Cholesterol is fatty substance found in both foods and the human body. It is needed by the body to make hormones, vitamin D and bile acids for digestion. However, high blood cholesterol is one of the major risk factors for cardiovascular diseases (CVD) such as stroke and heart disease, therefore reduction of high blood cholesterol is vital in prevention of these conditions. For the vast majority of people, reduction of high blood cholesterol will involve taking prescribed cholesterol- lowering drugs such as statins, modification of diet and increased physical activity. However, when it comes to dietary modification, it can be confusing which foods can increase or decrease blood cholesterol levels. For example, do cholesterol-rich foods such as eggs and prawns increase blood cholesterol levels and therefore need to be excluded from our diet? To better understand this, we need to define the terms ‘dietary cholesterol’ and ‘blood cholesterol’ and review the evidence. What is Blood cholesterol? Blood cholesterol is the total cholesterol circulating in the blood. The liver produces most of the cholesterol the body needs and this is bound to special proteins and transported around the body. Cholesterol bound to these transport proteins are known as lipoproteins. The two main types of lipoproteins are low-density lipoprotein (LDL) and high density lipoprotein (HDL). LDL cholesterol is from liver being transported to the cells. cholesterol is extra cholesterol being transported from cells to liver for breakdown. LDL cholesterol is called the ‘bad cholesterol’ because it is the main source of cholesterol build-up in the walls of the blood vessels. Over time, this build-up results in hardening and narrowing of the blood vessels which in turn increases the risk of heart disease, strokes and other circulatory diseases. HDL cholesterol is called the ‘good cholesterol’ because it helps to keep cholesterol from building up in the arteries. Total cholesterol level is a combination of LDL cholesterol, HDL cholesterol and other fats in the blood. Another form of fatty substance in the blood that can also raise the risk of heart diseases is called triglycerides. Raised blood cholesterol is a major prevalent yet modifiable cardiovascular disease risk factor. Use of statins such as Lipitor® and Crestor® has proven to reduce both CVD incidence and related deaths1. What is Dietary Cholesterol? Dietary cholesterol is the cholesterol found in all animal foods, however foods such as eggs, liver, kidney and shellfish including shrimps and prawns are particularly rich in cholesterol. Dietary cholesterol and its effect on blood cholesterol has been the subject of much controversy. The research evidence on this matter however, has been quite clear for a long time – the amount of cholesterol in the diet does not significantly affect blood cholesterol levels when compared to the fat content of the diet2. Other dietary fats known as saturated fats and trans fats have more impact in raising blood cholesterol levels. Saturated fat from the diet is known to raise LDL cholesterol and total cholesterol levels. It is found mainly in fats from animal origin and their products including fatty meats and products, poultry skin, full fat milk, butter, baked foods like cakes, biscuits and other processed foods. Oils such as coconut oil and palm oil also contain saturated fat and known to affect blood cholesterol levels to varying degrees, though recent evidence suggests we need further scientific review regarding the extent to which blood cholesterol levels are affected. Trans fats also raise LDL cholesterol and lower the “good” HDL cholesterol. Trans fats around in some fried and processed foods and made when hydrogen is added to vegetable oil to harden it. International guidelines on intake of dietary cholesterol Guidelines on dietary cholesterol have been a controversial issue for many years. US dietary guidelines have for a long time recommended restriction of dietary cholesterol intake to below 300 mg per day. However, this recommendation was reviewed as part of the “2015-2020 Dietary Guidelines for Americans”. No recommendation was made in 2015 for specific limits on dietary cholesterol intake as more scientific evidence was required regarding the relationship between amount of dietary cholesterol intake and blood cholesterol levels. However, recommendation for individuals to eat as little cholesterol as possible while consuming a healthy eating pattern still stands 3. UK dietary guidelines do not recommend a dietary cholesterol intake restriction. However, in a few people who have been diagnosed with a condition known as Familial hypercholesterolaemia (FH), it is recommended a sensible practice to restrict dietary cholesterol to less than 300mg per day4. Therefore, current international leading dietary guidelines are in agreement that cholesterol-rich foods such as eggs and sea food including crabs, shrimps and prawns) need not be routinely restricted in an attempt to manage or prevent high blood cholesterol. Summing it all up The limited contribution of dietary cholesterol to raised blood cholesterol is well established. High intake of saturated fats in our diet is one of the commonest causes of high blood cholesterol. However, there are other causes of high blood cholesterol such as chronic kidney disease, thyroid problems and inherited genetic disorders. In Ghana, research is needed to investigate the dietary factors associated with high blood cholesterol and cardiovascular diseases. This will help with the formulation of local dietary guidelines to reduce CVD risks and improve the health of our population. Overall, a healthy balanced diet which is low in saturated fats, replaced with small amounts of unsaturated fats (groundnuts, egusi, avocado pear, canola oil), high in fibre-rich foods (whole grains, fruits, and vegetables) and especially soluble fibre (oats, all types of beans and sweet potatoes) can help lower your blood cholesterol by at least 10% or more and reduce your risk of cardiovascular diseases. Olivera Kegey (MSc, Registered Dietitian) Laurene Boateng (MPhil, Registered Dietitian) References
- Nayor M, Vasan RS. Recent Update to the US Cholesterol Treatment Guidelines. Circulation. 2016 May 3;133(18):1795-806.
- Perk J, De Backer G, Gohlke H, Graham I, Reiner Ž, Verschuren M, Albus C, Benlian P, Boysen G, Cifkova R, Deaton C. European Guidelines on cardiovascular disease prevention in clinical practice (version 2012). European heart journal. 2012 Jul 1;33(13):1635-701.
- S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/.
- Wierzbicki AS, Humphries SE, Minhas R. Familial hypercholesterolaemia: summary of NICE guidance. BMJ: British Medical Journal (Online).