TRANS FATS and HEALTH*
Trans fat is the common name for a type of unsaturated fat with trans-isomer fatty acid(s). Trans fats may be monounsaturated or polyunsaturated.
They are created in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid and less likely to spoil. This process is called hydrogenation.
Another name for trans fats is ‘partially hydrogenated oils’
Using trans fats in the manufacture of foods helps foods stay fresher longer, have a longer shelf-life and have a less greasy feel.
Initially, trans fats were thought to be a healthy alternative to animal fats because they are unsaturated and come primarily from plant oils.
However in 1990, scientists discovered that trans fats appeared to both increase low density lipoprotein (LDL) cholesterol (the ’bad’ cholesterol … the lower it is the better) and decrease high density lipoprotein (HDL) cholesterol (the ‘good’ cholesterol … the higher it is the better). High LDL and low HDL cholesterols are major risk factors for heart disease.
Fats are large molecules consisting of three fatty acid groups connected to a single glycerol derivative.
Fatty acids are molecules made up essentially of long-chain hydrocarbons having a methyl group at one end and a carboxylic acid group at the other end.
Fatty acids are characterised as saturated or unsaturated based on the number of hydrogen atoms in the acid. If the molecule contains the maximum possible number of hydrogen atoms, it is said to be saturated; otherwise, it is unsaturated to some degree.
—HCH—HCH—HCH—HCH— is saturated
—HCH—CH = CH—HCH— is unsaturated
— represents a single bond
= represents a double bond.
C is the symbol for a carbon atom which has a valency of 4
H is the symbol for a hydrogen atom, which has a valency of 1, hence a single bond to C
Each C must have 4 bonds for it to be ‘balanced’
Types of Fats in Food
· Saturated fat
Saturated fat is fat that consists of triglycerides containing only saturated fatty acids. Thus a saturated fat is ‘saturated’ with hydrogen atoms.
Saturated fats, such as butter, lard and coconut oil, are mainly solid at room temperature, and hard when refrigerated.
· Unsaturated fat
An unsaturated fat is a fat or fatty acid in which there are one or more double bonds between carbon atoms in the fatty acid chain. A fat molecule is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond.
Where double bonds are formed, hydrogen atoms are eliminated. In cellular metabolism hydrogen-carbon bonds are broken down, or oxidised, to produce energy. Thus an unsaturated fat molecule contains somewhat less energy (i.e. fewer calories/kilojoules) than a comparable sized saturated fat.
The greater the degree of unsaturation in a fatty acid (i.e. the more double bonds in the fatty acid), the more vulnerable it is to lipid (fat) peroxidation or rancidity. Antioxidants can protect unsaturated fat from rancidity.
Fatty acid fluidity increases with increasing number of double bonds. Therefore, monounsaturated fatty acids have a higher melting temperature than polyunsaturated fatty acids but lower than saturated fatty acids. Monounsaturated fatty acids are liquids at room temperature and semisolid or solid when refrigerated. Polyunsaturated fatty acids, such as unsaturated vegetable oils, remain liquid even at relatively low temperatures.
Hydrogenation of an unsaturated fatty acid refers to the addition of hydrogen atoms to the acid, causing double bonds to become single ones as carbon atoms acquire new hydrogen partners (to maintain 4 bonds per carbon atom). Full hydrogenation results in a molecule containing the maximum amount of hydrogen (in other words the conversion of an unsaturated fatty acid into a saturated one). Partial hydrogenation results in the addition of hydrogen atoms at some of the empty positions, with a corresponding reduction in double bonds. Commercial hydrogenation is typically partial in order to obtain a malleable fat that is solid at room temperature, but melts on heating as in baking or when eaten.
· Omega Fatty Acids
1) Omega-3 fatty acids. These are a family of unsaturated fatty acids that have in common a C=C (ie a double bond) in the n-3 position, the third bond in the carbon chain from the methyl end of the fatty acid. Omega-3 fatty acids are essential as the body cannot synthesise them. Important omega-3 fatty acids include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA is an essential nutrient which must be obtained from food.
2) Omega-6 fatty acids. These are a family of unsaturated fatty acids that have in common a C=C (ie a double bond) in the n-6 position, the sixth bond in the carbon chain from the methyl end of the fatty acid. A common omega-6 fatty acid is linoleic acid, found in many vegetable oils, which is also an essential nutrient which must be obtained from food.
3) Omega-9 fatty acids. These are a family of unsaturated fatty acids that have in common a C=C in the n-9 position.
Animals cannot create double bonds at the third and sixth carbon on the chain of a fatty acid. Only plants can make this arrangement. The result is that only plants can synthesise omega-3 and omega-6 fats. These are referred to as essential fats. We, like all other animals, must get these essential fats directly by eating plants, or indirectly by eating animals that ate plants and stored these essential fats in their tissues. For example, fish store the omega-3 fats made by algae. Fish cannot synthesise this kind of fat.
