eMJA: Dietary implications: Advising patients about fat in the diet

Based on the information in this Supplement, the following dietary suggestions for fat consumption are a handy guide for doctors advising their patients on diet and nutrition. These pointers should be communicated within the context of a healthy diet including vegetables, fruit, whole grains, lean meat, fish, chicken and dairy foods.

Key points on fat for all patients

Fat is an essential nutrient — our bodies need some fat.
Reduce the saturated fats which Australians overconsume.
Choose fats in the form of monounsaturated and polyunsaturated fats from oils, spreads, avocado, nuts and seeds.
Consume some omega-3 fats (see Box 1 and Box 2).
Low-fat diets appear adequate and can be introduced after the age of two years for children at high risk of obesity and heart disease.

Key points on fat for infants and very young children

Fat is an essential nutrient — babies need fat to fulfil their energy requirements for growth.

Women should be encouraged to breastfeed their infants for at least six months and preferably 12 months.

A low fat intake is not recommended for children under two years.

From the age of six months, fat can come from basic foods like vegetable oils, spreads, eggs, full-fat milk and meat, which provide other key nutrients (see Box 1).

Big fat myths — common myths relating to fat

There are many food myths relating to fat and its role in the diet. This is understandable when, for so long, the dietary message has been to reduce fat intake and fat has been cast as the "villain" of the modern, affluent Western diet.

Myth: "I don't need to eat any fat"

Incorrect: Fat is an essential nutrient required for health and growth, like protein, carbohydrate, vitamins and minerals. Fats supply essential fatty acids such as linoleic acid and alpha-linolenic acid, which our bodies cannot manufacture.

Nutritionists suggest that, for adults, about 30% of the kilojoules consumed should be derived from fat. This translates to 50–60 grams of fat daily for a sedentary adult woman consuming 7500 kilojoules (1800 calories) a day. The type of fat is important — no more than 15 grams a day should be saturated fat. This figure will be easier for patients to comprehend when labelling of saturated fat on food products becomes mandatory by the end of 2002.

Myth: "Fats don't give us anything except kilojoules (calories)"

Incorrect: Fat serves many functions in nutrition. Fat:

provides insulation and "cushioning" for internal organs;
"spares" protein for its primary role of building; and
serves as a "carrier" of fat-soluble vitamins (vitamins A, D, E and K) and fat-soluble antioxidants like beta-carotene and other carotenoids.

Myth: "I must eliminate all fat from my diet to lose excess weight"

Incorrect: It is not necessary to follow a fat-free diet for weight loss. Energy density of the diet and total kilojoules consumed now appear to be a more critical determinant of weight loss than simply the amount of fat consumed.4,5

However, fat is the most concentrated of all nutrients (see Box 3), so cutting back on fat may be the quickest way to lower energy density for some people. Nevertheless, a balanced weight-loss plan would allow for 30–40 g of fat a day for women, and 40–50 g a day for men.

Myth: "Canola is the same as rapeseed"

Incorrect: Canola oil is extracted from the seed of the canola plant (Brassica napus or Brassica campestris), a variety of rapeseed that belongs to the Brassica family. While it is derived from the same species of plant, canola oil is distinguished from rapeseed oil by lower levels of erucic acid. By definition, the name "canola" oil can only be used if the level of erucic acid is less than 2%. "Canola" oil was initially a name trademarked by Canadian developers in the 1960s. The original rapeseed is still grown for its oil in some countries, but is only used for non-edible purposes, such as in the production of nylon.

Myth: "Canola oil is toxic/contains a poison"

Incorrect: This myth has been circulating on the internet with no substantiation. It probably arose from canola's association with its parent, rapeseed, which contains naturally high levels of erucic acid, but this characteristic has been bred out of canola (see above).

Myth: "Olive oil is the best oil to use"

Incorrect: Olive oil is only one of a number of healthy oils. It is rich in monounsaturates, as are canola oil, peanut oil and macadamia oil. It rose to fame as a key ingredient of the heart-protective Mediterranean diet, but there are many other dietary factors in that diet, such as fish, seafood, garlic, wine and vegetables, that could also contribute. Olive oil has virtually no omega-3 fatty acids.

