Rice can be primarily distinguished as:
A)polished termed as "white rice"
B)unpolished(whole)termed as "brown rice"
HOW ARE THEY PRODUCED:
When only the outermost layer of a grain of rice (the husk) is removed, brown rice is produced.
When the next layers underneath the husk (the bran layer and the germ) are removed, leaving mostly the starchy endosperm,white rice is produced.
WHY BROWN RICE IS NUTRITIONALLY BETTER THAN WHITE RICE:
Several vitamins ,dietary minerals and essential fatty acids are lost in this removal and the subsequent polishing process.Vitamins lost are-B1,B3 ,traces of vitamin A and E.Minerals lost are iron,magnesium etc.Essential fatty acids in the bran oil and fibres are also lost.
Germinated brown rice is nutritionally better because germination activates various enzymes in the rice, giving rise to a more complete amino acid profile, including GABA.
MEASURES TAKEN TO IMPROVE WHITE RICE:
Fortified rice has been produced with the help of biotechnology which is fortified with traces of the lost minerals,vitamins and other substances into the starchy grain matter itself.Such bio fortified white rice may be nutritious.One such is called golden rice which is fortified with added micronutrients.
Another measure is parboiling the rice before polishing.Parboiling helps the minerals and vitamins to be impregnated to some extent into the starchy grain.
CONCERNS ABOUT ARSENIC CONTENT OF RICE:
FIRSTLY,it depends on the type of soil,pesticide used during farming and varies from place to place.
Indeed it possess more threat to people eating brown rice than those eating parboilt, fortified white rice.
SECONDLY several measures are being taken to prevent such casualties.(pls check the reference below)
THIRDLY,researchers have discovered a transporter protein in rice that sequesters arsenic in vacuoles, preventing the toxic element from traveling into grains.
REFERENCES:11. ^ Yandell, Kate (2014-10-04). "How Rice Overcomes Arsenic" . Retrieved 2015-03-27.[source]
WHY IS COLOURED RICE GRAIN MORE NUTRITIOUS THAN THE WHITE:
The genetic colouration of the grain is due to the higher iron,anthocyanin and other antioxidant concentration,absent in white rice.