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Fallon and Mary G. Enig, PhD
Says Wolke: "I found no
research studies indicating that today’s low-erucic-acid canola oil,
as distinguished from ordinary rapeseed oil, is harmful to humans."
That’s because, even though canola oil now has Generally Recognized
as Safe (GRAS) status, no long-term studies on humans have been done.
Animal studies on Low Erucic
Acid Rapeseed oil were performed when the oil was first developed and
have continued to the present. The results challenge not only the health
claims made for canola oil, but also the theoretical underpinnings of
the diet-heart hypothesis.
The first published studies
on the new oil were performed in 1978 at the Unilever research facility
in the Netherlands.11 The industry was naturally interested to know whether
the new LEAR oil caused heart lesions in test animals. In earlier studies,
animals fed high-erucic-acid rape seed oil showed growth retardation and
undesirable changes in various organs, especially the heart, a discovery
that touched off the so-called "erucic acid crisis" and spurred
plant geneticists to develop new versions of the seed.
The results of the LEAR study
were mixed. Rats genetically selected to be prone to heart lesions developed
more lesions on the LEAR oil and the flax oil, than those on olive oil
or sunflower oil, leading researchers to speculate that the omega-3 fatty
acids (not erucic acid) in LEAR and flax oil might be the culprit. But
rats genetically selected to be resistant to heart lesions showed no significant
difference between the four oils tested and LEAR oil did not cause heart
problems in mice, in contrast to high-erucic oil which induced severe
In 1979, researchers at the
Canadian Institute for Food Science and Technology pooled the results
of 23 experiments involving rats at four independent laboratories. All
looked at the effects of LEAR and other oils on the incidence of heart
lesions. They found that saturated fats (palmitic and stearic acids) were
protective against heart lesions but that high levels of omega-3 fatty
acids correlated with high levels of lesions. They found a lesser correlation
with heart lesions and erucic acid.12
In 1982, the same research
group published a paper that looked at the interaction of saturated fats
with LEAR oil and soybean oil. When saturated fats in the form of cocoa
butter were added to the diets, the rats in both groups had better growth
and a significant lowering of heart lesions. Said the authors: "These
results support the hypothesis that myocardial lesions in male rats are
related to the balance of dietary fatty acids and not to cardiotoxic contaminants
in the oils."13
Canadian researchers looked
at LEAR oils again in 1997. They found that piglets fed milk replacement
containing canola oil showed signs of vitamin E deficiency, even though
the milk replacement contained adequate amounts of vitamin E.14 Piglets
fed soybean oil-based milk replacement fortified with the same amount
of vitamin E did not show an increased requirement for vitamin E. Vitamin
E protects cell membranes against free radical damage and is vital to
a healthy cardiovascular system.
In a 1998 paper, the same research
group reported that piglets fed canola oil suffered from a decrease in
platelet count and an increase in platelet size.15 Bleeding time was longer
in piglets fed both canola oil and rapeseed oil. These changes were mitigated
by the addition of saturated fatty acids from either cocoa butter or coconut
oil to the piglets’ diet. These results were confirmed in another
study a year later. Canola oil was found to suppress the normal developmental
increase in platelet count.16
Finally, studies carried out
at the Health Research and Toxicology Research Divisions in Ottawa, Canada
discovered that rats bred to have high blood pressure and proneness to
stroke had shortened life-spans when fed canola oil as the sole source
of fat.17 The results of a later study suggested that the culprit was
the sterol compounds in the oil, which "make the cell membrane more
rigid" and contribute to the shortened life-span of the animals.18
These studies all point in
the same direction -- that canola oil is definitely not healthy for the
cardiovascular system. Like rapeseed oil, its predecessor, canola oil
is associated with fibrotic lesions of the heart. It also causes vitamin
E deficiency, undesirable changes in the blood platelets and shortened
life-span in stroke-prone rats when it was the only oil in the animals’
diet. Furthermore, it seems to retard growth, which is why the FDA does
not allow the use of canola oil in infant formula.19
When saturated fats are added
to the diet, the undesirable effects of canola oil are mitigated. Most
interesting of all is the fact that many studies show that the problems
with canola oil are not related to the content of erucic acid, but more
with the high levels of omega-3 fatty acids and low levels of saturated
Oil In Traditional Diets
Rapeseed oil has been used
in China, Japan and India for thousands of years. In areas where there
is a selenium deficiency, use of rapeseed oil has been associated with
a high incidence of fibrotic lesions of the heart, called Keshan’s
disease.20 The animal studies carried out over the past twenty years suggest
that when rapeseed oil is used in impoverished human diets, without adequately
saturated fats from ghee, coconut oil or lard, then the deleterious effects
In the context of healthy traditional
diets that include saturated fats, rapeseed oil, and in particular erucic
acid in rapeseed oil, does not pose a problem. In fact, erucic acid is
helpful in the treatment of the wasting disease adrenoleukodystrophy and
was the magic ingredient in Lorenzo’s oil.
