Last partial update: July 2016 - Please read disclaimer before proceeding.
Dietary nutrient groups
The nutrients in food are divided into two main groups; those present in large amounts, called macronutrients, and those in small amounts, called micronutrients. The macronutrients consist of carbohydrates, fats, fibre and protein, while the micronutrients consist mainly of vitamins and minerals. The table below indicates the energy content and functions in the body of each of these groups. The roles nutrient groups play in causing and preventing illness in Western society are discussed in detail throughout this book. It needs to be emphasized that the majority of Australian diets are not nutrient deficient. In fact, most Australian diets contain too much energy and too much fat. There are, however, a few groups of people who are likely to have micronutrients deficiencies. This issue is discussed in the sections on micronutrients, vegetarian diets, and osteoporosis. The role of antioxidants in disease prevention is also discussed later in this section.
Function and energy content of nutrient groups
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Nutrient |
Foods sources |
Energy content |
Function / use |
|
cal |
kJ |
|||
Fat - Fatty acids |
Mainly animal sources and vegetable oils. |
9 |
37 |
Mostly stored as fat for later energy use by the body when needed. Also an integral part of cell membranes. |
Fat - Cholesterol |
Lambs brains, liver, eggs and some seafood. |
Synthesis of body compounds including cell membranes and body chemicals, such as steroid hormones. |
||
Alcohol |
Alcoholic beverages |
7 |
29 |
Used for energy. Alcohol is not converted to fat but is metabolized to provide energy before fat and thus reduces the rate of fat breakdown. |
Protein |
Meats, fish, poultry, eggs, milk products, cereals, nuts and legumes, including soy beans, lentils, beans and peas |
4 |
17 |
Mostly used in the synthesis of body components. Only rarely used as an energy source, such as in starvation. |
Carbohydrate - Starches (complex carbohydrates) |
Pasta, potato, breads, cereals, fruit, legumes |
4 |
16 |
Provides energy for the body’s functions and some energy storage. It is usually stored as glycogen in the liver (and the muscle) but may be converted to fat if consumed in excess. (Glycogen is just many glucose molecules joined together.) The sugar that circulates in the blood and provides energy for the body is glucose. The brain relies almost solely on this glucose for energy and thus it is very important for blood glucose levels to be maintained. |
Carbohydrate - Simple sugars (sucrose, glucose, fructose, lactose) |
Fruit, honey and other sweet syrups |
|||
Fibre |
Bread, cereals, vegetables, fruit. |
0 |
0 |
Fibre keeps the bowel functioning normally and has a role in protection of the bowel from cancer causing substances. Soluble fibre can reduce blood cholesterol levels. |
Vitamins and minerals |
A wide variety of foods is needed, especially vegetables, fruit, low-fat dairy and lean meat. |
0 |
0 |
They are essential for the synthesis of many body components, especially enzymes. These nutrients have no significant energy function. Some are also important antioxidants. |
Water |
Fluids, fruit and vegetables |
0 |
0 |
70% of the body is composed of water. |
The major groups listed in the above table (and other nutrition topics) are dealt with in detail in other sections of this web site. (Links to these sections are listed below.)
Fatty acids
Fatty acids are the principal type of fat used by the body. They are simple compounds made up of a single chain of carbon atoms with an acid group at one end and hydrogen atoms attached to the sides of the carbon chain. The number of carbon atoms varies, with the most common ones having between twelve and twenty two. The type of bond that joins the carbon atoms together determines whether a fatty acid is saturated or unsaturated. Saturated fatty acids have single bonds joining all the carbon atoms in the chain. Unsaturated fatty acids have a double bond between either one pair of adjacent carbon atoms (i.e. monounsaturated fatty acids) or two or more pairs of adjacent carbon atoms (i.e. polyunsaturated fatty acids)
Fatty acids have several very important functions. Firstly they are the principle way the body stores energy for later use. Secondly, they make up about 75 per cent of the membranes that surround every cell in the body (and the membranes than surround structures inside cells). These membranes have the important function of determining what goes into and out of cells and in order to do this job properly, they need to contain the correct proportions of the different types fatty acids. This is partially determined by how much of each type is eaten and partly by the types the body makes. (The body cannot make all the types of fatty acids it requires.) Thirdly, fatty acids are used in the production of important body compounds, such as prostoglandins. Finally, fatty acids are used as thermal insulation and also as cushioning to protect joints and important body organs such as the kidneys.
