The humble egg has been a part of the human diet since our ancestors first thought to check out was in bird’s nests. The place of the egg in myths of creation and rebirth is well known. Then came the dark days of the 1970s when misunderstandings and confusion about cholesterol gave eggs a bad name. Now the truth about eggs has been unscrambled and the “bad egg” turns out to be a good egg in more ways than one.
Ancient myth
Since the times of the first hunter-gatherers until relatively recently, eggs have been valued as a rich source of nutrients from vitamin A to zinc. The Chinese saw the universe as starting from an egg with the yolk becoming the earth (ying) and the white becoming the sky (yang). The Egyptians and Romans would give gifts of eggs to symbolise the cycle of life and the continuation of life after death. This tradition was adopted by Christianity and Easter eggs today still represent the rebirth of Christ.
The strong link between eggs and the cycle of life is not surprising given the egg’s obvious role in the life cycle of a bird. However, the egg’s representation in myth and tradition may also arise due to the egg’s life-giving properties as a food source.
Modern myth debunked
This positive view of eggs in relation to good health was challenged in the later part of the 20th century when cholesterol became a health buzz word. Misunderstandings about the healthiness of eggs resulted from confusion about different types of cholesterol and how they function in the body.
It had been mistakenly thought that because eggs contain cholesterol, blood (serum) cholesterol levels would increase, causing damage to your cardiovascular system. Dietary cholesterol is thought by many to aid plaque formation in the arteries and lead to higher rates of stroke and heart attack. More recently, researchers have begun to understand that in most people this is not the case at all.
Numerous recent studies have found no link between increased egg consumption and stroke or heart attack. One such study found that those eating more than six eggs a week had the same risk of heart disease as those consuming one or less. It is now understood that dietary cholesterol is a fairly minor factor in serum cholesterol levels. The main contributors to higher serum cholesterol levels are saturated fats and trans fats. Eggs have only moderate levels of saturated fats and no trans fats so they have minimal effect on cholesterol levels. Rather than harming your heart, eggs may even be good for it.
The hearty egg
Some researchers theorise that eggs may be beneficial to heart health due to their content of choline, which plays a role in fat metabolism. Improved fat metabolism by the liver creates a healthier serum cholesterol profile and thereby a healthier heart. This is not the only aspect of the egg that can contribute to heart health.
One 50gm egg contains approximately 56mg of omega-3 fatty acids. While not as rich a source as fish, omega-3 in eggs is a positive addition in the diet of vegetarians and the many Australians who aren’t getting adequate levels in their diet. Omega-3 is anti-inflammatory and helps positively balance blood fats, both actions that support your heart.
The good levels of B9 and B12 found in eggs are another helping hand for your heart. These two nutrients play an essential role in reducing levels of an amino acid called homocysteine in your body. Homocysteine is thought to reduce the elasticity of the cardiovascular tissue and so contribute to heart disease.
Nutrition packed
In addition to their heart benefits, eggs have a range of other beneficial effects in your body that arise from the many nutrients that they carry.
Lutein
Eggs are one of the very best sources of lutein. They not only contain very high levels but seem to be the source from which our bodies most easily absorb this useful nutrient. Lutein is an antioxidant that falls into the category of carotenoids. Due to its protective role against cholesterol oxidation, it is another component of eggs thought to be beneficial for heart health. Its antioxidant capacity reaches even further than this, though. Lutein is also a crucial part of the macular of the eye and one of its major roles is as a UV filter of blue light. There is a lot of research supporting lutein’s use as a preventative for macular degeneration, cataracts and general structural degeneration of the eye. Combine this with its ability to protect skin cells from certain cancers and you can see why getting more lutein is enough incentive to increase egg consumption.
Choline
Eggs are one of the richest available sources of choline. As mentioned above, choline is involved in healthy fat and cholesterol metabolism and therefore heart health but its main role is in the nervous system and brain. Studies on this nutrient in the diet have shown that greater consumption of choline results in lowered inflammation in the body as well as improved memory and healthier liver function. Other studies have also shown that low consumption is linked to an increased risk of neural tube defects in babies.
