14 1.Rice Bran: Production, Composition,Functionality and Food Applications, IPhysiological Benefits

Taiwinder S. Kahion

CONTENTS

Production ............................................................................................................305Composition.........................................................................................................307FoodApplications...............................................................................................308Safety.....................................................................................................................30)PhysiologicalBenefits .........................................................................................309

Cholesterol Lowering with Rice Bran.....................................................309HamsterStudies ............................................................................. .309RatStudies ......................................................................................312OtherSpecies ...................................................................................313HumanStudies...............................................................................314

Bile Acid Binding by Rice Bran.........................................................................316Whole Grain Recommendation..........................................................................MarketPotential..................................................................................................316

Summary.............................................................................................................. 316References.............................................................................................................318

Production

The world production of rice paddy in 2006 was 631 million metric tons. Itresulted in 421 million tons of milled rice, of which 372 million tons wereconsumed as food. At least 114 countries grow rice and more than 50 havean annual production of 100,000 metric tons or more. The 11 top rice-grow-ing countries are China, India, Indonesia, Bangladesh, Vietnam, Thailand,Myanmar, Philippines, Brazil, Japan, and the United States, producing 28.2%,22.4%, 8.8%, 6.5%, 5.9%, 4.6%, 4.2%, 2.4%, 1.7%, 17%, and 13% of the world

305

306 Til,ir Iu'i -cilii',iIs: Teed .Applicatiwis III ii 1 icaItli Bcne/its

rice crop, rvsprctl\cl\. The United States contributes 9.5 million metric tonsto the annual world rice production. Thailand, Vietnam, the United States,India, Pakistan, and China exported 8.9, 5.9, 4.5, 4.2, 4.2, and 1.2 million tons,respectively: a total of 28.9 million tons of milled rice. Rice, wheat, and corncontribute to 50% of the human caloric intake; rice comprises 23%, wheat17%, and corn 10% of the calories consumed [1]. Rice is primarily used forhuman consumption, whereas a larger proportion of wheat and corn areused as animal feed. On average, per capita rice consumption is 56.9 kg peryear. Consumption in the developing countries is around 68.5 kg per capitaper year, and 12.8 kg per year for developed countries. More than 60 0/,, of thecalories consumed by the populations of East Asian countries such as Ban-gladesh, Cambodia, Laos, Myanmar, and Vietnam come from rice. Most riceis consumed as white, milled, polished rice.

Rice as harvested from the field is called paddy. In the rice milling process,first the outermost layer, the hull, is removed to produce brown rice. Thisprocess is least damaging to the nutritional value of the rice and avoids theunnecessary loss of nutrients that occurs with the further processing to pro-duce white milled rice. Brown rice would be considered whole grain. Onehundred kilograms of paddy on milling yields 56 to 58 kg white rice, 10 to12 kg broken rice, 18 to 20 kg husk, and 10 to 12 kg rice bran. Rice bran, a by-product of the milling process, contains the enzyme lipase, which rapidlydegrades the oil making the bran rancid and inedible. Researchers at theWestern Regional Research Center, USDA-ARS, Albany, California, success-fully stabilized rice bran by heating it to 125°C-135C for 1 to 3 seconds at 11%to 15% moisture, and holding the extruded bran at an elevated temperature97°C-99°C for 3 minutes prior to cooling, thereby deactivating the lipase [2].Stabilized rice bran (SRB) has an estimated shelf life of about six months andcould potentially be used as a food ingredient. Oil can be extracted from thebran and used as a healthful food component.

Each year, 63 to 76 million tons of rice bran (rice milling by-product) isproduced in the world and more than 90% of rice bran is sold cheaply asanimal feed. The remainder is stabilized and could be used as a value-addedhealth food product. Currently there is some market for SRB as a horse-feedsupplement. In the United States, rice oil is being extracted from 15% to 20%of the rice bran.

Parboiling, a steam treatment of paddy, gelatinizes the starch beneath thebran layer of the rice kernel, and yields more white rice, less broken rice,and higher fiber bran. Parboiling stabilizes rice bran by deactivating lipase,but it could destroy the beneficial antioxidants responsible for its health-promoting properties. Steam cooking conditions destroy antioxidants [3].Antioxidants derived from the diet scavenge and neutralize free radicals,a by-product of metabolism. Free radicals have been implicated in heartdisease and cancer.

TABLE 14.1

Composition of Rice Bran- Percent of

StabilizedRice Bran

ParboiledRice Bran

L20.9

1.92.4

22.4

271.'

29.6

%

4.1

17.01.7(1.6

39.40.)0.6

34.31.3

Rice Bran307

Total Dietary FiberSoluble Dietary Fiber

NitrogenFat

Source: 1141

TABLE 14.2

Composition of Rice Bran Oil

Component

Unsaponifiable MatterSaturated Fatty Acids:

PalmiticStearicArachidic

Monounsaturated Fatty Acids:OleicVaccenicGadolcic

Polyunsaturated Fatty Acids:LinoleicLinolenic

Source: 1151

CompositionThe composition of stabilized and parboiled rice bran is given in Table 14.1,and of rice bran oil in Table 14.2. Nutritional studies have identified dietaryfiber, bran oil, unsaponifiable matter, sterols, and protein as rice bran's health-ful components. The total dietary fiber (TDF) content of rice bran ranges from21% to 270%, with less than 2% as soluble dietary fiber (Table 14.1). The proteincontent of stabilized rice bran ranges from 12% to 16%, and in parboiled ricebran from 14% to 20%. Rice bran protein is efficiently digested and has highnutritional value; it has a protein efficiency ratio of 1.6. Concentrates from

tul

308 Fifier liigiedie;its: Food Applications and Health Benefits

TABLE 14.3

Composition of Rice Bran Oil Unsaponifiable Matter

Sterol %

'lint Sterols 43CainpesterolStigmasterol[i-Sitosterol

Triterpene Alcohols 2824-Methylene CycloartenolCycloartenol

Aliphatic alcohols, hydrocarbons 194-Methyl Sterols 10

Source: [7]

rice bran protein have an efficiency ratio of 2.0 to 2.2, comparable to casein(2.5), a milk protein [4]. Rice bran contains 22% to 30% crude fat including1.8% gum and 0.4% wax [5]. The crude fat content of commercial stabilizedrice bran is 18% to 22%. The fatty acid composition of rice bran oil consists of41% monounsaturates, 36% polyunsatu rates, and 19% saturates (Table 14.2).

