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Facts and figures
There is a lot of talk these days about lipids and cholesterol and now I’ve seen something about triglycerides! I am rather muddled about it all. Can you tell me what all these words mean?
Cholesterolis a fatty or oily substance and is one of a group of fatty substances we call lipids.
Lipids are essential for the normal functioning of the body’s cells. Problems develop when there is too much lipid in the blood. It then settles in the walls of the arteries. The arteries then develop the narrowings which cause heart attacks and angina by restricting the flow of blood to the heart (see the Introduction to this chapter). Doctors often ask for a ‘lipid profile’: this is a check on the levels of cholesterol and triglycerides in your blood. (Triglyceride is another fatty substance – see below).
Cholesterol plays an essential role in helping our glands make hormones, but its biggest role is in the formation of cell walls. We are able to make all the cholesterol we need in the liver, where it is made from fat. Our problems begin if we have a higher blood cholesterol than we need; this is usually due to eating too much fat (see the question later on hypercholesterolaemia).
Triglycerides (pronounced ‘try-gli-sir-ides’) are the major form of saturated fats (see later question) which come from food and they are also made in the body to provide energy. If you have a high level of triglycerides and a low level of high density lipoproteins (see next question), you have a greater chance of developing coronary disease. Triglycerides are commonly raised in people who are very overweight, people with diabetes and those who have a high alcohol intake.
I was told that all cholesterol is bad for you. Now I read that there is a ‘good’ cholesterol and ‘bad’ cholesterol. What’s the difference?
Cholesterol and other fats do not dissolve in the blood. They hitch a ride on proteins which are the taxis transporting the fats around. The combination of fat and protein is a lipoprotein (pronounced ‘lie-po-pro-teen’). The ‘bad’ cholesterol is the low density lipoprotein (LDL): this is the main carrier of harmful cholesterol to your arteries where it builds up to cause narrowings. The high density lipoproteins (HDL) are the good guys: HDL tends to pick up excess cholesterol taking it awayfrom the arteries and transporting it back to the liver for removal. So, for maximum protection, you need:
• your LDL low (L for lousy);
• your HDL high (H for happy).
I’m going to have a complete check-up next month. When I have my cholesterol profile checked, what levels should all these different fats be?
Your total cholesterol should not be above 5.0mmol/litre. The HDL (see question above) should be greater than 1.0 mmol/L
in a man, and 1.3 mmol/L in a woman. The LDL should be 3.0 mmol/L or less – the ideal is2.6 or less. Your triglyceridesshould be less than 1.7mmol/L, ideally 1.6 or less. As a rule of thumb,a total cholesterol of 5.0equals an LDL of 3.0. However, for coronary patients and those with chronic renal
disease or diabetes, the targets are lower:
• cholesterol 4 mmol/L or less;
• LDL 2.0 mmol/L or less. So remember 5 and 3,and 4 and 2.
Research has shown that lowering cholesterol to these levels in normal people, as well as in coronary patients, helps prevent heart disease in the future. The benefits apply to both men and women.
When I had a lipid profile done on my blood, the doctor told me I had hypercholesterolaemia. What does this mean?
Hypercholesterolaemia (pronounced ‘hi-per-kol-esterol-eemia’) means that the total cholesterol is high in the blood. Usually the LDL (see question above) is raised; in women the HDL is higher before the menopause – an effect of their hormones. It is always better to know both profiles (HDL and LDL), as well as the total level, because you don’t want to lower a high HDL by mistake. For example, a woman before the menopause may have a high total cholesterol (e.g. 5.8) which is made up mainly of the good HDL (e.g. 2.0).
When I look at a food label, there are different types of fats listed, such as saturated and unsaturated fats. Can you explain more about the differences between the types of fats?
There are two main sorts of fats.
• Saturated fatsare mainly of animal origin. They are the bad fats and it is the saturated fat that raises your cholesterol levels.
• Unsaturated fatsare mainly of vegetable origin and they lower your cholesterol levels.
Saturated fatsare a mixture of alcohol, glycerol and fatty acids. The fatty acids contain long chains of carbon atoms – most commonly 12, 14 or 16. These are the most effective at raising the LDL (‘bad cholesterol’) in the blood. The more saturated fat we eat, the higher the cholesterol; if we eat less, our cholesterol will fall over 3–4 weeks. Unsaturated fats contain carbon atoms that are joined (with double bonds) at certain points; this leads to the fats being liquid or soft at room temperature. When there is one double bond, the fat is monounsaturated; when there are two or more, it is polyunsaturated. Monounsaturated fats include olive, rapeseed and peanut oils and are contained in avocados, almonds and oily fish. Polyunsaturated fats include sunflower oil and most soft margarines (always read the label!). Polyunsaturated fats help prevent blood clots forming, which is another benefit in addition to their cholesterol-lowering effect.
