Estimation of Cholesterol Level in Different Brands of Vegetable Oils
An analysis of twenty one assorted brands of vegetable
oils in Lagos Metropolis Nigeria, reveals varying levels of cholesterol
content. Cholesterol was found to be present in most of the oil brands
sampled using three standard methods. Cholesterol was detected in seventeen
of the vegetable oil brands with concentration of less than 1 mg/ml while
seven of the oil brands had cholesterol concentrations ranging between
1-4 mg/ml. Low iodine values were obtained in four of the vegetable oil
brands and three of them had high acid values. High performance liquid
chromatography (HPLC) confirmed the presence of cholesterol at varying
concentrations in all the oil brands and gave the lowest detectable cholesterol
values in all the oil brands. The Laser brand made from rapeseed had the
highest cholesterol concentration of 3.2 mg/ml while Grand brand made
from groundnuts had the least concentration (0.12 mg/ml) of cholesterol
using HPLC analysis. Leibermann-Burchard method showed that Gino brand
from palm kernel had the least concentration of cholesterol (3.86 mg/ml
±0.032) and the highest concentration of 3.996 mg/ml ±0.0404
was obtained in Sesame seed oil brand. This report is important in view
of health implications of cholesterol in our diets. Consequently, we have
been able to show that there is no cholesterol free oil in the market
as shown on the vegetable oil brand labels. Therefore, companies producing
and marketing vegetable oils are enjoined to desist from misleading the
public by labeling their products as “cholesterol free”. They
should indicate the amount of cholesterol present in the vegetable oil,
no matter how small the quantity may be.
Many vegetable oils are consumed directly or used as ingredients in food.
Reports show that approximately 75% of the World’s production of
oils and fats come from plant sources (Raven and Johnson, 1999). Although
many plant parts yield oil, in actual commercial practices, oil is extracted
primarily from seeds of oilseed plants and according to the USDA (WASDE-320,
1996), the oilseed plants commonly used worldwide include; soybean, cotton,
palm, rape and groundnut. Cholesterol, contrary to popular belief, is
present in plants (Behrman and Venkat, 2005). Cholesterol has been detected
in vegetable oils, where it could make up to 5% of the total sterols and
a relatively high amount of cholesterol was described in camelina oil
(about 200 mg/kg) (Shukla et al., 2002). It has also been found
to be a major constituent of the chloroplasts, shoots, pollens, seeds
and leaf surfaces (Behrman and Venkat, 2005, Noda et al., 1988).
Cholesterol, a lipid, plays a vital role in the physiological regulation
of membrane fluidity and proper functioning of cells. It is also a major
precursor in the production of bile acids, steroid hormones as well as
vitamin D. Cholesterol found in the cell membrane of all cells, has been
of great medical importance in recent years, because its high level in
the body has been associated with coronary heart diseases (CHDs) (Laker,
2003). Coronary heart disease (CHD) is the leading cause of death in most
industrialized countries and its importance as a major public health problem
is increasing in developing countries (Murray and Lopez, 1996).
However, what is becoming clearer and clearer is that it is not the amount
of fat in the diet that matters but the type of fat (Hu et al.,
2001). Metabolic studies have shown that Trans fats have adverse effects
on blood lipid levels, increasing LDL ("bad") cholesterol while decreasing
HDL ("Good") cholesterol. This combined effect on the ratio of LDL to
HDL cholesterol is double that of saturated fatty acids (Mensink et
Industrial processing especially catalytic hydrogenation of vegetable
oils affects their fatty acid composition (Gur and Harwood, 1991). Processing
increases saturated fatty acids component of oils. Saturated fatty acid
rich diets have been found to increase the level of cholesterol (Keys
et al., 1965).
Thus, we are concerned by the fact that Nigerian markets are flooded
with assorted processed vegetable oils from different parts of the world
all labeled to be cholesterol free. In this study, cholesterol content
was determined by three different methods, in 21 brands of vegetable oils
sold in Lagos metropolis in order to ascertain this claim. The acid and
iodine values of some of the samples were also determined.
