FEDIOL

Misunderstood for a long time, their function seemed to be limited to temperature regulation of the body. Lipids are fats. Vegetable oils contain 100% of lipids. Today, the reputation of good fats has finally been rehabilitated, now we even know that some are essential. Lipids give energy. Each gram supplies 9 kilocalories. This energy serves to maintain body temperature at 37°C whatever the external temperature.

Dietary fats are fats found in foods. They are an essential part of a healthy diet. Dietary fats that are liquid at room temperature are usually called oils. Dietary fats that are solid or partially solid at room temperature are called fats. Most of the naturally occurring fats consist of a combination of triglycerides. A triglyceride is composed of glycerine and fatty acids. The properties of a triglyceride depend on the chemical and physical properties of its fatty acids, such as their chain length, number of double bonds and their location on the hydrocarbon chain.

Fats and oils are recognized as essential nutrients in both human and animal diets. The body's fat deposits are used to meet energy demands when dietary energy is limited, as well as to protect vital organs and help insulate the body. Essential fats are vital for the formation of hormones.

Fat is the main energy store in the body and the most concentrated source of energy in the diet - 1g of fat provides 37kJ (9 kcal), more than double that provided by either protein or carbohydrate (4 kcal).

In the diet, fat is a carrier for the fat-soluble vitamins A, D, E and K, and enables their absorption. It provides the essential fatty acids, linoleic acid (omega-6) and alpha-linolenic acid (omega-3).

Fats contribute greatly to the feeling of satiety after eating and serve to make foods more palatable. Fats and oils are present in varying amounts in many foods. The principal sources of fat in the diet are meats, dairy products, poultry, fish, nuts, and vegetable fats and oils.

It is now considered that a diet with around 30 - 35% of daily energy coming from fat is consistent with good health. This corresponds to some 70 g per day for a female adult, 90 g for a male adult. Additionally total calories from saturated fat should be kept low, with a tolerable upper limit of 10-11% of daily calories. The intake of trans fatty acids should be kept below 2%.

*1 Deutsche Gesellschaft für Ernährung, Nutrition Report 2000.
*2 Gezondheidsraad, 2001. † 20-40% range suitable for individuals with optimum and constant weight:
20-30 or 35% range for individuals who are overweight or who experience undesirable weight gains.
*3 Agence Française de Sécurité Sanitaire des Aliments, 2000.
*4 Committee on Medical Aspects of Food and Nutrition Policy (COMA), 1991. †† Diet including or excluding alcohol.
*5 Linee guida per una sana alimentazione Italiana - Istituto Nazionale della Nutrizione - 2° edizione 1997
*6 Die Ernährung in Deutschland, 1998.
*7 Dutch National Food Consumption Survey, 1997-98.
*8 Étude INCA, 1999.
*9 Livelli di assunzione raccomandati di energia e nutrienti per la popolazione italiana - LARN - S.I.N.U. - Rev. 1996.
*10 National Dietary and Nutrition Survey: Adults aged 19-64, 2000-2001.

All dietary fats contain a mixture of saturated and unsaturated fatty acids. The type of fatty acid that predominates determines whether a fat is solid or liquid, and whether the dietary fat is characterized as saturated or unsaturated according to its chemical structure.

Fats such as tallow, lard and butter, and vegetable oils such as palm, palm kernel and coconut oils, which are harder at room temperature, contain higher levels of saturated fatty acids. They are considered saturated fats.

Oils such as soybean, rapeseed, cottonseed, maize and other vegetable oils, which are liquid at room temperature, contain higher levels of unsaturated fatty acids. They are considered unsaturated fats. Unsaturated fats are further subdivided into monounsaturated and polyunsaturated fats.

Polyunsaturates are divided into two groups: omega 3 and omega 6 fatty acids. Omega 3 is found in oils from rapeseed, soybeans and linseed, and in certain kinds of fish. Omega 6 is present in oils from maize, sunflower and soybeans.

Trans fat acids are fatty acids in which the hydrogen atoms attached to the carbon-carbon double bond are located on opposite sides of the chain.

What are the differences between saturated, monounsaturated and polyunsaturated fats?

The distinction corresponds to zero, one or several double bonds to "unsaturations" of the fatty acids' (FA) structure. More specifically, all fat substances naturally contain all three types of fatty acids in varying quantities.