In our bodies these plant-derived, essential fats are used for many purposes, including the formation of all cellular membranes, and the synthesis of powerful hormones known as eicosanoids, such as prostaglandins and leukotrienes. Our requirement of these is quite small, and even the most basic diets provide sufficient of them.
The correct ratio of omega-3 to omega-6 is very important. There is an agreement that early humans consumed these fatty acids in a ratio of 1:1. This ideal ratio has been upset by our use of oils and seeds, which has skewed it heavily towards omega-6. It is recommended that the ratio to be between 1:1 and 1:4. However most of us consume these fatty acids in a ratio between 1:10 and 1:30. We consume far too much omega-6. Between 0.5 and 3% of our caloric/kilojoule intake should come from omega-3, and between 3 and 5% from omega-6.
· Free oils
When the fatty acids, as oils, are removed from their natural environments, for example from the seeds of corn, soybeans, safflowers or canola, or from the fruit of olive or avocado, they are no longer food. Yes, they do supply concentrated calories/kilojoules, but the rest of the original nutrition found in the plant is absent.
What happens in an oil processing plant? In the September 2008 issue of Natural Health and Vegetarian Life, page 46, the purification process is described:
“The seeds are first ground by a grinding machine, then steam cooked, and then mixed with solvents to dissolve out the oils. The most popular solvents used are hexane or trichloroethylene, both being very carcinogenic. The oils and solvents are now separated, but minimal traces of hexane remain in the oil. The oil is refined with the addition of sodium hydroxide and increasing the temperature to over 200 degrees C (400F). Thereafter the oil is treated with carbon that removes all the vitamins A and E, lecithin, chlorophyll and other nutrients. Preservative and/or antioxidant additives like BHA (no.320) or BHT (no.321) are added later.”
Thus we have, for example, canola (rapeseed) oil, safflower oil, flaxseed oil, peanut oil, rice bran oil.
This is why oils extracted by the cold pressed method, for example from olives, are the only type that should be consumed.
Cold pressed is a process, at room temperature, that involves only pressure to extract the olive oil, and results in a natural level of low acidity. The best olive oil is called ‘extra-virgin’. Extra-virgin olive oils must have an acidity of less than 0.8 percent. Virgin olive oils, on the other hand, may have an acidity of between 0.8 and 2 percent. Extra-virgin olive oil must also have a minimum organoleptic rating of 6.5 out of 10. ‘Organoleptic’ properties refer to the olive oil flavour, bouquet and colour. Thus cold pressed extra-virgin olive oil is the olive oil of the highest quality, and boasts a perfect, fruity taste and with a colour that can range from champagne to greenish-golden to bright green (colour not being an indication of quality).
· Cis or Trans
Polyunsaturated fatty acids can assume a cis or trans conformation, depending on the geometry of the double bond.
In most naturally occurring unsaturated fatty acids, the hydrogen atoms are on the same side of the double bonds of the carbon chain. This is the cis configuration (meaning ‘on the same side’ in Latin).
However partial hydrogenation reconfigures most of the double bonds that do not become chemically saturated, twisting them so that the hydrogen atoms end up on different sides of the chain. This type of configuration is called trans (meaning ‘across’ in Latin).
The conformation has implications for the physical-chemical properties of the molecule. The trans configuration is straighter, while the cis configuration is noticeably kinked. Trans fats are more similar to saturated fat than are cis fats in many respects, including the fact that they solidify at a lower temperature (due to the ability of the trans molecules to pack more tightly, forming a solid that is more difficult to break apart).
The Presence of Trans Fats in Food
A type of trans fat occurs naturally in the milk and body fats of ruminants, such as cattle and sheep, at a level of 2-5% of total fat. These trans fats originate in the rumen of these animals.
Animal-based fats were once the only trans fats consumed. Today, by far the largest amount of trans fat consumed is created by the processed food industry by partially hydrogenating unsaturated plant fats (generally vegetable oils). These partially hydrogenated fats have displaced natural solid fats and liquid oils in many areas, notably in the fast food, snack food, fried food and baked food industries.
Reasons for this include increased product shelf-life, decreased refrigeration requirements, ability to replace animal fats traditionally used by bakers, and as an inexpensive alternative to other semi-solid oils such as palm oil.
Foods containing artificial trans fats formed by partially hydrogenating plant fats may contain up to 45% trans fat compared to their total fat. Animal fats from ruminants, such as butter, contain up to 4% only. Those margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight. Trans fats are also found in shortenings commonly used (and reused) for deep frying in restaurants. As fast food chains use different fats, the trans fat level in products can have a large variation, up to 45% of the total fat in the product.
Nutritional Guidelines for Trans Fats
In 2002, The National Academy of Sciences (NAS) published recommendations regarding the consumption of trans fat.
Their recommendations were based on two key facts.