Unsaturated fatty acid are shaped like bent rods The way a fatty acid functions when it is incorporated into body structures or used in producing compounds depends on its shape. Saturated fatty, which have no double bonds between the carbon atoms, have an overall shape of a straight rod. In all naturally occurring unsaturated fatty acids, double bonds occur in the cis-form and the presence of a ‘cis’ double bond causes a bend in the rod shape of the fatty acid. The more ‘cis’ double bonds, the more bends and the more irregular the shape. Such bends alter the way fatty acids work, especially their effect on membrane functioning.
The body can make most but not all fatty acids The body can make most of the fatty acids that it requires, although there are two important groups of polyunsaturated acids that it cannot make without precursor fatty acids provided in the diet. These precursors are termed essential fatty acids. (These are discussed later.)
Triglycerides
Triglycerides are made up of three (tri-) fatty acids joined together by a small compound called glycerol. They are the form in which most fatty acids are consumed in the diet, transported in the blood and stored in the body. There are many types of triglycerides, depending on the combinations of fatty acids that they are made from.
A list of the foods that have a high fatty acid content and a table comparing the types of fat present in oils and spreads appears in the section 'Fats in our food - More information'.
Approximate energy intake needed to maintain a healthy weight |
||
|
Energy intake in kilojoules (calories) |
Fat intake in a diet with 25% of energy intake as fat (g per day) |
Women |
|
|
Moderately active |
8,400 (2,000) |
54 |
Sedentary |
6,300 (1,500) |
40 |
Attempting weight loss |
5,000 (about 1,200) |
*See below. |
Men |
|
|
Moderately active |
10,500 (2,500) |
70 |
Sedentary |
8,400 (2,000) |
54 |
Attempting weight loss |
6,300 (1,500) |
*See below. |
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Saturated fatty acids
Saturated fatty acids do not have any double bonds between their carbon atoms. (This means they are saturated with hydrogen, hence the name.) These are the fats being referred to when mention is made of lowering dietary saturated fats. All types of saturated fatty acids can be produced by the body, although in Australia this is usually not necessary as most of us already consume excessive amounts of saturated fatty acids. This excess intake means that cell membranes contain relatively more saturated fatty acids than is ideal. Reducing their intake to the recommended level stated above will help overcome this imbalance and make cell membranes function better. Having said this, it is important to realise that fat intake is all about getting the right balance. Saturated acids need to be present in membranes too and eliminating saturated fats completely from our diets is probably just as harmful as consuming too many. We just need them in the right amount.
Excessive saturated fat intake is the main dietary cause of raised blood cholesterol and it is important that all Australians take measures to restrict their saturated fat intake. A list of the sources of saturated fats is provided in table below.
Food sources of saturated fatty acids*
Traditionally, saturated fats sourced from our diet mainly came from animal products. In modern Australia, however, a significant proportion comes from vegetable sources. The main sources are palm oil, coconut oil and unsaturated vegetable oils that have been modified to give them a much higher content of saturated fats. Such modified oils are easier to use in making processed foods, such as cakes, pastry and biscuits. They are also often used in the deep-frying of takeaway foods, such as fish and chips, as they taste better than unsaturated oils, which go off when repeatedly heated. Thus, while these oils are vegetable in origin, they are generally a less healthy choice for most Australians. Signs saying a product contains ‘no cholesterol’ or ‘only vegetable oils’ are no reassurance that the product is healthy. Dietary recommendations to lower saturated fat include –
- If overweight, restrict total fat intake to about 25 to 30 per cent of total energy intake. For people who are a normal weight, a fat intake between 25 to 35 per cent of total energy intake is recommended. (See table below
- Restrict saturated fat intake to not more than 10 per cent of total energy intake. This is an issue for all Australians
- Increase the proportion of omega-3 polyunsaturated fats and monounsaturated fats in daily dietary fat allowance. Again, this is important for everyone.
