Class A eggs (UK/UE)

Grade A eggs USA (Gallus gallus domesticus)
Natural food composed of albumen (protein solution) and yolk (lipid emulsion rich in phospholipids and carotenoids) enclosed in a calcareous shell. Grade A eggs are intended for direct consumption, not washed nor artificially refrigerated before retail; shell is stamped with the farm/country code and the best-before date appears on pack.

Caloric value (per 100 g and per medium egg)
• Whole raw egg: ~140–155 kcal/100 g; protein ~12–13 g; fat ~10–11 g; carbohydrates ~1 g.
• Medium egg (M, 53–60 g with shell): ~85–95 kcal (edible ~45–50 g).
• Albumen: ~45–55 kcal/100 g; protein ~10–11 g; fat ~0 g.
• Yolk: ~310–330 kcal/100 g; protein ~16–17 g; fat ~27–32 g.

Key constituents (whole egg, per 100 g)
• Water ~73 %.
• Proteins ~12–13 g; high biological value (ovalbumin, ovotransferrin, ovomucin, livetins).
• Lipids ~10–11 g; cholesterol ~370–400 mg (per M egg ~180–220 mg).
• Vitamins: A, D, E, K; B-group (B12, B2, B5, folate, biotin).
• Minerals: selenium, phosphorus, zinc, iron (higher in yolk); iodine varies with feed.
• Bioactives: choline (mainly phosphatidylcholine), lutein and zeaxanthin (yolk).
• Quality markers: Haugh Unit, yolk index, air-cell height, albumen pH (≈7.6 when fresh → rises with age).

Lipid profile (yolk fat fraction)
• SFA (saturated fat) ~31–36 % → palmitic (C16:0), stearic (C18:0).
• MUFA (monounsaturated fat) ~40–45 % → oleic (C18:1 n-9).
• PUFA (polyunsaturated fat) ~18–22 % total:
– n-6: linoleic (C18:2), arachidonic (C20:4) ~14–18 %.
– n-3: ALA (C18:3; precursor), EPA/DHA present at meaningful levels mainly in enriched eggs.
• Phospholipids: lecithins (phosphatidylcholine) ~28–32 % of yolk lipids.

Production process
• Collection & grading: on-farm collection → packing center; candling; grading by quality (A/B) and weight (S, M, L, XL).
• No industrial washing or pre-retail refrigeration for Grade A to preserve the shell cuticle.
• Marking & packaging: shell code, protective packs against shocks/light/odors.
• Quality control: shell integrity/cleanliness, low air cell, high Haugh Unit, absence of internal defects; full traceability under GMP/HACCP.

Classification and quality
• Grades: A (retail fresh), B (industry).
• Sizes: S, M, L, XL.
• Shell color: white/brown—no nutritional impact.
• “Extra fresh”: stricter freshness window (very small air cell) shortly after lay.

Technological properties
• Emulsifying (yolk/lecithins) → mayonnaise, sauces.
• Foaming (albumen proteins) → meringues, soufflés.
• Gelling/coagulating → custards, flans, pasta.
• Color & flavor → carotenoids/volatile compounds of the yolk.

Food uses
• Whole eggs: omelets, breading, baked goods.
• Albumen: light foams and high-protein products.
• Yolk: sauces/emulsions, fresh pasta, pastry.
• For raw or cold recipes use pasteurized egg products.

Food safety
• Main hazard: Salmonella (shell/content).
• Raw use (e.g., homemade mayonnaise, tiramisu): choose pasteurized eggs.
• Cooking: firm albumen and thickened yolk; for filled/combined foods reach ≥72 °C at core.
• Hygiene: prevent cross-contamination; wash hands/tools; do not wash shells at home (porous).

Storage and shelf-life
• Keep at 0–5 °C, pointed end down, in original carton; avoid temperature swings and strong odors.
• Best-before on pack. Hard-boiled eggs: refrigerate and consume within 3–7 days.
• Pasteurized products: follow label; egg powder stable if dry, cool, dark.
• Apply FIFO stock rotation.

Nutrition and health
• Protein quality: excellent; egg is a reference (high PDCAAS/DIAAS).
• Fats: presence of MUFA/PUFA supports a favorable lipid profile; SFA should be moderated.
• Cholesterol: consider clinical guidance in hypercholesterolemia; for most people, moderate intake fits a balanced diet.
• Choline and vitamin D are notable; lutein/zeaxanthin support visual function.

INCI functions (cosmetics)
• Typical entries: Hydrolyzed Egg Protein, Egg Yolk, Albumen, Lecithin (egg-derived).
• Roles: film-forming and hair conditioning, skin conditioning, emolliency and co-emulsifying (lecithin).