The composition of unsaponifiable matter (UM) in rice bran oil is listed inTable 14.3. Rice bran oil (RBO) contains over 4% of UM, but peanut oil containsonly 0.3% to 1% UM [6] . UM is a mixture of 430% plant sterols (campesterol,stigmasterol, 13-sitosterol, and others), 28% triterpene alcohols (24-methylenecycloartanol, and cycloartenol), 19% less polar compounds such as aliphaticalcohols and other hydrocarbons, and 10% 4-methyl sterols [7]. Oryzanol, amixture of ferulic acid esters of triterpenoid alcohols, composes 20% to 30%of UM and 1.1% to 2.60% of bran oil.

Food Applications

Rice bran has many food applications in prepared foods, nutraceuticals, andfunctional foods. Some of the common applications of rice bran are in snackfoods, bakery products, cereals, crackers, pasta products, dough conditioners,beverages, gluten-free foods, and medical foods. The USDA in partnershipwith a nonprofit organization provides a nutritious rice bran drink to pre-school children in the Latin American countries. Rice-bran-containing bev-erage base can be used for isotonic drinks, iced tea drinks, enhanced juices,mineral supplements, and sports beverages. "Rice Milk" non-dairy alterna-tive to milk is made from organically grown rice. Healthy meal replacementdrinks made from stabilized rice bran are being introduced in the market.

309Rice Bran

SafetyStabilized rice bran has shown no negative influence on shelf life or organo-leptic properties of the various foods when used as an ingredient. Stabili7iirice bran has been shown to have no adverse effects on animal health or fecdnutritional quality when fed at 60% of the diet in chicks [8, 91 or up to 40'' i

diet of pigs [101.

Physiological Benefits

Cholesterol Lowering with Rice Bran

Hamster StudiesThe hamster has become the preferred rodent model for cholesterol stud-ies, since it has a gall bladder, which is absent in the rat, and the lipoproteinprofile of hamster plasma by density gradient ultracentrifugation containsdistinct very low-density (20%), low-density (25%), and high-density (55%)lipoprotein fractions. Furthermore, hamsters and humans are reported tobe similar in having significant levels of circulating plasma cholesterol andan intrinsically low rate of hepatic cholesterol synthesis, and a similarit y in

their response to diet modification and drugs 1111.

Cholesterol lowering in hamsters by stabilized or parboiled rice bran in theUnited States was first reported by USDA-ARS (Albany, California) scientists[12] and was acknowledged by a feature article in the Journal of the Ameri-

can Oil Chemists' Society [13] in which the need was expressed for funding ahuman study to validate these findings in hamsters. Diets containing 10%TDF from intact full-fat rice bran (stabilized or parboiled) resulted in signifi-cantly lower plasma and liver cholesterol compared with the 10% cellulosecontrol diet in hamsters fed 0.5% cholesterol [14]. Replacing one-third of thestabilized rice bran fiber with wheat bran fiber also resulted in significantlylower plasma and liver cholesterol (Table 14.4). In a subsequent study [15],diets containing 10% TDF from stabilized rice bran significantly reducedplasma cholesterol compared to those fed a cellulose control diet, both inthe presence and absence of 0.3% cholesterol in the diet. In the cholesterol-

fed hamsters, diets containing 11%, 22%, 33%, and 44% rice bran resulted in

plasma cholesterol reductions of 8%, ll%, 15%, and 21%, respectively, com-pared with control values. Plasma cholesterol reductions were significantonly with the diet containing 44% rice bran. Although plasma cholesterolreductions were significantly correlated with the level of rice bran in the diet

(r = 0.38), the low correlation coefficient suggested that the rice bran levelalone was a poor predictor of plasma cholesterol lowering.

310

I i/)ei lii'r'tlu';it: I-out] Applications and Health Benefits

TABLE 14.4

I lamster Studies: Plasma and Liver Cholesterol Lowering by Rice Bran

Plasma cholesteroling/d L)

I 'ui cholesterol(T11ig)

Control

402327322302281376573736544656

Rice Bran

274255237276266338

312823433249

Effect

SignificantSignificantSignificantNot significantNot significantSignificantSignificantSignificantSignificantSignificantSignificantSignificant

Ref.

1415516172114155161721

Several fractions of rice bran were evaluated for cholesterol-loweringproperties. Defatted rice bran resulted in a loss of cholesterol-lowering abil-ity [14, 151, suggesting that the lipid fraction was necessary for maximumcholesterol-lowering potential. A combination of defatted rice bran plus RBOor degummed, dewaxed RBO resulted in significant liver cholesterol reduc-tions [5,15]. However, RBO extracted at 4°C or 54°C and wax and gum frac-tions of RBO had no significant influence on cholesterol status comparedwith their respective oil controls [5]. When recombined, it appeared thatdefatted rice bran and RBO were less effective in lowering cholesterol com-pared with intact full-fat rice bran, suggesting that either intact RBO was lessavailable or there was a loss/inactivation of cholesterol-lowering activity inthe rice oil fractionation process.

