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Eggs have been the subject of debate in the nutrition world, having long been touted as the perfect food in some circles, and vilified by others for their cholesterol and fat content, as well as potential for allergy or contamination. Indeed, eggs could be considered a nutrition powerhouse with the wide array of nutrients they contain, but the research on their health impacts is also complex and confusing for consumers and health professionals alike.

Nutrients in Eggs

Nutritionally, eggs are an inexpensive source of high-quality proteins, unsaturated fat, cholesterol, and a spectrum of nutrients. In fact, eggs contain every vitamin except vitamin C, and those who eat two eggs per day can meet 10 to 30% of daily vitamin requirements, though the nutrient content of eggs depends on the diet fed to the hens. The white and yolk of the egg contain equal amounts of protein, but lipids and nutrients are concentrated in the yolk. The yolk of an egg serves as the primary source of nutrients for the growing embryo once fertilized, so it’s no wonder that the yolk contains a dense amount of nutritional value in a small package. Chicken egg proteins and their derived peptides, as well as lecithin from egg yolk, may have antioxidant properties as well. Lecithin – not to be confused with lectins – from egg yolk may also be neuroprotective and regulate blood lipids. Additionally, despite the popular belief that eggs are high in saturated fat, one large egg contains only 1.2 g saturated fat. To put it in perspective, one ounce of cheddar cheese contains about 5.5 g of saturated fat.

Eggs also contain tocopherols, folate, and carotenoids, such as lutein and zeaxanthin. Carotenoids in eggs yolks supply the yellow-orange hue. Eggs are also one of the best sources of choline, which supports cognitive development in infants during pregnancy, and they are a natural source of vitamin D, though some eggs are also fortified. A 2022 randomized controlled trial found that consuming just 7 eggs (extra-large, free range) per week for 12 weeks attenuated the decline in vitamin D in healthy adults without vitamin D deficiency during fall and winter months, whereas 12 eggs per week had no additional benefits. On the other hand, those consuming two eggs per week experienced a significant reduction in vitamin D concentrations.

While not commonly consumed, the eggshells are rich in calcium, and they can be dried, ground into a powder, and added to baked goods, smoothies, and spreads. Eggshells should be disinfected by boiling for 10 minutes before preparation. Eggs contain other minerals, including potassium, phosphorus, as well as all essential trace elements, including copper, iron, and zinc.

Health Benefits of Eggs

Cognitive Health. Though choline is well-known for its influence on cognitive development during pregnancy, a recent 2023 study found that choline from egg yolk improved cognitive function in healthy adults between the ages of 60 and 80 years. In this 12-week study, adults received either a supplement containing egg yolk choline (300 mg/day) or placebo (egg yolk supplement without choline). The choline group showed improved verbal memory, though other measures of cognitive function were not improved. Egg yolk is rich in phosphatidylcholine, which is a precursor to acetylcholine, a neurotransmitter that is believed to play a role in maintaining cognitive function.

Nonetheless, more evidence on the cognitive effects of consuming eggs is needed, as there are conflicting results. A 2022 study using data from the National Health and Nutrition Examination Survey (NHANES) did not find an association between egg consumption and cognitive function, whereas a 2021 study using data from the Biopsychosocial Religion and Health Study found consuming about 1 egg per week was associated with a slower memory decline in older adults. Along the same lines, a 6-year cohort study from 2023 found that egg consumption may be associated with a lower risk of depression in the elderly. Consuming eggs as part of a balanced diet may support cognitive and mental health in the aging population.

Macular degeneration. Lutein and zeaxanthin in the macula of the eye is linearly related to macular pigment optical density (MPOD), though it is often measured indirectly through xanthophyll. Increasing MPOD may help reduce the risk of age-related macular degeneration, which reduces vision in the aging population and makes it difficult to drive, read, and recognize faces. A 2021 meta-analysis found that daily egg consumption improved MPOD and serum lutein.

A 2020 population-based cohort study examined the association between egg consumption and age-related macular degeneration in 3,654 adults (ages 49 years and over) over 15 years. Results showed that those consuming 2-4 eggs per week had a reduced risk of late-stage age-related macular degeneration compared to those who consumed less than or equal to one egg per week. These individuals also reduced their risk of developing neovascular age-related macular degeneration by 62% compared to the same group.

