Sruthy Ravi1, Kanmoni Goyari1, Jaydip Rokade1 and Avishek Biswas1
1ICAR-Central Avian Research Institute, Bareilly, UP.
Egg as conventional food contains major nutrients that plays fundamental roles in human health. Beyond basic nutritional role, their usefulness as functional food should be considered. Eggs are of particular interest from a functionality point of view, as it can be incorporated in many food preparations.
Also, it offers a moderate calorie source (about 150 kcal/100 g), excellent source of good quality protein, essential amino acids, vitamins and minerals, which make egg as exceptional food relished by most of the population. The great culinary versatility and low economic cost add to beneficial role of egg as functional food. Therefore, eggs can be a nutritious inclusion in the diet for people of all ages and at different stages of life.
In particular, in the diets of those at risk of low-nutrient intakes such as the elderly, pregnant women and children. Additionally, it must be mentioned that eggs can be consumed throughout the world, having no use restrictions on religious grounds.
The public are confused and cautious against frequent egg consumption due to its high cholesterol content and the potential association with cardiac problems. It has been based on the assumption that high dietary cholesterol consumption is associated with high blood cholesterol levels and cardiovascular disease (CVD). Afterwards, subsequent research suggests that, dietary cholesterol in general and cholesterol in eggs in particular have limited effects on the blood cholesterol level and on CVD.
The food born illness linked with egg and egg-derived foods on the other side, notify the harmful effects. It has been caused by many microorganisms, especially Salmonella and characterised gastro-intestinal problems. But many technological and nutritional advancements are there to tackle the problems like egg pasteurization, designer egg production etc.
Advantages of egg on health
Eggs are affordable, highly nutritious food contains almost all essential nutrients in a balanced proportion. The composition of which can be influenced by several factors including hen diet, age and strain, as well as environmental factors. On average, one egg contains about 6 g protein of good quality and high biological value contains nine essential amino acids needed for muscle growth, maintenance and recovery. For the people involved in sports training, egg proteins as component in diet, may have a profound effect due to enhanced skeletal muscles synthesis, since it has a good proportion of essential amino acids.
The third most common amino acid in egg, leucine induces a maximal skeletal muscle protein anabolic response in young people, which suggests that egg white protein intake might have an important effect on body mass accretion. Furthermore, eggs represent as a valuable in the diets for patients with gout, because does not add purines.
The egg yolk constitute around 33 percent of egg is a greatest source of vitamin D needed for bone development and immunity functioning. Similarly, Eggs contain wide range of vitamins and minerals including vitamin A, vitamin E, selenium and zinc which all act as important antioxidants in supporting eye health. It was also noticed that, the combination of vitamin B2, B12, choline, iron and tryptophan are all associated with reduce the risk of anxiety, symptoms of depression and naturally aiding sleep, and improves the overall mental health.
Apart from the nutritional benefits, it also exhibits antimicrobial property due to presence of lysozyme, ovomucoid, ovoinhibitor and cystatin in albumen. The Industrial production of these proteins have been well established to exploit these benefits. The easily digestible nature of egg makes it as irreplaceable component in the diet of old aged people. Additionally, being rich in choline content, egg take parts in normal cell functioning, brain and spinal cord development during pregnancy, cognitive development in infants and to reduce cognitive decline in the elderly.
The high levels of good cholesterol ‘high density lipoproteins in egg reduce risk of heart related problems. Besides, a good quantity of omega 3 fatty acids is also present, make the egg superior to other food sources. The scientific evidence suggests that, eggs contain biologically active compounds that may have a role in the therapy and prevention of chronic and infectious diseases. The presence of compounds with, immunomodulator, anti-cancer or anti-hypertensive properties have been also reported in eggs.
Undesirable effects of egg on health
Despite forementioned benefits, egg consumption has many adverse factors linked with human health and nutrition. These are:
The proteins such as ovomucoid with in albumen can inhibit trypsin and avidin, which can bind tightly with biotin and make the vitamin unavailable for the body. However, these factors are thermo-labile, usually destroyed by cooking process after which no further detrimental effects on health
Dietary cholesterol level
Several authors state that dietary cholesterol of eggs origin could be a significant risk factor for cardiometabolic diseases including CVD and diabetes. Furthermore, lecithin present in egg yolk is converted by intestinal bacteria to trimethylamine, which is in turn oxidized by the liver to trimethylamine oxide, which act as pro-atherosclerotic. Moreover, a recent review revealed no clear relation between egg consumption and CVD among diabetic individuals. In addition, positive association between egg consumption and the risk of CVD also reported recently. The controversial dietary guidelines regarding egg consumption may be due to inconsistent results from many epidemiological studies.
Microbiological status of egg
In addition to nutrition-related risks, egg consumption can also act as major threat to consumer due to the microbiological status of the egg. Salmonella Enteritidis and S. Typhimurium are the common causative organisms behind the food-borne illnesses associated with the consumption of eggs and egg products. The consumption of contaminated food products of egg origin is the main reason for the outbreak of human salmonellosis. Most of the food borne illness is characterised by gastrointestinal disturbances in human.
Presence of residues or contaminants
The presence of residues of veterinary drugs, as laying hens treated with pharmaceutical products can produce contaminated eggs and cause potential health hazards. The environmental toxic contaminants being fat soluble can be present in fatty foods such as eggs. The high levels of persistent organic pollutants or dioxins, that are usually present in free-range act as potential source of residues in organic eggs.
Egg allergies represent one of the most common IgE-mediated food allergies in infants and young children. It is second most food born allergy in infant after cow’s milk allergy. The five notified allergens in eggs white are ovomucoid, ovotransferrin, ovalbumin, lysozyme and albumin. Other minor allergens present in yolk are vitellenin (apovitellenin I) and apoprotein B (apovitellenin VI) but their role is still unclear. Heat processing of egg can destroy the allergens, and allow the consumption of eggs without sensitive reactions.
The predicted upward trend in egg consumption is widely acceptable over world. The recently reported health benefit along with previous nutritional benefit make the egg as wholesome food source for wide variety of people. The use of egg in functional food formulations increases constantly. The affordable price, easy handling and processing and storage facilities are the added advantages of eggs. Still, the undesirable aspects of egg must to considered and addressed to promote and protect human health. The control and preventive measures for such undesirable effects can be adopted by newer technologies and concept like designer. Consequently, it gives new pathways for egg producers and food industries to gain more profit, in addition improves the general health condition of public.