Cooking
oil is a plant, animal or synthetic liquid fat used in cooking, frying and also
in food preparation and flavoring. It is one of the key items in our kitchen
and plays a crucial role in the body. There are wide varieties of cooking oils
such as olive oil, soybean oil, corn oil, canola oil, peanut oil etc. from
plant sources and butter and lard are examples of animal-based oils. Fats
are hydrocarbon molecules and formed through replacement of the hydrogen
of each hydroxyl group by a fatty acid. As three chains of fatty acids can be
attached to each glycerol molecule, the resulting molecule is called a
triglyceride (fat). Fats may be monounsaturated (MUFAs),
polyunsaturated (PUFAs), saturated or trans based on their fatty acid
composition.
Saturated and Unsaturated fatty acids
In
saturated fatty acids, the carbon chain has the maximum number of hydrogen
atoms attached to every carbon atom. If a pair of hydrogen atoms is missing
because of a double bond between two carbon atoms, it is called an unsaturated
fatty acid. A fatty acid with a single double bond is monounsaturated, whereas
a fatty acid with more than one double bond is polyunsaturated. Some fatty
acids that are released in the process of digestion are called essential
because they cannot be synthesized in the body from simpler
constituents. Sources of fatty acids include fruits, vegetable oils,
seeds, nuts, animal fats, and fish oils. Essential fatty acids, such as omega-3
fatty acids, serve important cellular functions. They are a necessary part of
the human diet because the body has no biochemical pathway to produce these
molecules on its own. All saturated fatty acids, with the notable
exception of stearic acid, raise serum low-density lipoprotein (LDL)
cholesterol or bad cholesterol levels. On the other hand, higher intakes of
unsaturated fatty acids raise serum high-density lipoprotein (HDL) cholesterol
or good cholesterol levels.
Trans Fatty acids
Dietary
fatty acids with trans double bonds come primarily from industrial sources i.e.
by partial hydrogenation of edible oils containing unsaturated fatty acids to
saturated fats and secondly from bacterial transformation of unsaturated fatty
acids in the rumen of ruminants. The primary dietary trans fatty acids are
vaccenic acid and elaidic acid. Vaccenic acid is the major ruminant trans fatty
acid, whereas elaidic acid is the main trans fatty acid isomer in industrial
hydrogenation. Processed foods and oils provide approximately 80% of trans fats
in the diet, compared to 20% that occur naturally in food from animal sources.
The major dietary sources of trans fats are cakes, cookies, crackers, animal
products, margarine, fried potatoes, potato chips and popcorn.
Hydrogenation
converts liquid vegetable oils to solid or semi-solid fats that remain stable
at room temperature. These fats can then be incorporated into certain food
products (e.g., cookies, chips) to increase the shelf life of
products. The consumption of trans fats has been directly linked
to an increase in cardiovascular diseases. Trans fats appear to have
a detrimental effect on serum lipids by increasing LDL (bad) cholesterol and
triglyceride levels, and reducing high-density lipoprotein (good) cholesterol
levels.
Plant-based cooking oils
1. Mustard Oil
Mustard
oil has about 70% monounsaturated fatty acids and 22% polyunsaturated fatty
acids content of which 10 % is the omega-3 alpha-linolenic acid and 12% omega-6
linoleic acid and 8% saturated fatty acids. Mustard oil also has high levels of
omega-3 (10%) fatty acids. Mustard oil is considered one of the healthiest
edible oils as it has low amount of saturated fatty acids and a high amount of
monounsaturated fatty acids and polyunsaturated fatty acids, which are good for
health. The slphalinolenic acid found in mustard oil reduces the
adhesion-aggregation tendency of blood platelets which decreases the risk of a
heart attack. Several clinical studies have found that mustard oil may be the
best for heart health.
2. Canola oil
Canola
oil is low in saturated fatty acids and high in monounsaturated fatty acids. It
also has a beneficial omega-3 fatty acid profile.
3. Olive oil
Olive
oil has the highest (75%) content of monounsaturated fatty acids and considered
to play a crucial role in the human nutrition. The use of monounsaturated fatty
acids leads lowering of LDL cholesterol and elevation of HDL cholesterol which
may lead to reduction in the risk of cardiovascular diseases. It also contains
more polyphenols, which may be responsible for beneficial effects on heart
health. The main limitation of this oil is that it does not have an ideal N-6:
N-3 ratio.
