I have always recommended the avoidance of all highly processed commercially produced fats and oils. These fats and oils are routinely found in many processed food products and are also used in home cooking.
The dietary use of commercially processed, refined fats and oils is having a significant negative impact on health and wellbeing. My aim is to help demystify the different classes of commercially processed fats so that a more informed decision about food choices can be made.
Commercial Extraction of Vegetable Oil from Seeds
Vegetable seed oils such as sunflower, soya bean, rape seed/canola and grape seed oils are commercially extracted from seeds. The process involves grinding the seeds followed by steam cooking. Solvents are then added to extract out the oils. The most popular solvents used are hexane or trichloroethylene and even though the oils and solvents are separated, traces of solvents often remain in the oil. Both hexane and trichloroethylene are toxic and may trigger abdominal pain, irritation, nausea and symptoms that parallel those of inhalation, including light headedness, nausea, headache and blurred vision.
The oil is then refined with the addition of sodium hydroxide and temperatures are increased to over 200ºC/400ºF. This level of heat disrupts the unsaturated bonds resulting in oxidation damage. The oil is then treated further with carbon. At this stage of processing there is a huge loss of protective nutrients including significant losses of vitamin A, E, F, lecithin and chlorophyll.
The commercially extracted oil has become oxidised and damaged. It has a sticky texture and is rancid and requires further processing to degum, deodorise and bleach it so that it flows, becomes pale in appearance and is virtually odourless. Preservatives and/or anti-oxidant additives are added at this stage to make up for lost nutrients.
If this oil is used in home cooking there is the potential to further damage any remaining unsaturated bonds by exposure to heat and light during cooking.
Seed oils tend to contain high levels of the polyunsaturated omega 6 essential fatty acid. When taking the context of the diet as a whole, excess omega 6 consumption has an inflammatory effect on body tissues.
Hydrogenation and Partial Hydrogenation
Hydrogenation is the commercial process of transforming an unsaturated fat (liquid oil) to a solid fat. This is achieved by heating the oil to a high temperature and bubbling hydrogen through in the presence of a catalyst (usually nickel).
This process alters any unsaturated bonds (double carbon bonds) so that they become saturated, which means that they form single bonds with carbon and hydrogen.
During complete hydrogenation, the oil is transformed from being unsaturated and liquid to fully hydrogenated and solid. Manufacturers stop the hydrogenation process when the desired consistency of the fat is achieved. This is known as partial hydrogenation.
Since the late 70s, hydrogenated and partial hydrogenated fats have been extensively used in many processed foods such as cakes, pastries, crisps and fried foods. The main advantage of hydrogenated fat is that it has an extended shelf life and gives a lighter texture to baked and fried goods. However the partial hydrogenation process creates unusual fats known as Trans fats.
When fats are described as unsaturated, this means that there is at least one double bond of carbon with its remaining bonds filled with hydrogen. In the cis bond, hydrogen connected to either side of the double carbon bond is found on the same side.
During partial hydrogenation some unsaturated bonds remain but the high temperatures and the catalyst used to create partially hydrogenated oil weakens the double bonds between the carbon atoms. As a result a large percentage of the natural Cis double bonds are changed to Trans double bonds. In the Trans bond, hydrogen connected to either side of the double carbon bond is now found on opposite sides. This type of bond is known as a Trans bond and is not naturally apart from trace amounts in animal products from ruminants (cows, goat, sheep etc)
Summarising there are 2 sources of Trans fat (also known as Trans fatty acids:
- Formed during food processing - this type of Trans fat is created when hydrogen is added to vegetable oil (a process called hydrogenation) to make it more solid. Partially hydrogenated oils are used by food manufacturers to improve the texture, shelf life and flavour stability of foods
- Formed naturally - this type of Trans fat is produced in the gut of some grazing animals. That’s why small quantities of Trans fat can be found in animal products like milk, milk products and meat.
Trans fats are therefore a by-product from partial hydrogenation
Trans Fats and Health
A number of studies have shown that regular consumption of foods containing Trans fats are detrimental to health. The health implications of consuming Trans fats include:
- Increased blood levels of low density lipoproteins (LDL) which transport cholesterol from the blood to body cells.