Since the liver is the principal organ responsible for the regulation ofplasma cholesterol levels, liver cholesterol levels also provide a measure ofthe influence of diet on cholesterol metabolism. Liver cholesterol was signifi-cantly lowered in hamsters by diet containing 10% TDF from rice bran or a 5:5TDF combination of rice bran and a 13-glucan-enriched (19% total 3-glucans)barley fraction in diets containing 0.25% cholesterol [16]. In the same study, adiet containing a combination of rice bran and oat bran (5:5, TDF) with 2.6%total 13-glucans (0.3% from rice bran, 2.3% from oat bran) resulted in signifi-cant plasma and liver cholesterol reductions, suggesting that the contributionof rice bran in lowering cholesterol in hamsters is likely due to componentsother than 3-glucans or soluble fiber (Table 14.4). Measurement of diet slurryviscosities revealed rice bran diet viscosity to be similar to that of the cel-lulose (insoluble fiber) control diet (<10 cP over a three-hour period), ratherthan to oat bran diet viscosity (104 cP), indicating that cholesterol lowering

LI311

Rice Bran

by rice bran is related to a mechanism other than gel forming and sequester-ing or entrapment of lipid, bile acids, or their metabolites.

In the earlier studies [5, 14, 151 in which either 0.3% or 0.5% cholesterol wasfed, rice bran resulted in significant plasma cholesterol reductions, but whendietary cholesterol was lowered to 0.25%, plasma cholesterol was not signifi-cantly reduced by the rice bran diet, suggesting that the plasma cholesterolresponse is dependent on the level of hypercholeSterOlemia induced in the

animals [16].The source of dietary protein is an additional influence on plasma choles-

terol elevations. It is common knowledge that vegetarians have lower plasmacholesterol levels than persons consuming animal protein. In each of theaforementioned hamster studies, the control diets contained casein as thesole source of protein, while treatment diets contained some plant protein.Therefore, a study was designed in which the contribution of plant proteinwas made equal in all treatments [17]. Diets contained 0.3% cholesterol, 100%TDF, 10.1% fat, and 31/o nitrogen with the same plant-to-animal N ratio (44:56),using soy protein and casein in the control diet. Plasma cholesterol was ele-vated in the control animals to 281 mg/dL, 13% lower than that (322 to 325mg/dL) observed in previous studies [5,15] in which hamsters were fed 0.3%cholesterol with casein as the sole source of protein in the control diet. In thisstudy, the unsaponifiable matter (UM) was isolated from rice bran oil andadded to cellulose or rice bran diets to provide a total of 0.4 9% or 0.8% UM inthe diets. Probably as a result of the lower level of hypercholesterOlemia inthe control animals, plasma cholesterol was not significantly lower in ani-mals fed rice bran without added UM but was significantly lower in animalsfed stabilized or raw rice bran with 0.4% additional UM from RBO, com-pared to the control group. Liver cholesterol was significantly lowered bystabilized or raw rice bran with or without added U (0.8% or 0.4% U, respec-tively), and by cellulose diets with added U (0.8%). Plasma and liver choles-terol reductions were proportional to the amount of UM in the hamster diet.Rice bran diets lowered cholesterol up to twice as much as cellulose dietswith equivalent levels of UM. Fecal fat excretion was significantly negativelycorrelated to liver (r —0.97) and plasma (r = —0,83) cholesterol values. Theresults of these hamster studies suggest that UM and other components ofrice bran have cholesterol-lowering activity, possibly through increased fecalexcretion of lipids.

Kahlon et al. [18] observed a reduction 49% to 65%) in foam cells in theinner bend of the aortic arch in hamsters consuming rice bran diets contain-ing 20% fat and 0.5% cholesterol for six weeks. The size of the plaque areaon the inner bend of the aortic arch is a marker for arteriosclerosis and heartdisease. Adding a megadose of vitamin E (1000 lU/Kg) resulted in furtherreduction in the aortic plaque area, but the difference was not significantover animals fed an adequate level (50 lU/kg) of vitamin E. Animals on therice bran diet excreted more neutral sterols compared to the control animals.Animals consuming megadoses (21 times the normal dosage) of vitamin Ewith their rice bran diets excreted more neutral sterols than animals receiv-

ia

T312 Fiber Ingredients: Food Applications and Health Benefits

ing an adequate level of vitamin E. Plant sterols as a major component ofthese rice bran diets inhibit cholesterol absorption in the intestinal tract andare a proposed mechanism for cholesterol lowering [19].

Rong et al. [20] reported significant reductions in plasma cholesterol (PC),very low density lipoprotein cholesterol (VLDL-C), and low density lipopro-tein cholesterol (LDL-C) in hamsters fed 1% oryzanol in diets containing 5%coconut oil and 0.1% cholesterol for seven weeks. Areas of aortic foam cellswere reduced (679%) in animals on the oryzanol diet.

Kahlon et al. [211 reported significant reductions in PC, VLDL-C, and livercholesterol in animals on rice bran diets compared with corn bran or wheat brandiets. Extrusion cooking (processing at two energy levels, 221 and 442 Wh/kgdm) did not change the hypocholesterolemic properties of the rice bran.

