Rice = Carbohydrate? That’s your misunderstanding!

Rice has been consumed for 10,000 years, and it has been one of the most popular staple foods in the world for thousands of years, but until today, we still don’t really know all the secrets of this grain of rice. You can probably tell you how many layers of its physical structure it has, and how much fiber, energy, minerals, and vitamins it contains, but that’s just the tip of the iceberg compared to the rich phytoactive substances it contains. These active substances are present in tiny amounts, but they play an important role in affecting the health of the body.

Scholars from India systematically analyzed these bioactive substances and published the results in the top international food journal Trends in Food Science and Technology. Let’s take a look!

01 **Nutritional ingredients in rice: ** General nutritional ingredients

Rice contains 80% carbohydrates, 7-8% protein, 3% fat, 3% dietary fiber and 6-7% minerals and other biologically active substances.

Nutritional composition of rice

Special nutritional ingredients

The main aroma compound in rice is 2-acetyl-1-pyrroline. Anthocyanins and proanthocyanidins are natural pigments in colored rice (such as black rice, red rice, etc.).

Plant active substances include phenols, polyphenols, flavonoids, glycosides (anthocyanins), saponins, carotenoids, flavonoids, flavonols, etc. Phytosterols, tocopherols, and tocotrienols are the main fat-soluble antioxidants in aromatic rice. The specific compounds in different parts of rice reported in the literature are shown in the table below.

Table: Phytochemical components in rice (click on the picture to enlarge it)

Studies have shown that different rice varieties contain specific compounds . For example, the straw and husk of Iranian rice varieties contain gallic acid, pyrogallol, apigenin and rutin , while black sticky rice from northern India contains compounds such as arachidic acid, behenic acid, gamma-aminobutyric acid (GABA), lutein, zeaxanthin and hydroxyanisole butyrate .

0 2 Health Benefits of Rice

According to comprehensive literature reports, due to the presence of rich and diverse plant active ingredients, rice has many health-enhancing effects, including ① antioxidant, ② anti-inflammatory, ③ anti-cancer, ④ anti-diabetic activities and ⑤ protective effects on multiple organ systems.

1. Antioxidant

Rice is a source of various antioxidant active molecules, such as vitamin E, γ-oryzanol, phenolic acids (i.e., ferulic acid, gallic acid, vanillic acid, syringic acid, p-coumaric acid, etc.), anthocyanins and proanthocyanidins (i.e., catechin, epicatechin, cyanidin-3-O-glucoside, etc.), flavonoids (i.e., quercetin, apigenin, kaempferol, hesperidin, naringenin, rutin, tricin, myricetin), carotenoids (i.e., lutein, zeaxanthin, β-carotene), and phytosterols (e.g., stigmasterol, β-sitosterol).

Among the above substances, anthocyanins and proanthocyanidins present in colored rice are potent antioxidant molecules with significant biological activity in both in vivo and in vitro models. In in vivo experiments, anthocyanin-rich rice extracts produced significant antioxidant activity in alcohol-induced rats.

Several factors, including the degree of grinding, cooking, equipment, and storage conditions, can affect the antioxidant content of rice. **For example, the finer the rice is ground, the more antioxidants are lost. In addition, studies have reported that cooking methods such as microwave heating can reduce the content of anthocyanins and phenolic acid compounds in purple rice.

2. Anti-cancer

At present, many studies have shown that rice and its active ingredients such as GABA, anthocyanidins, proanthocyanidins, phytosterols, γ-oryzanol , etc. may have anti-cancer effects, and the anti-cancer and antioxidant effects of these ingredients may complement each other. Endogenous reactive oxygen species play a key role in the development of cancer. Bioactive ingredients with antioxidant effects may enhance the apoptotic effect of cancer cells by regulating the activity of antioxidant enzymes, thereby fighting cancer and tumors.

It is worth noting that colored rice or rice bran are rich in bioactive ingredients and have strong anti-cancer activity.

3. Anti-inflammatory

Several studies have demonstrated the anti-inflammatory effect of rice, but the substances with anti-inflammatory activity have not yet been determined. They may be biological molecules such as γ-oryzanol, ferulic acid, and flavonoids , all of which have shown anti-inflammatory properties in in vitro experiments.

It is worth mentioning that rice bran and rice bran oil, both byproducts of rice, have shown good anti-inflammatory properties. In in vitro and animal experiments, dietary γ-oryzanol extracts from rice bran oil prevented inflammation, and colored rice showed the same effect. Interestingly, cooked rice extracts can still show anti-inflammatory effects in in vitro experiments.