Materials and Methods
Samples of 21 brands of vegetable oil produced from a variety of oil
seeds (oil palm. Soya bean, rapeseed, sesame seed, cottonseed and peanut)
were purchased from various markets in Lagos Metropolis. The label on
each sample container was “NO CHOLESTEROL”.
Chemicals, reagent and equipment: All chemicals were supplied
by BDH chemicals Ltd, Pool. England. Spectrophotometer is Spectronic Genesys
Tim8, HPLC analysis carried out using Agilent 1100 series,
C18 column (250*4.0 mm, 5 μm).
Determination of cholesterol content:
Method 1: As described by Ojiako and Akubugwo (1997).
Total 0.1 mL of sample oil each and standard cholesterol dissolved in
chloroform in ratio 1:10 was evaporated to dryness in a water bath at
50oC. Glacial acetic acid (3.0 mL) and 3.0 mL of colour reagent
(a solution of ferric chloride/glacial acetic acid/sulphuric acid), was
added to each sample and the standard, then shaken vigorously to dissolve
the oil. Blank contained 2.0 mL of chloroform, 3.0 mL glacial acetic acid
and 3.0 mL of colour reagent. After cooling for 30 mins at room temperature,
absorbance of standard and samples were read at 560 nm. Cholesterol content
was estimated with the formula:
||Absorbance of oil sample.
||Absorbance of Standard cholesterol.
||Concentration of Standard cholesterol.
Method 2: Liebermann- Burchard method as described by Bloor, 1916.
The Liebermann-Burchard reaction method is a colorimetric method in which
cholesterol is treated with chloroform, acetic anhydride and concentrated
sulfuric acid to produce a green colour which is measured spectrophotometrically.
Method 3: High Performance Liquid Chromatography.
The oil samples were first saponified with 3% ethanolic KOH and the resulting
nonsaponifiable lipids were then dissolved in chloroform and the analysis
was carried out immediately. The HPLC analysis was done using an Agilent
1100 series, C18 column (250*4.0mm, 5 μm), acetonitrile/water (1:1)
mobile phase and a UV detector at 239 nm at a flow rate of 0.4 ml/min.
Determination of iodine and acid values: The methods of British
Pharmacpoeia (2000) were used to determine the Acid and Iodine value of
Iodine value: Chloroform (2%, 2.0 mL) and 5.0 mL of WIJ’s
solution (8.5g iodine/7.8 g iodide trichloride/450 mL glacial acetic acid
in 1 liter acetic acid) were added to sample from a burette and mixed
thoroughly. Blank contained 2 mL of chloroform and 5 mL of WIJ’s
solution. The test samples and the blank were left in the dark for 5 min
and 3.0 mL of 7.5% w/v potassium iodide was added to all test samples
and blank. Starch indicator (0.1 mL) was added to each sample and blank
and titrated to a colorless end point using 0.1N sodium thiosulfate solution.
Iodine value was calculated using the formula:
Acid value: Each oil sample (1.0 g) was weighed and neutralized
with 50 mL of fat solvent. 2 drops phenolphthalein indicator were added
and titrated to pink end point (which persisted for 15 mins) with 0.1
N potassium hydroxide solution. Acid value was calculated using the formula:
V = Volume of 0.1N KOH used.
The analytical data for cholesterol content of twenty-one oil samples
from the retail markets are shown Table 1. Seventeen
of the samples had cholesterol levels lower than 1 mg/ml while cholesterol
levels of seven of them ranged between 1-4 mg/ml. Paradoxically, HPLC
method did not detect cholesterol in Lesieur oil brand and Coconut oil.