Rat Studies

Although the current preference among researchers is to use the hamstermodel for the evaluation of diet ingredient effects on cholesterol metabolism,earlier work was conducted primarily with the laboratory rat. In cholesterol-fed rats, Ayano et al. [22] reported that the neutral detergent fiber fraction(high in hemicellulose) of rice bran had serum cholesterol-lowering effects,while the acid detergent fiber fraction was ineffective. The hemicellulosefraction was isolated from defatted rice bran and fed to rats at 2% of the diet,resulting in significantly reduced plasma cholesterol (PC) levels (23); how-ever, liver cholesterol was not significantly influenced in either study. Datafrom the latter investigation suggested that the hypocholesterolemic effect ofrice bran hemicellulose involved increased excretion of bile acid, but not liveraccumulation of cholesterol or suppression of cholesterol absorption. Othersreported no significant PC reductions with diet containing 10% stabilizedrice bran from parboiled rice compared to 10% cellulose or fiber-free controldiets fed to rats for four weeks [24]; however, none of the diets containedadded cholesterol and the level of rice bran in the diet was low. When dietscontaining 1% cholesterol, 0.2% cholic acid, 10% TDF from raw or parboiledrice bran, and 17% to 19% fat were fed to rats for 21 days, both plasma andliver cholesterol levels were significantly reduced by the rice bran diets com-pared with the fiber-free control diet [25]. Topping et al. [26] found signifi -cantly lower plasma and liver cholesterol in rats fed cholesterol-free dietscontaining 79/o TDF from heat-stabilized rice bran compared to 7% TDF fromunprocessed wheat bran. The cholesterol reductions were related to increasein hepatic low-density lipoprotein (LDL) receptor activity. Supplementing5% fish oil in the diet achieved further reductions in PC.

Cholesterol-lowering effects of rice bran oil and rice bran oil UM werereported in rats fed 1% cholesterol and 0.5% cholic acid diets for eight weeks[27]. Results showed that either 10% RBO or 0.4% rice bran oil UM signifi-cantly lowered PC and liver cholesterol compared to peanut oil. In anotherstudy with cholesterol-fed rats, significantly lower PC, LDL-C, and VLDL-Cwere observed with 10% RBO compared with those fed peanut oil [28]. An

LRice Bran313

addition of 0.5% oryzanol to RBO diet showed a further significant decreasein PC. Rice bran oil also lowered liver cholesterol and triglycerides signifi-cantly. Evidence of a possible mechanism for the hypocholesterOlemic activ-ity of oryzanol was reported in a subsequent study in which a significantincrease in fecal cholesterol and bile acid excretion and a 20% reduction incholesterol absorption in vitro were observed after rats were fed 0.5% oryz-anol and 1% cholesterol diet [29]. An additional mechanism for reducingatherosclerotic risk with oryzanol was suggested by significantly lower ADP-induced platelet aggregation and total inhibition of aggregation by collagenwhen 0.5% oryzanol was added to 1% cholesterol rat diet [30].

Other components of rice bran reported to have cholesterol-lowering activ-ity in rats include wax isolated from RBO, which significantly lowered plasmaand liver cholesterol and increased fecal fat excretion when fed at 10% of thediet [31], and rice bran protein, which significantly lowered serum choles-terol compared to casein or fish protein in rats fed cholesterol-free diet [32].The hypocholesterolernic effect of rice protein was attributed to the higherarginine/lysine ratio in rice protein relative to animal protein.

Morita et al. [33] reported significant serum cholesterol reduction in ratsfed a rice protein diet compared with those fed a casein diet. Sunitha et al.[341 observed significant reduction in PC, LDL-C, and liver cholesterol in ratsfed rice bran oil plus safflower/sunflower oil in a 70:30 ratio for four weeks.The fecal neutral sterols and bile acid content increased in animals on a dietcontaining rice bran oil.

Other SpeciesRabbits fed 20% rice protein diet had significantly lower PC, VLDL-C, andLDL-C compared to those fed casein [35]. In addition to the higher argin-ine/lysine ratio of rice protein compared to that of casein [1.13 vs. 0.44), theauthors also suggested that the lower percentage of acetate-generating aminoacids (valine, leucine, isoleucine, phenylalanine tryptophan, and lysine) inrice protein versus casein (33.49% vs. 38.17%, respectively) may have beenpartly responsible for the cholesterol-lowering effects.

In male cynomolgus monkeys, rice bran oil significantly lowered PC andLDL-C without affecting high density lipoprotein cholesterol (HDL-C) com-pared with a diet containing a mixture of butter oil, corn oil, and olive oil inan eight-week feeding study [ 361 . In contrast, feeding a 50% rice bran dietto female cynomolgus monkeys fed increasing amounts of cholesterol for9 months resulted in no PC reductions [37] A stabilized rice bran diet with7% TDF significantly lowered PC but not liver cholesterol in C5713L/6 micecompared to a fiber-free control diet when diets contained 0.06% cholesterolfrom ground beef [381.

In chicks fed a diet containing 0.5% cholesterol, 60% full-fat rice bran, and24% fat, PC and LDL-C were significantly lowered while HDL-C was signifi-cantly increased, compared with the 7% fat control diet; however, when dietswere made isocaloric (10.8% fat), LDL-C significantly increased and HDL-C

Mi

314 Fth'r liir'djeizt: Tood Applications and Health Benefits

TABLE 14.5

Human Studies: Plasma Cholesterol Lowering by Rice Bran (RB) and RiceBrnn Oil RBO

21 days (bog RB)

21 days (bOg RB)IS days (RBO)

30 days (RBO)

4 weeks (60g RB)

21 days (15g RB)

21 days (30g RB)

42 days (84g RB)

Plasma Cholesterol, mg/dL -

Control Treatment

235

211217

208247

204247

183245

242176

172176 169267

245

Effect

Significant

Not significant

Significant

Significant

Not significant

Not significant

Not significant

Significant

Ref.

43

43

49

49

42

46

46

44

increased with no effect on PC [39]. Defatted rice bran increased PC, LDL-C,and HDL-C, suggesting that PC-lowering properties of rice bran in chicksmay be associated with rice bran oil.

