|
|
Nutritional
Significance Of Rice bran Oil
Dr. Shashank R
Joshi, MD, DM, FICP, FICN
Endocrinologist, Lilavati Hospital.
Hon. Asst. Prof, Grant Medical College, Mumbai
Hon. Editor, JAPI *
* (The views of the expert are on good quality Oryzanol Rich
Rice Bran oil and /or its blends and not for any specific brand)
Basics
Fat is an important ingredient of human diet. The functional role
of fat in the diet is manifold. Fat is a most concentrated source
of energy. One gram of fat gives 9 kcal of energy.
Carbohydrates and proteins provide only 4 kcal of energy per gram.
Hence fat provides calorie density to the diet. Secondly, fats are
essential in the diet for the absorption and mobilization of
fat-soluble vitamins such as vitamin A, vitamin E and fat-soluble
antioxidants. These vitamins are not utilized by the body if fat
is not available in the diet.
|
Thus
fat works as a vehicle to carry the fat-soluble vitamins,
nutrients and antioxidants in the body. Thirdly, vegetable oils
are the only sources of essential fatty acids to the body.
Essential fatty acids (EFA) are those fatty acids which the body
cannot synthesize and need to be supplied through diet. EFAs are
the precursors for a group of chemically related compounds, known
as prostaglandins that are synthesized in the body from EFA. If
EFA is not supplied through diet to the body, the body cannot
synthesize prostaglandins. Prostaglandins play a key role in
regulating many physiological processes in the body, such as
controlling blood pressure, vascular damage in the brain and the
heart, preventing blood clot in the arteries, lowering
cholesterol, uterine contractions during child birth and menstrual
cycles, inflammation and other conditions.
Fourthly, fat also helps in raising HDL, the so-called good
cholesterol. Low-fat diets can result in reduction of HDL
cholesterol. Fifthly, fat in the diet imparts certain textural
qualities, taste and palatability to the food. Fats and oils are
integral lubricants of foods in two ways: through use as release
agents as a part of the cooking process and as a lubricant during
mastication (chewing). Fats and oils modify flavor release and
improve palatability.
Thus fat is an essential nutrient in our balanced diet. Since
several studies in literature have directly implicated the amount
and type of fat intake to specific diseases such as cardiovascular
disease, cancer, high blood pressure and obesity, so one has to be
very particular as to quantity as well as quality of fat in the
diet to maintain good health.
The quantity and quality of fats determine the intakes of various
fatty acids in the total diet. Several studies have indicated that
the hypocholesterolemic action of a dietary fat depends on the
fatty acid composition and also to some extent on the
micronutrients like tocopherols and tocotrienols present in them.
The optimal balance of saturated, polyunsaturated and
monounsaturated fatty acids make an ideal oil.
Quantity of fat
According to the American Heart Association, the optimum intake of
fat for an adult is 30% of its total caloric intake. Therefore for
an adult man consuming 2000 calories, the upper limit of total fat
(visible and non-visible) is 65 gm/day.
Apart from visible fat some amount of fat is present in food items
like cereals, pulses, milk, eggs, meat etc. as invisible fat. From
the database generated on fatty acid composition in Indian foods
and National Nutrition Monitoring Bureau diet surveys, the daily
invisible fat intake is estimated to be 15gm in rural poor and
25gm in the urban middle and high-income groups. Thus the daily
requirement of visible fat intake works out to be some where
between 20 to 50 gms depending upon physical activity and
physiological status.
Quality of fat
Choice of a healthy cooking oil is a controversial subject. The
ideas keep on changing as new evidence accumulates. Desi Ghee
(butter Oil) used to be the conventional cooking oil of the
Indians. There was nothing wrong with this most favourite cooking
medium of Indian households. But the problems started with the
change in our eating and living habits. Desi Ghee being rich in
saturated fats has the tendency to increase total cholesterols
including HDL (so called "good cholesterols") and LDL
& VLDL (so called "bad cholesterols"). As such
consumption of desi ghee coupled with fibre rich diet which
reduces LDL bad cholesterol & physical activity which reduces
VLDL bad cholesterol brings about a favourable lipid profile. In
the good olden days, our forefathers used to take fibre rich diet
such as chapattis made out of flour of wholegrains & lots of
leafy vegetables along with desi ghee and the nature of work
involved lots of physical labour. All this used to neutralize the
adverse effects of desi ghee on LDL & VLDL while retaining its
positive effects on HDL and thereby this favourite cooking medium
used to bring about a favourable lipid profile.
