Issue 147 Eggs: Friend or foe?

EGGS: FRIEND OR FOE?

COMPETITION WINNER

This review aims to explore the nutritional composition of eggs, as well as examine the wide range of health benefits associated with including eggs as part of a balanced diet.

“An egg a day is okay…” So, will it be poached, fried or scrambled? Boiled, soft or hard? With smashed avocado, smoked salmon, or the old reliable Marmite? Will you have the whole egg, or just the whites? Or should we be eating eggs at all? For such a seemingly unassuming food, eggs have stirred up much debate and even now there are still many misconceptions regarding their place in a healthy diet.

Around the world, habitual egg consumption varies hugely, with intakes as high as 358 eggs per capita per year in Mexico and as low as 36 per year in certain African countries.1 In the UK, the NHS guidelines state that, ‘There is no recommended limit on how many eggs people should eat’3 and eggs are included in the Eatwell Guide,18 alongside meat, fish, beans and nuts.

Two eggs are considered as one serving.19 In Ireland, Safefood does not include specific recommendations for eggs for the healthy general public.2 There are of course certain subgroups of the public who will need to be mindful of egg consumption, eg, those with metabolic disorders, including hypercholesterolemia, or those with an egg allergy.1 However, the majority of people can safely consume eggs on a regular basis.

WHY THE CONFUSION?

In the past, eggs have gained a bad reputation due to their high cholesterol content: 400mg/100g, or approximately 213mg per large egg/186mg per medium egg.1,4,5

Laura Kaar Student, Trinity College Dublin and Technological University of Dublin

In 1986, the American Heart Association brought out new guidelines recommending that people consume no more than three whole eggs per week and less than 300mg of cholesterol a day, in an attempt to prevent heart disease.4 These recommendations resulted in a sharp decline in egg consumption, as people began to limit their intake.4 Thankfully, much more research has been carried out since then and such recommendations have been removed from the majority of national dietary recommendations.

In 1999, a large long-term population study found no difference in heart disease risk between those consuming one egg per day compared with those having one egg per week, and many studies, including epidemiological studies and meta-analyses, have reported similar findings.4.6 This, in part, may be due to poor absorption of cholesterol in eggs, since consumption of eggs is not associated with an increase in total plasma cholesterol concentration.7 The antioxidants found in eggs may also play a protective role with respect to heart disease, as discussed further below.6 It is also important to remember that the vast majority of an individual’s serum cholesterol comes from endogenous cholesterol biosynthesis (up to 75%), with dietary cholesterol responsible for the remainder.5

Having just finished her final year in Dietetics, Laura is very much looking forward to starting work as soon as possible.

She previously completed a degree in biochemistry and is also a qualified horse-riding instructor.

REFERENCES Please visit the Subscriber zone at NHDmag.com

Look for the British Lion mark when buying eggs to ensure the highest standards of food safety.

More info at: egginfo.co.uk

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Laura's winning article, in our NHD/British Lion eggs competition, was judged by Dr Carrie Ruxton and NHD Editor Emma Coates.

Our thanks to everyone who took the time to enter.

FAT: THE GOOD, THE BAD OR THE UGLY?

Water makes up the majority of an egg (76%), while fats and protein account for 9.5% and 12.6% respectively.1 In total, one medium egg will provide approximately 78kcal, 5.3g of fat and 6.29g of protein.5 Despite what was previously thought, in 2017, Lopez-Sobaler et al went as far as describing the fatty acid profile of eggs as ‘favourable’ with respect to heart disease.8 In comparison with other animal food sources, eggs have a high ratio of unsaturated fat to saturated fat and are a useful source of many essential fatty acids, including linoleic acid.1 Of the 5.3g of fat found in one medium egg, approximately 1.6g is saturated, 2g is unsaturated and 0.7g is polyunsaturated.5 A systematic review published in 2017, found that replacing saturated fat in the diet with polyunsaturated and monounsaturated fats was protective with respect to coronary heart disease.9 The daily reference intake for adults is 70g total fat and 20g saturated fat,20 and so, a serving of two medium eggs would contribute approximately 15% of total fat and 16% of saturated fat for an adult.10 This serving would also provide approximately 150kcal and 13g of protein, equating to 7.5% of the daily energy requirements for an adult female requiring approximately 2000kcal per day. Finally, eggs contain less than 1% carbohydrates and do not provide any fibre.1 THE ORIGINAL PROTEIN BALLS?