Metabolic Health. Eggs may benefit some aspects of metabolic health. A 2023 study looked at the effects of egg consumption in healthy adults (ages 18-35 years). Participants consumed either no eggs, three egg whites per day, or three whole eggs per day in a randomized crossover design over a course of 16 weeks. The study found improvements in micronutrient intake, lutein and zeaxanthin intake, choline status, and HDL profiles with the consumption of whole eggs. Whole egg intake did not alter fasting glucose, high-sensitivity C-reactive protein (hs-CRP), or the liver enzymes ALT or AST. The results suggest that healthy individuals may benefit from consuming whole eggs.

A prospective study involving participants from the Framingham Offspring Study investigated the effect of egg consumption on cardiometabolic risk factors. Results showed that moderate egg intake may support healthy blood glucose levels and reduce the risk of impaired fasting glucose and type 2 diabetes.

A 2023 study found that egg consumption in overweight and obese teenagers was related to a decreased chance of being metabolically unhealthy, and the association appeared to be stronger in boys and overweight individuals rather than girls and obese individuals. Higher consumption of eggs was also associated with reduced risk of metabolic syndrome in a 2022 meta-analysis.

The evidence for the effect of egg consumption on cholesterol levels and cardiovascular disease risk is conflicting, and it is discussed in more detail below.

Health Concerns

Allergy. Eggs are one of the most common allergens in children with peak prevalence in children between the ages of 1 and 2 years. However, early egg consumption in infants may prevent allergy, and the allergy is often outgrown. Additionally, some egg proteins that are implicated in allergic reactions are denatured during cooking, and cooking eggs thoroughly may increase tolerance in some individuals. Importantly, children who are allergic to eggs may react to other common allergens like milk and peanuts. Egg allergies appearing in adulthood are rare and may be related to intestinal inflammatory disorders or changes in the intestinal microbiota. Nonetheless, allergic reactions to eggs can be dangerous, and anyone who suspects an allergy to eggs should seek help from a healthcare professional.

Raw Eggs. Eggs and egg products are two of the most implicated foods in cases of food poisoning caused by Salmonella. Several factors influence the presence of Salmonella in eggs, including the flock density, stress level of the hens, location of nesting boxes, and exposure to contaminated feces. Cooking eggs reduces the risk of foodborne illness caused by Salmonella. Pasteurization inactivates this pathogen and is required for any egg products (i.e., eggs outside of the shell) in the United States, but whole eggs do not have to be pasteurized.

Some concern may be over anti-nutritional factors of raw eggs. Egg whites contain proteins such as ovomucoid, which inhibits trypsin, and avidin, which can bind biotin. These compounds are primarily found in the egg white, are heat-sensitive, and usually destroyed when cooked.

For those using eggs to support muscle growth, a 2022 study found that consuming five raw eggs after exercise attenuated the rise in circulating essential amino acid concentrations compared to five boiled eggs, but the muscle protein synthesis rates did not differ between the two groups. Despite popular trends to eat raw eggs, eating cooked eggs is just as effective for muscle growth, tastes better, and has less risk for food poisoning.

Cholesterol. The effect of egg consumption on cholesterol levels and heart health has conflicting evidence. It’s further complicated by the fact that humans endogenously produce most of the cholesterol found in the body, and the mechanisms behind cholesterol homeostasis are not completely understood. It appears that cholesterol is under negative feedback control, in which genetics play a role in controlling cholesterol biosynthesis and metabolism.

Despite containing cholesterol, a 2023 review found that eggs have an overall small effect on cholesterol levels, and in healthy populations, they have no association or a modest beneficial association with cardiovascular disease risk. However, this same study concluded that high intakes of eggs may increase cardiovascular disease risk in those with diabetes. Similarly, a 2020 review reported that increased consumption of eggs by the general population is not associated with cardiovascular disease risk, but more evidence is needed to reach conclusions regarding how egg consumption impacts cardiovascular disease risk in those with diabetes. Additionally, according to the aforementioned study involving participants from the Framingham Offspring Study, moderate egg intake was associated with a significantly reduced risk of developing high blood pressure, though the study had several limitations including self-reported dietary intake.

