Cholesterol and blood pressure are closely linked. People with high blood pressure often have a raised cholesterol and vice versa, as both conditions are associated with abnormal liver metabolism in people who are overweight.
Having high levels of ‘good’ HDL-cholesterol can lower your risk of heart disease, but having high levels of so-called ‘bad’ non-HDL cholesterol has been linked with a higher risk of heart disease.
Why you need cholesterol
Cholesterol is a waxy substance made in the liver and released into the circulation for use elsewhere in the body. Cholesterol is vital for life, and is needed to make healthy cell membranes, vitamin D, co-enzyme Q10, sex hormones and bile acids.
HDL cholesterol versus non-HDL cholesterol
As cholesterol is insoluble, it is transported within the circulation within a bubble-wrap of lipoproteins, in which insoluble cholesterol stays on the inside, and the water-loving proteins remain on the outside. These lipoproteins are also made in the liver and come in a variety of forms, which have different actions.
High density lipoprotein (HDL) binds cholesterol and carries it back from the tissues to the liver for processing, so HDL-cholesterol is referred to as ‘good’ cholesterol as it reduces furring up of the arteries (atherosclerosis).
Low density lipoprotein (LDL) binds cholesterol and transports it from the liver to the cells. LDL-cholesterol is found in the plaques that cause furring up of the arteries.
Very low-density lipoprotein (VLDL) mainly transports triglycerides from the liver to fat stores, and raised levels are associated with an increased risk of heart disease.
Intermediate-density lipoprotein (IDL) is formed from VLDL when it releases its triglycerides. IDL then absorbs more cholesterol until it becomes LDL cholesterol and is also associated with furring up of the arteries.
Lipoprotein(a) is another LDL-like particle which increases the risk of atherosclerosis.
While LDL- cholesterol was once called ‘bad’ cholesterol, it’s now clear that every type of lipoprotein-cholesterol that isn’t HDL is bad when it comes to cardiovascular risk. Blood test results have therefore changed to measure total cholesterol, HDL-cholesterol and non-HDL cholesterol to assess your long-term risk.
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%.
Normal range cholesterol levels
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
High-density lipoprotein (HDL) cholesterol
- Above 1mmol/l for men (40mg/dl or above in the US)
- Above 1.2mmol/l for women (50mg/dl or above in the US).
Low-density lipoprotein (LDL) cholesterol
- 3mmol/l or less in the UK
- 100mg/dl or less in the US
- UK guidelines: less than 4 mmol/L
- US guidelines: your non-HDL cholesterol level goal should be 30 mg/dL higher than your LDL cholesterol level goal so, if your target LDL cholesterol is 100 mg/dL, your non-HDL goal is 130 mg/dL.
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.
Total cholesterol / HDL-cholesterol ratio
The most important measure is your ratio of total cholesterol to HDL- cholesterol, as this takes your non-HDL cholesterol into account. Your ratio of total cholesterol divided by HDL-cholesterol should ideally be less than 6. A ratio above 6 is considered high risk, so the lower the ratio the better.
This total/HDL ratio is used to estimate your cardiovascular risk, along with other health and lifestyle risk factors to assess your qrisk2 score.
Based on this calculation, NICE now recommends lipid-modification treatment (usually a statin) for people whose risk of having a heart attack or stroke over the next 10-years is 10% or greater.
What causes a raised total cholesterol level?
As cholesterol is so important for health, the body holds on to it as much as possible. The only way you excrete cholesterol is via the liver into your bile. Almost all (97%) of the cholesterol reaching your gut in the bile is absorbed straight back into your blood stream, however, and sent back to the liver for processing. The only other significant way to lose cholesterol from your body is to break it down and burn it as a fuel.
Your blood cholesterol level is a balance between the amount of cholesterol released into your circulation by the liver, and the amount removed from your circulation by body cells. When a cell needs cholesterol it makes the necessary receptors and sends them to its surface, to act like fishing hooks. These receptors catch passing lipoprotein-cholesterol particles and draw them inside the cell.
