One day a few months ago, I asked my friend Scarlet, who is Korean and makes a rice cooker full of rice every evening, about the importance of rice washing. She was quite adamant that rice must be washed, and her primary reason had nothing to do with taste or quality-- her rice tends to be gummy too-- but with removal of pesticides. She washes her rice like I wash my apples (though to be honest I just give them a quick rinse also). This would never have occurred to me. Rice comes hermetically sealed in plastic bags at the store! Of course it is clean!
I started (often) washing my rice. And then, taking a page out of my stepmother's book, frying it in a bit of oil before adding the cooking water. And putting a bit of salt in. And, by god, it does taste better now. But, the question remains, is washing necessary, or only culinarily desirable? My mushroom-washing research, anecdotal and scientific, suggested that misinformation is everywhere regarding everyday kitchen topics.
This article on Chowhound sounded very authoritative. The gist: not rinsing rice makes it sticky, so while you may want to rinse long-grain rice to promote fluffiness, don't worry about rinsing short-grain rice (aka "sticky rice"). On the other hand, the powder on the outside of the rice is fortified nutrients, so don't rinse that away if you want the nutrients. Imported rice sometimes has talc or other powders on the outside, so rinsing imported rice may be desirable.
All of these points are backed up by a number of other sources. Basically, my initial assumption was correct: one major reason to rinse rice is to reduce surface starch and improve texture. U.S.-grown white rice is legally required to be fortified with an external nutrient powder to improve its nutrient profile vis-a-vis brown rice. Imported rice can be treated with a variety of substances to improve its appearance and texture, but is not likely to be coated with fortified nutrients; therefore imported rice is best washed (in addition, Asian consumers traditionally rinse rice, so rice producers would assume this practice on the part of the cook).
Some sources suggest that rinsing is also important to reduce the natural arsenic levels found in rice. Website after website in 2012 repeated that rinsing the rice can remove up to 30% of arsenic, and sometimes cited the FDA for this number. However, the FDA currently states that "rinsing rice before cooking has a minimal effect on the arsenic content of the cooked grain but washes enriched iron, folate, thiamin and niacin from polished and parboiled rice." What does work? "Published studies, including new research by the FDA, indicate that cooking rice in excess water (six and ten parts water to one part rice), and draining the excess water, can reduce from 40 to 60 percent of the inorganic arsenic content, depending on the type of rice. The FDA recognizes that consumers do not typically prepare rice in this manner, similar to preparing pasta, and some may not wish to do so."
Well, no kidding. I do not typically prepare rice in this manner. And I do not wish to do so.
What about Scarlet's claim that unwashed rice is covered with pesticides? While some pesticide residues may remain in white rice, it is important to note that most pesticide residues are concentrated in the rice bran (i.e., the outer portion of brown rice). This is even true of arsenic. There wouldn't be much point in peeling your apple, then washing the inside, after all. Brown rice, though more nutritious, is also more contaminated.
As far as arsenic in rice goes, the region of production is important. Rice from the American South contains higher levels of arsenic than other rice (from California, or from elsewhere in the world). Apparently this is because lots of high-arsenic pesticides (now banned) remain in the soil there from cotton farming. Indian basmati rice is the lowest in arsenic.
Honestly, I am finding this topic overwhelming. I eat rice and rice products a lot, probably something close to daily. I serve them to my husband and my 14-year-old daughter. And then there are the billions of Asian people who eat more rice than I do (although hopefully they mostly don't eat rice imported from the American South). And the gluten-free trendsetters and also true sufferers of celiac disease (like my sister), all of whom have a tendency to live off rice (I know, I tried it). Where do we draw the line on worrying? Wouldn't I just be better off not knowing about arsenic levels, especially when apparently your fruits and vegetables are dangerously chock-full of arsenic too?
Some useful discussions: