Rice Bran

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Rice Bran
Pennington Biomedical Research Center
Division of EducationHeli J. Roy PhDShanna
Lundy, BSPhillip Brantley, PhD, Director
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Rice Bran Contents

• Rice bran is composed of the aleurone layer of
  the rice kernel and some part of the endosperm
  and germ, which are rich sources of proteins,
  lipids, vitamins, and trace minerals
• Rice brans oil and unsaponifiable lipid content
  is high compared with other grains
• Unrefined rice bran oil consists of 20
  saturated, 40 monounsaturated, and 40
  polyunsaturated fatty acids and contains
  tocotrienols, ?-oryzanol, and ß-sitosterol

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• Rice bran and its oil contain large
  concentrations of several compounds that could
  potentially prevent chronic diseases such as
  coronary heart disease and cancer
• The LSU AgCenter has been actively identifying,
  extracting, purifying, and evaluating the
  functionality of several of these compounds

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• Their initial studies with rice bran focused on
  stabilizing against lipid degradation that leads
  to flavor problems
• During these studies, it was noted that rice bran
  contained high levels of both tocopherols and
  tocotrienols, which compromise vitamin E and act
  as antioxidants in the body
• Also, high levels of a mixture of compounds
  referred to collectively as oryzanol were
  identified within rice bran

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• Oryzanol components are complex compounds that
  can act as an antioxidant, improving solubility
  in cell membranes and potentially lowering
  cholesterol by competitive inhibition of
  absorption and synthesis

• Methods of separating the individual components
  of the oryzanol mixture have come about, leading
  to the identification of 3 major fractions of
  oryzanol
• Cycloartenyl ferulate
• 24-methylene cycloartanyl ferulate
• Campesteryl ferulate

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• Because the causes associated with almost all
  chronic disease can be traced to the effects of
  oxidants, both in the environment and in our
  bodies, interest arose in the area of rice bran
  and its antioxidant capacity

• Specifically, cholesterol oxidation products
  have been suggested as a major cause of heart
  disease

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Rice bran components do reduce
cholesterol oxidation

• The antioxidant activities of four of the vitamin
  E and three oryzanol components purified from
  rice bran were investigated in a chemical model
  of cholesterol oxidation
• All components exhibited significant antioxidant
  capacity in the inhibition of cholesterol
  oxidation!
• All three oryzanol components were higher than
  any of the four vitamin E components

Found that
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Rice bran Osteoporosis

• Osteoporosis affects more than 20 million older
  Americans, with the number increasing every year
• Because of the risk for cancer associated with
  hormone replacement therapy in women, alternative
  methods to reduce bone loss are currently being
  investigated
• Studies on rice bran and its role in osteoporosis
  have been conducted

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• Ovariectomized rats (who typically lose
  substantial bone mineral density after the
  ovariectomy) were used as a model for
  postmenopausal osteoporosis
• Found that with the addition of a 7 oryzanol
  rice bran oil (RBO) concentrate to the diets of
  these rats that reductions in bone loss at
  several bone sites occurred
• The beneficial effect of the RBO concentrate
  appeared to be primarily on cortical bone in the
  long bones, and not on the trabecular bone in
  vertebrae

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• Crystalline oryzanol and crystalline oryzanol
  dissolved in corn oil had no effect on bone
  mineral density
• Suggesting that either the oryzanol as it occurs
  naturally in rice bran oil is more biologically
  active than crystalline oryzanol or that
  something else in the rice bran oil is affecting
  bone density positively

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• More studies are needed to identify the active
  elements in rice bran oil beneficial in reducing
  bone loss and in determining their mode of action
• Rice bran oil concentrate appears to primarily
  act on preserving the slow turn-over cortical
  bone in the long bones
• Other functional foods, such as soy protein, act
  on rapid turnover trabecular bone in vertebrae
• The possibility of using the two together in
  combination is an area currently under
  investigation

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More on Rice Bran

• In the past, human consumption of rice bran has
  been limited, primarily because of the rapid
  onset of rancidity in rice bran, but methods to
  stabilize rice bran and to extract its oils have
  been developed
• Interest in rice bran grew from the determination
  that the inclusion of oat bran in the diet lowers
  serum cholesterol
• Rice bran contains less total dietary fiber and
  less soluble fiber than oat bran

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Studies of Rice Bran ..

• Based on its soluble fiber content alone, rice
  bran should have less hypolipidemic effects than
  other sources of fiber
• However, studies of rice bran supplementation in
  humans found similar beneficial effects on
  lipoproteins
• In a 10-week controlled feeding trial, rice bran
  was as effective as oat in lowering blood
  cholesterol concentrations in men and women with
  moderately high blood cholesterol concentrations
• Has shown reductions in cholesterol levels in
  pigs, hamsters, rats, humans, and nonhuman
  primates

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• What exact component found in rice bran is
  responsible for its cholesterol-lowering effects?
  
• Possible suggestions have included
• The fiber that is present
• The Fatty acid composition
• Or the Unsaponifiables present
• Oryzanol, phytosterols (campesterol and
  ß-sitosterol)

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• Evidence from 2 well-controlled studies at
  Pennington Biomedical Research Center confirms
  that it is the rice bran oil (RBO), and not the
  fiber, that lowers blood lipids in men and women
  with borderline high total cholesterol
• Although RBO does contain about 20 saturated
  fatty acids and approximately equal amounts of
  oleic and linoleic fatty acids, its cholesterol
  lowering ability is due to its unsaponifiable
  components more so than by its fatty acid
  composition

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• In a recent study, by matching the fatty acids of
  the rice bran oil with a control oil blend, it
  was shown that the effect of RBO on serum
  cholesterol concentrations is due to the
  unsaponifiables present in it and not to its
  fatty acid profile
• It is believed that RBO containing these
  compounds could become an important functional
  food with cardiovascular health benefits

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References

• http//www.agctr.lsu.edu/Communications/LouisianaA
  griculture/agmag/45_4_articles/ricebran.asp
• http//www.nutrition.org/cgi/content/full/128/5/86
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• http//www.ajcn.org/cgi/content/full/81/1/64