- Eat red meat that is lean and trimmed of all fat. Two to three servings a week is optimal. Servings should be about the size of a pack of cards or weigh about 80g.
- Use lean servings of chicken with the skin removed.
- Use unsaturated oil for cooking. Cooking oils should preferably have a saturated fat content of not more than 15 per cent and a large monounsaturated fat content. (Extra virgin olive oil is a good choice as it contains numerous antioxidants and other nutrients and contains mostly monounsaturated fat.)
- Do not use (or use very occasionally) coconut or palm oils or coconut milk.
- Try to reduce the use of spreads or don’t use them at all. Most margarines have a saturated fat content of about 20 to 25 per cent of their total fat content. Butter has a lot more!
- Use reduced-fat or low-fat dairy products. Watch intake of cheese and minimise intake of butter, cream and fried take away foods and home-fried foods. (When oils for frying at home, most oils should only be used once. This is because heating oxidizes them, producing harmful free radicals that adversely affect body compounds by oxidizing them. Olive oil can be used a few times.)
- Eat minimal amounts of biscuits, cakes and pastries. Low-fat (check the label!) muffins, cakes etc are often relatively high in energy and are thus still not a healthy choice, especially for those who are overweight. Additionally, as people assume low fat foods are good for them, they tend to eat a larger quantity of low fat foods, worsening the situation.
- Eat minimal amounts of processed snack foods such as potato crisps, chocolate bars etc.
- Eat less prepared foods / takeaway food. Prepare more foods at home.
Food sources of saturated fatty acids*
|
|
Animal Sources (About 60% of total saturated fat intake) |
Vegetable Sources (About 40% of total saturated fat intake) |
|
|
Trans Fatty Acids |
|
Most trans fatty acids that occur naturally in foods are not harmful and some are beneficial. However, the trans fatty acid called elaidic acid that is formed during the processing of food is harmful, having similar effects to saturated fatty acids (i.e. raising LDL and total cholesterol and lowering HDL). It also increases the potentially harmful lipoprotein (a). Elaidic acid is mostly found in fats produced for use in deep frying (takeaway foods) and in processed foods such as margarines Most margarines are now available with reduced (1 to 2%) or no trans fatty acids.)
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|
Notes *All fat containing foods have both saturated and unsaturated fats present. The foods in this list have a large component of saturated fat in their total fat content. The percentages mentioned indicate the percentage of saturated fat in relation to the total fat content of the food. They do not indicate the overall fat content of the food. **These oils are often used in processes foods and in commercial frying as they do not go off as quickly as unsaturated oils. ***Unsaturated vegetable oils are often modified so that they become more saturated and do not go off as quickly. This process removes some of the double bonds in the fatty acids, thus increasing their hydrogen content (i.e. they become increasingly saturated with hydrogen). These oils are also used in processes foods and in commercial frying.
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Unsaturated fatty acids
Monounsaturated fats have one pair of carbon atoms in their carbon chain joined by double bond and polyunsaturated fats have more than one pair of carbon atoms in their carbon chain joined by double bond. Polyunsaturated fatty acids are divided into two main groups, the omega-3s and the omega-6s, according to the position of the double bonds.
Unlike saturated fats, unsaturated fats are not responsible for raising blood cholesterol and in fact most help to do the opposite. (The advantages of unsaturated fats are mentioned later in the section on lowering blood cholesterol through diet.
Unsaturated fatty acids should represent at least 70 per cent of total fat intake. Most Australians are relatively low in their intake of omega-3 fats and their contribution to total fat intake should be increased. On the other hand, people who consume lots of margarines and oils with predominantly omega-6s may have relatively too much of this type of fat. Dietary sources of theses fats are shown in the table below.
