1. Introduction to Eggs and Their Nutritional Value

Eggs are widely consumed in various countries and cultures around the world, as they are obtained from birds and serve as a staple food for people. The egg, which is a highly nutritious food, is rich in essential amino acids and highly bioavailable nutrients such as vitamins and minerals. In addition, it gives a feeling of fullness and has a positive effect on appetite management. There are several methods for cooking eggs, for example: hard-boiled, over-easy, scrambled, boiled, and poached. Each of these cooking methods results in a different flavor and texture. Generally, eggs should be cooked before eating. Most people consume eggs by boiling, frying, or cooking them in different ways. It is necessary to examine the contents of eggs and their significance in the diet in detail. The main objective of this study is to explore the substances and vitamins contained in eggs that are primarily of interest to consumers but have not been widely discussed in the context of analyzing eggs in recent years.

The nutritional profile of an egg has a significant effect on its utilization in human nutrition. An egg contains carbohydrates, lipids, two vitamins, and a protein-rich yolk and albumen. In the egg, approximately one-fourth of the egg rests on the yolk. Due to different compositions of nutrients in the yolk and albumen, eggs are a good source of all the basic macro and micronutrients. It provides between 75 and 80% protein. Carbohydrates and fats, which are carbohydrates, make up more than 21% of eggs. This research aimed to measure the macronutrients and micronutrients in eggs. The various myths about eggs spread so much that people were unaware of the facts about eggs containing various macro and micronutrients. This analysis was expected to provide complete information about the nutrients found in eggs. We hope that consumers will be able to take advantage of this information as a source when they are concerned, and choices are made about which nutrients they should consume and which they should avoid.

2. Macronutrient Composition of Eggs

Eggs are a nutritious choice when included in a diet because of their balance of lean protein, healthy fat, and a variety of vitamins and minerals they contain for about 70 calories. Eggs are an excellent and inexpensive source of bioavailable proteins, which are essential to human health. Eggs are considered to be low in energy due to their high-quality protein and nutrient content. The average egg contains 5 g of fat, the majority of which is polyunsaturated and monounsaturated fatty acids. Eggs are a low-carbohydrate food that is a cheap and rich source of high-quality protein, essential vitamins, some essential minerals, and lipids. The absence of dietary fiber in eggs complements the dietary constituents classified as macronutrients: proteins, fats, and carbohydrates.

In human nutrition, proteins represent a considerable macronutrient, which plays a crucial role in building organs and muscles. In one large egg weighing approximately 57 g, the protein content is 6 g, accounting for approximately 13% of the egg. Because of the proportion of fat and carbohydrate content, eggs are valuable sources of protein. Eggs could be an important nutritional ingredient in a balanced diet, where dietary fat and cholesterol should be limited to prevent chronic diseases such as cardiovascular disease. Eggs are categorized as a nutrient-dense food for all age groups because they are functional to ingest nutrient-dense products in proportion to the total caloric intake to satisfy nutrient needs.

2.1. Protein Content

Protein content: Dietary protein is an essential nutrient for human beings, and one of the protein-rich foods is eggs. Apart from the rats, hens can lay eggs, and they are able to produce a lot of eggs. An average large egg contains 6.5 g of protein (the white contains about 3 g), and the protein contributes about 40% of the total nutrient content in an egg. Among all the food proteins, egg protein is considered the gold standard due to its high biological value. Besides this, eggs contain a complete amino acid composition, which the human body needs and cannot synthesize. Protein is important in supporting various vital functions in the body, such as repairing and growing muscle, assisting in enzymes, body defense, transporting oxygen, and regulating blood circulation.

Studies have shown that there are differences in the amino acid uptake rate caused by different processing methods and degrees of egg protein cross-linking, thus affecting the egg protein uptake rate and utilization rate. The heat used during cooking does not have an effect on the bioavailability of egg protein nutrition, but it will affect the digestibility and absorbability. In general, the nutritional composition can quantify the health-promoting components within the egg while also limiting individual component comparisons. If a dietary goal for protein is 10% energy, this would equate to approximately 0.8 g of protein per kilogram of body weight per day, or 56 g based on a 70 kg person. However, as egg protein is more bioavailable, it contributes 11 g of available protein to the daily total.

2.2. Fat Content

Humans are frequently concerned about the fat content of foods and choosy about the types of fats they eat. These fats come in two types: saturated fats and unsaturated fats. Unsaturated fats come in two subtypes, both of which are central to the nervous and endocrine systems, among other aspects, and are essential for health. Eggs, like most parts of the body, contain a mixture of the two types of fats. The cholesterol in egg yolks, together with the amount of fat in a single egg, has long been a reason why people are concerned about consuming eggs. It’s now known that dietary intake of cholesterol, especially the cholesterol in eggs, makes very little difference to blood cholesterol. Research shows that, with the possible exception of those with diabetes or metabolic syndrome, one yolk per day and up to three yolks per day do not negatively influence heart disease risk in the majority of individuals. Quite the opposite, in some cases, eating eggs may help.