As well as lowering your LDL (bad) cholesterol by switching you away from saturated fat, unsaturated fats also appear to have an additional good effect on lowering cholesterol. Monounsaturated fat may raise the HDL (good) cholesterol as well. All kinds of fat, whether saturated or unsaturated, are rich in calories, so you need to bear in mind, when you change to a healthy diet, not to go overboard on unsaturated fat.
Chapter 9 gives lots of information about which foods contain the different types of fats and gives you lists from which you can choose a healthy diet.
The media has also talked about the harmful effects of trans fatty acids. How can I avoid them?
Trans fatty acids are present in small quantities in meat and dairy products but are present in larger quantities in those oils which have been manufactured to be firmer at room temperature (i.e. when oils have been made into margarines or spreads) by a process known ashydrogenation. Trans fatty acids raise LDL and lower HDL cholesterol levels. When you are selecting vegetable oils and margarine it is important to look for the trans content. The best oils are blended vegetable oils, rapeseed oil and soft margarines that are low in saturates and trans fatty acids, but high in polyunsaturates and mono ¬unsaturates (see the question above). Always read the margarine label.
The article that I read also mentioned vitamin E as being beneficial. Why is it important?
Vitamin E is anantioxidant; antioxidants help protect the body from ‘free radicals’. Free radicalsare produced by some of the normal chemical reactions in the body cells. They are unstable and, in excess, can damage the lining of the cells by oxidising LDL (‘bad’) cholesterol, causing it to stick to the walls of the arteries.
Antioxidants are present in fruit and vegetables and can prevent cholesterol being oxidised so that it does not tend to stick to the artery wall.
Some early studies suggested that vitamin E protects against heart disease, but unfortunately subsequent studies have not shown any benefit from tablet supplements. Vitamin E is present in food containing a lot of polyunsaturates, such as vegetable oils (especially sunflower) and deep green leafy vegetables. Nuts and vegetable oils, although good sources of vitamin E, are also high in calories, so these should not be eaten too frequently. There is a small amount of vitamin E in wholemeal bread. Some margarines are enriched with vitamin E. If your food intake is high in polyunsaturates, it will contain a lot of vitamin E. Because some of the major sources are high in calories, you may be advised to take extra vitamin E as supplementary tablets by some specialists to avoid putting on weight, but for most of us this will not be necessary. Chemists and health food shops sell vitamin E preparations and the recommended dose is 100–200 units a day (70–140 mg). However, as vitamin supplements have been shown to be of no benefit – save your money!
You have talked about vitamin E. What about vitamin C – isn’t this an antioxidant as well?
Yes, and it is safe to take, but medical trials have demonstrated no benefit for heart disease. It is found in citrus fruits (oranges, grapefruits, lemons), kiwi fruit, soft fruit (strawberries, raspberries, blackberries), red and green peppers and spring greens. Try to eat 150–200 g (6–8 oz) of this group a day and you will not need tablet supplements.
I have always believed taking vitamin supplements would protect me – are you saying this is not true?
Unfortunately yes. The Heart Protection Study involved thousands of patients and those taking vitamins did no better or worse than those taking placebos (fakes). In other words, vitamins do not protect against the effects of hardening of the arteries and are of no benefit to the heart. The vitamin story is a good example of an idea that is theoretically good but, when tested, does not work.
I know of people taking beta carotene supplements and our health food shop is always marketing it. What is beta carotene, and should I be taking it?
No. Beta carotene is converted in the body to vitamin A. It is an antioxidant and is found in brightly coloured fruit and vegetables (carrots, broccoli, tomatoes, melons, yellow and orange peppers, spinach, peaches). So you might think that extra supplements would be good for you. However, medical trials have failed to show that they have any benefit, and researchers are now worried that they may lead to an increased risk of some cancers and heart disease. Do not waste your money on beta carotene supplements – fruit and vegetables are all that you need.
I thought that people supplementing their diet with extra beta carotene from the health food shops had a lower chance of developing heart disease or cancer. You say that there may be risk of developing these conditions – which view is right?