Monounsaturated fatty acids
Monounsaturated fatty acids can be sourced from food or produced in the body. A list of foods containing significant quantities of monounsaturated fatty acids appears in the table above. The most common is Oleic acid, a fatty acid with 18 carbon atoms and a double bond between the ninth and tenth carbons.
Polyunsaturated fatty acids
Polyunsaturated fatty acids have more than one double bond in their carbon chain. Unlike the other fatty acids mentioned above, our bodies are not able to make polyunsaturated fatty acids from scratch and require consuming precursor essential fatty acids present in plants (and sea food).
Food Sources of unsaturated fatty acids
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|
Monounsaturated Fats |
|
|
|
Polyunsaturated oils |
|
Omega 6 types |
Omega-3 Types |
|
|
Notes *Fat content percentages relate to total polyunsaturated fat content (including both omega 3s and omega 6s)
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Essential fatty acids
Polyunsaturated fatty acids are divided into two groups, the omega-3s and the omega-6s, according to where the first double bond appears in the carbon chain. In the omega 3 group, it appears after the third carbon and in the omega-6 after the sixth carbon. There are numerous different types of polyunsaturated fatty acids in each group and most have numerous double bonds in their structure. Most of these double bonds can be added by the body. However, the body can not add the first double bonds; those that are inserted in either the third or sixth position. Only plants and fish can do this. Unfortunately all the polyunsaturated acids need one or the other of these bonds and thus the precursors of all the polyunsaturated fatty acids we use must come from fatty acids contained in the plants or seafood consumed in our diet that possess such double bonds. Such fatty acids are termed essential fatty acids, as it is essential that our diet contains them.
There are two essential fatty acids for humans; linoleic acid, which has a double bond at the 6 position and is the essential fatty acid required for our bodies to make all the fatty acids in the omega-6 group, and alpha-linolenic acid, which has double bonds at both the 3 and 6 positions and is the essential fatty acid required for our bodies to make all the fatty acids in the omega-3 group. Both these are provided by plant seeds but linoleic acid (the omega-6 precursor) is much more prevalent in our diets than alpha-linolenic acid, the omega-3 precursor. These two fatty acids themselves are not very useful in the body, partly because they are too short to be incorporated into membranes, and they need to be modified to make useful omega-3 and omega-6 fatty acids. (The body does this by adding double bonds in other positions in the chain and by lengthening the chain.) It is also possible to consume in our diets some of these useful longer types of omega-3 fatty acids that can be used without need of modification. Two important ones that are found in seafood, especially oily fish, are eicosapentaenoic acid and docosahexaenoic acid. The consumption of seafood is important as it has a high content of these ‘ready-to-use’ omega-3s and our diets are generally low in the essential omega-3 alpha-linolenic acid, which is mostly sourced from plants (e.g. from linseeds and to a lesser extent canola).
These essential fatty acids and their derivative fatty acids are vital for health for two reasons. Firstly, they are important components in the structure of the membranes that surround all body cells (especially in the retina of the eye and the brain). Membranes also surround structures within cells, such as the cell nucleus which controls cell functioning. Healthy membranes are very important for proper cell and body functioning.
Secondly, they are used in the production of substances called eicosanoids. These substances, which include prostoglandins, thromboxanes and leukotrienes, help control blood clotting, blood pressure, inflammatory reactions and the reproductive cycle. Compounds produced by the two essential fatty acid groups (the omega-6s and the omega-3s) tend to act in opposite ways and preventing problems such as high blood pressure, an increase in inflammatory diseases such as arthritis, and an increase in the tendency to clot, which can worsen vascular diseases such as coronary artery disease (heart attacks) requires a balanced intake of both omega-3s and omega-6s. (See boxed section.) For example, an excess omega-6s relative to omega-3s can actually increase blood clotting and inflammatory diseases while excessive amounts of omega 3s can cause excessive bleeding from a cut.