Figure: Different inflammatory mediators and sites of action of rice, rice bran and rice phytochemicals (click on the image to enlarge it)

COX, cyclooxygenase; LOX, lipoxygenase; PGG2, prostaglandin G2; PGH2, prostaglandin H2; prostaglandin E2; PGD2, prostaglandin D2; prostaglandin F2α; prostaglandin I2, prostacyclin; TXA2, thromboxane A2; TXB2, thromboxane B2; LT, leukotriene; HPETE, hydropereicosatetraenoic acid; HETE, hydroxyeicosatetraenoic acid; reactive oxygen species; AP-1, activating protein 1; κB, nuclear factor κB; TNF, tumor necrosis factor; IL, interleukin; MMPs, matrix metalloproteinases; platelet-derived growth factor; transforming growth factor β; JNK, c-Jun N-terminal kinase; ERK, extracellular signal-regulated kinase; NOS, nitric oxide synthase; iNOS, inducible nitric oxide synthase; NO, nitric oxide; LPS, lipopolysaccharide; [‘-’, inhibition; ‘+’, induction]

4. Anti-diabetes

Studies have found that the less the rice is ground, the more nutrients it contains, the lower the glycemic index, and the lower the risk of diabetes.

In addition, rice bran and rice bran oil significantly reduced blood lipids and glycosylated hemoglobin levels in patients with type 2 diabetes. This effect may come from the active ingredients in them such as γ-oryzanol, tocotrienols, and ferulic acid .

Sprouted colored rice has an excellent effect on blood sugar control, which may be related to the fact that different components in rice, such as GABA, γ-oryzanol and tocopherol, can improve glucose metabolism in rats, or it may be because anthocyanins and proanthocyanidins can lower blood sugar levels in humans or rats.

Figure: Possible anti-diabetic/hypoglycemic mechanisms of rice, rice bran and rice components (γ-oryzanol, tocotrienols, anthocyanins, etc.) (Click on the picture to enlarge it)

(1) Reduce ROS production/prevent oxidative stress (2) Increase endogenous antioxidant levels (3) Increase insulin release (4) Enhance glucose uptake (5) Inhibit α-amylase and α-glucosidase (6) Prevent β-cell destruction (7) Prevent insulin resistance (8) Reduce aldose reductase activity in the polyol pathway (9) Inhibit AGE formation (10) Inhibit pro-inflammatory mediators such as NFκB (11) Increase glucokinase activity (12) Reduce glucose-6-phosphatase activity (13) Reduce phosphoenolpyruvate (PEP) carboxykinase activity

GIT: gastrointestinal tract; CRP: C-reactive protein; NFκB: nuclear factor κB; IL: interleukin; ROS: reactive oxygen species; PKC: protein kinase C; AGE: advanced glycation end product; UDPGlcNAC: uridine diphosphate N-acetylglucosamine

5. Protective effects on multiple organ systems

It is reported that the active ingredients in rice, such as γ-oryzanol, γ-tocotrienol, ferulic acid, and phytosterols, can exert antihypertensive, hypolipidemic, and cholesterol-lowering effects in rodents, rabbits, non-human primates, and humans.

Rice bran and rice bran oil have shown cardiometabolic protective effects in diabetic, hypercholesterolemic, obese, and healthy subjects. In addition, multiple prospective studies have shown that habitual brown rice intake has a protective effect against lipid disorders, cardiovascular disease, ischemic heart disease, chronic heart disease, diabetes, and many other non-cardiometabolic syndromes .

Anthocyanins in black rice bran, GABA and phenolic substances in brown rice are all considered to be potential liver protectors , and they have all shown liver protective effects in mouse models.

Figure: The role of rice and rice components in oxidative stress and liver disease (click on the image to enlarge it)

TNF: tumor necrosis factor; GR: glutathione reductase; GPx: glutathione reductase; SOD: superoxide dismutase; CAT: catalase; GSH: glutathione; MDA: malondialdehyde; PDGF: platelet-derived growth factor; TGFB: transforming growth factor β; NFκB: nuclear factor κB

In addition to the liver protection effect, researchers also believe that brown rice and germinated brown rice have kidney, reproductive system, and nerve protection effects , but this has not yet been confirmed in the human body. At the same time, the dietary fiber and rich bioactive components in rice bran, especially γ-oryzanol, have shown gastrointestinal protective activity in vitro and in animals.

03Application of Rice

Rice is widely used in the food and pharmaceutical industries due to its rich functional ingredients.

In the food industry, in addition to rice, which can be eaten directly, many by-products from rice processing can be reused. The rich dietary fiber and biomolecules they contain are important sources of functional foods.

In the pharmaceutical industry, rice starch is often used to synthesize nanofilms to instantly release drug particles in specific drug delivery systems. Phytic acid, γ-oryzanol and ferulic acid in rice can be used to develop a nanovesicle drug to improve the absorption efficiency of existing drugs. Rice is also a source of different therapeutic agents, and focusing on its application in therapeutic biomolecules and pharmaceutical excipients is another key goal of the pharmaceutical industry.

Conclusion

After reading this, I believe you have a better understanding of rice, understand its magical effects on the human body, and know that it is not just a plain rice to fill your stomach. In this case, you should eat enough but not too much rice every day, so as not to waste the health and taste of rice. Of course, we recommend rice with color or less grinding!

References:

S. Sen, R. Chakraborty, P. Kalita, Rice - not just a staple food: A comprehensive review on its phytochemicals and therapeutic potential. Trends in Food Science and Technology. 97 (2020), pp. 265–285.