganic arsenic and oryzanols decreased northwards. There was a longitudinal gradient for iron, potassium, and vitamin B6. The greatest changes ~ twofold for cadmium and vitamin B6, and 1.5 for zinc across these gradients. The gradients may be driven by climate, geographical setting, soils, or cultivar, or a combination of all. The most obvious gradient was the transition from high to low altitude and from Pleistocene to Holocene soils as land transitioned from the upland plains of the north to sea-level in the south. Rice is a very important source of copper, phosphorus, vitamin B1, and zinc, and to a lesser extent iron, B3, B6, potassium. It is a poor source of vitamin E and calcium.