On the other hand, a 2021 population-based cohort study involving more than 520,000 participants found that the consumption of whole eggs was associated with higher all-cause and cardiovascular disease mortality, which was reportedly largely influenced by cholesterol intake. Additionally, dietary cholesterol may increase risk of cancers like breast and pancreatic cancer. The authors suggest that using egg whites or cholesterol-free egg substitutes in place of whole eggs may improve health outcomes.

It is likely that egg consumption should be evaluated on a case-by-case basis, especially for those with pre-existing health conditions. Other sources of dietary cholesterol present in one’s diet, such as meat and full-fat dairy, should be considered as well. Those who follow a diet rich in plants and low in saturated fats may be able to safely consume more eggs.

Contamination. Animal feed, including soil and insects for free-range hens, are a source of dioxins and polychlorinated biphenyls (PCBs) that are ultimately transferred from the chicken to the egg. Consuming eggs from free-range hens may increase consumption of dioxins and PCBs if they forage in a contaminated environment, as opposed to hens that are kept in cages and therefore do not have access to a contaminated environment. Children and breastfeeding or pregnant women may be at increased risk of consuming unhealthy levels of toxins from eggs. Additionally, eggs may contain heavy metals like lead and chromium due to contaminated feed. Lead has also been found in eggs from backyard chickens, and owners should test their soil and remediate contaminated soil as needed. As with other toxins, children are particularly vulnerable to lead exposure. If consuming store-bought eggs, it may be ideal to alternate brands to reduce exposure to and accumulation of a particular toxin.

Choosing and Preparing Eggs

Diet, environment, and treatment of hens impact the nutritional contents of eggs. For example, hens that are allowed to forage produce eggs that contain more phytochemicals like tocopherols and carotenoids compared to those that are conventionally raised in cages. When hens have access to pasture and a biodiverse diet, they also tend to produce eggs with a more favorable fatty acid profile, including higher levels of omega-3 fatty acids.

Though eggs can be enriched with omega-3 fatty acids via the hens’ diet – for example, with flaxseeds – reactive oxygen species formed during long storage periods can result in lipid oxidation and reduce egg quality. Because of this, antioxidants may be added to the hens’ diet to maintain egg quality. The label “enriched” is not indicative of raising methods, and hens can be either conventionally cage-raised or exposed to outdoor environments.

Organic eggs are required to be cage free, and some research suggests this may confer a nutritional advantage compared to non-organic eggs because of their access to a biodiverse diet and less inflammatory feed. However, this certainly depends on the conditions of the environment as free range hens may be exposed to contaminated soil or infection by rodents and birds.

Options besides chicken eggs include quail and duck eggs, which are smaller and larger than chicken eggs, respectively. In general, duck eggs tend to have a higher proportion of lipids compared to chicken and quail eggs. Duck eggs also have a higher mineral and trace mineral content compared to chicken eggs. They are particularly rich in iron and contain about twice as much compared to chicken eggs per 100 g.

A variety of cooking methods can be used to prepare eggs. Fried eggs may have better antioxidant activity compared to eggs that are baked, steamed, or microwaved as they contain more fat, amino acids, and vitamins A and E. It is speculated that this may be due to the lower moisture content. However, fried eggs are also shown to contain higher levels of advanced glycation end products (AGEs) compared to eggs that are scrambled or poached. Therefore, it may be best practice to cook eggs over low to medium heat using non-toxic cookware. To give eggs a nutritious boost, scramble them with spices like garlic, black pepper, and turmeric. Consuming whole cooked eggs with carotenoid-rich and vitamin E-rich foods, such as a raw mixed-vegetable salad, has also been found to be an effective way to increase the absorption of carotenoids, α-tocopherol, and γ-tocopherol.

Final Remarks

Eggs can be a nutritious addition to someone’s diet. However, they may not be appropriate for everyone, especially if there is a pre-existing health condition or egg allergy. If you have questions about eggs and whether they are appropriate for you, talk to your doctor, nutritionist, dietician, or another healthcare team member for personal options based on your circumstances.