This question is a good example of the need always to make sure that a good idea works when put into practice. Beta carotene has antioxidant properties and, in theory, could help prevent cancer and
coronary heart disease. Indeed, people who took beta carotene supplements were observedto be less likely to develop these diseases – but an observation is not proof. Four research studies involving thousands of people set out to prove whether a benefit existed when beta carotene was compared to placebo (see the section Other treatments for angina in Chapter 3). These were proper scientific studies. Surprisingly and alarmingly, beta carotene supplements were shown to increase heart disease and cancer risks, especially in smokers and people exposed to asbestos. Ideas, whether based on good scientific theory, as in the case of beta carotene, or dreamed up in the bath, should always be validated! Beta carotene should be consumed normally in fresh fruit and vegetables.
There is so much advice about fat intake that I really don’t know what to believe. How much fat should we eat a day?
This depends on whether you need to reduce weight, that is, reduce calories. Remember that fat, whether good (unsaturated) or bad (saturated) is high in calories. We need 50–90 g of fat a day of which 22–27 g, only, should be saturates. Always look on the food labels to help you choose foods that contain less saturated fats.
Let’s work out some numbers. Doctors recommend that no more than30% of your calorie intake is fat, and 10% of that is saturated fat, regardless of whether or not you are overweight. If your daily calorie intake is 1500 kcal, this means 50 g of fat at most (1 g of fat equals 9kcal). If your daily calorie intake is 2000 kcal, this means 65–70 g of fat; if it is 2500 kcal, this means 85–90 g of fat. (See Chapter 9 for further information on fats in food. )
My father had a high cholesterol level and died aged 55. My wife is concerned that I may be like him – I am now 52. Can this be inherited?
Some people may inherit a high cholesterol level (usually over 8.0mmol/litre). A good diet changes these people’s levels only marginally and they will need medication. Make sure that all members of your family are checked for an inherited pattern and, if this is detected, you will be recommended medication. Other people inherit a tendency to a high cholesterol level but respond to diet, plant stanols or, more usually, a combination of diet and medications.
Should I know my cholesterol and other test level numbers? Will it do any good?
If you want to reduce your chances of heart disease, you must take charge of your lifestyle, and that includes knowing your numbers and keeping track of how they respond to any changes in your eating pattern or medication.
How well will a healthy diet lower my cholesterol?
Ahealthy diet may reduce your cholesterol by 10%. Obviously the higher your cholesterol at the start, the more likely you will need medications as well, but a period of healthy diet restricting your fat intake for 3 months is normally recommended first (see Chapter 9). However, if you already have heart problems, most doctors advise immediate medication to take full advantage of its cholesterol-lowering effect.
Which is more important – to avoid foods high in cholesterol or saturated fats?
Cholesterol in your food has a smaller effect on the blood cholesterol level than do foods high in saturated fat. It is more important therefore to cut down on foods high in saturated fat. This means, for example, that you can have three to four eggs a week (the yolks are high in cholesterol). Cutting down on saturated fat (and all fats) will help you to lose weight (see Chapter 9).
I am told that I have a high cholesterol level. If I manage to lower this level, will this really prevent heart disease?
We now have overwhelming evidence that lowering your cholesterol level not only reduces your risks of heart disease by an average of over 30%, but also reduces the need for heart bypass surgery and angioplasty (see Chapter 3). If you lower your cholesterol over a 5-year period, you improve your chances of living longer by an amazing 30%. Treating a high cholesterol is one of the most important means of preventing and reducing the complications of coronary artery disease. Some doctors believe it is negligent not to lower a raised cholesterol.
What should I get my cholesterol levels down to in order to see a benefit to my heart?
Most of the benefit occurs when the LDL (‘bad’) cholesterol is lowered by 30% or more; your aim should be to get this level below 3.0mmol/litre with an ideal of 2.0mmol/litre, or less if you have coronary disease, diabetes or a chronic renal condition. This leads to removal of the soft part of the narrowings in the arteries making them less likely to tear or split. It is known as stabilising the plaque (see the Introduction to this chapter). Unstable plaque that ruptures releases soft cholesterol into the blood which then causes a clot to form and a possible heart attack to occur – removing the soft cholesterol helps to prevent this happening.
I have reduced my cholesterol level so that the tests are now normal. Can I go back to smoking?
No. Risk factors, which increase your chances of developing heart problems, are independent of each other. If you have more than one risk factor, however, they don’t just add up, they multiply.
Reference:
http://www.pubmed.com |