Human Studies

Unpolished rice showed a repressive effect on serum cholesterol and trig-lyceride elevations in adult males compared with those fed polished rice;the beneficial effect was attributed to the dietary fiber of the unpolished rice[401. Five healthy young men consumed brown rice with 279 g of neutraldetergent fiber (NDF) per day for 14 days, resulting in significant increasesin fecal wet weight, dry weight, water, and fat excretion compared with thosefed white rice with 13.7 g of NDF per day E411. PC and HDL-C levels werenot significantly different from those with a polished rice diet, possibly dueto the fact that total cholesterol concentrations in the subjects were in thelower part of the normal range. In a four-week study, 24 mildly hypercholes-terolemic men consuming 60 g/d of rice bran diet containing 11.8 g dietaryfiber, had 49/o (nonsignificant) reductions in LDL-C and apo-B, significantincreases in their HDL-C/PC ratio, and no change in PC compared to thoseconsuming wheat bran [42] (Table 14.5). It was concluded that a consumptionof realistic amounts of a single food source of dietary fiber could providea modest benefit to the antiatherogenic profile of plasma lipoproteins. In athree-week crossover design study, significant reductions in PC and LDL-Cwere observed in 11 subjects with moderately elevated blood cholesterol afterconsuming 100 g/d of rice bran or oat bran [43]. Reductions were 10% (signifi-cant) during the first three weeks and 5% (nonsignificant) during the secondthree-week period, with an overall reduction of 7% (Table 14.5). Cholesterolreductions with rice bran and oat bran were similar. In a six-week non-cross-over design study [44], moderately hypercholesterolemjc adults achieved sig-nificant reductions in serum total and LDL cholesterol by consuming 84 g/d

315Rice Bran

of heat-stabilized, full-fat medium grain rice bran product or oat bran. Thebran supplements were added to the subjects' usual daily intake of a low-fat,low-cholesterol diet and did not replace any dietary components. There wereno significant differences between the serum cholesterol reductions with therice bran product (8.3%) versus those with the oat bran (13.0%).

Addition of a mixture of 30 g each of rice bran and oat bran to the dailydiets of 17 moderately hypercholesterolemic and hypertriglyccridemic indi-viduals for six weeks resulted in no significant reductions in TC or HDL

cholesterol [45] . The authors suggested that the level of dietary fiber testedmay have been inadequate or that increasing soluble fiber intake may notbe the sole answer to reduce hyperlipidemia. Consuming 15 or 30 g/d ofrice bran by 18 normocholesterolemic subjects for three weeks resulted inno significant changes in TC, LDL cholesterol, or I-IDL cholesterol, althoughtriglycerides (a risk factor) were significantly reduced with 15 g/d rice branconsumption compared with 15 g/d wheat bran [46]. Again, the normocho-lesterolemic state of the subjects may have been partly responsible for thelack of effect on TC and LDL-C and HDL-C.

A 60 g mixture of rice bran oil and safflower oil (70:30) given for seven daysto 10 females per group was more effective in lowering TC than either of the

oils alone [47, 481; most of the subjects had normocholesterolemic basal levelsat the start of each treatment. Other investigators also reported a beneficialeffect when customary cooking oil was replaced with rice bran oil for 15and 30 days, resulting in significant reductions in TC and triglycerides in 12hypercholesterolemic and hypertriglyceridemic subjects [49] (Table 14.5). Sig-nificant cholesterol-lowering effects of y-oryzanol were reported in hyperlip-idemic patients who were given 300 mg/d y-oryzanol for three months [50].Consuming a diet supplemented with 35.5 g/d of full-fat rice bran for 18 dayssignificantly lowered serum cholesterol in 10 subjects, compared to a fiber-free control period, whereas 30 g/d of defatted rice bran was not effective[51], suggesting that cholesterol reductions were due to the lipid component

of rice bran.HypercholeSterolemic human subjects showed the same cholesterol-

lowering effect as the animal model when fed cereal fiber, rice bran, andoat bran diets. In experiments conducted over 15 and 30 days, Raghuramet al. [49] reported a reduction in TC among 12 hypercholesterOlemic men,who replaced their normal diet of peanut cooking oil with rice bran oil(Table 14.5). However, there were no reductions in total cholesterol in nor-mocholesterolemic men who ate 15 or 30 grams of dietary fiber per day [46].HypercholesterOlemic subjects who consumed the NCEP step-1 diet and atocotrienol-rich extract of rice bran oil significantly reduced TC and LDL-C[52]. Hypercholesterolemic individuals who consumed rice bran oil or thetocotrienol-rich fraction from rice bran oil reduced TC and LDL-C [53, 541.Numerous and exhaustive human and animal studies have shown that sta-bilized rice bran, rice bran oil, and tocotrienol-rich fraction of rice oil lowerTC, LDL-C, and improve the HDL/TC ratio.

-

ILA

316 Fiber Ingredients: Food Applications and Health Benefits

Bile Acid Binding by Rice Bran

Binding bile acids and increasing their fecal excretion has been linked withcholesterol lowering in plasma and liver [55-57]. in vitro bile acid binding bystabilized rice bran on dry matter basis has been observed to be 12% to 25%of that by cholestyramine (a bile acid binding drug) [58, 59].

Whole Grain Recommendation

USDA's new food guide (2005) recommends consuming 50% of grains aswhole rather than refined. The healthful potential of rice bran has been doc-umented by various in vitro, animal and human studies. It would be advis-able to consume brown rice as whole grain rice rather than fortifying milledwhite rice with stabilized rice bran. Brown rice takes 45 minutes to cookas compared with 20 minutes for white rice. Process technologies need tobe perfected to reduce cooking time for brown rice and consumers need toreceive the information that brown rice is a preferred food. Instant brownrice, partially cooked brown rice, or rice flour blasted brown rice to facilitatewater penetration are in the works at various research facilities to reduce thecooking time for brown rice and to facilitate its consumer acceptance.

