The milling and polishing processes both remove nutrients. A diet based on unenriched white rice leaves many people vulnerable to the neurological disease beriberi, due to a deficiency of thiamine (vitamin B1). White rice is often enriched with some of the nutrients stripped from it during its processing.
Enrichment of white rice with B1, B3, and iron is required by law in the United States. As with all natural foods, the precise nutritional composition of rice varies slightly depending on the variety, soil conditions, environmental conditions and types of fertilizers. At various times, starting in the 19th century, brown rice and wild rice have been advocated as more healthful alternatives.
The bran in brown rice contains significant dietary fiber and the germ contains many vitamins and minerals. Typically, 100 grams of uncooked rice produces around 240 to 260 grams of cooked grains, the difference in weight being due to absorbed cooking water.