Extraordinary Eggs: Shelling Out the Science

Extraordinary Eggs: Shelling Out the Science

Photo credit: Klaus Nielsen/Pexels

21 November 2023

The non-expiring nutritional benefits of eggs

Nutritional benefits of eggs across the lifespan

What makes eggs a “superfood”? In this Brain Food podcast episode, we invited Dr Lora Iannotti from the Brown School, Washington University in St. Louis, USA and Dr Nelly Zavaleta from the Nutritional Research Institute in Lima, Perú to explain the facts. We explored the egg’s nutritional aspects and myths about egg consumption, cholesterol, and allergies. We also scrambled the fascinating potential of eggs as a solution for tackling malnutrition in low- and middle-income countries (LMICs).

What are the key nutrients and potential health benefits of eggs?

Eggs have played an essential role in diets worldwide for centuries, recognized as one of the healthiest and most nutritious foods available on the planet, often described as “nature’s own multivitamin.” Eggs have a low energy-to-nutrient density ratio, with 78 kcal per medium egg, and contain a whole package of important nutrients (1) . Dr Lora highlights three of the many nutrients in this superfood.

Especially in the current environment, we need to speak to the evidence; what do we know (about the key nutrients in eggs) based on experimental studies and strong, rigorous evidence base.

- Dr Lora Iannotti

 

1. Choline. Choline is an essential nutrient for normal cellular function, cell membrane integrity, child growth, and development (2) . A study conducted in Malawi showed that young children with low serum choline concentrations are more likely to have linear growth failure (3) .


2. Docosahexaenoic acid (DHA). DHA is an omega-3 fatty acid, the primary long-chain fatty acid in the brain. It is essential for the growth and functional development of the brain in infants and improves learning ability (4) . In a study conducted in Malawi, consuming one egg per day improved the DHA status of children aged 12-59 months (5) . The study also highlighted the association between stunting and low serum omega-3 and omega-6 fatty acids (5) .


3. Amino acids. Eggs are a great source of high-quality protein, containing all the essential amino acids, and are recognized for their high biological value (6) . In fact, the egg is being held up as the perfect protein source and is even used as the gold standard against which other protein sources are compared (i.e. Digestible Indispensable Amino Acid Score, DIAAS). Studies have even revealed associations between stunted growth and deficiency in essential amino acids, pointing towards the potential of eggs to alleviate this form of malnutrition (7,8) .


In Figure 1, you will find more information on the broad range of vitamins and minerals present in eggs and their respective key function in the human body.

Figure 1 : Infographic showing key vitamins and minerals present in eggs

Worldwide egg consumption

The consumption of eggs varies widely. Hong Kong leads the list with 24.5 kg of eggs per year per capita (490 medium-sized eggs), and the United States consumes 15.9 kg per year per capita (9) . However, the consumption of eggs in LMICs is lower due to accessibility and affordability issues (10) . In India, the per capita egg consumption is 3.8 kg, although it varies largely by state, and in West, Central, and East Africa, the per capita egg consumption is even lower than 2 kg (40 medium-sized eggs) (9).

In very low-income settings, people have low consumption of eggs, whereas in high income, we have a very different scenario and high intake. What this comes down to is thinking about redistribution and making sure that vulnerable populations have access to not just eggs, but other animal source foods.

- Dr Lora Iannotti


Consumer perceptions and households’ income highly influence the adoption of eggs in population diets. For instance, it is well recognized that wealthy households have higher dietary diversity, shaping the quality and quantity of children’s diets. A recent UNICEF report demonstrated this when it revealed that children from the wealthiest households are more likely to consume nutritious foods like eggs (30%) compared to those in less affluent families (17%)(11).

 

What about egg consumption during pregnancy and lactation?

Eggs are a critical part of a healthy diet during pregnancy and lactation. Research has shown that they positively impact fetal development because of choline and a myriad of other nutrients(1). While choline during pregnancy is thought to be crucial for neonatal brain development (inadequate intake is associated with neural tube defects) (12), most prenatal vitamins contain little to no choline(13). Maternal consumption of eggs during lactation may also enhance the breastmilk composition of nutrients (thiamin, riboflavin, vitamin B12, and choline), thereby contributing to the nutrition and the development of the breastfed child(12).

 

Myths and cultural beliefs surrounding eggs

Can infants and young children safely eat eggs? Even though eggs are consumed worldwide and considered a nutritious and affordable high-quality source of protein, controversy is widespread. Some believe that introducing eggs in the early stages of life may create allergies, but what does science say about this endless question? Contrary to popular belief, studies have proven that the late introduction of eggs into children’s diets can increase the risk of egg allergy (14,15). In addition, some caregivers have even reported no allergic reactions while introducing eggs into the diets of older infants (6 to 9 months).