Market Potential

Currently only a small fraction of the rice bran produced worldwide is sta-bilized and sold as health food. Rice bran and its fractions are sold at differ-ent price levels depending upon the final use or application. The wholesaleprice for stabilized rice bran ranges from $2.92 to $4.25 per Kg. Retail pricesvary from $6.14 to $58.64 per Kg (Table 14.6). If all the rice bran and rice oilproduced were sold as health food, the price would lower to encourage con-sumer preference. The stabilized rice bran at $1 per Kg would have a poten-tial market value of $63 to $76 billion per year (world production = 63 to 76million tons). It would be utilized as a food ingredient and its full healthfulpotential could be realized.

Summary

Animal and human studies show cholesterol lowering with rice bran inhypercholesterolemic individuals, with reductions occurring usually in the

p.--.

317Rice Bran

TABLE 14.6

Stabilized Rice Bran Prices

Source

Wholesale

Rice Bran (spot price) 2.92

Rice Bran Deoiled 4.25

Retail

Health Foods MarketsRice Bran Organic 9:50

Rice Bran Soluhles 87.89

Rice Bran 6.14

Rice Bran Syrup 27.48

Rice Bran (low fiber) 55.01

Rice Bran (with fiber) 58.64

Rice Bran (with fiber) 49.50

Rice Bran Beverage 102.65

Rice Bran Oil 4.45-15.38

Notes: 63-76 million toils/year. 863-76 billion potential value per year.

LUL (atherogenic) fraction. Specific rice bran fractions showing hypocholes-terolemic activity include rice bran oil, unsaponifiable matter, dietary fiber,and protein. There is a dose response to the level of rice bran and rice bran oilunsaponifiable matter for cholesterol reductions, but intact full-fat rice branappears to be the most effective. This suggests that incorporation of intactstabilized rice bran into food products would be more effective than the for-tification of food with isolated individual concentrated fractions of rice bran.Consuming brown rice as whole grain would be highly desirable.

Possible mechanisms for cholesterol lowering with rice bran include inter-ference with absorption/reabsorptio n of dietary and/or endogenous lipid inthe gastrointestinal tract and increased excretion of bile acids, which resultsin utilization of more cholesterol for bile acid synthesis. In addition, changesin hepatic LDL receptor activity have been reported with rice bran feeding[18], and the inhibition of cholesterol synthesis by tocols and tocotrienolSpresent in rice bran oil may also contribute to cholesterol reduction [ 421 . The

evidence to date suggests that several mechanisms may be simultaneouslyinvolved in the cholesterol-lowering effects of rice bran.

Atherosclerosis is a disease that apparently takes from 40 to 50 years todevelop. The concept of a 2% reduction in risk with each 1% reduction incholesterol in high-risk individuals is well accepted. With reported plasmatotal and LDL cholesterol reductions of 4% to 10% in subjects with moderatehypercholesterolemia the available information suggests that inclusion ofrice bran in the diet, along with a reduction of fat calories to 30% and satu-

1

318 Fiber Ingredients: Food Applications and Health Benefits

rated fat to less than one-third of total fat, could prove to be healthful for thegeneral population. Commercial interest generated by the health effects ofrice bran has contributed to the introduction of numerous value-added rice-bran-containing foods and food products such as breads, breakfast cereals,cakes, cookies, extruded snacks, muffins, pies, and snack bars. The popular-ity of the new rice bran products is encouraging and expected to continuewith health-conscious consumers. Incentives are needed for the rice industryto increase the production and availability of stabilized rice bran for its incor-poration into more healthful, value-added foods for human consumption.

References

I. Khush, G. 2003. Productivity improvements in rice. Nutr. Rev. 61:114-116.2. Randall, J . M., R. N. Sayre, W. G. Schultz, R. Y. Fong, A. P. Mossman, R. E. Tn-belhorn, and R. M. Saunders. 1985. Rice bran stabilization by extrusion cookingfor extraction of edible oil. I. Food Sci. 50:361-364.

3. Steinhart, H., T. Rathjen. 2003. Dependence of tocopherol stability on differentcooking procedures of food. lot. I. Vitam. Nutr. Res. 73:141-151.

4. Connor, M. A., R. M. Saunders, G. 0. Kohler. 1976. Rice bran protein concen-trates obtained by wet alkaline extraction. Cereal Chem. 53:488-496.5. Kahlon, T. S., R. M. Saunders, R. N. Sayre, F. I. Chow, M. M. Chiu, and A. A.Betschart. 1992. Cholesterol-lowering effects of rice bran and rice bran oil frac-tions in hypercholesterolemic hamsters. Cereal Cheni. 69:485-489.

6. Sharma, R. D., C. Rukmini. 1986. Rice bran oil and hypocholesterolemia in rats.Lipids 21:715-7177 Itoh, T., T. Tamura, and T. Matsumoto. 1973. Sterol composition of 19 vegetable

oils. J. Am. Oil Chemists Soc. 50:122-125.8. Sayre, R. N., L. Earl, F. H. Kratzer, and R. M. Saunders. 1987 Nutritional quali-

ties of stabilized and raw rice bran for chicks. Poii1tr 1 Sd. 66:493-499.9. Sayre, R. N., L. Earl, F. H. Kratzer, and R. M. Saunders. 1988. Effects of diets con-

taining raw and extrusion-cooked rice bran on growth and efficiency of foodutilization of broilers. Brit. Poultry Sd. 29:815-823.

10. Calvert, C., K. Parker, Z. J . Parker, R. N. Sayre, and R. M. Saunders. 1985. Ricebran in swine rations. Calif. Agric. May-June, 19.

11. Spady, D. K., J . M. Dietschy. 1985. Rates of cholesterol synthesis and low-densi-lipoprotein uptake in the adrenal glands of the rat, hamster and rabbit in viva.Biochini. Biophys. Acta 836:167-175.

