Cholesterol and blood pressure are closely linked, in that people with a high blood pressure often have a raised cholesterol and vice versa. There is a lot of confusion around whether or not a raised cholesterol or foods containing cholesterol are bad for you. Despite its reputation, cholesterol is vital for life and is needed to make sex hormones, vitamin D, bile acids and for maintaining healthy cell membranes.
HDL versus LDL
Cholesterol is a waxy substance that’s made in the liver and released into the circulation for use elsewhere in the body. As cholesterol is insoluble, it is transported within the circulation bubble-wrapped inside a cocoon of lipoproteins. These lipoproteins are also made in the liver and come in a variety of forms, the most important of which are low density lipoprotein (LDL) and high density lipoprotein (HDL).
Cholesterol bound to LDL is often referred to as ‘bad’, as the resulting particles are small enough to seep into artery walls and to become engulfed by scavenger cells. These scavenger cells soon become over-laden, and when they attempt to leave the circulation, become lodged in artery linings. They are literally too bloated to squeeze through the turnstiles between neighbouring artery cells. Raised LDL-cholesterol levels therefore hasten hardening and furring up of the arteries (atherosclerosis) and are associated with an increased risk of heart attack and stroke. You want your LDL-cholesterol to remain relatively low.
Cholesterol that is bound to high-density lipoprotein (HDL) is often referred to as ‘good’ HDL-cholesterol, as these heavier particles are too large to seep into artery walls. This form acts rather like a juggernaut, patrolling the circulation and mopping up LDL-cholesterol, returning it to the liver for processing. Having a raised HDL-cholesterol level protects against heart disease and stroke so you want your HDL-cholesterol to remain relatively high. Researchers have calculated that, for every 1% rise in your HDL-cholesterol level, your risk of a heart attack falls by around 2%.
What is a healthy cholesterol level?
Blood levels of cholesterol are measured in units called millimoles per litre of blood (mmol/l) in some countries, such as the UK, and in milligrams per deciliter (mg/dl) in the US.
The understanding of what represents an ideal cholesterol level is not clear cut, and acceptable values are revised regularly – usually in a downward direction. The following levels are currently considered desirable for otherwise healthy adults but do check with your own doctor to confirm the levels that apply to you:
- 5mmol/l or less in the UK
- 200mg/dl or less in the US
Low-density lipoprotein (LDL) cholesterol
- 3mmol/l or less in the UK
- 100mg/dl or less in the US
High-density lipoprotein (HDL) cholesterol
- Above 1mmol/l for men (40mg/dl or above in the US)
- Above 1.2 mmol/l for women (50mg/dl or above in the US).
For some people, such as those with diabetes, a previous heart attack or who are otherwise considered at high risk for cardiovascular disease, a lower total cholesterol target (eg 4mmol/l) and a lower LDL-cholesterol target (eg 2mmol/l) may be advised. This usually means taking a cholesterol-lowering medication such as a statin.
Your cholesterol levels are only part of your overall risk of future health problems, however. Other factors such as your blood pressure, weight, smoking status and whether or not you have diabetes are also important.
Cholesterol tests should ideally be carried out every 5 years from the age of 40, and every year if you are on cholesterol lowering medication.
Why is my total cholesterol level raised?
The main determinants of your cholesterol level at any one time are a combination of the genes you’ve inherited, your age and lifestyle – including your diet, alcohol intake and physical activity level. Poor functioning of the kidneys, liver or thyroid gland can also raise cholesterol levels, so it’s good to get these checked, too.
If you smoke, do your utmost to stop as smoking cigarettes releases a chemical called acrolein, which stops HDL- cholesterol from transporting LDL-cholesterol back to your liver for processing. Smoking is also bad for your health in many other ways, constricting and damaging blood vessels so that blood pressure rises.
Is a raised cholesterol level bad?
Whether or not a raised cholesterol is a cause for concern depends on the balance between HDL and LDL-cholesterol. If much of your circulating cholesterol is in the HDL form, then you have a lower risk of heart disease than if most of it is in the LDL form.
Many national guidelines no longer focus on a target total or LDL-cholesterol level for preventing a first heart attack or stroke (primary prevention). The evidence from large clinical trials does not support this approach, even in people who are taking a statin drug.
Whether or not to treat a raised LDL-cholesterol will depend on other risk factors such as your age, gender, smoking status, blood pressure, cholesterol balance and whether or not you have diabetes. These factors are used to estimate your chance of developing a heart attack of stroke over the next 10 years. If your risk is 10% or higher, then treatment may be offered.
For secondary prevention (avoiding another heart attack or stroke after you have already experienced once) your lipid-lowering medication (eg statin) may be increased in dose if a total cholesterol of 4mmol/l or an LDL-cholesterol level of less than 2mmol/l is not achieved.
You can calculate your own risk of heart disease if you know your blood pressure and cholesterol/HDL ratio (calculated by dividing your total cholesterol by your HDL level) on-line if you live in the UK at QRisk and if you live in the US via the National Institutes of Health.
How can I raise my ‘good’ HDL-cholesterol?
Your HDL-cholesterol level largely depends on your genes, but diet and lifestyle factors can boost the amount in your circulation to help protect against heart disease. The good news is that following a DASH style diet to lower your blood pressure will have beneficial effects on your overall cholesterol balance due to the high amount of antioxidants, fibre, vitamins, minerals, omega-3s and monounsaturated fats it provides.