Ojiaku and Akubugwo and Liebermann-Burchard, methods detected cholesterol
(0.907±0.095mg/ml and 3.116±0.266mg/ml) respectively in
Lesieur oil while Liebermann-Burchard method detected cholesterol (1.642
± 1.198) in Coconut oil. Sesame seed oil brand which had the highest
cholesterol content according to the methods of Ojiako & Akubugwo
and Liebermann-Burchard however showed a moderate amount of cholesterol
from our HPLC observations.
|| Concentrations of cholesterol of oil samples
|*nd- not determined
|| Elution profile of standard cholesterol and Turkey
brand of vegetable oil
Table 2 shows that the iodine values of seventeen of
the oil samples including century, laser, sesame and Lesieur brands of
vegetable oils were relatively high but lower than the values obtained
for Oki, Havop and Envoy. The elution profiles of Turkey brand of vegetable
oil and standard cholesterol are shown in Fig. 1. The
profile shows that there is cholesterol (1.9 mg/ml) in Turkey oil brand.
This is also the case in all other brands except Lesieur and coconut oil
brand (profile not shown).
||Iodine and acid values from 18 brands of vegetable oil
We have used three different methods in our quest to find out if there
is any Cholesterol in vegetable oils processed in or imported into Nigeria.
There are so many different varieties of vegetable oil brands in our markets
and all of them claim to be cholesterol free. Due to increasing awareness
on the health implications of high cholesterol in our diets, most people
now prefer to purchase cholesterol free vegetable oils.
Our findings from this study supports previous work by Shukla et al.
(2002), which showed that cholesterol is present in vegetable oils, although
in small proportion, (up to 5% of the total sterol). Indeed, an unusually
high amount of cholesterol was detected in Camelina oil (about 200 mg/kg).
Furthermore, cholesterol has been detected as one of the major sterols
in the surface lipids of higher plants especially in the leaves of rape
(Noda et al., 1988). Our results may substantiate this claim as
all the samples analysed by the three methods led to the detection of
cholesterol in varying proportions. This contradicts the label claim by
most of the producers of these vegetable oils.
As earlier stated, what is important in oil consumption is not the amount
of fat but the type of fat. Lichtenstein et al. (1999) showed that
consumption of products low in trans fatty acids has beneficial effects
on serum lipoproteins. In his review Wilson et al. (2001) opined
that trans fat is moderately hypercholesterolemic.
Cholesterol has been known as the ‘oily killer’ since the
early-mid 60s, especially since several works then showed that it is the
main cause of atherosclerotic lesions which are the major causes of coronary
heart disease (Anthony, 2000; Hayden and Tyagi, 2005; Nicolosi et al.,
2004; Jaquish, 2007). Works done by Brown and Goldstein (1986) report
on individuals with familial hypercholesterolemia (a rare genetic disorder
characterized by a high cholesterol level), showed that the rate of LDL
uptake and degradation affects the level of cholesterol in the body.
Some of the oils (Century, Sesame, Lesieur and Laser) had high iodine
values suggesting that these oil brands have a high content of unsaturated
fatty acids. The lipid profile of oils is considered contributory to the
risk of Cardiovascular diseases and some oil seeds possess a higher ability
to lower the level of low density lipoproteins than others as shown in
Corn oil or olive/sunflower oil mixture (Wagner et al., 2001);
in soybean oil (Lichtenstein et al., 2006); in sunflower oil (Binkoski
et al., 2005) and in Corn oil (Cuchel et al., 1996). Almendingen
et al. (1995) showed that serum level of total and low density
lipoprotein cholesterol was elevated in hydrogenated fish oil diet compared
to soybean oil diet.
High acid values indicative of high free fatty acids obtained from Sesame
and Kings oil brands showed rancidity. Long storage of the oil seeds before
or after processing may have been responsible. Kalua et al. (2008)
showed that there were changes in oil quality during cold temperature
storage of the fruit.
Moreover, the nutritional value of processed oils is lowered by processing,
as nature designed foods so that both unsaturated fatty acids and vitamin
E complex occur together in the same foods (Gur and Harwood, 1991). Processing
destroys this vitamin. There was a modification of the volatile compounds
in virgin olive oil after treatment with hot water (Perez et al.,
2003). Vega-Lopez et al. (2006) reported that plasma fatty acid
profiles are altered when palm and partially hydrogenated soy oils are
compared to soy and canola oils. Trans fatty acids are formed during dehydrogenation
of oils and this is done to improve oxidative stability and functionality
of oils (King and White, 1999). Several workers have associated changes
in lipid profile of oils, to processing (Wilson et al., 2005; Pedersen
et al., 2005). Ortiz et al. (2004) also showed that mode
of extraction of oil has an effect on the microstructure of Avocado pulp.