Unfortunately, omega-3s are relatively lacking in many Australian diets, which is unfortunate as they have many health benefits including benefits regarding vascular disease prevention, including lowering blood triglyceride levels, helping prevent blood clotting, and reducing the likelihood of harmful irregular heart rhythms occurring. They also help reduce high blood pressure. In addition to these benefits, Omega-3s are thought to be important for maintaining optimum brain function in both adults and children and may help in the prevention of illnesses such as depression. (Studies are under way to substantiate any such benefit.) Thus, an important priority in regulating fat intake should be to ensure an adequate intake of omega-3 essential fatty acids is consumed.
Omega-3 fats
Sourcing Omega-3 fats – A preferred fatty acid choice
Fish are by far the best source of omega-3 oils for two reasons both because they have higher concentrations of omega-3s than plant sources and because they have more ‘ready-to-use’ omega-3s. Two to three servings of fish per week provide an adequate amount of omega-3s for the general population.
The National Heart Foundation recommends (March 2012) that all Australians should comsume about 500mg of long chain omega-3s per day and that people with heart disease should consume about 1000mg per day. Traditionally, oily fish such as salmon were thought to be the best source. However, it is now recognised that all fish are good sources.
Other sources include nuts, legumes, soy beans, breast milk, lean meat, vegetable based oils and margarines, and even vegetables. Animal fats, (including milk fats and formula milks used in place of breast milk) and fats used in processed foods are poor sources.
A new source of omega-3s is low fat milk that has had omega-3s added. A 250ml glass will contain about 200mg of omega-3 fats. It needs to be stressed that there is little evidence proving that such supplements provide the same benefits as omega-3s found naturally in fish. Other sources are shown in Table 10.
While nutrients gained from fresh food are always best, fish oil capsules can be used as a source of omega-3s. Be sure to purchase capsules produced by reputable companies as all omega-3s are unstable and can easily oxidise if not handled carefully. This is why fish ‘goes off’ more quickly than most other fresh foods. It is also the reason that linseed oil, which has a high omega 3 content, is not used very often. (Oxidised omega-3s smell off.) To help prevent oxidation, all sources of omega-3s should be kept in the fridge.
The balance between dietary omega-3s and omega-6s
With the increased use of polyunsaturated margarines and oils there has been a rise in the consumption of omega-6 fatty acids, altering the balance between the omega-6s and omega-3s. This is a problem as it may adversely affect blood clotting, blood pressure and inflammation in the body. At present, the ratio of omega-6 to omega-3 fats in the diet is typically about fourteen to one. This figure should be about six to one. A high intake of linoleic acid (the omega-6 precursor) is also a problem because it can act to reduce the amount of vegetable sourced alpha-linolenic acid (the omega-3 precursor) that can be modified to make useful longer omega-3s. (The enzyme needed for the first step in this modification is the same one that is used in the modification of linoleic acid and a relative excess of linoleic acid means less of this enzyme is available for use in modifying alpha-linolenic acid.) This problem can be overcome either by increasing the intake of longer omega-3s sourced from fish, which do not need to be modified before being used in the body or by using oils and margarines containing predominantly monounsaturated fats rather than those with mostly polyunsaturated fats (i.e. linoleic acid).
Luckily, this is already being achieved through the increasing popularity of olive oil and canola-based margarines, which contain predominantly monounsaturated fatty acids. Having said all this, omega-6 fats are healthy and their consumption has repeatedly been shown to reduce the incidence of heart attacks. Thus, they should be an important part of a normal diet; just not too much.
Extra-virgin olive oil – Another preferred fatty acid choice
Olive oil, like most oils, is about 90 per cent fat. About three quarters of this is monounsaturated fat with the other quarter being made up of equal amounts of saturated and polyunsaturated fats. Being low in saturated fats and high in monounsaturated fats, olive oil helps reduce vascular disease and assists in reversing any omega-3/omega-6 imbalance. Another important vascular disease benefit is its high antioxidant content and there is some evidence to suggest that olive oil may also help in lowering blood pressure and in reducing clotting.