But with the lack of physical activity in the recent years coupled
with intake of diet devoid of fibre such as chappaties and other
snack foods made from flour of decorticated foodgrains,
consumption of desi ghee started raising total cholesterol levels.
Therefore, the search started for an alternative cooking oil which
could reduce the cholesterol levels. Short-term scientific studies
conducted in this regard found that vegetable oils rich in
polyunsaturated fats had the ability to reduce total cholesterols.
Thus the recommendations tilted in favour of PUFA rich oils such
as safflower oil.
In due course of time evidence began to accumulate establishing
that although polyunsaturated fats were effective in reducing LDL
cholesterol, very high content of polyunsaturated fats had the
undesirable affect of reducing HDL cholesterol as well. It further
came to light that since oils with high levels of polyunsaturated
fats oxidize faster than those with MUFA or SFA profiles,
therefore, the excessive intake of these oil could impair the
ability of the anti-oxidants in the human system to control free
radicals and thereby enhance the risk of certain cancers,
cataracts, rheumatoid arthritis, Parkinson's disease and
contribute to the ageing problem. All these findings have led to a
change with respect to the earlier recommendations and a delicate
balance between cholesterol balancing(instead of cholesterol
lowering) properties and oxidative stability has become an
important concern nowadays.
The American Heart Association now recommends use of oils having
an equal proportion of saturated, monounsaturated and
polyunsaturated fats. The World Health Organization (WHO)
recommends polyunsaturated fatty acid (PUFA)/saturated fatty acids
(SFA) ratio of 0.8 to 1.0 and linoleic acid (Omega6) alpha
linolenic acid (Omega3) ratio of 5-10 in the diet. The most recent
recommendations according to the National Research Council,
Washington DC are 10% saturates, 12 to 13% for monounsaturates,
not more than 7 to 8% for polyunsaturates. Japan's Ministry of
Health & Welfare suggests fatty acid ratio of
saturated/monounsaturated/ polyunsaturated as 1:1.5:1 and a 4:1
ratio of omega 6 to omega 3 fatty acids. A further noteworthy
point in this recommendation is that the intake of polyunsaturated
fat should be accompanied by vitamin E, vitamin C or carotene
consumption to help prevent lipid peroxidation.
A perusal of these recommendations would reveal that there are
basically three parameters to adjudge any oil as the healthiest
cooking oil. i.e. ratio of saturated/ monounsaturated/
polyunsaturated fatty acid, ratio of essential fatty acids
(Omega6/Omega3) and presence of natural antioxidants.
If we look to the composition of the various vegetable oils
commonly used in India, we shall find that no single oil could
meet the requirement of these recommendations but some are nearer
to the recommendations.
COMPOSITION OF COMMON VEGETABLE OILS
| |
Fatty
Acids
% Weight |
Essential
Fatty Acids |
Antioxidants |
| SFA |
MUFA |
PUFA |
Omega6/Omega3 |
|
| Mustard
Oil / Rapeseed Oil |
6 |
67 |
27 |
2 |
Tocopherols |
| Sunflower
Oil |
12 |
38 |
50 |
57 |
Tocopherols |
| Safflower
Oil |
10 |
15 |
75 |
69 |
Tocopherols |
| Soyabean
Oil |
16 |
24 |
60 |
10 |
Tocopherols |
| Groudnut
Oil |
20 |
50 |
30 |
32 |
Tocopherols |
Rice
Bran Oil
Recommended |
20
below 33% |
45
above 33% |
35
about 33% |
15
5-10 |
Tocopherols
Tocotrienols& Oryzanol
Maximum possible |
| Soyabeen
Oil |
16 |
24 |
60 |
10 |
Tocopherols |
The use of
any one of the oils like safflower and soyabean furnish very high
PUFA/SFA ratio. The use of safflower & sunflower also provide
high ratio of Omega6/Omega3. Though the levels of Omega3 will be
in the desirable range when mustard and rapeseed oils are used,
these oils furnish very high levels of erucic acid. The use of
groundnut or rice bran oils ensure optimal intake of MUFA and
ratio of PUFA/SFA. But rice bran oil, a unique cooking oil
produced from rice, is the only oil which besides having balanced
fatty acid composition and an ideal Omega6/Omega3 ratio contains
three categories of natural anti-oxidants i.e. tocopherols,
tocotrienols & oryzanol as against only one category i.e.