Biotin
This component of eggs is a little more complex than others. It is found in high levels in egg yolk but raw egg whites contain “avid”, a substance that limits its absorption by your body. The easy solution is to minimise your consumption of raw eggs (or the whites, anyway). In any case, a nice poached egg is a lot more pleasant than chugging back a raw one and it will also ensure good levels of this important nutrient. Biotin function in your body relates to tissue health generally especially hair and skin. In fact, low levels have been linked to deformities in newborns.
Protein
Eggs are considered a complete protein, which means they contain all the essential amino acids (EAAs). Without all nine of these building blocks in the right proportion, your body is unable to form new tissue such as skin, hair and hormones. Due to its excellent levels of all these EAAs, the egg is considered one of the richest and most usable forms of protein available. Sufficient protein is vital for everybody’s health but certain groups have higher demands. Pregnant or lactating women, children, the elderly, sportspeople and those recovering from illness all require more. Eggs are a simple way to boost your current intake, with one egg providing around 6gm of pure protein. The recommended intake per day of protein is around 0.75gm per kg of body weight, which means an average woman requires around 45gm per day. For those of you without a calculator handy, this means that two eggs a day will give you more than one quarter of your daily protein requirement.
A-Zinc vitamins and minerals
Eggs provide all the nutrients required for baby chicks so it’s no surprise they have good levels of a broad range of essential vitamins and minerals. Below is a table of the ones found in the highest levels — but don’t forget that eggs contain virtually every vitamin or mineral to some degree.
TABLE Egg vitamins and minerals Nutrient Recommended Daily Intake (RDI) percentage per 2 eggs Functions of nutrient Vit A 22% Essential for healthy skin, eyes and mucous membranes Vit B2 24% Essential for healthy skin, eyes and mucous membranes as well as foetal development, and support of energy production and a healthy nervous system Vit B3 36% Important for energy and hormone production. Also required for a healthy digestive system due to its role in digestive and bile secretion Vit B5 29% Important for hormone production as well as fat and protein metabolism. Also needed for a healthy immune system due to its role in antibody production Vit B9 (folic acid) 25% Important for DNA synthesis and so healthy tissue formation and nervous system function. Also vital to avoid spina bifida in newborns Vit B12 68% Required for cell repair and turnover and a healthy nervous system Vit D 9% Although this percentage is fairly small there aren’t many food sources of Vit D so every bit counts! It is especially important for bone, reproductive and immune health and Australia has a rising rate of deficiency. Iron 14% Important for bone and blood health as well as immune function Phosphorus 15% Necessary for bone growth, energy production and muscle health Selenium 47% Vital due to its antioxidant and anti-cancer role as well as its importance in reproductive health Zinc 8% Important due to its roles in immune function, reproductive and skin health as well as a healthy digestive system
Egg vitamins and minerals
| Nutrient | Recommended Daily Intake (RDI) percentage per 2 eggs | Functions of nutrient |
|---|---|---|
| Vit A | 22% | Essential for healthy skin, eyes and mucous membranes |
| Vit B2 | 24% | Essential for healthy skin, eyes and mucous membranes as well as foetal development, and support of energy production and a healthy nervous system |
| Vit B3 | 36% | Important for energy and hormone production. Also required for a healthy digestive system due to its role in digestive and bile secretion |
| Vit B5 | 29% | Important for hormone production as well as fat and protein metabolism. Also needed for a healthy immune system due to its role in antibody production |
| Vit B9 (folic acid) | 25% | Important for DNA synthesis and so healthy tissue formation and nervous system function. Also vital to avoid spina bifida in newborns |
| Vit B12 | 68% | Required for cell repair and turnover and a healthy nervous system |
| Vit D | 9% | Although this percentage is fairly small there aren’t many food sources of Vit D so every bit counts! It is especially important for bone, reproductive and immune health and Australia has a rising rate of deficiency. |
| Iron | 14% | Important for bone and blood health as well as immune function |
| Phosphorus | 15% | Necessary for bone growth, energy production and muscle health |
| Selenium | 47% | Vital due to its antioxidant and anti-cancer role as well as its importance in reproductive health |
| Zinc | 8% | Important due to its roles in immune function, reproductive and skin health as well as a healthy digestive system |
All eggs aren’t equal
So it’s pretty clear that eggs are a warehouse of nutrients — but are all eggs as good as the next? Like anything, if you’re missing some of the ingredients, you won’t get the dish you want. If chickens aren’t fed good levels of all the nutrients they need, their eggs will be of inferior quality. This means the soil in which their food is grown must be nutrient rich so that the best possible egg can be produced.