The recent rise in popularity in processed (and often rather expensive) protein balls would have been hard to miss for anyone who has set foot in a supermarket or health food shop in the past few years. Not to mention the abundance of 'bliss' balls, energy balls and, 34

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of course, protein bars now available at every checkout. However, when we look at what the humble egg can deliver in terms of macro- and micronutrients, we may be better off holding onto our well-earned pennies and popping a hard-boiled egg or two into a lunch box instead. Eggs are well known as an accessible economical source of high biological value protein.11 At present, six medium sized freerange eggs from a national retailer costs £1.59 (0.27p per egg).12 That is excellent value for a food product that has been described as being one of the ‘best sources of high quality protein only inferior to breast milk’.5 The protein found in eggs is also a valuable source of the essential amino acid leucine, which is proven to have a role in stimulating muscle protein synthesis.11 The protein found in an egg is split between the white and the yolk, with the yolk also housing the vast majority of the fatty acids and micronutrients.1 Contrary to the beliefs of bodybuilders who avoid the yolk to save a tiny amount of fat and calories, consumption of whole eggs appears to be more beneficial in stimulating muscle protein synthesis than egg whites alone.13 This is why it is better to eat the whole egg in order to reap the full health benefits.

THE WHOLE EGG

As with any food, it is important to consider the overall picture and not focus solely on the potential adverse or beneficial impact of one or two nutrients. Beyond calories and macronutrients, eggs provide a rich source of micronutrients and bioactive compounds. The main role of the yolk is nutritive; however, it doesn’t simply provide essential nutrients, but contains formats that are readily available

COMPETITION WINNER and easily metabolised.14 Examples include the minerals iron and zinc, which are important for normal cognitive and immune function.

Eggs are known to be a valuable source of choline, which has many essential roles, particularly in infant development and in the eye, since it is a precursor for the phospholipids required for cell growth, division and signalling.14 Higher dietary intakes of choline have been associated with lower circulating markers of inflammation, including C reactive protein (CRP) and so may be protective against inflammatory process and related diseases.15 Eggs also provide a rich source of antioxidants including vitamins, minerals and bioactive compounds.1 Examples include the carotenoids, lutein and zeaxanthin, which are highly bioavailable in egg yolk, even more so than in supplements or plant sources.11 Interestingly, research has shown that the levels of both of these carotenoids can be increased by as much a tenfold by adding marigold to hens’ diets.4 This could be very beneficial, as the antioxidants present in eggs may inhibit oxidative damage and potentially protect against degenerative processes, including those characteristic of cardiovascular disease.5 Eggs are one of the few foods naturally containing vitamin D, with approximately 41IU (1.02mcg) per egg, most of which is in the yolk.11 A serving of two eggs would, therefore, provide just over 20% of the 400IU (10mcg) RNI as recommended by SACN.16 A 2016 study

involving an animal model of diabetes, found whole eggs to be more beneficial for maintenance of vitamin D levels than supplementation.17 Reaching and maintaining recommended vitamin D levels is notoriously difficult for many reasons. This is partly due to a lack of foods that naturally contain this essential nutrient. However, regularly including whole eggs in the diet may be an effective way to help people achieve requirements, alongside the relevant recommended supplementation.

CONCLUSION

This article has briefly touched on a range of the benefits of eggs documented to date. It is clear that despite previously held beliefs in relation to heart disease, for the general healthy population, eggs are now widely considered a useful source of high-quality protein and healthy fats. Based on the current evidence available, the inclusion of eggs in a healthy balanced diet is not associated with an increased cardiovascular disease risk.

Eggs will provide a rich source of many essential micronutrients, including vitamin D, choline and iron. In the future, even more benefits of the bioactive compounds in eggs, in particular certain egg proteins, may be found, as the role of many of these compounds has yet to be identified.1 When considering the wide range of benefits associated with egg consumption, it is clear that eggs have the potential to play an important role in any healthy balanced diet, whatever way people choose to eat them.

Obituary IN MEMORY OF DR BRIONY JANE THOMAS PhD RD 28th June 1950 – 28th May 2019 Family, friends and colleagues came together in June to say goodbye to Briony Thomas, Editor of The Manual of Dietetic Practice. Briony devoted 23 years (1984-2007) to this book, which has become known and loved, not just in the UK, but internationally and is now in its 6th edition. The first was published in 1988 with Briony as Editor and author of a large number of the chapters. She continued as Editor for the next three editions and, being a scientist and dietitian herself, was able to choose appropriate authors as the book developed.

Briony was made a BDA Fellow in 1994 and appeared on the BDA roll of honour 2007 for her contribution to dietetics through what has fondly become known as The Manual. To quote one tribute: “Briony was The Manual”. The profession owes her a great debt of gratitude for leaving such a legacy.

For the full obituary written by Dr Jacki Bishop, along with Briony’s husband Dick Thomas, please visit www.NHDmag.com/briony-thomas

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