Sustainability and supply chain
• Farming system code (0/1/2/3) informs on husbandry and production method; conscious purchasing can drive the chain.
• Recyclable packaging and stable cool logistics reduce waste.
• Valorization of shells (calcium carbonate) and membranes; manage packing-center effluents with attention to BOD/COD.
• End-to-end GMP/HACCP helps minimize risk, loss, and environmental impact.

On the intake of chicken eggs as regards its impact on human health, in recent decades, there are conflicting views.

Doubts focus on the cholesterol content and its potential role in cardio-metabolic outcomes.

A whole or boiled chicken egg contains about 15 micrograms of selenium and in addition iron, Vitamin B2, B12, D, E

It also contains lutein, a carotenoid that can be protective against diseases such as age-related macular degeneration (1) and choline, a cellular and nervous restructurer and anti-inflammatory.(2)

Recent studies have also shown that the egg, due to its vitamin D content, helps protect the eyes from cataracts and other degenerative diseases due to ageing.

On the other hand, health recommendations indicate that dietary cholesterol should be limited to less than 200 mg per day; a single large egg yolk contains about 275 mg of cholesterol (3), so taking even a single egg increases LDL cholesterol.

 The consumption of whole egg in the middle-aged and elderly population has long been discussed in the scientific literature.  The impact on the cardiovascular system with possibility of disease has been under observation for several years. However, this study considers that the intake of whole egg does not affect the risk of cardiovascular disease (4).

This study, on the other hand, considers that a high consumption of eggs is significantly associated with a higher risk of contracting incidental cardiovascular diseases (5).

Mini-glossary
• SFA — Saturated fatty acids: limit excess; can raise LDL cholesterol.
• MUFA — Monounsaturated fatty acids (e.g., oleic): generally favorable/neutral for blood lipids.
• PUFA — Polyunsaturated fatty acids: include n-6 and n-3; beneficial when balanced.
• n-6 — Omega-6: essential; excess vs n-3 may promote pro-inflammatory balance.
• n-3 — Omega-3: supportive for cardiovascular and neural function.
• ALA — Alpha-linolenic acid (n-3): precursor to EPA/DHA; limited conversion.
• EPA — Eicosapentaenoic acid (n-3): cardiovascular/anti-inflammatory support.
• DHA — Docosahexaenoic acid (n-3): structural for brain and retina.
• TFA — Trans fatty acids: natural traces in animal foods; industrial TFAs should be avoided.
• PDCAAS — Protein Digestibility-Corrected Amino Acid Score: protein quality index (egg ≈ 1).
• DIAAS — Digestible Indispensable Amino Acid Score: modern protein quality metric (egg high).
• GMP — Good Manufacturing Practice: hygiene and process consistency standards.
• HACCP — Hazard Analysis and Critical Control Points: preventive food-safety system with defined CCP.
• BOD/COD — Biochemical/Chemical Oxygen Demand: indicators of effluent impact on water quality.
• FIFO — First In, First Out: stock rotation using older lots first.
• LDL — Low-density lipoprotein cholesterol: elevated levels increase CVD risk. 

Egg studies

References____________________________________________________________

(1) Chung HY, Rasmussen HM, Johnson EJ. Lutein bioavailability is higher from lutein-enriched eggs than from supplements and spinach in men. J Nutr. 2004 Aug;134(8):1887-93. 2004. 

Abstract. Lutein may be protective against diseases such as age-related macular degeneration (ARMD). At present, data regarding bioavailability of lutein from various sources are insufficient. Healthy men (n = 10) participated in an intervention study with a crossover design. After a 2-wk washout period during which they consumed a low-carotenoid diet, the men were administered 1 of 4 lutein doses (lutein supplement, lutein ester supplement, spinach, and lutein-enriched egg) for 9 d. All lutein doses provided 6 mg lutein except for the lutein ester dose, which provided 5.5 mg lutein equivalents. Serum samples were collected from fasting subjects on d -14, 1 (baseline), 2, 3, and 10 and analyzed for changes in lutein concentration. Triacylglycerol-rich lipoproteins (TRL) were separated from postprandial blood samples (0-24 h) after the first lutein dose and analyzed for lutein concentration. Subjects completed all 4 treatments of the study in random order. Results from repeated-measures 1-way ANOVA showed that the baseline and dose-adjusted lutein response in serum was significantly higher after egg consumption than after lutein, lutein ester, and spinach consumption on d 10. There was no significant difference in TRL response. In conclusion, the lutein bioavailability from egg is higher than that from other sources such as lutein, lutein ester supplements, and spinach. The lutein bioavailability from lutein, lutein ester supplements, and spinach did not differ. This finding may have implications for dietary recommendations that may decrease the risk of certain diseases, e.g., ARMD.

(2) Zeisel SH. Choline: critical role during fetal development and dietary requirements in adults. Annu Rev Nutr. 2006;26:229-50. 2006. 