A number of factors will affect the quality of chicken feed and therefore egg quality. Organic feed, for instance, generally contains higher levels of nutrients than non-organic. This is due to the different fertilisers used in organic farming and the fact that the same crops aren’t grown over and over on the same soil. When crops are varied, soils are given a chance to recover their nutrient levels rather than being continually depleted of the same nutrients.
Variety in feed will also impact on the nutrients available to chickens in order to create eggs. For instance, the use of foods such as alfalfa and marigolds will lead to increased levels of the important antioxidant lutein as well as a marvellous orange of the yolk.
A final factor in the nutrients chickens get fed and so pass into their eggs is attributable to marketing. You might recognise “omega-3” from the media and from claims made by egg producers and marketers. People seem to know that they need more omega-3, an essential fatty acid, in their diets. Some egg producers have tapped in on this. Certain eggs come from chickens fed high levels of fish concentrates, resulting in eggs with much greater levels of this essential fatty acid. The difficulty is determining how much omega-3 these eggs actually contain and what other nutrients it may be at the expense of.
Egg Label Decoding
Free-range eggs account for nine per cent of the egg market (85 per cent is cage eggs and six per cent is barn-laid). However, the market for free-range and barn-laid eggs is growing. So what do these terms mean?
Free-range eggs come from chickens that are free to range over an area of ground during the day.
Barn-laid eggs come from chickens housed in large barns, divided into pens, each containing up to 1000 birds. They have the freedom to spread their wings, stretch and socialise, as well as dust-bathe, perch and scratch for food. Limited beak trimming is carried out.
Cage-laid eggs come from chickens kept in small wire cages holding up to five birds. Cages have a minimum height of 40cm and each bird has a minimum floor space of about 500–550 square centimetres. Chickens in cages have their beaks trimmed to prevent them attacking each other.
If the label doesn’t state otherwise, then the eggs are from caged hens.
Choosing your eggs
The fresher the egg the better and most recommendations suggest eggs need to be consumed within four weeks of being laid. It is widely agreed that putting your eggs in the fridge will keep them fresh longer, though. Choice magazine tested a range of different eggs and found that generally the free-range eggs were fresher than cage eggs. Interestingly, the testing model used was an American standard called the Haugh unit and 53 per cent of the eggs checked were of a poor enough standard to be considered “weak and watery”.
If you want to do a basic check yourself, putting an egg in water will give you an indication of freshness. Eggs have an air sac at one end and, as an egg ages, more water is lost and the air sac becomes bigger. Therefore, if the egg sinks completely it is very fresh. If it sinks but has one end tilting up is not as fresh but still fine to eat. Finally, if it floats, whatever you do don’t break it as it’s probably off.
When choosing a good egg, consider the ethics. Aside from the nutritional advantages of free range and organic eggs there is also the moral benefit. Do you want to be responsible for perpetuating the practice of caged farming? Even some government bodies within Australia have decided to phase it out, the ACT leading the way for caged eggs to be banned in any ACT government kitchen.
Don’t be swayed by packaging claims: “antibiotic-free”, “hormone-free” or “preservative-free” are irrelevant in Australia where egg production methods prohibit the use of antibiotics, hormones and preservatives in laying hens. Eggs cannot be collected if chickens are on antibiotics and hormones have not been part of their diet since the 1950s.
All eggs have natural preservatives and vitamins and they cannot be added. Don’t forget the level that eggs may be “enriched” by various nutrients may be to only very small levels or could be at the expense of other nutrients. The only really important information you should look for on the carton will tell you the production method (free range, certified organic or caged) and the “best before” date. The best-before date is usually five weeks from the date of collection.
It is clear that eggs are not the cholesterol-raising monsters that they were once thought to be. In fact, as well as the addition to your diet of a whole range of nutrients, one or two a day can actually be beneficial to heart health. Just steer clear of the floaters.
Rowena York ND, DBM, is a naturopath, herbalist and nutritionist with a practice on the mid-north coast of NSW. She conducts nutritional counselling and specialises in stress and anxiety related conditions as well as digestive disorders. Rowena can be contacted on 04312 38001