Drinking sensible amounts of alcohol also has an effect on the liver to boost synthesis of HDL-cholesterol. Initially this effect was thought to explain half the level of protection associated with drinking red wine. However, more recent findings, involving almost 150,000 Norwegians, found that men and women who drank sensible amounts of alcohol more than once a week are less likely to die from CHD compared with those drinking alcohol rarely or never, irrespective of their HDL-cholesterol concentration, so that’s not the whole story.
As alcohol increase blood pressure, stick within the safe alcohol limits suggested by your doctor.
What medical treatment can lower my cholesterol?
Your GP may offer lipid modification therapy (a statin) if your estimated risk of a heart attack or stroke over the next 10 years is calculated as 10% or more, regardless of your overall cholesterol balance.
Statins (eg atorvastatin, fluvastatin, lovastatin, pravastatin, pitavastatin, rosuvastatin, simvastatin) act on the liver to reduce the amount of cholesterol produced. They work by blocking an enzyme (HMG-CoA reductase) that regulates the first step in a series of chemical reactions known as the mevalonate pathway. By slowing the whole pathway, all products made below this step are reduced – you make less cholesterol, but you also make less of a vitamin-like substance called co-enzyme Q10 (CoQ10) which is critical for energy production in cells. Taking a statin can halve your circulating levels of co-enzyme Q10 within two to four weeks. This may contribute to the muscle-related side effects that some people experience when taking a statin.
You can replenish your CoQ10 levels (without affecting the cholesterol-lowering action of the statin drug) by taking a co-enzyme Q10 supplement (eg ubiquinol 100mg or ubiquinone 200mg). I’ve covered this more fully in my nutritional medicine blog in a post on Statins and Co-enzyme Q10.
By lowering cholesterol levels, statins also reduce the amount of vitamin D you can produce in the skin during exposure to sunlight. If you are taking a statin, a vitamin D supplement is a good idea and may also help to reduce or prevent muscle-related statin side effects. You can read more about this on my nutritional medicine blood in a post on Statins and Vitamin D.
What about a low-cholesterol diet?
On average, someone following a typical western diet eats around 300mg cholesterol per day, but makes three times this amount (900mg per day) in the liver. If you inherit ‘good’ genes, then your liver production of LDL-cholesterol should reduce as your dietary cholesterol intake increases.
If you inherit one of at least a thousand recognised gene variants associated with high cholesterol, however, this negative feedback mechanism doesn’t work as well as it should. As a result, your liver continues to churn out cholesterol regardless of that fact that you get plenty in your diet, and already have plenty in your circulation. This means that the amount of pre-formed cholesterol you eat (found in animal products such as liver and meat) usually has little impact on circulating blood levels if they are already raised.
Traditional advice to lower your intake of cholesterol-rich foods (especially liver and caviar) and to cut back on saturated fats (which your liver uses to make cholesterol) is not that effective. There is a move away from these low-fat, low-cholesterol diets towards sensible intakes of healthy sources of fat such as those found in the Mediterranean style of eating such as olive oil, nut oils and oily fish. Following the DASH diet, for example, will help to lower both your blood pressure and your LDL-cholesterol.
Are eggs ok?
Although eggs used to be frowned on, researchers have found that, for most people, eating eggs has minimal impact on circulating LDL-cholesterol levels. This is partly because also eggs provide numerous antioxidants, lecithin, omega-3 fatty acids, vitamins and minerals which have desirable effects on overall cholesterol balance. Research involving over 100,000 men and women confirmed that eating up to seven eggs per week – the equivalent of one egg a day – does not increase the risk of coronary heart disease or stroke even if your cholesterol level is raised.
A large analysis of 17 studies, involving almost 264,000 people, has confirmed that eating one egg a day (seven a week) does not increase the risk of coronary heart disease or stroke – even if your cholesterol level is raised. Even if you have type 2 diabetes, the recent DIABEGG study concluded that you can safely include eggs in your diet, with those eating as much as two eggs a day, six days a week, not showing any adverse effects on their cholesterol balance over a three month period.
Some people may benefit from cutting back on dietary cholesterol, however, so always follow your doctor’s advice on how many eggs and how much saturated fat you are able to eat.
Take plant sterols
Plant sterols are present in vegetable oils, nuts, seeds, grain products, fruit and veg and are the equivalent of animal cholesterol in the vegetable world. Their structure is similar enough to block cholesterol absorption in the intestines without being significantly absorbed themselves. The excess, unabsorbed cholesterol is then flushed from the body (via the bathroom) along with most of the plant sterols.
For an optimum cholesterol-lowering benefit, you need at least 2g sterols per day, yet the average diet provides less than 500mg plant sterols daily. Avocados are a particularly good source.
Foods fortified with sterols (and stanols, which are similar) are also available, such as spreads and yoghurts. Using these products can lower your LDL-cholesterol by 10% within as little as three weeks, and by as much as 15%.
Because statins work in a different way to plant sterols, the two can be used together to lower cholesterol levels even further. In fact, adding sterols to statin medication is more effective than doubling the statin dose.
Plant sterol supplements are widely available, and a typical dose is 800 mg, three times a day.
You can also help your cholesterol balance by losing at least some excess weight – your cells will burn more cholesterol as fuel so your readings will tend to reduce, along with your weight.
Aim to exercise more, too, as physical activity also burns off some cholesterol as fuel to significantly lower a raised cholesterol level. Even better, exercise improves the balance between HDL and LDL-cholesterol, as well as having beneficial effects on blood pressure.
Aim for at least 30 minutes – and preferably 60 minutes – brisk walking on most days. Getting a pedometer and aiming for 10,000 steps a day is an excellent goal.
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