tocopherols found in all other conventional oils. These natural
anti-oxidants help in controlling production of free radicals in
the body which can cause injury to the inner lining of blood
channels and initiate coronary diseases, certain cancers,
cataracts, rheumatoid arthritis, Parkinson's disease and
contribute to the ageing process.
High content of natural anti-oxidants present in the rice bran oil
impart higher oxidative stability and have a longer shelflife as
compared to other edible oils. In a recent study conducted by the
Central Food Technological Research Institute, Mysore, oxidative
stability of natural anti-oxidants enriched refined rice bran oil
has been found to be five times more than the groundnut oil.
Although the PUFA content of rice bran oil is much lower than the
other conventional oils, but it has higher cholesterol reduction
power than even the PUFA rich oils.
Human trials conducted by the National Institute of Nutrition,
Hyderabad, have confirmed significant reduction in total
cholesterols particularly the triglyceride levels by using rice
bran oil as compared to conventional cooking oils. In this study
21 subjects with high total cholesterols (>225 mg/dl) or high
triglycerides(>190 mg/dl) were randomly divided into
experimental and control groups. Twelve subjects, who constituted
experimental group, were instructed to use rice bran oil in place
of their usual cooking oil which they were using earlier. The
remaining nine who served as controls, were allowed to continue
the use of their habitual edible oil. There was a significant
reduction in total cholestrol and triglyceride levels 15 and 30
days after the use of rice bran oil. However, in control subjects
there were no changes in serum lipids.
SERUM LIPIDS IN CONTROL & EXPERIMENTAL SUBJECTS
| Subjects |
Cholesterol
(mg./dl) |
Triglycerides
(md/dl) |
| 1.
Control Group Basal |
244.0
+_ 14.0 |
295.5
+_ 33.0 |
| After
30 days |
249.6
+_ 16.1 |
286.3
+_ 34.9 |
| %
change from Basal |
2.3 |
-3.1 |
| 2.
Experimental group Basal |
247.3
+_ 10.5 |
349.8
+_ 42.4 |
| 15
days after RBO |
204.0
+_ 6.6 |
236.5
+_ 31.9 |
| 30
days after RBO |
182.7
+_ 8.4 |
212.9
+_ 20.0 |
| %
change from Basal after 15 days |
-17.5 |
-32.4 |
Similar
findings have been reported in the animal studies coupled with the
human clinical trials recently completed and published by the
University of Lowell, USA. These studies have confirmed that rice
bran oil has the ability to reduce blood cholesterol levels up to
40 percent and has significantly better cholesterol lowering than
the popular olive oil. Experiments conducted by the Human
Nutrition Res. CTR., WASHINGTON ST., showed a greater reduction in
the total & LDL cholesterol in animals fed with the RBO diet
than those consuming CANOLA Oil diet.