While all fats have somewhere between 9 kcal/g, the potential health effects of different fats vary significantly. Fats in eggs, particularly polyunsaturated fats, are predominantly of the heart-healthy kind. Flaxseed and omega-3 enriched eggs have an even higher and healthier fat profile. This is largely attributed to the hens’ diets, which include high levels of flaxseeds year-round. The type of egg that is best for you will largely depend on how the eggs are used in the diet; however, the nutritional contribution will be minimal as long as the diet is balanced. The healthiest way to consume eggs is to select from those that have less than 1 g of saturated fat, 150 mg of cholesterol, and trans fat or more than 50 mg of omega-3 fatty acids.

2.3. Carbohydrate Content

Carbohydrates are notably low in eggs compared to the major macronutrients protein and fat. Since eggs contain a small fractional amount of carbohydrates and 1 g of carbohydrate yields 4 kilocalories (kcal), the carbohydrate contribution to the overall calorie content of eggs is negligible even when considering the slight overestimation of calorie content in raw eggs. There are 0.36 g of total carbohydrates per 50 g medium egg and 0.4 g per large 56 g egg. Of the 0.4 g of total carbohydrates in an egg, 0.4 g exist in the form of sugar. Although the sugar content is equally insignificant and contributes an extra 1.6 kcal (less than 1%) to the energy value of eggs relative to calories from protein, the amount of carbohydrates in eggs remains critical to define. Carbohydrates are an essential dietary component and would not be consumed at all if they were completely devoid in eggs.

Three types of carbohydrates are present in eggs, each contributing 0.4 kcal/g to 4.6% of the egg’s energy value. The most significant sugar in the egg is glucose, followed by cholesterol and galactose, each of which are directly available for absorption into the bloodstream and peripheral tissues. When a product contains less than 0.5 g of fat or sugar per serving, the value can be expressed as ‘0’ on the Nutrition Facts label. Thus, eggs can technically be labeled as ‘sugar-free’ or ‘fat-free’. Eggs could also be labeled ‘carbohydrate-free’ for containing a fractional amount of less than 0.5 g of carbohydrates, although current nutrition labeling guidelines dictate carbohydrate labeling to the nearest 1 g. Contrary to widespread belief, eggs actually do contain a very small and fractional amount of carbohydrates, fat, and sugar. Though carbohydrates are not typically associated with increasing energy levels or satiety compared with protein and fat, they still play a role in enhancing performance during high-intensity exercise. Athletes have falsely recommended against consuming eggs prior to sports events due to the negligible amounts of carbohydrates present, especially those on low carb diets.

3. Micronutrient Profile of Eggs

Eggs contain a wide variety of micronutrients, including vitamins and minerals, that fulfill a plethora of functions in the body, such as immune function, red blood cell synthesis, electrical signaling for muscle contraction, and maintaining the structural integrity of bones and teeth. Water-soluble vitamins are critical for maintaining health and are largely involved with metabolism. Eggs contain substantial amounts of some B vitamins. Particularly, eggs are abundant sources of vitamins B12, B2, B7, B5 and are categorized as good sources of vitamins B6, B9, and B1. The majority of the vitamins are present in the yolk of the egg, with B vitamins and fat-soluble vitamins residing within the lipid phase of the egg. One large egg contains 2 mcg of vitamin B12, which meets 83% of the dietary reference intake (DRI).

Eggs also contain many different minerals, including iron, zinc, phosphorus, potassium, sodium, magnesium, copper, and selenium. For every element, except for sodium, roughly 80% of the element in an egg is in the yolk. One large egg contains 83 mg of phosphorus, which meets 12% of the DRI for an average adult. Not all minerals are abundant in eggs, however. While several minerals are well represented in eggs, some are only marginal sources. A large egg contains 0.541 mcg of selenium, which meets 6% of the DRI for an average adult. It is also important to consider the bioavailability of these nutrients—micronutrients in eggs may not be absorbed as well as those from other foods. Micronutrient deficiencies also exist in developed countries, with an estimated 30% of the world population suffering from iron deficiency. Those most at risk of micronutrient deficiencies include lower-income populations who cannot afford fortified or nutrient-dense foods, and hospitalized patients who may have low appetite and/or who are unable to prepare meals due to illness or injury. Nutrient-dense eggs used in hospital feeds can promote quicker recovery times for patients and subsequently reduce hospital costs. For the above reasons, there is increasing interest in the production and subsequent human consumption of micronutrient-fortified eggs.