- Lower blood levels of high density lipoproteins (HDL) which transports unused cholesterol from the blood to the liver. Low HDL and high LDL are risk factors for cardiovascular disease
- Increases blood levels of the lipoprotein known as lp(a). This is also a risk factor for cardiovascular disease
- Increase blood platelet stickiness which hinders the flow of blood through the blood vessels
- Trans fats interfere with enzymes which process and break down the essential fatty acids: alpha linolenic acid (parent omega 3) and linoleic acid (parent omega 6). This will have a detrimental effect on prostaglandin production within the body
- Trans fats, formed during hydrogenation, are unnatural, toxic substances for our cell membranes. When our cells contain an overabundance of trans fats, the cells become leaky and distorted. This can promote vitamin and mineral deficiencies
The health issues associated with Trans fats seem are linked with those formed during the hydrogenation process and not those found naturally in certain animal products. For example even though it is now known that coconut oil has many health benefits, past research which vilified coconut was conducted using partially hydrogenated coconut oil which contained Trans fats.
Avoid Trans Fats as much as possible by reading labels and avoid foods containing:
- hydrogenated fat
- partially hydrogenated oils
- vegetable shortening
Check the Ingredient List as the ‘Nutrition Information’ label can state 0 grams of Trans fat if the food product contains less than 0.5 grams of Trans fat per serving. If a product contains partially hydrogenated oils then it may contain small trace amounts of Trans fat even if the label says 0 grams of trans fat. This means that the consumer would not know they had ingested Trans fats.
Although food processors have made recent efforts to reduce the Trans fat content of some margarines. Many processed foods and baked goods still contain partially hydrogenated oils and Trans fats.
Interesterification – The Replacement for Trans fats
In order to remove dangerous Trans fats from commercial foods like margarine, a process called interesterification is now used. Interesterification is a process that alters the molecular structure of fats and oils.
Let's look at the process of interesterification in more detail.
- Vegetable oil is commercially extracted from seeds as described
- The vegetable oil is then converted to a solid fat which is fully saturated by the chemical process of hydrogenation. Full saturation results in no trans fats being formed
- An enzyme is then added to the fully saturated vegetable fat which acts as a catalyst and separates each fatty acid molecule from its glycerol backbone.
- After breaking the triglycerides apart, the factory then re-configures each triglyceride molecule by combining three fatty acids from a pool of Omega 3, Omega 6, Omega 9, and saturated fatty acid molecules. The combination determines how hard, soft or liquid the resultant fat is. The higher the percentage of Omega 3 or omega 6 used results in a softer/more liquid fat. Conversely the higher the percentage of Omega 9 and Saturated fatty acid molecules the harder the interesterified fat.
Depending on the combination of fatty acids used to reconstitute the triglycerides, the interesterification process can produce any type of fat or oil. This includes solid fats suitable for deep-frying, semi-solid fats to make margarine, or liquid oils for bottling.
The end result is a product that has an indefinite shelf life, targeted at the unsuspecting consumer. In my view a Frankenstein fat!
These new vegetable oil/fats made via interesterification have a molecular structure that the human body has never seen before!
There lies the problem. No one knows the consequences of eating the newer interesterified oils/fats because no long term trials have been done and health issues like cancers and heart disease take years to develop!
Some preliminary testing indicates that interesterified oils have the same risks as Trans fats. For example, some studies show this new interesterified fat increased blood sugar by 20% in just one month, and greatly increased insulin resistance. It also decreased HDL and increased LDL like trans fats do.
Currently there is no legislation covering interesterification, and you are unlikely to see it mentioned on any food labels.
So if margarine, cakes, biscuits or other food product states 'vegetable oil' then you can be absolutely certain that it contains either interesterified fats, or Trans fats. There is simply no other commercially viable way to produce a solid fat from vegetable oils that are suitable for baked goods.
In other words, if you see 'No Trans Fats' on a packet of cake or biscuits made from vegetable oils then you can be certain that it contains highly processed interesterified, or fully hydrogenated vegetable oils.
Margarine - Should we be Eating this?