In Ecuador, we tested blood for an immunoglobulin IgE, which can indicate egg allergies, and we found very low levels in this population. Even the American Academy of Pediatrics is no longer contraindicating the introduction of eggs in young children; eggs might reduce the risk of allergy by introducing it early.

- Dr Lora Iannotti

 

By contrast, a study from Dr Lora Iannotti and colleagues provided 1 egg per day for 6 months to young children in Ecuador and showed a remarkable 47% reduction in stunting and a 74% decrease in underweight prevalence compared to the control group (15) . Children in the treatment group (1 egg per day) also exhibited healthier dietary habits and fewer sugar-sweetened foods than the control group (15) . This study, a component of the Lulun Project, led to a significant revision of infant feeding policies, culminating in the Ecuadorian Ministry of Public Health adopting new guidelines that advocate for the early introduction of eggs in complementary feeding practices (16) .

Cracking more egg myths:

Cholesterol

There have been a multitude of other misleading myths about eggs. The most contentious topic in the nutrition and eggs domain is cholesterol content! Of all the foods consumed globally, only the egg has ever been explicitly singled out with consumption limits to reduce cardiovascular disease risk.

The story began in 1968 when the American Heart Association announced a dietary recommendation that all individuals consume less than three whole eggs per week (1,17) and no more than 300 mg of dietary cholesterol per day. Eggs contained more than half of this daily intake and were quickly labeled as “unhealthy.” Despite this upper limit lacking a scientific rationale, it became conventional dogma in the nutrition and health community and the public at large.

This outdated misconception comes from the misunderstanding that the dietary cholesterol in eggs directly converts into serum cholesterol, thereby increasing cardiovascular disease (CVD) risk(18–20). Numerous rigorous studies have demonstrated that dietary cholesterol is not associated with an increased risk of heart disease(21,22) nor is egg consumption associated with an elevated risk of CVD(23,24). Eggs are, in fact, low in saturated fatty acid compared to other animal-source foods but are also nutrient-dense and affordable(25).

Cholesterol is a type of fat that plays an important role in the integrity of the cell membrane to protect cells, for the production of hormones, especially steroid hormones and for cardiovascular health. Evidence has shown that the benefit of egg consumption is due to its essential fatty acid content, DHA, which is also good for cardiovascular health. Nowadays, regular consumption of eggs has not proven any cardiovascular risk.

- Dr Nelly Zavaleta

Judging the egg nutrition by its shell color

A wide variety of chicken eggs can be found worldwide, exhibiting a diverse spectrum of shell colors ranging from light to dark brown, blue/green, white, and every shade in between. Some shells are smooth and glossy, and others are more textured. Where do these come from? The differences in eggshell colors depend on the breed and hen age and are a result of the pigments the hens produce (26,27) .

While people across the globe often express a taste preference for eggs from backyard chickens, the egg production method and eggshell color do not inherently impact an egg’s nutritional content and taste(26,27). However, variations in the nutritional composition of eggs are observable and are primarily linked to the diet and nutrition of the chicken itself(28). The feed can have a profound influence on the nutritional content of the eggs, particularly with regards to fatty acids and choline concentration(29–31)

These disparities in nutritional content, while present, are not significant enough to warrant a specific recommendation for one type of egg over another. Regardless of their origin or shell color, all eggs are nutritious and can offer substantial health benefits.

In general, eggs are a very good source of nutrients, independent of the color of the eggs. But the feed is very important: the nutrients in the egg are related to the feeding of the chicken, of course.

- Dr Nelly Zavaleta

Listen to the episode: Shelling Out the Science (Part 1 | Part 2) and stay tuned for our upcoming episode, where we will dive into a sustainable and innovative solution for egg production and consumption in LMIC; the Egg Hub model.

 

References:

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  3. Semba RD, Zhang P, Gonzalez-Freire M, Moaddel R, Trehan I, Maleta KM, et al. The association of serum choline with linear growth failure in young children from rural Malawi. The American Journal of Clinical Nutrition. 2016 Jul;104(1):191–7.
  4. Horrocks LA, Yeo YK. Health benefits of docosahexaenoic acid (DHA). Pharmacol Res. 1999 Sep;40(3):211–25.
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Mathilda Freymond

Nutrition Associate

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