1) “…trans fatty acids are not essential and provide no known benefit to human health”, whether of animal or plant origin.
2) While both saturated and trans fats increase levels of LDL cholesterol, trans fats also lower levels of HDL cholesterol, thus increasing the risk of coronary heart disease. The NAS is concerned “that dietary trans fatty acids are more deleterious with respect to CHD (coronary heart disease) than saturated fatty acids”.
The NAS has concluded that there is no safe level of trans fat consumption. There is no adequate level, recommended daily level or tolerable upper limit for trans fats. This is because any incremental increase in trans fat intake increases the risk of coronary heart disease.
This analysis of the NAS is supported by a scientific review published in the New England Journal of Medicine (NEJM) in 2006, which states that “from a nutritional standpoint, the consumption of trans fatty acids results in considerable potential harm but no apparent benefit.”
Despite this concern, the NAS dietary recommendations have not recommended the elimination of trans fats from the diet. This is because trans fat is naturally present in many animal foods in trace quantities, and therefore its removal from ordinary diets might result in nutritional imbalances. The NAS has therefore “recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet”.
The World Health Organization recommended, in 2003, that trans fats be limited to less than 1% of overall energy intake. If the daily energy intake, for example, is 2000 calories, this would mean that 20 calories only can come from trans fat. That is about 2 grams of trans fats a day. Given the amount of naturally occurring trans fats eaten each day, this leaves virtually no room at all for industrially manufactured trans fats.
Health Risks of Trans Fats
· Coronary Heart Disease
The primary health risk identified for trans fat consumption is an elevated risk of coronary heart disease (CHD). The review in the NEJM referred to above concluded that “On a per-calorie basis, trans fats appear to increase the risk of CHD more than any other macronutrient, conferring a substantially increased risk at low levels of consumption (1 to 3 percent of total energy intake)”. That study, published in 2006, estimates that between 30,000 and 100,000 cardiac deaths per year in the U.S. are attributable to the consumption of trans fats.
There are two acceptable tests that measure an individual’s risk for coronary heart disease, both blood tests.
1) The first is a measure of two types of cholesterol. These were outlined at the commencement of this newsletter. The lower the LDL cholesterol and the higher the HDL cholesterol, the better. Trans fats elevate the LDL and lower the HDL cholesterols. The cholesterol ratio compares the levels of LDL to HDL. Trans fat behaves like saturated fat by raising the level of LDL, but unlike saturated fat it has the additional effect of decreasing levels of HDL. The net increase in LDL/HDL ratio with trans fat is approximately double that due to saturated fat (higher ratios are worse).
2) The second is a measure of a cell-signalling cytokine called C-reactive protein. The importance of this is still being studied. One study of 700 nurses showed that those with the highest intake of trans fat consumption had blood levels of C-reactive protein that were 73% higher that those with the lowest intake.
· Other Possible Health Effects of Trans Fats
There is some supportive research (although much less scientific consensus, unlike that for coronary heart disease) that eating trans fats specifically increases the risk of:
cancer, especially prostate and breast cancers
Trans fat may increase inflammation, which is a process by which the body responds to injury. Trans fats appear to damage the cells lining the blood vessels, leading to inflammation. It is thought that inflammation plays a key role in the formation of fatty blockages in heart blood vessels.
Food-Labelling of Trans Fats
In January 2006, it became law in the U.S. that the content of trans fats has to be specifically listed on food labels. However if a food contains less than 0.5 gram of trans fats per serving, it can be labelled as being free of them! Furthermore, the regulations only apply to food labels. Foods served in restaurants and fast food outlets are not covered by this law.
In Australia, the Federal Government has indicated that it wants to pursue a policy of reducing trans fats in fast foods. Australia’s food labelling laws do not, at this time, require trans fats to be shown separately from the total fat content. In August 2008, Professor (of health policy) M. Daube, of Curtin University, said “we at least need mandatory food labelling of trans fats”. He also pointed out that “… in people whose diets are unhealthy, they may be totally unaware that the food they’re eating is heavy in trans fat”. It is estimated that 2.7 million people every day are going through the doors of the large fast-food chains.
As set out above, trans fats can be found in many foods, especially in fried foods like french fries, potato crisps, doughnuts, and baked foods including pastries, pie crusts, biscuits, pizza dough, cookies and crackers, but to name a few. All these should be avoided and regarded as poisons.
A healthy, safe diet is one which is unprocessed, unrefined, free from added chemicals and mainly plant based with a significant raw component. Energy from fat should be in the region of 10% of total dietary intake and not greater than 15%. This is the ideal way forward. This approach is described in detail in my book ‘How to Live to 100+ Years Free from Symptoms and Disease. The Dietary Guidelines’ (see home page).
Copyright 2008: The Huntly Centre.
Disclaimer: All material on the huntlycentre.com.au website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.
Back to the list Print friendly version