The process of interesterification is being used to manufacture margarines which are 100% trans fat free. Other margarines labelled as free from, or ‘virtually’ free from trans fats transform the vegetable oil to a solid fat by the use of thickeners and emulsifiers. Both types of margarine incorporate many additives: colours, synthetic vitamins, flavours, stabilisers and preservatives
Could these margarines be preferable to butter? Unlike butter margarine spreads easily and straight from the fridge. It might even contain healthy plant sterols with claims about cholesterol reduction and heart health benefits.
In my opinion any healthy oils found naturally within seeds/nuts which have been chemically processed and altered to make margarine will not have the same health benefits as the original oils contained within the seed/nut.
In contrast, the only additive allowed in butter is salt. I believe that it is always best to choose unsalted butter, as the added salt used is generally highly refined salt and not unprocessed salt packed with minerals and trace elements.
From research done in the last twenty years we've learned that processed vegetable oils are a serious threat to our health for the following reasons:
- The big problem with processed vegetable oils is at the cell level. Since these fats don't occur in nature, our bodies don't know how to deal with them. The body tries to use them, thinking they are normal fats, and they wind up in cell membranes and other places where they behave strangely. These man-made fats weaken the cell membrane, degrading their protective structure and function.
- Processed vegetable oils often contain the residue of toxic metals, usually nickel and aluminium, left behind in the finished product. These metals are used as catalysts in the hydrogenation reaction. They accumulate in our nervous system where they can lead to neurological conditions. These heavy metals also poison enzyme systems and alter cellular functions, and cause a wide variety of health problems. These toxic metals are difficult to eliminate, and our 'toxic load' increases steadily with small exposures over time.
- Processed vegetable oils appear to activate the body's immune responses when they enter the artery walls. These fats do not resemble anything that the body recognises, so the body attacks it. This directly leads to an inflammatory response in the arteries which leads to the formation of dangerous plaque build-up.
- When the body is unable to metabolise these highly processed fats they move further along into the body, and are deposited into the organs and fatty tissues such as in the breasts and liver where they may directly contribute to cancer.
My recommendation is – because these fats are unnatural and not proven safe avoid
- margarines, vegetable shortenings
- trans fats
- hydrogenated fats, partially hydrogenated fats
- interesterified fats
- highly processed vegetable oils and
- Any foods made with the above
Remember it took 30 years to learn that Trans fats were a disaster and it will probably take just as long to learn the same about interesterified fats.
Commercially Processed Foods
Most of these foods contain Trans Fats, Damaged Vegetable Oils or Interesterified fats. Avoid commercially produced
- Sandwiches containing margarine
- Crackers, biscuits, cookies, bread, pies
- Cakes, muffins and other baked goods
- Snack foods (such as microwave popcorn, crisps, chocolate/biscuit bars)
- Frozen foods (pizza, pies, chips etc)
- Fast food (chips, fried foods etc)
- Coffee creamer
- Ice cream, milkshakes
- Refrigerated dough products (pastry, biscuits and cinnamon rolls)
- Ready-to-use frostings
From the list it seems like all convenience/commercially prepared food should be kept to an absolute minimum.
In my opinion, the heat stable fats used historically such as butter, clarified butter, coconut oil and cold pressed monounsaturated fats like extra virgin olive oil should be the main source of fat within the diet.
- Brownstein D, Shenfelt S. (2006). The Guide To Healthy Eating. 2nd ed. Healthy Living.
- Cooper, F. (2008). Interesterification - The Dangerous Replacement for Trans Fats. Available: http://www.naturalnews.com/022759_oil_fat_oils.html. Last acessed 12th December 2013
- Enig, Mary. (2009). Some Additives in Vegetable Oils. Available: http://www.westonaprice.org/know-your-fats/some-additives-in-vegetable-oils. Last accessed 16th December 2013.
- Sundram K, Karupaiah T, Hayes K C. (2007). Stearic acid-rich interesterified fat and trans-rich fat raise the LDL/HDL ratio and plasma glucose relative to palm olein in humans. Available: http://www.nutritionandmetabolism.com/content/4/1/3. Last accessed 12th December 2013.