On average, a particle of lipoprotein-cholesterol circulates around your body for two-and-a-half days until it’s hooked into a cell. Seventy per cent of cholesterol removed from the circulation in this way is taken back up into liver cells for reprocessing.
If the mechanisms that balance your production of cholesterol do not work properly, then your cholesterol levels will rise. Excess cholesterol clogs your arteries and increases your risk of coronary heart disease and stroke through a process known as atherosclerosis.
The main determinants of your cholesterol balance are a combination of the genes you’ve inherited, your age and lifestyle – including your diet, alcohol intake and physical activity or exercise level.
Cholesterol and your genes
The way your body handles cholesterol and other fats depends on your genes. You inherit two copies of every gene, one from your mother, and one from your father. Over a 1000 different mutations in the LDL-receptor gene are known. which can cause cholesterol levels to rise.
For example, an estimated 1 in 500 people across the world possess one faulty copy of the gene that makes the LDL-receptors that hook LDL-cholesterol into their cells. Although they also inherit a normal copy of the gene from their other parent, their uptake of LDL-cholesterol is inefficient and LDL-cholesterol particles stay in their circulation longer than usual – typically, four-and-a-half days rather than the more usual two-and-a-half days. As a result, cholesterol levels rise leading to premature atherosclerosis and increased risk of heart attacks in their 30s and 40s.
Your liver normally makes around 800mg to 1g cholesterol every day, from certain saturated fats, while a typical diet provides between 250mg and 300mg pre-formed cholesterol per day from animal-based foods.
Having a good circulating supply of cholesterol normally suppresses production of new cholesterol in the liver.
If you inherit ‘good’ genes, then liver production of LDL-cholesterol reduces as your dietary cholesterol intake increases and your cholesterol balance remains ideal.
If you inherit ‘bad’ genes, however, the negative feedback mechanism which should reduce cholesterol production can malfunction, so your liver continues churning out cholesterol even though you get plenty in your diet, and have plenty in your circulation.
Excessive intake of pre-formed cholesterol and saturated fats increases LDL-cholesterol levels in some people.
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 your blood pressure rises.
Is a raised cholesterol level bad?
There is a lot of controversy over cholesterol as, despite its reputation, cholesterol is vital for life.
Whether or not a raised cholesterol is a cause for concern depends on the balance between HDL and non-HDL-cholesterol. If much of your circulating cholesterol is in the HDL form, you have a lower risk of heart disease than if most of it is in the non-LDL cholesterol 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. The focus is therefore shifting away from LDL-cholesterol towards non-HDL-cholesterol levels which are a better predictor of long-term cardiovascular risks.
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.
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 American College of Cardiology.
How to increase ‘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-3 fish oil 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.
A number of supplements have beneficial effects on cholesterol balance and HDL-cholesterol levels, which I’ve covered in my post on the Best Cholesterol Lowering Supplements.
Medical treatment to lower 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.
You can also read a post on the best cholesterol lowering supplements if you are unable or unwilling to take a statin drug.
Lower cholesterol diet
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.
Eating Brazil nuts has a powerful cholesterol lowering action, too.
Cholesterol diet and eggs
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 and 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 to lower cholesterol
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 in managing blood cholesterol levels than doubling the statin dose.
Plant sterol supplements are widely available, and a typical dose is 800 mg, three times a day.
Supplements tend to provide 800mg plant sterols per tablet, and taking 3 tablets a day can have a significant cholesterol-lowering effect within 2 to 3 weeks.
Lifestyle changes to lower cholesterol
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 non-HDL-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. Using a pedometer or fitness tracker and aiming for 10,000 steps a day is an excellent goal.
If you’ve found success in lowering your cholesterol levels – with or without medication, please share your experience via the comments below.
If your blood pressure is raised, self-monitoring is key to maintaining good control.
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