All these studies conducted in India & abroad have attributed
the cholesterol reducing properties of rice bran oil to the
presence of a unique component in this oil known as "Oryzanol"
which is not found in any other edible oil. This fact has been
re-confirmed in a most recent study conducted by the Central Food
Technological Research Institute, Mysore. In this study it was
observed that although the fatty acid composition of groundnut oil
and rice bran oil is almost similar but use of rice bran oil
significantly raises good cholesterols and reduces bad
cholesterols due to "Oryzanol" present in the rice bran
oil. Serum lipid levels of rats fed with diet containing 10%
groundnut oil & refined rice bran oil containing about 10,000
P.P.M. of oryzanol produced through the latest techniques of
refining, were reported as under after 11 weeks of feeding :-
Parameters
mg/100/ ml |
GroundnetOil
(control)
(mg./dl) |
Refind
Rice Bran Oil |
HDL
Cholesterol
(Good cholesterol) |
33.8
+ 6.69 |
50.57
+ 3.57 |
LDL
+ VLDL
(Bad cholesterol) |
23.48
+ 8.51 |
15.75
+ 6.68 |
| Triglycerides |
272.8
+ 59.7 |
118.7
+ 34.55 |
Besides beneficially influencing the lipid profile, oryzanol is
also known to have anti-itching, anti-dandruff & anti-ageing
properperties. It is effective in treating a broad range of
gastrointestinal disorders including stress-induced gastric and
duodenal ulcers. Oryzanol is also sold abroad as an agent for body
building in humans & for treatment of nerve imbalance and
disorders of menopause.
Tocotrienols which are found only in rice bran oil and in no other
conventional Indian oil, besides being a cholestrol reducing agent
& a powerful antioxidant are also known to have anti-thombotic,
anti-cancer & anti-ageing properties.
Compared to other edible oils, rice bran oil has high content of
squalene which is reported to be a quencher of singlet oxygen and
a free radical scavenger and it has been shown to maintain the
texture of skin. It is well known for its anti-wrinkle properties.
Thus rice bran oil is the healthiest cooking oil having desirable
fatty acid composition with higher oxidative stability alongwith
better cholesterol reducing power than all other edible oils. It
contains certain unique micro-nutrients which are important for
promotion and maintenance of good health.
"The World's healthiest oil" is also the best tasting. A
properly refined rice bran oil has a pale yellow colour and is
completely odourless & tasteless. In a blind taste test at the
university of Oregon U.S.A., comparing refined rice bran oil, palm
oil, safflower oil, soyabean oil, corn oil, and sunflower oil,
rice bran oil won hands down.
Rice Bran Oil is extensively used in Japan, Korea, China, Taiwan
and Thailand as a premium edible oil. It is the conventional &
the most favourite cooking medium of Japanese, the longest living
human beings on this earth and is popularly known as a "Heart
Oil" in Japan. In recent years U.S. Scientists have also
shown a tremendous interest in the cholesterol lowering properties
of rice bran oil & this oil has acquired the status of health
food with Americans.
Only recently some of the Indian markets too have started
witnessing some brands of refined rice bran oil. As India is the
second largest producer of crude rice bran oil in the world, some
of the leading national & multi-national players in this field
are keeping an eye over this largely untapped potential and are
planing to enter in a big way in the branded refined rice bran oil
segment. The time is not very far when the leading brands of
refined rice bran oil will be available in all the markets of
India & consumers in India too could enjoy the benefits of
this unique gift from mother nature.
It will be the cooking medium of first choice. Our group is
collecting evidence based work on the oil to prove its real
benefits. Its equivalent to olive oil which is the oil of choice
for Italians. Therefore for Indians we have Indian made rice bran
oil.
References:
| 1. |
Dr.
T.N.B. Kaimal, Why Rice Bran Oil, OTA Journal, vol.30,
No.2, dated April-June,1998. |
| 2. |
Dr.C.
Rukmani, Nutritional Significance of Rice Bran Oil, Indian
J. Med. Res. 102, November, 1995,pp 241-44. |
| 3. |
Johan
R. Campen, Research Shows promise for Rice Bran Oil,
www.usarice.com/branoil.html |
| 4. |
Dr.
T.N.B. Kaimal, r-oryzanol from Rice Bran oil, OTA Journal
vol.31, No.2, April-June 1999. |
| 5. |
Joshi
SR. Bypass/Bypass: Rice Bran Oil. Proceedings of 33rd
Annual Conference General Practitioners' Association -
Greater Bombay. |
| 6. |
www.californiariceoil.com |
|
|