The health-related benefits of consuming rice (Oryza sativa) are for the most part limited to whole grain rice, not white rice (polished or milled rice), which incorporates low levels of beneficial micronutrients. Brown rice has been shown to have antioxidant, hypoglycemic, anti-inflammatory, antimutagenic and cardioprotective properties.
White rice is a dietary source of potassium, magnesium, and calcium, as well as copper, iron, molybdenum, manganese, zinc, and selenium. Dietary selenium has been shown to be associated with reduced risk of breast cancer. Brown rice contains numerous additional biologically active substances, including tricin, α-tocopherol, ү-tocotrienol, ү-oryzanol, ferulic acid, methoxycinnamic acid, phytic acid, momilactone B and insoluble fiber. 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 has been shown to inhibit the growth and proliferation of mouse mammary tumors. Rice components have been reported to inhibit the growth of breast cancer cells without harming normal cells. In addition, rice has been shown to reduce colony formation of triple negative (ER-/PR-/HER2-) breast cancer cells. The anthocyanins and melatonin found in black, purple and red rice have additional chemopreventive properties. However, rice must be selected carefully since rice plants tend to take up and accumulate heavy metals such as cadmium and arsenic.
Brown rice has been shown to inhibit the growth and proliferation of mouse mammary tumors. Phytic acid (found in rice bran) has been shown to induce marked growth inhibition in breast cancer cells without harming normal cells.
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.
Rice components have been reported to increase the treatment effects of the chemotherapy drugs Adriamycin (doxorubicin) and Taxol (paclitaxel). One study reported that a compound found in rice bran sensitized metastatic hormone receptor positive (ER+/PR+) breast cancer cells to Taxol. In addition, rice compound gamma-tocotrienol (a form of vitamin E, discussed below) has been shown to reverse multi-drug resistance in ER+/PR+ breast cancer cells.
Vitamin E comprises a group of eight related vitamins, including four tocopherols (α, β, γ, and δ-tocopherol) and four tocotrienols (α, β, γ, and δ-tocotrienol). Alpha-tocopherol (α-tocopherol) is the most abundant form of vitamin E and is the isoform typically found in vitamin E supplements.
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 ER+/PR+ and triple negative (ER-/PR-/HER2-) breast cancer cell growth in a dose-dependent manner, without affecting normal breast cells. Gamma-tocotrienol also has been reported to inhibit important steps in the metastasis of both ER+/PR+ and triple negative breast cancer cells.
One study using a mouse model of breast cancer reported that gamma-tocotrienol given as part of the diet suppressed tumor growth. The same study also reported that gamma-tocotrienol inhibited colony formation of both mouse mammary and human breast cancer cell lines. Colony formation refers to the ability of a single cell to grow into a colony consisting of at least 50 cells.
An anthocyanin-rich extract from black rice was shown to reduce the viability of several breast cancer cell lines in one study. The same study found that the extract significantly suppressed tumor growth and angiogenesis in mice implanted with HER2 overexpressing (HER2+) tumors. Purple rice bran extract reduced vascular endothelial growth factor (VEGF)-induced angiogenesis by inhibiting proliferation and migration in another study.
The melatonin in black, purple and red rice protects against breast cancer in several ways. Melatonin protects against ER+ breast cancer by reducing aromatase activity within the breast, thereby decreasing estrogen production. Melatonin has also been found to reduce triple negative breast cancer growth, proliferation and migration in cell and animal studies. In addition, melatonin has been shown to reduce the cardiotoxicity associated with Adriamycin (doxorubicin) chemotherapy.
Rice represents a major path of inorganic arsenic exposure for people who depend on a rice-based diet. Generally speaking, rice has the potential to incorporate more elevated arsenic levels than all other grains — brown rice tends to have even 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. 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-based herbicides were used in cotton fields in the early- to mid-20th century. A 2008 report that received a lot of attention 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 were organically grown rice. Similar concerns have been raised concerning rice in U.S. baby foods.
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.
Organic brown rice grown in California is most likely to have low levels of arsenic, cadmium and other contaminants. Consumption of brown rice has been reported to be associated with reduced risk of pancreatic cancer in a San Francisco bay area population. On the other hand, high rates of pancreatic cancer in southern Louisiana have been explained, in part, by consumption of locally grown rice incorporating high levels of cadmium.
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 normally is not possible for consumers to determine the source or evaluate the safety of brown rice syrup, consumption of foods containing this ingredient should be limited.
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 very similar to lovastatin, 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 percentage monacolin content ranged from 0% to 0.58% and only one of the preparations contained all 10 possible monacolins.
Wild rice (e.g., Zizania palustris) refers to four species of plants, three of which are native to North America, that are distantly 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.
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.
The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list of studies, please click on rice.