3.1. Vitamins

Eggs are a good source of fat-soluble vitamins, such as retinol and vitamin D. Vitamin A, in the form of retinol, is essential for vision, healthy skin, and a well-functioning immune system. Vitamin D is also crucial for health and well-being; it is vital for bone health, regulates the inflammation response, and may play a role in disease prevention. Fatty fish are the best food sources of vitamin D. They carry a different form than the vitamin D found in eggs but can still supplement the vitamin D found in eggs fairly well. Eggs are also one of the few food sources of vitamin D3. Eggs are rich in several B-group vitamins, some of which play substantial roles in energy metabolism. In particular, choline and vitamin B12 are found in meaningful amounts in eggs. The nutritional content of the choline found in eggs is especially well-studied and well-documented. Choline aids in liver function, brain development and function, and muscle movement. People’s susceptibility to developing a deficiency in these nutrients varies depending on the vitamin in question and on an individual’s overall diet, but some populations are at greater risk. In any event, regular egg consumption can significantly contribute to the human body’s ability to maintain necessary amounts of these nutrients. Uncooked egg white is different in its vitamin content than pasteurized and cooked egg white. Some of that difference comes from the stability and bioavailability in the body of vitamins in egg white before and after pasteurization and cooking. In any case, beyond the direct comparisons that can be made between raw and cooked eggs for preference and performance. In addition to being a very rich source of choline, eggs contain some of the vitamin A precursor, lutein, in a form that is well-absorbed and used by the body. Eggs are a good source of retinol, which the body uses directly, and some of the water-soluble B vitamins, although unsupplemented eggs are not a substantial source of these vitamins alone in a well-balanced diet.

3.2. Minerals

3.2. Mineral

An egg is a good source of essential minerals. Among the minerals, eggs are a good source of calcium and iron. Before moving on to detailed discussions of particular minerals, there is a report on the mineral content of typical eggs reported at 88% moisture. Chicken eggs contain between 0.68 and 1.43 mg of iron per 100 g of eggs or 2.5 to 5.2 mg of calcium per 100 g of eggs. Although the mineral profiles of 100 g of eggs and some other sources are very similar, these functional components are not typically exchanged for one another. For example, 100 g of green beans contains 2 mg of calcium and 1.03 mg of iron, and the mineral bioavailability of green beans is naturally low because it is a plant-based non-heme source of iron and contains high levels of phytates, tannins, and polyphenolic compounds that inhibit mineral absorption.

In contrast, the mineral bioavailability of eggs is relatively high. Calcium content is not typically used as a reason to consume eggs, and pregnant women are encouraged to pursue calcium-rich pregnancy diets. Nonetheless, it is interesting to note that one egg contains 0.004 g of calcium. Embryos produced in one of two different production systems, and maternal calcium-to-phosphorus diet ratios are associated with increased zinc content relative to eggs with low maternal calcium-to-phosphorus diet ratios. Other essential minerals can be commercially added to laying hen diets to fortify eggs, including selenium, phosphorus, iodine, zinc, and copper.

4. Health Benefits of Consuming Eggs

Eggs are popular, delicious, and versatile foods that can promote health and well-being by providing essential nutrition. The high-quality protein in eggs can aid weight management and enhance muscle strength and function. Eating eggs has a positive impact on satiety. On account of their nutrient profile, eating eggs is especially beneficial to the brain. This is because eggs contain a variety of vitamins and minerals that are involved in mental health. Specifically, eggs are a good source of choline, which is a nutrient needed for brain health. Consuming enough choline can support the memory and attention of older adults. In addition, eating eggs might help to protect the eyes in older adults. This is because eggs contain two powerful antioxidants called lutein and zeaxanthin. These antioxidants can protect the eyes from the damage caused by ultraviolet light and also play a role in reducing the risk of cataracts and macular degeneration. Additionally, eating one egg a day is not associated with an increased risk of heart disease in the majority of people. The exceptions are patients diagnosed with type 2 diabetes. Otherwise, heart-healthy adults can eat an egg a day to meet their nutritional needs without increasing their risk of death from any cause or stroke. Importantly, the nutritional recommendations for athletes and older adults include eggs as highly nutritious and essential foods. Although eggs are very healthy, they should be consumed as part of a healthy eating plan that supports good health. Half a dozen eggs a week is one healthy option, providing essential nutrition for a good and diverse diet.

5. Conclusion and Implications for Dietary Recommendations

The present analytical study has shown that eggs, although high in fat and cholesterol, are highly nutritious, providing several important nutrients, including vitamin D and iodine, which are often difficult to source from other foods. Nevertheless, several of the included studies showed inconsistent findings related to egg consumption and blood lipid concentrations. Further, the chronic effects of egg consumption on several other non-communicable diseases have not been adequately studied, meaning that an egg diet will likely not be suitable for everyone across the whole lifespan. Rather, an emphasis on overall dietary diversity and following national and international dietary guidelines is likely to be the most viable option as it pertains to egg intake. Although background dietary intakes of carbohydrates, fats, and proteins are important to consider, the influence of these factors on the health outcomes included in this review was not addressed. This review suggests that national and international dietary guidelines should consider promoting overall dietary patterns and foods that are high in certain nutrients. Eggs could, therefore, be included in the diets of people who are reasonably healthy and have low or normal LDL cholesterol concentrations as part of a nutritious diet that emphasizes whole grains, vegetables, and fruits, among other foods. Future research should continue to assess the potential health benefits and risks of eggs and recommend different intakes of eggs according to pregnancy, age, or lipid levels. Public health policies and guidelines should make it very clear that there is no need to avoid eggs in the diet.