4. Soyabean oil
It
is rich source of polyunsaturated fatty acids. The major unsaturated fatty acids
in soybean oil triglycerides are 7–10% alphalinolenic acid; 51% linoleic acid;
and 23% oleic acid. It also contains the saturated fatty acids 4% stearic acid
and 10% palmitic acid which are long chain saturated fatty acids.
5. Rice bran oil
It
is extracted from the germ and inner husk of rice. It is mainly utilized for
deep frying and one of the most popular cooking oils in Japan and China. Rice
bran oil has 47% monounsaturated fatty acids, 33% polyunsaturated fatty acids,
and 20% saturated fatty acids. It is also rich in vitamin E, gamma-oryzanol
which may help prevent heart attacks, and phytosterols, which may provide
associated health benefits. A major limitation of this oil is less than ideal
N-6/N-3 ratio of 23:1.
6. Sunflower oil
It
is high in polyunsaturated fatty acids and vitamin E and low in saturated fatty
acids. It is also rich in lecithin, tocopherols, carotenoids and waxes. It also
has a high content of omega-6 polyunsaturated fatty acids. Some studies have
suggested that it may increase the likelihood of breast and prostatic cancer.
Another major limitation of this oil is very poor N-6 / N-3 ratio of 120:1.
7. Cotton seed oil
It
contains 18% monounsaturated fatty acids and 52% polyunsaturated fatty acids.
But the health benefits of this oil are controversial, it has too high a
content of saturated fat and too low in monounsaturated fat. Furthermore,
cottonseed oil may contain natural toxins (gossypol) and unacceptably high
levels of pesticide residues. Being cheap it is now a component of a much wider
range of processed foods, including cereals, breads and snack foods like chips.
8. Corn oil
It
contains 55% polyunsaturated fatty acids, 30% monounsaturated fatty acids, and
15% saturated fatty acids. It is very useful for frying purposes. Refined corn
oil has excessive levels of omega-6 fatty acids, relative to omega-3 fatty
acids, may increase the probability of a number of diseases and depression.
9. Ground nut oil
Its
major component fatty acids are oleic acid, linoleic acid, and palmitic acid.
The oil also contains some stearic acid, arachidic acid, arachidonic acid,
behenic acid, lignoceric acid and other fatty acids. This is one of the heart
friendly oils which are not only rich in monounsaturated fatty acids but
otherwise also well balanced.
10. Safflower oil
Being
low in saturated fatty acids, it was initially used as a substitute for ghee
and butter as health consciousness developed in India. However, being rich in
polyunsaturated fatty acids and very low in monounsaturated fatty acids (13%),
it is also not the healthiest of oils. Its consumption may cause the lowering
of total and LDL cholesterol and also lowering of HDL cholesterol. Being high
in polyunsaturated fatty acids it is more likely to turn rancid and although it
has the highest smoke point and as such can be used for deep frying, it must be
remembered that polyunsaturated fat possibly turn toxic when exposed to high
temperature.
11. Coconut
oil
Coconut
oil contains no cholesterol but consists of more than 90% of saturated fatty acids,
with traces of few unsaturated fatty acids. Studies revealed that, it may
raises blood cholesterol levels by increasing the amount of HDL cholesterol.
Animal-based cooking oils
1. Butter
It
is a fat derived from animal source and is high in saturated fatty acids and
cholesterol as such it can raise serum total, LDL cholesterol and HDL
cholesterol.
2. Ghee
It
is basically clarified butter but it can be used even for frying because it has
got a higher smoke point. Though ghee is rich in fat, it contains high
concentrations of monounsaturated Omega-3s. These healthful fatty acids support
a healthy heart and cardiovascular system. Studies show that using ghee as a
part of a balanced diet can help reduce unhealthy cholesterol levels.
3. Vanaspati ghee
It
is the unhealthiest of all oils because not only is it devoid of natural
vitamins and bioactive compounds but as a result of hydrogenation process it
contains an undesirable type of fat called trans fat. Consumption of this fat not only leads to the worst
type of lipid profile possible but also has been directly co-related with
development of cardiovascular diseases.
Source
Mishra, Sundeep, and S. C. Manchanda. "Cooking oils for heart health." J Prev Cardiol 1.3 (2012): 123-131.