When we talk about saturated fat substances we are referring to a fat substance, but not exclusively, composed of saturated fatty acids. Olive oil is a monounsaturated oil that is composed of 75% monounsaturated fatty acids, 15% of saturated fatty acids, and 10% of polyunsaturated fatty acids.

What are "essential" fatty acids and why are they important?

Essential fatty acids are fatty acids that the human body cannot produce by itself, and therefore must be supplied in the diet. Such fatty acids are based on linoleic acid (omega-6 family) and alpha-linolenic acid (omega-3 family). They are necessary for growth, regulation of widely diverse physiological processes and for maintaining health.
Vegetable oils like maize, sunflower and soybean oil are rich in omega-6, as is rapeseed oil although at somewhat lower levels. Omega-3 acid it is naturally present in linseed oil (high contents) and in rapeseed and soybean oil (moderate contents).

How much fat is in the diet?

Fats in the diet are often referred to as "visible" or "invisible."

The invisible fatty acids are an integral part of food. Those that are naturally occurring in foods such as cold meats and fatty meats, fish, eggs, cheeses, pastries, savoury, biscuits, peanuts, walnuts, avocados, frozen meals and catered dishes.

Visible fats are the ones added to the diet. Those you add when preparing meals such as salad dressings oils, butter, margarine, cream, whipped cream, goose fat, bacon, and lard.

Which are the sources of animal and vegetable fat?

Animal fats are found in butter, cream, lard, goose poultry, horse meat, whipped cream, fish oil, cold meat, pastries, cheese, biscuits and ice creams.

The sources of vegetable fat are:

Why fats are so much used in foodstuffs manufacturing?

In developed countries where food is plentiful and varied, palatability is a major determinant of food choice. Fat contributes to the palatability of foods by its texture or mouthfeel, and its flavours. All fats and oils act as carriers for fat-soluble flavour compounds.

The characteristics of fats and oils also play a very important role in the manufacture and cooking of foods and in the texture and appearance of the final product.

Can peanut or soybean oil cause allergies?

Food allergies are caused by the protein components of food. Edible oils consumed in the EU are highly refined, a process which removes proteins from the oil to the extent that are not present in detectable amounts. Refined edible oils therefore do not cause allergic reactions because they do not contain allergenic protein.

Food products containing refined edible oils as ingredients are also non-allergenic unless the food products contain other sources of protein.

What is cholesterol?

Cholesterol is a fat-like substance that occurs naturally in all animal tissues including the human body. We use it every day to maintain, repair, regenerate and build membranes that envelop each of our cells. It also plays a role in our digestion: it serves in producing bile salts that make digestion possible. Finally, cholesterol is indispensable in the production of vitamin D, which is important for children and the elderly because it strengthens bones.

An excess of cholesterol or triglycerides in the blood can cause heart and blood vessel abnormalities. Human liver produces over three quarters of the cholesterol in blood, while the rest comes from our diet.

Cholesterol is carried in the blood in the form of lipoproteins: LDL (low density lipoprotein) and HDL (high density lipoprotein). A high concentration of LDL-cholesterol is a risk factor for coronary heart disease; hence this is sometimes called ''bad cholesterol''.

HDL-cholesterol is associated with cholesterol removal and high concentrations are beneficial, hence this is often called "good cholesterol''. The higher someone's HDL the lower the risk of heart disease. It makes sense to eat foods which help to lower LDL levels and raise or maintain HDL levels.

For most people eating foods that contain cholesterol like eggs, shellfish and liver has little effect on blood cholesterol levels. However, there is a small number of people who are 'hyper-responders' to dietary cholesterol. These people need to restrict their cholesterol intake. Physical activity also raises HDL levels.

Vegetable products, such as vegetable oils and fats, do not contain cholesterol.

What effect do 'saturated' fats have on blood cholesterol?

Because they are derived from a ruminant animal, lard, dripping, butter and cream contain far more saturated fat than do the polyunsaturated or monounsaturated margarines and cooking oils.

In the body, cholesterol production can be increased in response to the consumption of foods rich in particular saturated fatty acids. High blood cholesterol is associated strongly with increased risk of heart disease.

Coconut and palm-kernel oil also contain the saturated fatty acids found in butter, so they can promote higher blood cholesterol too. These two plant-derived oils are similar to butter in their ability to raise blood cholesterol. Most other plant oils have little saturated fat - eg, avocados and peanut (and other nut) oils are largely monounsaturated and/or polyunsaturated and are therefore considered to be relatively heart-friendly.