Olive oils are classified according to how the olives are pressed (crushed) to extract the oil. In times past they were pressed several times. Today they are usually only pressed once. However, the oil that comes out at the beginning of the pressing is different to that which comes out at the end.
The oil that comes out first (the initial pressings) is called ‘extra virgin olive oil’. It is generally darker in colour and contains many more flavour compounds. (To be called ‘extra virgin’, the oil must meet certain flavour criteria.) Many of these flavour compounds, such as phenolics, are antioxidants. There are over 35 antioxidants in extra virgin olive oil and they are thought to be beneficial in protecting against vascular disease.
Later pressings are called ‘light olive oil’. It is a lighter colour, and contains less flavour compounds and less antioxidants. Light olive oil is not lighter in fat content. It needs to be stressed that all olive oils contain the same amount of fat and the same energy content (ie the same number of kilojoules or calories).
Thus, extra virgin oil is preferable to other forms both in taste and health benefits. However, as it is almost all fat, it should be consumed in moderation as part of a person’s daily fat allowance.
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Cholesterol
Dietary cholesterol only accounts for about two per cent of the total fat we eat, with the rest being made up of fatty acids. The body can make all the cholesterol it requires in the liver. However, the liver typically produces only about 75 per cent of our cholesterol needs with the rest coming from our diet.
Cholesterol is the fat that is deposited in artery walls, causing vascular disease such as coronary artery disease (heart attacks). For this reason, it is often viewed as a compound that is harmful to the body. However, this is only the case when it is in excess. Cholesterol is in fact an essential component of many important body structures including the protective membrane that surrounds all cells, vitamin D, all steroid compounds (e.g. steroid hormones), and bile salts, which are produced by the liver to help digest dietary fat.
The two dietary components that can increase a person’s blood cholesterol level are saturated fatty acid intake and cholesterol intake, with the saturated fat component being usually more important. Thus, from a fat content point of view, stating that a food is cholesterol free does not mean that it is helpful in reducing vascular disease (i.e. helps reduce heart attacks). To be good for a person’s arteries, the food should also have a low a low saturated fat content. (Beware of foods stating that they are low in just cholesterol.)
While dietary cholesterol is less important than saturated fatty acid in determining blood cholesterol levels, restricting cholesterol consumption still makes a significant contribution to lowering blood cholesterol and is important in those with risk factors for vascular disease or those who already have vascular disease. Foods especially high in cholesterol include lambs brains, offal, tripe, liver, pate, fish roe and egg yolks. Prawns, lobster and squid also have a relatively high cholesterol content but their low total fat and high protein content makes this relatively unimportant. Other foods that contribute to dietary cholesterol are similar to those that contribute to saturated fat intake; mainly meats and to a lesser extent full-fat diary foods.
Good and bad cholesterol - Lipoproteins and cholesterol transport
Fats, such as cholesterol and triglycerides, are generally not water-soluble and thus cannot be easily transported in blood on their own (as blood is mostly composed of cells floating in salty water). For this reason, special compounds with a water-soluble outer coating called lipoproteins are used to transport fats in the blood. A lipoprotein consists of a central core of mainly cholesterol (as cholesterol esters) and triglycerides surrounded by a membrane (a phospholipid monolayer). Because they contain many fat molecules, lipoproteins are much larger than the fatty acids or cholesterol they contain.
There are several types of lipoproteins and these vary according to their size, the type and amounts of the fats that they contain, and their actions in the body. They are generally divided into two groups that have been termed ‘good cholesterol’ and ‘bad cholesterol’, depending on their effect on vascular disease. These terms are unfortunate as they incorrectly imply that there are different types of cholesterol itself. This is not true. It is the structures that the cholesterol is carried in, the lipoproteins, that are different. The ‘good’ or ‘bad’ grouping depends on whether the lipoprotein decreases (good) or increases (bad) cholesterol deposits in arteries. (i.e. increases or decreases vascular disease).
The term ‘good cholesterol’ refers to high density lipoproteins (HDL). These carry cholesterol from the body back to the liver. In doing this they actually reduce the amount of cholesterol in artery walls and thus reduce artery blockages.
