While all types of rice (Oryza sativa) are a good source of energy, white rice (polished or milled rice) contains a limited amount of micronutrients. White rice is a dietary source of potassium, magnesium, and calcium, as well as copper, iron, molybdenum, manganese, zinc, and selenium. However, the health-related benefits of consuming rice are for the most part limited to unmilled whole grain rice, not white rice. Brown rice has been shown to have antioxidant, hypoglycemic, anti-inflammatory, antimutagenic and cardioprotective properties. Brown rice contains numerous biologically active substances, including tricin, α-tocopherol, ү-tocotrienol, ү-oryzanol, ferulic acid, methoxycinnamic acid, phytic acid, and momilactone B. Black, purple and red rice also contain melatonin and the anthocyanins cyanidin-3-glucoside, peonidin 3-glucoside, malvidin, and cyanidin hexoside, as well as several cyanidin dihexosides.
Brown rice or its components have been shown to induce apoptosis and inhibit proliferation of human lymphoma, Ehrlich ascites carcinoma, myeloma, colorectal cancer and liver cancer cells and carcinogen-induced colon cancer in laboratory rats. Fermented brown rice has been shown to inhibit carcinogen-induced development of oral, stomach, and colon cancer in rats. Consumption of brown rice has been shown to be associated with reduced risk of pancreatic cancer in a San Francisco bay area population (however, note that high rates of pancreatic cancer in southern Louisiana have been explained, in part, by consumption of locally grown rice incorporating high levels of cadmium).
Breast cancer-related effects of eating brown rice
Phytic acid (found in rice bran) has been shown to induce marked growth inhibition in breast cancer cells without harming normal cells. Purple rice bran extract reduced vascular endothelial growth factor (VEGF)-induced angiogenesis by inhibiting proliferation and migration in one cell study. A study that examined the anti-cancer activity of eight brown rice phenols (protocatechuic acid, p-coumaric acid, ferulic acid, sinapic acid, vanillic acid, methoxycinnamic acid, and tricin) found that ferulic acid and tricin each were effective in reducing the colony-forming ability of triple negative breast cancer cells.
An anthocyanin-rich extract from black rice reduced the viability of several breast cancer cell lines in another study. The same study found that the extract significantly suppressed tumor growth and angiogenesis in mice implanted with HER2/neu overexpressing (HER2+) tumors. Brown rice has been shown to inhibit the growth and proliferation of mouse mammary tumors. One study reported that a compound found in rice bran sensitized metastatic hormone receptor positive breast cancer cells to Taxol (paclitaxel).
Rice bran and rice bran oil are good sources of the gamma-tocotrienol (γ-tocotrienol) form of vitamin E, which has been shown to inhibit important steps in metastasis in both (ER+/PR+) and triple negative (ER-/PR-/HER2-) breast cancer cells.
Heavy metal contamination of rice
Rice represents a major path of arsenic exposure for people who depend on a rice diet. Generally speaking, rice has more elevated arsenic levels than all other grains, with brown rice having higher levels than white rice. Arsenic is contributed both by arsenic in the soil and arsenic in rice field water, much of which is naturally occurring. A 2008 report found unacceptable arsenic levels in common U.K. brands of baby foods. Most of the rice in the baby foods were thought to come from Europe. Ten of the 17 samples tested used organically grown rice. Similar concerns have been raised concerning rice in U.S. baby foods.
High levels of arsenic have been reported in rice from areas of the United States where former cotton fields have been converted to rice production. Arsenic herbicides were used in cotton fields in the early to mid-20th century. In addition, southern Louisiana is home to numerous oil refineries and petrochemical plants that have introduced cadmium and other carcinogenic contaminants to some of the soil used for rice production. Cadmium exposure has been associated with increased risk of breast cancer, among other cancers. Although the U.S. is a net rice exporter, it imports specialty rice varieties such as jasmine and Basmati rice from countries such as Thailand and India. This rice is often grown under conditions and using pesticides and fungicides that would be unacceptable inside U.S. borders. Rice grown in California is most likely to have low levels of arsenic, cadmium and other contaminants.
Brown rice syrup, which is not regulated in the U.S. with respect to arsenic and other heavy metal content, may be produced from rice sourced from countries with high levels of contamination. Brown rice syrup is a sweetener found in some cereal and high energy bars and high energy drinks, including those with the "organic" label. Since it is impossible for consumers to evaulate the safety of brown rice syrup, foods containing this ingredient should be limited or avoided.
Chinese red yeast rice
Chinese red yeast rice (red mold rice) is a food spice and medicinal herb made by fermenting a type of yeast (Monascus purpureus Went) with white rice. It contains a mixture of monacolins, one of which is essentially identical to lovastin, a statin used for lowering cholesterol. Chinese red yeast rice has been shown to inhibit tumor cell growth and enhance apoptosis of breast and colon cancer cells. It also has been found to inhibit both androgen-dependent and androgen-independent prostate tumor growth in human prostate cancer xenografts in mice. However, note that when nine different commercially available Chinese red yeast rice dietary supplements were tested in one study, the total monacolin content ranged from 0% to 0.58% w/w and only one of the preparations contained all 10 possible monacolins. In addition, measurable concentrations of citrinin, a mycotoxin known to cause kidney damage, was found in seven of the nine samples.
Wild rice (e.g., Zizania palustris) refers to four species of plants, three of which are native to North America, that are closely related to rice. The anthocyanins in wild rice, black rice and other darkly pigmented rice are degraded least by stovetop cooking. Using a pressure cooker results in the most thermal degradation, followed by using a rice cooker.
White rice has been stripped of much of the chemopreventive compounds and fiber that make brown rice a healthy food choice. A 2011 study found a link between increased starch intake after a diagnosis of early-stage breast cancer and a greater risk of recurrence.
Rice bran oil is used as a cooking oil and salad oil in parts of Asia. It is valued for its high smoking point and delicate flavor. While rice bran oil appears to have some chemopreventive properties, not enough information is available to make a recommendation with respect to its consumption.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on rice.