High levels of omega-3 fatty
acids, present in unprocessed rapeseed oil, don’t pose a problem
either when the diet is high in saturates. A 1998 study indicates that
diets with adequate saturated fats help the body convert omega-3 fatty
acids into the long-chain versions EPA and DHA, which is what the body
wants to do with most of the 18-carbon omega-3s.21
Conversion is reduced by 40-50
percent in diets lacking in saturated fats and high in omega-6 fatty acids
from commercial vegetable oils (particularly soybean oil). In the animal
studies on canola oil, dietary saturated fats mitigated the harmful effects
A 1995 Wall Street Journal
article reported that use of rapeseed oil in cooking was associated with
greatly increased rates of lung cancer in the women breathing the fumes.22
Once again, a lack of saturates in the diet may explain the association,
because the lungs can’t work without adequate saturated fats.23 In
India, rapeseed oil has been used as a cooking oil for thousands of years,
but only recently have Indian housewives been cajoled into the belief
that saturated butter and ghee should be avoided. Many now use vanispati,
an imitation ghee made of partially hydrogenated soybean oil.
Rapeseed has been used as a
source of oil since ancient times because it is easily extracted from
the seed. Interestingly, the seeds were first cooked before the oil is
extracted. In China and India, rapeseed oil was provided by thousands
of peddlers operating small stone presses that press out the oil at low
temperatures. What the merchant then sells to the housewife is absolutely
Modern oil processing is a
different thing entirely. The oil is removed by a combination of high
temperature mechanical pressing and solvent extraction. Traces of the
solvent (usually hexane) remain in the oil, even after considerable refining.
Like all modern vegetable oils, canola oil goes through the process of
caustic refining, bleaching and degumming -- all of which involve high
temperatures or chemicals of questionable safety.
And because canola oil is high
in omega-3 fatty acids, which easily become rancid and foul-smelling when
subjected to oxygen and high temperatures, it must be deodorized. The
standard deodorization process removes a large portion of the omega-3
fatty acids by turning them into trans fatty acids. Although the Canadian
government lists the trans content of canola at a minimal 0.2 percent,
research at the University of Florida at Gainesville, found trans levels
as high as 4.6 percent in commercial liquid oil.24 The consumer has no
clue about the presence of trans fatty acids in canola oil because they
are not listed on the label.
A large portion of canola oil
used in processed food has been hardened through the hydrogenation process,
which introduces levels of trans fatty acids into the final product as
high as 40 percent.25 In fact, canola oil hydrogenates beautifully, better
than corn oil or soybean oil, because modern hydrogenation methods hydrogenate
omega-3 fatty acids preferentially and canola oil is very high in omega-3s.
Higher levels of trans mean longer shelf life for processed foods, a crisper
texture in cookies and crackers -- and more dangers of chronic disease
for the consumer.26
Myth Of Monounsaturates
Consumer acceptance of canola
oil represents one in a series of victories for the food processing industry,
which has as its goal the replacement of all traditional foods with imitation
foods made out of products derived from corn, wheat, soybeans and oil
seeds. Canola oil came to the rescue when the promotion of polyunsaturated
corn and soybean oils had become more and more untenable. Scientists could
endorse canola oil in good conscience because it was a "heart-healthy"
oil, low in saturated fat, high in monounsaturates and a good source of
omega-3 fatty acids.
But most of the omega-3s in
canola oil are transformed into trans fats during the deodorization process;
and research continues to prove that the saturates are necessary and highly
At least it can be said that
canola oil is a good source of monounsaturated fat -- like olive oil --
and therefore not harmful. . . Or is it? Obviously monounsaturated fatty
acids are not harmful in moderate amounts in the context of a traditional
diet, but what about in the context of the modern diet, where the health-conscious
community is relying on monounsaturated fats almost exclusively?
There are indications that
monounsaturated fats in excess and as the major type of fat can be a problem.