Bad cholesterol refers to several types of lipoprotein, the main one being low density lipoprotein (LDL). These develop in the blood from another bad lipoprotein called very low density lipoprotein (VLDL), which is made in the liver. The LDL takes cholesterol to other tissues, such as muscles, and as it travels through the arteries to get to these tissues, some is deposited into artery walls. The higher the blood level of LDL, the more the vessel walls are exposed to cholesterol deposition.
When blood cholesterol measurement is determined, it usually includes HDL, LDL and total cholesterol. The total cholesterol is made up of HDL, LDL and other cholesterol sources.
(See section on Cholesterol in the body.)
Foods containing plant sterols
Plant sterols (and stanols) are compounds that are chemically similar to cholesterol. They occur naturally in small amounts in some foods. Unlike cholesterol, the body absorbs sterols only in very small amounts. Thus, almost all sterols are excreted in the faeces.
Sterols act to reduce blood cholesterol by reducing cholesterol absorption from the small intestine. This is accomplished by the sterols competing with cholesterol for absorption sites on the bowel surface. The effect of sterols on blood cholesterol is in addition to the reduction in blood cholesterol achieved through reducing dietary cholesterol intake or by taking cholesterol-lowering medication.
Sterols are found in soy beans, leaves, nuts, vegetable oils, corn and rice. A normal Australian diet contains about 200 to 400mg per day of these compounds. (Vegetarian diets may contain higher levels, up to 600 to 800mg.) This dietary intake is insufficient to have any significant affect on reducing cholesterol levels in the blood. To achieve its cholesterol lowering effect, sterol intake needs to be about 3g per day. This can be achieved by eating about 25g of sterol-enriched margarine. (This equates to about one and a half tablespoons full of margarine or the amount needed to cover 4 slices of bread.)
Plant sterol products reduce the absorption of some fat-soluble vitamins and carotenoids that are found in fruit and vegetables and which are thought to give protection against numerous diseases, including cancer. For this reason, it is recommended that children and pregnant or lactating women should not use these sterol containing products. People who use plant sterol products should eat extra fruit and vegetables (i.e. more than the recommended five to seven servings per day). The intake of plant sterols should not be greater than 3g per day as a greater intake is no more beneficial and reduces the absorption of these nutrients further. Sterols should not be used as a substitute for a low-fat diet.
Nutrient deficiencies and low fat diets
Low fat diets have the potential to provide an inadequate intake of the calcium, iron and zinc unless food choices are made carefully.
Many people significantly reduce their intake of dairy products when reducing the fat content in their diet and thus greatly reduce their calcium intake. This is not necessary as low fat milk products are a healthy substitute for full-fat dairy products, containing virtually no fat.
Red meat, and to a lesser extent chicken and fish, are still valuable sources of iron in low fat diets. Iron can also be obtained from plant foods but this iron is less well absorbed. (The absorption can be improved by eating foods rich in vitamin C at each meal.) See section on Dietary vitamins and minerals. Excess iron intake can be harmful and it is important not to take iron supplements unless advised to do so by a doctor because blood tests have shown that an iron deficiency exists.
Zinc is important in enzymes (chemicals that help speed up reactions inside cells) and helps immune system maintenance. As intake can be low in people on low fat diets, foods containing zinc should be encouraged and a good diet can supply all that is required. (Excess intake from supplements can be harmful.) Zinc is available from oysters, lean red meat, wholegrain cereals and legumes. See section on Dietary vitamins and minerals.
Children under five are growing quickly and need lots of energy. A strict low fat diet is thus not appropriate in this group and they require some good quality foods that contain fat. One really good source is whole milk and this should be used in preference to low fat varieties in this age group. Others are cheese, lean meats, peanut butter, yoghurt and eggs. (Nuts, especially peanuts, should not be given as they can cause choking.) Poor quality fatty foods, such as crisps, chocolate and takeaways, should still be omitted or used as occasional (not daily) treats. Otherwise, poor eating habits will be established that will be hard to break later on.