Abstract. Choline is an essential nutrient needed for the structural integrity and signaling functions of cell membranes; for normal cholinergic neurotransmission; for normal muscle function; for lipid transport from liver; and it is the major source of methyl groups in the diet. Choline is critical during fetal development, when it influences stem cell proliferation and apoptosis, thereby altering brain and spinal cord structure and function and influencing risk for neural tube defects and lifelong memory function. Choline is derived not only from the diet, but from de novo synthesis as well. Though many foods contain choline, there is at least a twofold variation in dietary intake in humans. When deprived of dietary choline, most men and postmenopausal women developed signs of organ dysfunction (fatty liver or muscle damage), while less than half of premenopausal women developed such signs. Aside from gender differences, there is significant variation in the dietary requirement for choline that can be explained by very common genetic polymorphisms.

(3)  Spence JD, Jenkins DJ, Davignon J. Dietary cholesterol and egg yolks: not for patients at risk of vascular disease Can J Cardiol. 2010 Nov;26(9):e336-9. 

A widespread misconception has been developing among the Canadian public and among physicians. It is increasingly believed that consumption of dietary cholesterol and egg yolks is harmless. There are good reasons for long-standing recommendations that dietary cholesterol should be limited to less than 200 mg/day; a single large egg yolk contains approximately 275 mg of cholesterol (more than a day's worth of cholesterol). Although some studies showed no harm from consumption of eggs in healthy people, this outcome may have been due to lack of power to detect clinically relevant increases in a low-risk population. Moreover, the same studies showed that among participants who became diabetic during observation, consumption of one egg a day doubled their risk compared with less than one egg a week....

(4)   Wang MX, Wong CH, Kim JE. Impact of whole egg intake on blood pressure, lipids and lipoproteins in middle-aged and older population: A systematic review and meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis. 2019 Jul;29(7):653-664. doi: 10.1016/j.numecd.2019.04.004.

(5)  Zhong VW, Van Horn L, Cornelis MC, Wilkins JT, Ning H, Carnethon MR, Greenland P, Mentz RJ, Tucker KL, Zhao L, Norwood AF, Lloyd-Jones DM, Allen NB. Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality.  JAMA. 2019 Mar 19;321(11):1081-1095. doi: 10.1001/jama.2019.1572.

Abstract. Importance: Cholesterol is a common nutrient in the human diet and eggs are a major source of dietary cholesterol. Whether dietary cholesterol or egg consumption is associated with cardiovascular disease (CVD) and mortality remains controversial. Objective: To determine the associations of dietary cholesterol or egg consumption with incident CVD and all-cause mortality. Design, setting, and participants: Individual participant data were pooled from 6 prospective US cohorts using data collected between March 25, 1985, and August 31, 2016. Self-reported diet data were harmonized using a standardized protocol. Exposures: Dietary cholesterol (mg/day) or egg consumption (number/day). Main outcomes and measures: Hazard ratio (HR) and absolute risk difference (ARD) over the entire follow-up for incident CVD (composite of fatal and nonfatal coronary heart disease, stroke, heart failure, and other CVD deaths) and all-cause mortality, adjusting for demographic, socioeconomic, and behavioral factors. Results: This analysis included 29 615 participants (mean [SD] age, 51.6 [13.5] years at baseline) of whom 13 299 (44.9%) were men and 9204 (31.1%) were black. During a median follow-up of 17.5 years (interquartile range, 13.0-21.7; maximum, 31.3), there were 5400 incident CVD events and 6132 all-cause deaths. The associations of dietary cholesterol or egg consumption with incident CVD and all-cause mortality were monotonic (all P values for nonlinear terms, .19-.83). Each additional 300 mg of dietary cholesterol consumed per day was significantly associated with higher risk of incident CVD (adjusted HR, 1.17 [95% CI, 1.09-1.26]; adjusted ARD, 3.24% [95% CI, 1.39%-5.08%]) and all-cause mortality (adjusted HR, 1.18 [95% CI, 1.10-1.26]; adjusted ARD, 4.43% [95% CI, 2.51%-6.36%]). Each additional half an egg consumed per day was significantly associated with higher risk of incident CVD (adjusted HR, 1.06 [95% CI, 1.03-1.10]; adjusted ARD, 1.11% [95% CI, 0.32%-1.89%]) and all-cause mortality (adjusted HR, 1.08 [95% CI, 1.04-1.11]; adjusted ARD, 1.93% [95% CI, 1.10%-2.76%]). The associations between egg consumption and incident CVD (adjusted HR, 0.99 [95% CI, 0.93-1.05]; adjusted ARD, -0.47% [95% CI, -1.83% to 0.88%]) and all-cause mortality (adjusted HR, 1.03 [95% CI, 0.97-1.09]; adjusted ARD, 0.71% [95% CI, -0.85% to 2.28%]) were no longer significant after adjusting for dietary cholesterol consumption. Conclusions and relevance: Among US adults, higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner. These results should be considered in the development of dietary guidelines and updates.