Cholesterol is a type of fat made by the liver and present in every cell in an animal’s body, including humans. Cholesterol is only found in foods of animal origin – meat, dairy, eggs, fish, shrimps, prawns and shellfish - and is particularly concentrated in organ meats and eggs. Plant foods contain none. Even high-fat plant foods (such as avocados, nuts and seeds), contain no cholesterol whatsoever, so a vegan diet is cholesterol-free.
As our liver makes all the cholesterol we need there is no dietary need for cholesterol at all.
However, it's not just cholesterol in the diet that increases our blood cholesterol levels. Saturated fats and trans (hydrogenated) fats are a major contributor as the liver turns these into cholesterol. There is no mechanism limiting the amount of cholesterol produced by the liver and it can rise to unhealthy levels.
High cholesterol levels in the blood increase the risk of heart disease and stroke. All major health organisations (WHO, American Dietetic Association, Dietitians of Canada, British Dietetic Association, American Heart Association, British Heart Foundation, World Heart Federation, British National Health Service, US Food and Drug Administration and European Food Safety Authority) agree that saturated fat is a risk factor for heart disease.
Cholesterol in the blood exists in two forms. So-called bad cholesterol (low-density lipoprotein or LDL) is dumped on the artery walls (forming artery plaques), which reduces blood flow and can lead to heart attack or stroke. Good cholesterol (high-density lipoprotein or HDL) is carried to the liver so the body can get rid of it. Around 70 per cent of the UK population have been shown to have bad cholesterol levels above the recommended levels.
In the UK, it is recommended that people reduce their cholesterol levels down to 5.0 (mmol/l) even though the level to avoid heart attacks entirely is 3.9.
Research shows that replacing saturated fat in the diet with polyunsaturated fat is more effective in lowering cholesterol than reducing the total amount of fat in the diet. This means replacing meat, dairy and eggs with wholegrains, pulses, fruit, vegetables, nuts and seeds. Vegans have the lowest cholesterol levels and always come on top (ie are at the lowest risk) in studies comparing the effect of various diets on the risk of heart disease.
Foods high in saturated fat include: meat pies, sausages and fatty cuts of meat, butter, ghee, lard, cream, hard cheese, cakes and biscuits and foods containing coconut or palm oil.
High intakes of animal protein are also linked to heart disease - this is attributed to the cholesterol-raising effect of animal protein. Plant protein, on the other hand, lowers cholesterol. One particular plant protein has been shown to be particularly effective in lowering cholesterol – soya protein. The most popular theory is that soya protein reduces cholesterol production in the liver by increasing the removal of LDL ‘bad’ cholesterol.
Read more about the prevention and treatment of heart disease through diet.
See detailed information on the links between diet and heart disease.
And see our Nutrition News on the topic.