Fat content of foods in a healthy diet
On average, Australians consume about 35 to 40 per cent of their energy as fat. Ideally this should be more like 25 to 30 per cent; a reduction by about a quarter. In most people this equates to between 40 and 60 g of fat per day. Where does this fat come from in a healthy diet? The table below shows amount of fat (and fibre and energy) in a sample of good foods that can be eaten each day as part of a healthy diet.
Fat, fibre and energy content in a sample healthy diet
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Food |
Total fat in g |
Fibre in g |
Energy in kJ |
Fruit 2 serves
|
0.0
0.0 0.0 |
6.0
3.0 3.0 |
580
310 270 |
Vegetables
|
0.0
0.0 0.0 |
9.0
6.0 3.0 |
360
270 90 |
Carbohydrates (five serves)
|
12.0
1.5 6.5
2.0 2.0 |
17.0
5.0 6.0
3.0 3.0 |
3405
1430 835
600 540 |
Protein – one and a half serves of:
|
7.5
8.5
4.5
2.0 |
0.0
0.0
0.0
0.0 |
1030
685
780
600 |
Dairy products
|
0.6
0.3 0.5 |
0.0
0.0 0.0 |
1135
505 630 |
Oils and spreads
|
24.0
14.0
10.0 |
0.0
0.0
0.0 |
960
590
370 |
Total |
44.1 |
32.0 |
7470 |
Varying fat content
This total fat figure can be varied up or down by altering food choices. A reduction can be achieved by not using spreads on bread and by reducing the fat content of cereals. Increases can be caused by poorer food choices. An example would be using lamb chops without removing excess fat, which would add well over 20 g of fat to the total or using full cream milk, which would add 10g of fat.
Choosing sauces and treats
The above table does not include sauces used with pasta or meat. Sauces or marinades based on low-fat ingredients such as tomatoes, vegetables, wine and herbs add little in the way of fat. Cream-based sauces on the other hand can add significantly to total fat intake. Remember that fat is added to foods to enhance flavour. It is not necessary if flavoursome foods are chosen to begin with.
The above table also doesn’t include treats. Again choosing low-fat treats such as jams, a glass of alcohol, a scone and sorbets are good choices. High fat treats should be consumed only very occasionally, perhaps once or twice a week.
Major foods contributing to fat intake in Australian diets
The major sources of fat in Australian diets are shown in the table below and the regular consumption of any of these will significantly increase fat intake.
Most important are fats consumed as additives to food such as fast foods and takeaways, crisps, chips, biscuits, pastries, confectionary (chocolates etc), cakes, and fried foods. It is very difficult to know how much fat has been added to meals that are prepared outside the home or are prepared using bought pre-made foods such as pasta sauces. For example, pasta prepared in a restaurant will often have oil added to it to help separate the strands. Thus, it is best to prepare as many meals as possible at home.
Other common sources are meat products and dairy foods. Eggs contribute only about two per cent of our total fat intake and only one per cent of saturated fat.
The foods in the table below are divided into two groups. The first group consists of foods containing beneficial fats, such as monounsaturated fats and omega-3s, or which contain other nutrients such as vitamins, iron, calcium and antioxidants. The second group consists of those that contain high amounts of total fat or saturated fat (usually both) and whose nutrients can be provided by alternative foods with lower fat levels. They should be used only occasionally as treats or avoided.
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The information in this section has been adapted from information contained in
Stanton R. Good fats, bad fats. Published by Allen and Unwin
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What is a healthy diet?
There are many nutritional factors that require consideration in formulating a healthy diet and these will be discussed in the rest of this section. Below is a table summarising what most nutritionists and dietitians would consider a healthy diet.
Recommended food intake for a healthy diet low in fat
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Bread, pasta, potatoes (prepared without fat), grains
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Meat, fish, chicken, eggs, legumes: Meat must be lean with all visible fat removed and chicken should be skinless.
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Vegetables
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Fruit
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Nuts
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Milk products
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Fats and oils
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Indulgences
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Fluids
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