12. Kahlon T. S., R. M. Saunders, R. N. Sayre, F. I. Chow, M. M. Chiu, and A. A.Betschart. 1989. Effect of rice bran and oat bran on plasma cholesterol in ham-sters. Cereal Foods World 34:768 (Abstract).

13. Haumann, B. F. 1989. Rice bran linked to lower cholesterol. J. Am. Oil ChemistsSoc. 66:615-618.14. Kahlon T. S., R. M. Saunders, R. N. Sayre, F. I. Chow, M. M. Chiu, and A. A.

Betschart 1990. Influence of rice bran, oat bran, and wheat bran on cholesteroland triglycerides in hamsters. Cereal Chem. 67:439-443.

II

Rice Bran 319

15. Kahlon T. S., F. I. Chow, R. N. Sayre, and A. A. Betschart. 1992. Cholesterol-lowering in hamsters fed rice bran at various levels, defatted rice bran and rice

bran oil. J . Nutr. 122:513-519.16. Kahlon T. S., F. I. Chow, B. E. Knuckles, and M. M. Chiu. 1993. Cholesterol-

lowering effects in hamsters of 3g1ucanenriched barley fraction, dehulledwhole barley, rice bran, and oat bran and their combinations. Cereal Cheni.

70:435-440.17.Kahlon T. S., F. I. Chow, M. M. Chiu, C. A. Hudson, and R. N. Sayre. 1996. Cho-

lesterol-lowering by rice bran and rice bran oil unsaponifiable matter in ham-

sters. Cereal Chem. 73:69-74.18. Kahion, T. S., F. 1. Chow, and D. F. Wood. 1999. Cholesterol response and foam

cell formation in hamsters fed rice bran, oat bran, and cellulose + soy proteindiets with or without added vitamin E. Cereal Chem. 76:772-776.

19. Mattson, F.H., S. M. Grundy, and J . R. Crouse. 1982. Optimizing the effect of

plant sterols on cholesterol absorption in man. Am. J . Clin. Nutr. 35:697-700.

20. Rong, N. L., L. M. Ausman, and R. J . Nicolosi. 1997 Oryzanol decreases choles-terol absorption and aortic fatty streaks in hamsters. Lipids. 32:303-309.

21. Kahlon, T. S., R.H. Edwards, and F. I. Chow. 1998. Effect of extrusion on hypo-cholesterolemic properties of rice, oat, corn, and wheat bran diets in hamsters.Cereal Chein. 75:897-903.

22. Ayano Y., F. Ohta, Y. Watanabe, and K. Mita. 1980. Dietary fiber fractions indefatted rice bran and their hypocholesterolernic effect in cholesterol-fed rats.

I. Nutr. Food (Japan). 33:283-291.23. Aoe S., F. Ohta, and Y. Ayano. 1989. Effect of rice bran hemicellulose on the cho-

lesterol metabolism in rats. Nippon Eiyoshokuryo Gakkaishi. 42:55-61.

24. Johnson I. T., J . M. Gee, and J . C. Brown. 1989. A comparison of rice bran,wheat bran and cellulose as sources of dietary fibre in the rat. Food Sci. Nutr.

42:153-163.25. Rouanet, J-M, C. Laurent, and P. Besancon. 1993. Rice bran and wheat bran:

selective effect on plasma and liver cholesterol in high-cholesterol fed rats. Food

Chem. 47:67-71.26. Topping D. L., R. J . lllman, P. D. Roach, R. P. Trimble, A. Kambouris, and P. J.

Nestel. 1990. Modulation of the hypolipidemic effect of fish oils by dietary fiberin rats: studies with rice and wheat bran. J. Nutr. 120:325-330.

27.Sharma R. D., and C. Rukmini. 1987. Hypocholesterolemic activity of unsaponi-fiable matter of rice bran oil. Indian J . Med. Res. 85:278-281.

28. Seetharamaiah, G. S., and N. Chandrasekhara. 1989. Studies on hypocholester-olemic activity of rice bran oil. Atherosclerosis 78:219-223.

29. Seetharamaiah, G. S., and N. Chandrasekhara. 1990. Effect of oryzanol on cho-lesterol absorption & biliary & fecal bile acids in rats. Indian 1 . Med. Res. [B]

92:471-475.30. Seetharamaiah, G. S., T. P. Krishnakantha, and N. Chandrasekhara. 1990.

Influence of oryzanol on platelet aggregation in rats. J . Nutr. Sci. Vitaminol.

36:291-295.31. Ishibashi, G., and M. Yamamoto. 1980. Effect of rice wax, garlic, and gingko

seed component on plasma and liver cholesterol levels in rats. Kynshi Women's

Univ. 16:115-127.32. Sugano, M., N. Ishiwaki, and K. Nakashima. 1984. Dietary protein-dependent

modification of serum cholesterol level in rats. Ann. Nutr. Metb. 28:192-199.

F

320Til'i l'zgredu'nts: Food Applications and Health Benefits

33. \iortta, L, \. ()h-hashi, K. fakei, M. lkai, S. Kasaoka, and S. Kiriyama. 1997.Cholesterol-lowering effects of soybean, potato and rice proteins depend ontheir low rnethionine contents in rats fed a cholesterol-free purified diet.]. Nutr.27:470-477

34. unitha, 1., R. Manorama, and C. Rukmini. 1997 Lipid profile of rats fed blendst rice bran oil in combination with sunflower and safflower oil. Plant Foods forIlioflan Nutr. 51:219-230.