Apart from processing technique, variability may reflect the differences
in the growing season of the oilseed plant source. Some plant characteristics
are affected by season of harvest. All the oil sample brands used for
the study showed that the concentration of cholesterol depends on the
sensitivity of the method. While the Libermann-Burchard method gave the
highest cholesterol values, followed by Ojiako and Akubugwo, the HPLC
method however, shows that only Lesieur and coconut oil brands have no
cholesterol. The HPLC, due to its sensitivity confirms that there is really
no cholesterol free oil in our markets as advertised. It is pertinent
that oil producers and marketers should label their products correctly
with the quantity of cholesterol in the oil brand no matter how minute
the quantity therein. It is then left to the consumers to make up their
minds which oil brand satisfies their culinary needs.
Almendingen, K., O. Jordal, P. Kierlf, B. Sandstad and J.I. Pedersen, 1995.
Effect of partially hydrogenated soybean oil and butter on serum lipoproteins and Lp(a) in men. J. Lipid Res., 36: 1370-1384.
Anthony, M.S., 2000.
Soy and cardiovascular disease: Cholesterol lowering and beyond. J. Nutr., 130: 662-663.Direct Link |
Behrman, E.J. and G. Venkat, 2005.
Cholesterol and plants. J. Chem. Educ., 82: 1790-1793.
Binkoski, A.E., P.M. Kris-Etherton, T.A. Wilson, M.L. Mountain and R.J. Nicolosi, 2005.
Balance of unsaturated fatty acids is important to cholesterol-lowering diet: Comparison of mid-oleic sunflower oil and oil on CVD risk factors. J. Am. Diet Assoc., 107: 1080-1086.
Bloor, W.R., 1916.
The determination of cholesterol in small amounts of blood. J. Biol. Chem., 24: 227-231.
Cuchel, M., U.S. Schwah, P.J. Jones, S. Vogel and C. Lammi-Keefe et al
Impart of hydrogenated fat consumption on endogenous cholesterol synthesis and suspectibility of LDL to oxidation in moderately hypercholeserolemic individuals. Metabolism, 45: 241-247.
Gur, M.I. and J.L. Harwood, 1991.
Lipid Biochemistry: An Introduction. Chapman and Hall, London, pp: 406
Hayden, M.R. and S.C. Tyagi, 2005.
Isolated low high density lipoprotein-cholesterol (HDL-C): Implication of global risk reduction. Case report and systematic scientific review. Cardiovasc. Diabeteol., 4: 1-9.
Hu, F.B., J.E. Menson and W.C. Willet, 2001.
Types of dietary fats and risk of coronary heart diseases: A critical review. J. Am. Coll. Nutr., 20: 5-49.
Jaquish, C.E., 2007.
The framingham heart study on its way to becoming the gold standard for cardiovascular genetic epidemiology. BMC Med. Genet., 8: 63-65.
Kalua, C.M., D.R. Bedwood, A.G. Bishop and P.D. Pienzler, 2008.
Changes in virgin oil quality during low-temperature fruit storage. J. Agric. Food Chem., 10: 2415-2422.Direct Link |
Keys, A., J.T. Anderson and F. Grande, 1965.
Serum cholesterol response to change in diet: Particularly saturated fatty acids in the diet. Metabolism, 14: 776-787.
King, J.M. and P.J. White, 1999.
Impact of processing on formation of trans fatty acids. Adv. Exp. Med. Biol., 459: 51-65.Direct Link |
Laker, M., 2003.
Understanding Cholesterol. Family Doctor Publications Ltd., Dorset, United Kingdom, pp: 116
Lichtenstein, A.H., L.M. Ausman, S.M. Jalbert and E.J. Schaefer, 1999.
Effects of forms of dietary hydrogenated fats on serum lipoprotein cholesterol levels. New Engl. J. Med., 341: 1396-1407.
