Certain types of fat can cause problems in the diet (cholesterol, trans-fatty acids and palm kernel oil), while others are beneficial to health such as the essential fatty acids (omega-6 and omega-3 fatty acids, and red palm oil). In this article, DietDoc clears up a few common misconceptions.
Most people have heard about cholesterol, how it raises blood cholesterol levels and that we should cut out foods with a high cholesterol content.
The cholesterol in your body comes from two sources: cholesterol in the food you eat and cholesterol that is produced in the body. In other words, human beings can only control the amount of cholesterol they eat.
Even if you follow a zero-cholesterol diet, your body will still carry on making cholesterol. The reason for this is that we need some cholesterol to make other useful compounds, such as vitamin D and the male and female hormones.
If you have a genetic tendency to produce very large amounts of cholesterol in your body, and you have tried a low-cholesterol diet without it lowering your blood cholesterol levels significantly, you need to take cholesterol-lowering medication, such as statins. Discuss this kind of medication with your physician.
However, if you have high blood cholesterol levels that can be lowered with the help of a diet, you should cut down on foods with a high cholesterol content.
Foods with a high cholesterol content:
- fatty meat
- organ meats
- shell fish
- full cream milk and dairy products (hard cheeses, cream)
Recommended daily intake:
No more than 300 mg of cholesterol a day.
Take note that these dietary guidelines don't entail cutting out all meat and dairy products.
Tips to reduce cholesterol intake:
- choose lean meat, cut off the visible fat, eat chicken (without the skin) and lean pork
- eat smaller portions of meat and only eat red meat three or four times a week
- only eat 3-4 eggs a week
- eat milk and dairy products, but select the low-fat, skim or fat-free varieties
All fats are made up of fatty acids. Some of these fatty acids such as saturated fatty acids are seen as harmful and we need to cut down on how much we eat. Other fatty acids like monounsaturated and polyunsaturated fatty acids, and the essential fatty acids (see below), are good for health.
There is, however, another class of fatty acids called “trans-fatty acids”. These fatty acids are produced when plant fats, which are usually liquid at room temperature, are processed to make them solid. This process, called hydrogenation, is used to produce hard or brick margarines.
Research has shown that trans-fatty acids are potentially just as harmful as saturated fat and cholesterol. Trans-fatty acids are capable of raising blood fat levels and blocking arteries, which may lead to heart disease.
The margarine paradox
We are told that we should eat margarine instead of butter, but some types of margarine contain trans-fatty acids that are atherogenic (contribute to heart disease). So what should we do?
Eating soft or tub margarine is a good idea because it contains plenty of monounsaturated and polyunsaturated fatty acids which help to lower blood fats, but eating hard or brick margarine may expose you to trans-fatty acids and have a negative effect on blood fats and health.
It is particularly worrying that many people can’t afford to buy the more expensive soft poly- and monounsaturated margarines and therefore rely heavily on brick margarines which may contain trans-fatty acids.
The good news is that manufacturers are starting to declare the trans-fatty acid content of food products on labels and are making concerted efforts to reduce the trans-fatty acid content of foods such as hard margarine.
Essential fatty acids
Research has shown that certain of the polyunsaturated fatty acids are particularly important to health. Because these fatty acids cannot be manufactured in the human body and we are dependent on dietary sources to obtain them, they have been called essential fatty acids.
There are two main types: omega-6 and omega-3 fatty acids. Generally speaking, most people who follow a western diet, which incorporates soft margarine and plant oils such as sunflower, peanut and maize oils and products made with these oils (mayonnaise, salad dressings), get plenty of omega-6 fatty acids in their diet.
However, omega-3 fatty acids are mainly found in fish oils (cod liver and tuna fish oil) and in some less common plant oils (flaxseed, canola, walnut and soya oils). These oils are usually not eaten regularly and deficiencies in omega-3 fatty acids are common.
The best solution to the lack of omega-3 fatty acids in western diets is to either increase the intake of fatty fish or of the above mentioned oils or to take supplements such as salmon oil capsules.
Fish oils or plant oils?
The reason why most nutrition experts recommend using salmon oil supplements rather than flax oil tablets, is that the latter contain an omega-3 fatty acid called AHA, which is not as easy for the body to use as the fatty acids EPA and DHA that are found in salmon and other fish oils.
Before we can use AHA found in flax and other plant oils, our bodies have to convert the AHA into EPA and DHA. In the new labelling regulations that will hopefully soon be published in South Africa, only the EPA and DHA content of foods will be regarded as sources of omega-3 fatty acids.
Because of the importance of omega-3 fatty acids in preventing diseases, boosting immunity and allowing the brain and nervous system of babies to develop properly, some food manufacturers are starting to enrich common foods with omega-3 fatty acids, for example eggs and milk.
Red palm oil vs. palm kernel oil
Although both oils are derived from the fruits of palm trees, palm kernel oil, which is produced from the kernel of the palm seed, is high in saturated fat and should be avoided, while red palm oil is produced from the fleshy parts of the palm fruit and is rich in healthy polyunsaturated fats.
As an added bonus, red palm oil contains many phytonutrients such as carotenes (hence its red colour) and tocotrienols (the most powerful form of vitamin E which lowers blood cholesterol levels and helps to prevent heart disease).
Red palm oil will soon be more readily available in South Africa and you should be able to buy it from health shops and certain supermarkets.
The bottom line
Remember to avoid the 'bad fats':
- too much fat in general
- saturated fat, cholesterol and trans-fats
- palm kernel oil and pies and pastries made with this kind of oil
Eat the following 'good fats' in moderation:
- monounsaturated and polyunsaturated fats and oils
- omega-6 and omega-3
- red palm oil
- (Dr Ingrid van Heerden, DietDoc)