Myth: "Light oils keep your fat intake low"

Incorrect: Light or "lite" oils have exactly the same fat and kilojoule content as regular oils. They are simply light in flavour or lighter in colour.

1: How-to tips

Reducing saturated fat

Limit intake of obvious sources of saturated fat such as butter, butter/oil blends, cream, sour cream, mascarpone, coconut cream/milk, fat selvage on meat, skin on chicken.
Limit intake of foods with hidden saturated fats, such as sausages, bacon, devon, salami and other deli meats, meat pies, sausage rolls, potato crisps, corn chips, salty packet snacks, hamburgers, pizza, fried fast foods (hot potato chips, fries, nuggets, potato scallops), gravy, rich sauces, full fat dairy products (milk, cheese, cream cheese and yoghurt), cakes, muffins, pastries, doughnuts, biscuits, chocolate, ice cream.
Check labels for saturated fat (note that new regulations to Australian food standards being phased in by the end of 2002 require all food products to list the content of saturated fat per serve and per 100 g).

Increase the "healthy" monounsaturated and polyunsaturated fats

Use a variety of oils for cooking and salad dressings
Swap butter for a soft margarine or spread for bread and toast
Consider alternative spreads such as avocado, hummus and peanut butter
Snack on unsalted nuts in place of potato crisps, corn chips and similar salty snacks
Sprinkle lecithin or wheatgerm over cereals

Increase omega-3 polyunsaturated fats

Eat fish (canned, frozen or fresh) and seafood (see Box 2) at least twice a week
Choose vegetable oils that are good sources of omega-3 fats, such as flaxseed and canola
Choose plant sources of omega-3 fats (see Box 2)

2: Sources of omega-3 fats (animal and plant sources listed in decreasing order of magnitude)1,2

Source	Examples

Animal sources*
Oily fresh fish	Mullet, Atlantic salmon, smoked salmon, trevally, yellowtail, scad, tailor, tarwhine, mackerel, tuna
Canned fish	Salmon (especially red salmon), sardines, tuna
Eggs	Omega-enriched eggs
White fresh fish	Snapper, perch, gemfish, garfish, flounder, whiting, bream, flathead, John Dory, ling, leatherjacket
Seafood	Oysters, prawns, mussels, scallops, squid, crab, octopus
Plant sources†,‡
Oils	Flaxseed, canola, wheatgerm, soybean
Spreads	Canola-based
Seeds	Linseeds (flaxseeds), soy and linseed bread
Nuts	Walnuts, pecans
Legumes	Soybeans, tofu, soy "milk", other beans and lentils
Whole grains	Wheatgerm, rye, barley, brans (wheat, oat, barley, rice)
Vegetables	Most green leafy vegetables

* Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). † Alpha-linolenic acid. ‡ Only a small proportion of these short-chain plant sources are converted into the long-chain desirable types by the body. The conversion is enhanced by a diet low in saturated fats and low in omega-6 polyunsaturates.

3: Energy density of selected foods

Kilojoules supplied per gram of:

Fat 37

Alcohol 29

Protein 17

Carbohydrate 16

References

Sinclair AJ, Oon KS, Lim L, et al. The w-3 fatty acid content of canned, smoked and fresh fish in Australia. Aust J Nutr Diet 1998; 55: 116-120.
Nichols PD, Mooney BD, Virtue P, Elliott NG. Chapter 10. In: Yearsley GK, Last PR, Ward RD, editors. Australian seafood handbook: an identification guide to domestic species. Hobart: CSIRO Division of Marine Research, 1999.
Emken E, Adolf RO, Gulley RM. Dietary linoleic acid influences desaturation and acylation of deuterium-labelled linoleic and linolenic acids in young males. Biochim Biophys Acta 1994; 1213: 277-288. <PubMed>
Rolls BJ, Bell EA, Castellanos VH, et al. Energy density but not fat content of foods affected energy intake in lean and obese women. Am J Clin Nutr 1999; 69: 863-871. <PubMed>
National Heart Foundation. NHF position statement on dietary fats. Aust J Nutr Diet 1999; 56 (4 Suppl): S1-S22. <PubMed>

(Received 12 Mar 2002, accepted 18 Apr 2002)