High cholesterol (hyperlipidemia)
Cholesterol is an essential fatty substance, or ‘lipid’, in our blood and is vital if our bodies are to function normally. Although high levels of cholesterol do not give us any symptoms, having too many lipids in the blood can affect our health, increasing the risk of coronary heart disease (damage to the arteries that supply blood and oxygen to the heart). Eating a healthy, balanced diet and staying active is enough to keep most people’s cholesterol levels healthy, but it’s important for diabetics to have their cholesterol levels checked every year.
Dyslipidemia is when there is an abnormal balance of lipids in the bloodstream. It normally refers to raised levels of lipids in the blood (hyperlipidemia). However, high insulin levels over a long period of time can also lead to an abnormal balance of lipids.
‘Good and ‘bad’ cholesterol
Cholesterol is carried in the bloodstream by proteins. It combines with these proteins to form ‘lipoproteins’ and there are three main types:
- LDL – low-density lipoproteins carry cholesterol from the liver to the cells via the bloodstream. If there is too much cholesterol it builds up in the arteries, hardening or narrowing them (atherosclerosis). s
- HDL – high-density lipoproteins return the extra cholesterol that is not required by the body to the liver, where it is broken down and excreted, rather than allowing it to accumulate in the arteries.
- Triglycerides – some of these are needed for good health, but high levels raise the risk of heart disease. They are produced by the body’s fat stores or by the liver but are also found in dairy products, meat and cooking oils
Ideally, we should aim to have low cholesterol, with:
- Low triglyceride levels
- Low LDL and
- High HDL
How does cholesterol affect health?
Too much cholesterol can build up in the coronary arteries, hardening or narrowing them (atherosclerosis) which causes coronary artery disease and conditions such as angina, where damage to the arteries means there is insufficient blood and oxygen supply to the heart muscle (ischemia). This increases the risk of a heart attack.
High cholesterol levels also increase the risk of peripheral arterial disease (PAD) by causing narrowing of the arteries that supply blood to the legs.
Cholesterol is measured in millimols per litre of blood or ‘mmol/l’. The blood test can be used to assess the risk of coronary heart disease, using the ratio of total cholesterol to HDL cholesterol. The higher the ratio, the greater the health risks. ‘Healthy’ levels vary between adults depending on risk factors that include:
- Being overweight
- Low levels of exercise
- Being of South Asian origin
- High blood pressure
- Family history of heart disease
- Family history of a cholesterol-related condition
The more risk factors you have, the more important it is to reduce cholesterol levels to lower the risk of coronary heart disease. ‘Healthy’ cholesterol levels, recommended by the National Institute for Health and Clinical Excellence (NICE) and the Department of Health in the UK suggest that:
- Total cholesterol should be less than 5.0mmol/l
- LDL cholesterol should be less than 3.0mmol/l
How can cholesterol be lowered by a healthy diet?
Having a healthy diet can lower blood cholesterol levels by 5-10% and this means sticking to a low-fat diet, and avoiding food containing saturated fat and trans fats. Opting for foods that are high in polyunsaturated fats (including omega-3) helps prevent blood clots and keeps the heart rhythm regular.
High fibre foods can also help to lower cholesterol levels by reducing the amount of LDL absorbed into the bloodstream from the intestine. These include: oats, lentils, pulses, nuts, beans, fruit and vegetables, garlic, soya, corn and selenium-enriched cereals.
Sterols and stanols
Sterols and stanols are naturally found in plants and are used in many branded products such as yoghurts and spreads that claim to lower cholesterol. Sterols and stanols can help to reduce cholesterol levels by up to 10-15% when 2g is eaten each day as part of a healthy balanced diet (check the label on branded foods for advice on how much to have). However, they should not take the place of a healthy balanced diet or replace cholesterol-lowering medication prescribed by the doctor.
Other ways to reduce your cholesterol include:
- Stop smoking: a chemical found in cigarettes called acrolein stops HDL from transporting LDL to the liver, leading to narrowing of the arteries (atherosclerosis)
- Increase physical activity to increase HDL cholesterol levels, lower blood pressure, reach a healthy weight and reduce the risk of diabetes