Brown rice and white rice have similar amounts of calories and carbohydrates. The main differences between the two forms of rice lie in processing and nutritional content. When only the outermost layer of a grain of rice (the husk) is removed, brown rice is produced.
Rice (Oryza Sativa) has an estimated 8,000 varieties but only two classifications in terms of extent of milling or grinding. White rice is prepared by completely removing the hull of the grain and exposing the endosperm which then undergoes a polishing stage. These procedures take out not only the husk but also the bran and germ layers beneath the husk. However, this also removes most of the nutrient content. Nutrients such as magnesium, Vitamins B1, B3 and B6, iron, and phosphorous are severely reduced. In making brown rice, only the outermost layer of the rice grain is removed. It is basically un-milled or partially milled rice. Thus, the essential parts of the rice kernel are preserved, including the fibers, fatty acids and the oil in the bran.
To produce white rice, the next layers underneath the husk (the bran layer and the germ) are removed, leaving mostly the starchy endosperm.
In general, rice is a good source of B vitamins, such as thiamin and niacin, and also provides iron, phosphorus, and magnesium. Although rice is lower in protein than other cereal grains, its protein quality is good because it contains relatively high levels of the amino acid lysine.
Several vitamins and dietary minerals are lost in this removal and the subsequent polishing process. A part of these missing nutrients, such as vitamin B1(thiamin), vitamin B3(niacin), and iron are sometimes added back into the white rice making it "enriched".
One mineral not added back into white rice is magnesium; one cup (195 g) of cooked long grain brown rice contains 84 mg of magnesium while one cup of white rice contains 19 mg. When the bran layer is removed to make white rice, the oil in the bran is also removed. Rice bran oil may help lower LDL cholesterol.
Brown rice that has had only its husk removed during milling. With the bran intact, retains more fiber, folacin, iron, riboflavin, potassium, phosphorus, zinc, and trace minerals such as copper and manganese, than other types of rice. Moreover, brown rice is the only form of the grain that contains vitamin E.