The consumption of dietary fats has fallen markedly in the past 20 years and now accounts for 13 per cent of dietary energy. In February 2009, the Food Standards Agency launched a campaign to reduce saturated fat intake further towards a target level of 11 per cent.
While most people recognise animal fat as the principal villain of modern diets and understand its relationship to the increase in heart disease, obesity and diabetes, there is still confusion over 'good' and 'bad' fats. Simply reducing the total consumption is far from the whole solution.
Saturated vs unsaturated
More than 95 per cent of dietary fat intake consists of triacyl-glycerols, which are formed of three fatty acids esterified to a glycerol backbone.
These fatty acids consist of a carbon backbone terminated by a carboxyl group (COOH) at one end and a methyl group (CH3) at the other.
It is the links within this carbon chain that determine the properties of these molecules and their health risks to the body. When all the carbon atoms in the chain are linked by single bonds the fatty acid becomes saturated.
Unsaturated fatty acids contain one (monounsaturated fatty acid) or more (polyunsaturated fatty acid) double bonds at specific positions in the carbon chain. It is these bonds and their constituent fatty acids which, in turn, determine the densities of lipoproteins.
Many of these fats can be considered non-essential, because they can be synthesised in the body. The polyunsaturated fatty acids linoleic acid and alfa-linolenic acid are essential nutrients as they cannot be synthesised but are required for normal physiological functioning, including cell replication.
Further complications arise because dietary fats not only add flavour to many foods, but are necessary for the absorption of certain 'fat-soluble' vitamins.
While a total reduction of dietary fats is a good starting point for weight loss, if it is not selective it may adversely affect the LDL/HDL ratio and therefore be associated with cardiovascular and other health risks.
Tips for patients on cutting saturated fat intake
1. Have smaller portions of cheese (grate it rather than slice) or eat it less often.
2. Limit intake of cakes, pastries, pies and biscuits.
3. Limit intake of sausages, salami, pate and beef burgers, as these are generally high in saturated fat and often high in salt.
4. Meat products in pastry, such as pies and sausage rolls, are high in saturated fat, as they may contain fatty cuts of meat and the fat in pastry.
5. Snack foods can be high in saturated fat and salt and should only be eaten as a treat.
The main dietary sources of saturated fatty acids are well known, with animal fat particularly from beef and lamb leading the field. Fish fried in batter (especially if it is fried in animal dripping - common in many fish and chip shops) and dairy products, including full fat milk and cheese, follow close behind.
Burgers are notorious for their fat content, as are snack foods including crisps, which are often coated in animal oils before they are cooked. Less well-recognised sources of saturated fat include plant derivatives such as peanut and other nut and seed oils, palm and coconut oil.
The food industry
The over consumption of saturated fatty acids is an important health issue for the UK.
In the past, the priority has been to reduce intake of dietary fats overall.
However, a more informed approach will be needed to reduce health risks while maintaining the general trend.
The food industry has a vital role to play since it can, to some degree, control the formulation of prepared foods if not the amount consumed.
The traditional objections based on costs and taste are giving way to an acceptance of more sophisticated manufacturing processes along with a general willingness to be part of the 'healthy food option' market.
Guideline daily amounts are appearing on many packaged foods. Standardisation is spreading through common symbols that indicate average portion sizes as well as a breakdown of the percentage of the recommended daily allowances.
What to advise patients
Primary care professionals also have an important role to play, as educators; translating complex and technical issues into straightforward understandable language for patients.
Studies have shown that interventions to change the fatty acid composition of the diet are more achievable than those that attempt to lower the total fat intake. Clearly the most favourable outcome would be to replace saturated fatty acids with unsaturated ones.
As an alternative, substituting carbohydrates would have benefits. However, high carbohydrate diets lower HDL while raising triacylglycerols, making replacement with poly- or monounsaturated fatty acids a more favourable option.
It should be noted that a reduction in saturated fats alone will not significantly lower total cholesterol. It is the replacement with unsaturated fatty acids that provides the benefit.
A simple example of this is the use of rapeseed or soyabean oil in place of saturated fatty acids, which could form the basis of a domestic dietary change.
A reformulation of commercial packaged foods could also help, although fatty acids in food processing are often chosen for their functional qualities - such as melting points and crystallisation - and as such important selling points like spreadability.
Many GPs struggle with the finer points of dietary advice. It is not part of our training, yet it is frequently sought by our patients. See the boxes for basic advice which that be helpful for your patients.
- Dr Stillman is a GP in Crawley, West Sussex, and member of The Fat Panel
Tips for patients on buying and cooking
In the supermarket
1. Choose lower-fat varieties of dairy foods such as semi-skimmed or skimmed milk and low-fat yoghurts and cheeses. Soft cheese tends to have less fat than hard cheese.
2. Check the labels to see if there is an alternative with lower saturated fat.
3. Buy turkey and chicken without the skin.
4. Opt for fish or a vegetarian option occasionally instead of meat.
5. Choose pies and tarts with only one crust - either a lid or a base.
6. Choose polyunsaturated or monounsaturated spreads instead of dairy-based spreads.
7. Meat can vary in terms of type, cut and method of preparation. The more white you can see on meat, the more fat it contains.
8. Cut out sauces that may increase the saturated fat levels of a food.
In the kitchen
1. Use unsaturated oils such as olive, sunflower or rapeseed instead of butter, lard and ghee.
2. Grill meat instead of frying it. Cut away any visible fat and remove the skin before cooking.
3. Use a non-stick pan and non-stick foil to avoid adding fat. If you need to add oil, use a spray or measure the oil using a spoon.
4. Make mashed potato with low-fat spread and semi-skimmed milk.
5. Use strong cheeses in sauces to reduce the quantity needed for good flavour.