3 Alladi S., R. Gilbert, and K. R. Sha nmugasundaram 1989. Lipids, lipoproteinsid lipolytic activity in plasma with dietary protein changes. Mar. Rep. lot.40:653-661

3 \icolosi R. J ., L. M. Ausman, and D. M. Hegsted. 1991. Rice bran oil lowersscrum total and low density lipoprotein cholesterol and apo B levels in nonhu-man primates. Atherosclerosis 88:133-142.

7. \lalinow, M. R., P. McLaugwin, L. Papworth, H. K. Naito, and L. A. Lewis. 1976.Lffect of bran and cholestyramine on plasma lipids in monkeys. Am. J. C/in..\ijtr, 29:905-911

38. 1 lundemer, J. K., S. P. Nabar, B. J . Shriver, and L. P. Forman. 1991. Dietary fiberSources lower blood cholesterol in C57BL/6 mice. I. Nutr. 121:1360-136539. Newman, R. K., A. A. Betschart, C. W. Newman, and P. J. Hofer. 1992. Effectof full-fat or defatted rice bran on serum cholesterol. Plant Foods Hun,. Nutr.42:37-43.

40. Suzuki, M. 1982. Repressive effect of dietary fiber fractions in unpolished riceon the increase in cholesterol and triglyceride. I. Nutr. Food (Japan) 35:155-160.41. Miyoshi, H., T. Okuda, Y. Oi, and H. Koishi. 1986. Effects of rice fiber on fecalweight, apparent digestibility of energy, nitrogen and fat, and degradation ofneutral detergent fiber in young men. J. Nutr. Sci. Vitnlninol.32:581_589.42. Kestin M., R. Moss, C. M. Clifton, and P. J . Neste]. 1990. Comparative effects ofthree cereal brans on plasma lipids, blood pressure, and glucose metabolism inmildly hypercho1esteroiemi men. An,. J. Cl/n. Nutr. 52:661-666.43. Hegsted M., M.M. Windhauser, S. K. Morris, and S. B. Lester. 1993. Stabilizedrice bran and oat bran lower cholesterol in humans. Nutr. Res. 13:387-398.44. Gerhardt A. L., and N. B. Gallo. 1998. Full-fat rice bran and oat bran similarlyreduce hypercholesterolernia in humans. J. Nutc 128:865-869.45. Ranhotra, G. S., J . A. Gelroth, R. D. Reeves, M. K. Rudd, W. R. Durkee, J . D.Gardner. 1989. Short-term lipidemic responses in otherwise healthy hypercho-lesterolemic men consuming foods high in soluble fiber. Cereal Client. 66:94-9746. Sanders, T. A. B., and S. Reddy. 1992. The influence of rice bran on plasma lipidsand lipoproteins in human volunteers Eu,-. I. Cl/n. Nut r. 46:167-172.

47 Suzuki, S., and S. Oshima. 1970. Influence of blending of edible fats and oils onhuman serum cholesterol level (Part 1). Blending of rice bran oil and saffloweroil. I. Nutr. (Japan). 28:3-6.

48. Suzuki, S., and S. Oshima. 1970. Influence of blending oils on human serumcholesterol (Part 2). Rice bran oil, safflower oil, sunflower oil.

J. Nutr. (Japan)28:194-198.49. Raghuram, T. C., D. B. Rao, and C. Rukrnini. 1989. Studies on hypolipideniic

effects of dietary rice bran oil in human subjects. Nutr. Rep. lot. 39:889-895.50. Yoshino, G., T. Kazumj, M. Amano, M. Tateiwa, T. Yamasakim, S. Takashima,M. Iwai, H. Hatanaka, and S. Baba. 1989. Effects of gamma-oryzanol and probu-col on hyperlipidemia. Current Therap. Res. 45:975-982.

F

321Rice Bran

51. Tsai, C. E., H. Ting, L . J. Wang, and T. Lin. 1992. The effect of rice bran on blood

lipids in man. J. Chinese Agric. Chen. Soc. 30:484-495.

52.Qureshi, A. A., B. A. BradloW, W. A. Salser, and L. D. Brace. 1997. Novel tocot-rienolS of rice bran modulate cardiovascular disease risk parameters of hyper-

cholester0lem humans. J . Nutr. Biocheni. 8:290-298.

53. Rajnara Ya K., M. C. Prabhakar, and D. R. Krishna. 2001. Influence of rice

bran oil on serum lipid peroxides and lipids in human subjects. Indian J . Physiol

PharnuicOl. 45:442-444.54, Qureslli, A. A., S. A. Sami, W. A. Salser, and F. A. Khan. 2002. Dose-dependent

suppression of serum cholesterol by tocotrienolri h fraction (TRF25) of rice

bran in lyperch0le5tlm ic humans. Atherosclerosis 161:199-207

55. Trowel1, H. C. 1975. Refined Foods and Disease, Burkitt and Trowell, Eds., Aca-

demic Press, London, 195-226.

56. Lund, E. K., J . M. Gee, J . C. Brown, Wood, P. J . , and Johnson, I. T. 1989. Effect of

oat gum on the physical properties of the gastrointestinal contents and on theuptake of D_galaCtose and cholesterol by rat small intestine in vitro. Br. J . Nutr.

62:91-101.57 Anderson,] W., and A. E. Siesel. 1990. Hypochole5ter0m K effects of oat prod-

ucts, in New DevelOp111e t5 in Dietary Fiber: Physiological, Physiocheinical, and Ana-

lyticalFurda, I., Brine, Cj., Eds., Plenum Press, New York, 17-36.

58. Kahlon, T. S., and F. I. Chow. 2000. In vitro binding of bile acids by rice bran, oat

bran, wheat bran and corn bran. Cereal Chein. 77: 518-521.

59. Kahlon, T. S., and Woodruf f, C. L. 2003. In vitro binding of bile acids by rice

bran, oat bran, barley and 3-glucan enriched barley. Cereal Chem. 80:260-263.