Overabundance of oleic acid (the type of monounsaturated fatty acid in
olive and canola oil) creates imbalances on the cellular level that can
inhibit prostaglandin production.27 In one study, higher monounsaturated
fat consumption was associated with an increased risk of breast cancer.28
Even the dogma that monounsaturated
fatty acids are good for the heart is at risk. According to a 1998 report,
mice fed a diet containing monounsaturated fats were more likely to develop
atherosclerosis than mice fed a diet containing saturated fat.29 In fact,
the mice fed monounsaturated fats were even more prone to heart disease
than those fed polyunsaturated fatty acids.
This means that the type of
diet recommended in books like The Omega Diet -- low in protective saturates,
bolstered with high levels of omega-3 fatty acids and relying on monounsaturated
fatty acids, whether from olive or canola oil, for the majority of fat
calories -- may actually contribute to heart disease. Such diets have
been presented with great marketing finesse, but we need to recognize
them for what they are -- payola for the food companies and con-ola for
Great Con-ola was published in Nexus Magazine, Aug/September 2002
as well as in Wise Traditions, the quarterly publication for the Weston
A. Price Foundation. To receive a free 12-page brochure containing
Myths and Truths about Nutrition and concise Dietary Guidelines, contact
the Foundation at (202) 333-HEAL or email@example.com.
is President of the Weston A. Price Foundation and author of Nourishing
Traditions: The Cookbook that Challenges Politically Correct Nutrition
and the Diet Dictocrats, NewTrends Publishing, 2000 (877-707-1776,
Enig, PhD, FACN, is Vice President of the Weston A. Price Foundation,
President of the Maryland Nutritionists Association and author of Know
Your Fats: The Complete Primer for Understanding the Nutrition of Fats,
Oils and Cholesterol, Bethesda Press, 2000 (301-680-8600, bethesdapress.com)
Vles and others. Nutritional Evaluation of Low-Erucic-Acid Rapeseed
Oils. Toxicological Aspects of Food Safety, Archives of Toxicology,
Supplement 1, 1978:23-32
Trenholm and others. An Evaluation of the Relationship of Deitary Fatty
Acids to Incidence of Myocardial Lesions in Male Rats. Canadian Institute
of Food Science Technology Journal, October 1979;12(4):189-193
Kramer and others. Reduction of Myocardial Necrosis in Male Albino Rats
by Manipulation of Dietary Fatty Acid Levels. Lipids, 1982;17(5):372-382.
Sauer and others. Additional vitamin E required in milk replacer diets
that contain canola oil. Nutrition Research, 1997;17(2):259-269.
Kramer and others. Hematological and lipid changes in newborn piglets
fed milk-replacer diets containing erucic acid. Lipids, January 1998;33(1):1-10.
Iunis and RA Dyer. Dietary canola oil alters hematological indices and
blood lipids in neonatal piglets fed formula. Journal of Nutrition,
Ratnayake and others. Influence of Sources of Dietary Oils on the Life
Span of Stroke-Prone Spontaneously Hypertensive Rats. Lipids, 2000;35(4):409-420.
Wallsundera and others. Vegetable Oils High in Phytosterols Make Erythrocytes
Less Deformable and Shorten the Life Span of Stroke-Prone Spontaneously
Hypertensive Rats. Journal of the American Society for Nutritional Sciences,
Levander and MA Beck. Selenium and viral virulence. British Medical
21. H Gerster.
Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic
acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? International Journal
of Vitamin and Nutrition Research 1998;68(3):159-73.
Street Journal, June 7, 1995, p. B6.
Enig. Benefits of Saturated Fats. Wise Traditions, Summer 2000;1(2):49.
24. S O'Keefe
and others. Levels of Trans Geometrical Isomers of Essential Fatty Acids
in Some Unhydrogenated US Vegetable Oils. Journal of Food Lipids 1994;1:165-176.
Sebedio and WW Christie, eds. Trans Fatty Acids in Human Nutrition,
The Oily Press, Dundee, Scotland, 1998, pp 49-50.
Enig, Trans Fatty Acids in the Food Supply: A Comprehensive Report Covering
60 Years of Research, 2nd Edition, Enig Associates, Inc., Silver Spring,
David F, Prostaglandins: Physiology, Pharmacology and Clinical Significance
The Book Press, Brattleboro, Vermont, 1978, p 20, 35
28. V Pala
and others. Erythrocyte membrane fatty acids and subsequent breast cancer:
a prospective Italian study. Journal of the National Cancer Institute,
July 18, 2001;93(14):1088-95.
Rudel and others. Dietary monounsaturated fatty acids promote aortic
atherosclerosis in LDL-receptor-null, human ApoB100-overexpressing transgenic
mice. Arteriosclerosis, Thrombosis and Vascular Biology, November 1998;18(11):1818-27.