What effects do polyunsaturated fats have on blood cholesterol?

Many of the polyunsaturated fats are believed to have cholesterol-lowering properties, particularly those rich in omega-6 fatty acids which are naturally present in many vegetable oils (e.g. safflower, sunflower, soybean, walnuts, sesame, maize and cottonseed oils.

The other major polyunsaturated fats - the omega-3 series (found in significant quantities in fish, but also in rapeseed, linseed, soybean and walnut oils) - are also believed to be helpful in reducing the risk of heart disease, but by means other than lowering cholesterol.

What is hydrogenation and why is it used by the food industry?

Hydrogenation is the process by which hydrogen is added directly to points of unsaturation in the fatty acids. Hydrogenation of fats has developed as a result of the need to convert liquid oils to the semi-solid form for greater utility in certain food uses and to increase the oxidative and thermal stability of the fat or oil.

Hydrogenation is an extremely important process as far as our food supply is concerned, because this processing gives the desired stability and other properties to many edible oil products. The level of unsaturated fatty acids present in some oils such as soybean oil is reduced in order for the oils to have functional properties in many food applications. Hydrogenation is the only practical way to convey these properties.

In the process of hydrogenation, hydrogen gas is reacted with oil at elevated temperature and pressure in the presence of a catalyst. The catalyst most widely used is nickel supported on an inert carrier which is removed from the fat after the hydrogenation processing is completed. Under these conditions, the gaseous hydrogen reacts with the double bonds of the unsaturated fatty acids.

The hydrogenation process is easily controlled and can be stopped at any desired point. As hydrogenation progresses, there is generally a gradual increase in the melting point of the fat or oil. If the hydrogenation of cottonseed or soybean oil, for example, is stopped after only a small amount of hydrogenation has taken place, the oils remain liquid. These partially hydrogenated oils are typically used to produce institutional cooking oils, liquid shortenings and liquid margarines. Further hydrogenation can produce soft but solid appearing fats which still contain appreciable amounts of unsaturated fatty acids and are used in solid shortenings and margarines. When oils are more fully hydrogenated, many of the carbon to carbon double bonds are converted to single bonds increasing the level of saturation. This conversion also affects trans fatty acids eliminating them from fully hydrogenated fats. If an oil is hydrogenated completely, the carbon to carbon double bonds are eliminated completely and the resulting product is a hard brittle solid at room temperature.

The hydrogenation conditions can be varied by the manufacturer to meet certain physical and chemical characteristics desired in the finished product. This is achieved through selection of the proper temperature, pressure, time, catalyst, and starting oils. Both positional and geometric (trans) isomers are formed to some extent during hydrogenation, the amounts depending on the conditions employed.

Biological hydrogenation of polyunsaturated fatty acids occurs in some animal organisms, particularly in ruminants. This accounts for the presence of some trans isomers that occur in the tissues and milk of ruminants.

What are Trans fats?

Trans fatty acids (TFAs) are polyunsaturated fatty acids that contain at least one carbon double bond in the trans configuration. The word 'trans' refers to the orientation of the carbon chains around a double bond - in this case the carbon chain ends are oriented on opposite sides of the double bond. It is thought that this actually makes the molecule behave like a 'saturated' fat because it is relatively straight in character. The other form of the 'isomer' is in the 'cis' orientation where the carbon chains occur on the same side of the double bond giving them a V-shaped character.

TFAs occur naturally in ruminant animals, which is way small amounts are found in dairy and meat products. It also occurs during hydrogenation, an industrial process through which food processors create shortenings and other solid or partially solidified fats, such as stick margarines, by reacting hydrogen with liquid oils. Hydrogenation also attaches hydrogen atoms to points of unsaturation on the fatty acid molecule. Food processors can manage the end results of the process so not all hydrogenated vegetable oils are high in trans fat.

What effect do Trans fats have on health?

Trans fatty acids are metabolised in a similar way to saturated fats, but there is still uncertainty about whether their effect on heart health is comparable. Trans fatty acids not only raise LDL-cholesterol in the same way as saturated fatty acids, but they also lower the level of the good HDL-cholesterol.

Concerns have been raised about high intakes of trans fatty acids but current intakes of trans fatty acids are relatively small in the EU and they are not considered to represent a nutritional hazard. However, from a public health point of view saturates could be more important because the diet contains 5-10 times more saturates than trans fats.