Lichtenstein, A.H., N.R. Matthan, S.M. Jalbert, N.A. Resteqhini, E.J. Schaefer and L.M. Ausman, 2006.
Novel soybean oils with different fatty acid profiles alter cardiovascular disease risk factors in moderately hyperlipidemic subjects. Am. J. Clin. Nutr., 84: 497-504.
Mensink, R.P., P.L. Zock, A.D.M. Kester and M.B. Katan, 2003.
Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: A meta-analysis of 60 controlled trials. Am. J. Clin. Nutr., 77: 1146-1155.CrossRef | PubMed | Direct Link |
Murray, C.J.L. and A.D. Lopez, 1996.
Evidence-based health policy, lessons from the global burden of disease study. Science, 274: 740-743.
Nicolosi, R.J., B. Woolfrey, I.A. Wilson, P. Scollin, G. Handelman and R. Fisher, 2004.
Decreased aortic early atherosclerosis and associated risk factos in hypercholesterolemic hamsters-fed on high or mid-oleic acid oil compared to a high-linoleic acid oil. J. Nutr. Biochem., 15: 540-547.
Noda, M., M. Tunaka, Y. Seto, T. Aiba and C. Oku, 1988.
Occurrence of cholesterol as major sterol component in leaf surface lipids. Lipids, 23: 439-444.
Ojiako, O.A. and E.I. Akubugwo, 1997.
An Introductory Approach to Practical Biochemistry. CRC Publications, Owerri, pp: 132
Ortiz, M.A., A.L. Dorantes, M.J. Gallndez and S.E. Cardenas, 2004.
Effects of a novel oil extraction method on avocado (Persea Americana
Mill). Plants Food Hum. Nutr., 59: 11-14.
Pedersen, J.I., H. Muller, I. Seljefot and K. Kickhaus, 2005.
Palm oil versus hydrogenated soya oil: Effects on serum lipids and plasma haemostatic variables. Asia Pac. J. Clin. Nutr., 14: 348-357.
Perez. A.G., P. Luaces, J.J. Rios, J.M. Garcia and C. Sanz, 2003.
Modification of volatile compoundprofile of virgin olive oil due to hot water treatment of olive fruit. J. Agric. Food Chem., 51: 6544-6549.
Raven, H.P. and B.G. Johnson, 1999.
Biology. 5th Edn., Mc Graw-Hill, New York, pp: 1231
Shukla, V.K.S., P.C. Dutta and W.E. Artz, 2002.
Camelina oil and its unusual cholesterol content. J. Am. Oil Chem. Soc., 79: 965-969.
Vega-Lopez, S., L.M. Ausman, S.M. Jalbert, A.T. Erkkila and A.H. Lichtenstein, 2006.
Palm and partially hydrogenated soyya oils adversely alter liprptein profiles compared with soybean and canola oils in moderately hyperlipidemic subjects. Am. J. Clin., 84: 54-62.
Wagner, K.H. and T.I. Elmadfa, 2001.
Impact of diets containing cornoil or olive/sunflower oil mixture on human plasma and lipoprotein lipid metabolism. Eur. J. Nutr., 40: 157-161.
Wilson, T.A., M. Mclintyre and R.J. Nicolosi, 2001.
Trans fatty acid and cardiovascular risk. J. Nutr. Health Aging, 5: 184-187.
Wilson, T.A., R.J. Nicolosi, T. Kotyla, K. Sundram and D. Kritchevsky, 2005.
Different palm oil proparations reduced plasma cholesterol concentration and aortic cholesterol accumulation compared to coconut oil in hypercholesterolemic hamsters. J. Nutr. Biochem., 16: 633-640.
World Agricultural and Demand Estimates, 1996.
Oilseeds and products: World markets and trade. Counselor and Attache Reports, Official Statistics, USDA Estimates, WASDE-320.
Brown, M.S. and J.L. Goldstein, 1986.
A receptor-mediated pathway for cholesterol homeostasis. Science, 232: 34-47.CrossRef | Direct Link |