Guest post by Paul Fairbairn, BSc (hons) in Sport and Exercise Science & Nutrition MSc studentHow do you like your eggs in the morning? I like mine with a side of evidenced based nutrition advice. Eggs have been a source of debate in nutrition for many years, mainly due to warnings over their cholesterol content. It’s true when you compare eggs to other foods they have a very high cholesterol content, typically having around 200mg per large egg, with the cholesterol being in the yolk. As high cholesterol levels are linked to heart disease this has often led consumers to reduce their egg intake and with some choosing to only consume the whites. Nutritional science is still in its infancy and researchers are constantly uncovering new information, for that reason it’s important to revisit and challenge the norms with the most up to date evidence available and it’s time to look at eggs.
A whip around cholesterol….
Before I go into eggs it’s important to understand cholesterol and what it does within our bodies. Cholesterol actually serves a number of important purposes within the body, including keeping our nerves healthy and producing hormones. Cholesterol is a waxy substance that doesn’t mix with water, so to transport it round the body it’s packed into particles to form ‘lipoproteins’.
“Good” and “Bad” cholesterol…
There are two main types of lipoprotein, these are low density lipoproteins (LDL) often referred to as “bad cholesterol” and high density lipoproteins (HDL) or “good cholesterol”. The reason LDL is referred to as “bad cholesterol” is because high levels are associated with the formation of plaques in the arteries which lead to heart disease. However it’s important to note that LDL also facilitates the transport of to where it is needed, so it’s a case of the devil being in the dosage. In contrast, HDL travels through the blood stream, vacuuming up excess cholesterol so as to help the body maintain healthy levels.
To put it another way – LDL particles are like reckless drivers , with HDL acting as the roadside assistance helping to clear things up and keep those roads safe/clear.
Cholesterol and Heart Disease risk…
The ratio between total cholesterol and HDL is often used to assess heart disease risk in studies and patients, because it’s shown to be more predictive for heart disease than other cholesterol measures like total cholesterol or total LDL (Millan et al., 2009; Lemieux et al., 2001). Because cholesterol is so important our body produces it in the liver. Most of our cholesterol is produced this way with only a small amount actually coming directly from our foods. And for this reason, it’s fairly well known that when we eat cholesterol it doesn’t actually have a huge impact on our body’s cholesterol levels.
Back to eggs….
So where does this leave the good old egg? Do they increase our cholesterol, and if so, how and, most importantly, what kind of effect might that have on our long term health?
Results from 8 large studies were pooled together in 2013 and the authors found no association between consumption of eggs and heart disease or stroke (Rong et al., 2013). More recently a study in Finland also showed no association between frequent consumption of eggs and heart disease, even in people who were genetically predisposed to have heart conditions (Virtanen et al., 2016). It is important to mention that most of the studies into egg consumption look at intakes of 1-2 eggs per day, and that there is a lack of evidence for intakes higher than this. So perhaps this is something to look out for in the future when more studies are published.
Not only does the current evidence show lack of a link between eggs and heart disease there are also plenty of benefits to eating them. Eggs are an inexpensive, readily available source of nutrients such as; quality protein, B vitamins, selenium and lutein. It’s important to note that most of the vitamins and minerals in eggs are actually in the yolk with the protein being in the whites.
So this all sounds very positive in favour of the humble egg, however it’s not quite that simple. With nutrition it’s often not just about one food or one meal. Our health and performance is shaped on our overall dietary patterns, what we do day in day out for months and years. The UK is almost synonymous with the breakfast fry up with eggs playing a pivotal part. In fact, egg consumption is associated with greater intakes of red and processed meat (Hu, 1999) of which there is some evidence, especially for processed meat, for increased heart disease risk (Micha et al., 2012). Even more interesting it has been noted that those who eat more eggs tend to exercise less and are more likely to smoke (Rong et al., 2013). This has led to the theory that it’s not about the eggs, but the behaviours and dietary patterns that seem to coincide with egg consumption. There is a big difference between the nutrition compositions of a fry up versus an omelette full of vegetables and fibre.
In recent times consumers have been paying more attention to where their food comes from and how it is produced, and eggs were really are the forefront of this movement. There has been a lot of media coverage on battery hens and the horrible conditions they are kept in, and a a real shift towards buying free range or RSPCA approved eggs, they may cost a fraction more, however the price is certainly worth paying to support an ethical and more humane production of eggs.
So there we have it, the link between eggs and heart disease appears to not be that strong, but there also isn’t too much evidence available for exceptionally high daily consumptions of eggs. Clearly this doesn’t give a free pass to the full English fry-up every day, as it’s essential to think about the whole diet rather than single foods and nutrients.
Photo credit: The Devilled Egg
Hu, F. (1999). A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women. JAMA, 281(15), p.1387.
Lemieux, I., Lamarche, B., Couillard, C., Pascot, A., Cantin, B., Bergeron, J., Dagenais, G. and Després, J. (2001). Total Cholesterol/HDL Cholesterol Ratio vs LDL Cholesterol/HDL Cholesterol Ratio as Indices of Ischemic Heart Disease Risk in Men. Arch Intern Med, 161(22), p.2685.
Micha, R., Michas, G. and Mozaffarian, D. (2012). Unprocessed Red and Processed Meats and Risk of Coronary Artery Disease and Type 2 Diabetes – An Updated Review of the Evidence. Curr Atheroscler Rep, 14(6), pp.515-524.
Millan, J., Pinto, X., Munoz, A., Zuniga, M., Rubiés-Prat, J., Pallardo, L., Masana, L., Mangas, A., Hernández-Mijares, A., González-Santos, P., Ascaso, J. and Pedro-Botet, J. (2009). Lipoprotein ratios: Physiological significance and clinical usefulness in cardiovascular prevention. VHRM, p.757.
Rong, Y., Chen, L., Zhu, T., Song, Y., Yu, M., Shan, Z., Sands, A., Hu, F. and Liu, L. (2013). Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies. BMJ, 346(jan07 2), pp.e8539-e8539.
Virtanen, J., Mursu, J., Virtanen, H., Fogelholm, M., Salonen, J., Koskinen, T., Voutilainen, S. and Tuomainen, T. (2016). Associations of egg and cholesterol intakes with carotid intima-media thickness and risk of incident coronary artery disease according to apolipoprotein E phenotype in men: the Kuopio Ischaemic Heart Disease Risk Factor Study. American Journal of Clinical Nutrition, 103(3), pp.895-901.