The Expert says
"Le Naturelle" reveal all the secrets of eggs with the collaboration of renowned experts:
Professor Nicolantonio D'Orazio
Professor of Nutrition and Human Diet at the Università degli Studi di Teramo, Faculty of Agriculture
Professor Antonello Paparella
Professor of Alimentary Microbiology at the Università degli Studi di Teramo
Is eating raw eggs a health hazard?
Like several other raw foods, raw eggs may be a source of pathogens, with possible effects on consumers' health. In particular, the well-known Salmonella spp. has, in Europe, a prevalence of 0.8% (EFSA, 2009). This micro-organism can contaminate eggs during or after laying, and in most cases remains on the outer surface of the shell. In a recent survey in Italy (Prencipe et al., 2010), 16.1% of the subjects interviewed consumed raw eggs, with a higher incidence in southern Italy, with eggs bought in bulk. From the point of view of hygiene and public health, it is not advisable to consume raw eggs, which may be highly dangerous for children, elderly people, and subjects with low immunity, in particular.
What's the best way to store fresh eggs?
The porous shell partially protects the egg from the external environment, but it can also allow the entry of undesired micro-organisms, in case of:
a) Dissolving or fracture of the outer cuticle that lines the shell;
b) Formation of condensation on the shell, increasing humidity locally, resulting in bacterial multiplication and their passage through the shell.
Both conditions can be favoured by variations in external temperature. For this reason, once purchased eggs should be stored in the fridge, at a constant temperature if possible. The most effective solution consists in keeping eggs in their original packaging, to be placed on the upper or central shelf of the fridge, away from prepared foods that are not suitably protected. In addition, it is a good idea to take out of the fridge only the eggs you need at any given time, to avoid the formation of condensation on eggs that are not used and are placed back in the fridge. In any case, avoid storing eggs at room temperature or on the door of your fridge, where they would be more exposed to temperature changes whenever the door is opened. These are not at odds with the commercial practice of selling eggs at room temperature or only slightly cooled: storing them like this means keeping them at a constant temperature, avoiding repeated entering and exiting refrigerated areas, which would result in condensation.
When does an egg expire?
European standards define 28 days as the maximum number of days an egg can be preserved, expressed as a minimum conservation deadline, indicated with a "best consumed by" label on the product. Throughout the European Union, category A table eggs must be removed from sales points 7 days before their minimum conservation deadline, i.e. 21 days after laying. The purpose of this is to provide consumers with at least 7 days of domestic conservation.
In a balanced diet, how many eggs should anyone eat in a week?
The issue of how many eggs a week should be determined by two assumptions: knowledge of cholesterol elaboration and of the quality of fats contained in eggs. Although the amount of cholesterol in an egg (about 240 mg) cannot be neglected, the amount introduced through diet, i.e. the so-called "exogenous cholesterol", represents only 20% of the total amount of cholesterol present in our bodies.
A 2007 study with 10,000 people (Regular egg consumption does not increase the risk of stroke and cardiovascular disease. - Atherosclerosis. 2013 March) has shown that a comparison between subjects who did not eat eggs and those that consumed about 6 eggs per week did not result in significant differences in terms of health.
What may make a difference when it comes to cardiovascular risk, in addition to an unhealthy lifestyle, is the constant ingestion of cholesterol and saturated fats, a particular category of fats contained, for instance, in butter and meat, which may amplify the risk of atherogenesis. The good news is that the saturated fats contained in eggs do not exceed 30% of their total fats. This means that the consumption of eggs by healthy subjects should not be demonised. The current recommended daily dose of cholesterol is 300 mg/day. In any case, subjects with hypercholesterolemia should eat only 2-3 eggs per week (EUFIC), keeping in mind that egg whites contain no cholesterol and can be consumed at will. It's important to keep in mind that there are several other hidden sources of cholesterol, such as creams and sweets.
How much fat does an individual need, on average, per day?
According to Reference Nutrient Consumption Levels (LARN, in Italian), defined in the autumn of 2012 by the Italian Society of Human Nutrition (SINU), the calories produced by the lipidic fraction of the diet should correspond to 20 to 30% of the overall daily calorie intake (35% in case of low-carb diets). This percentage may vary according to the presence or absence of pathologies. For instance, a healthy woman who consumes 1500 kcal per day should obtain 30% of these calories from fat, i.e.: 30% of 1500 kcal = 450 kcal.
How much protein does an individual need, on average, per day?
The new reference values for the daily ingestion of proteins per sample of population are:
- Adults and elderly people (both men and women): 0.9 g per kg of their body weight per day.
- Nursing babies, children and adolescents: between 0.9 and 1.32 g per kg of body weight per day, according to age and sex.
- Pregnant women: supplementary consumption of 1 g, 9 g and 29 g per day, respectively, in the first, second and third trimester.
- Breastfeeding women: supplementary consumption of 19 g per day in the first 6 months of breastfeeding and 13 g per day from then on.
For instance, a healthy 50-year-old man weighing 60 kg needs: 0.9 x 60 kg = 54 g of protein per day, ingested as food.
How much protein do eggs contain, when compared with meat (red or white), in grams?
A medium-sized egg, weighing about 60 g, contains approximately 7.4 g of protein, while fresh meats contain about 20 g protein per 100 g, therefore 12 g of protein per 60 g of meat. Eggs therefore contain half the amount of proteins contained in meat. Considering the excessive consumption of proteins in the Western world reported by numerous recent studies (the European Food Safety Authority, for instance, has estimated levels equivalent to 67-114 g per day for men and from 59 to 102 g for European women), and, in particular, the high biological value* (the topmost value when compared to all other foods) acknowledged for egg proteins, containing all the amino acids humans need, it becomes evident that eggs are precious food.
*The biological value of a protein is determined by the grams of protein formed in our body for every 100 g of protein ingested as food.
What's the healthiest/lightest way to prepare eggs?
Of course, the less fat is used to prepare them, the lighter the recipe, but soft-boiled eggs are the easiest to digest (1 hour and 45 minutes, while hard-boiled or fried eggs require 3 hours to be digested). Yolks are easier to digest when still runny, while whites should be well cooked due to an anti-nutritional factor, avidin, which binds to biotin (vitamin H). In addition, the albumin contained in eggs is only digestible when cooked at 70° C, which also protects other proteins from denaturation.
Which nutritional elements are contained in the yolk and the white?
The nutritional composition of eggs may vary according to the composition of what the chickens are fed, but in general eggs contain significant amounts of:
- vitamins: A, E, D, B group (B1, B2, PP, B12);
- minerals: magnesium, calcium, potassium, phosphorus, zinc and, in particular, iron;
- micro nutrients such as choline and methionine, amino acids indispensable for the metabolism of fats and for the formation of phospholipids, useful also for patients with liver conditions; anti-oxidants such as lutein and zeaxanthin, carotenes contained in the yolk and believed to reduce the risk of macular degeneration related to ageing.