Eggs, cholesterol, and health

In this Article (Index)

• About Cholesterol
• Dietary Cholesterol
• Eggs and Cholesterol
• Dietary Patterns Matter
• Japanese Diet and Eggs
• Chinese Diet and Eggs
• Cholesterol plus Saturated Fats is the real problem
• Are Eggs Bad For You?
• The TMAO controversy
• Adding Eggs to Your Healthy Diet
• Closing Comments

About Cholesterol

On our cholesterol page, we provide in-depth information on cholesterol and the important role it plays in the body and discuss the evidence that shows that dietary cholesterol shouldn't be taken isolated from the full array of health-damaging ingredients of the Western diet. Sugars, unhealthy fats, processed foods, lack of plant-based ingredients, and physical activity have a far more negative impact on cardiovascular health than dietary cholesterol.

Our cholesterol page also explains the different types of cholesterol, their sources, and cholesterol's link with cognitive decline.

A Brief introduction to cholesterol

Discovered in 1811, cholesterol is a waxy, fat-like compound that is used by the body to synthesize vitamin D and hormones; it also forms part of cell membranes.
Cholesterol is synthesized inside each nucleated cell in the human body, including the brain, and is transported through the blood to the liver for excretion through the gut as bile acid.

Cholesterol is also ingested with animal fats (plant-based foods do not contain cholesterol) and the body balances its internal (endogenous) production of cholesterol to compensate for higher intakes of external (exogenous) dietary cholesterol.

Cholesterol is transported by the blood as small ball-shaped particles called lipoproteins that have been classified according to their density into three types: Very Low-density lipoprotein (VLDL), Low-density lipoprotein (LDL) or "bad" cholesterol as it contributes to the buildup of fatty deposits, known as plaque, in arteries which can cause cardiovascular disease and death; and High-density lipoprotein (HDL) often called "good" cholesterol because they counteract the effects of LDL by promoting the transport of cholesterol to the liver for excretion. HDL also has antioxidant, anti-inflammatory, vasodilatory, and anti-blood clotting effects.

Dietary Cholesterol

The body absorbs cholesterol from certain foods such as animal fat found in meat, fish, dairy products, and eggs. Vegans and vegetarians have a much lower cholesterol intake than those eating a typical omnivore diet because plant-based foods do not contain cholesterol.
However, despite consuming 90% less cholesterol from food sources, their LDL cholesterol levels are only 13% lower than omnivores. This shows how the body maintains a balance of circulating cholesterol, compensating drops in dietary cholesterol with an increased output of endogenous cholesterol.

Eggs and Cholesterol

A boiled egg (50 g) is rich in protein (6.3 g) and low in carbohydrates (0.56 g) and though it also contains 1.6 g saturated fat, it is a good source of unsaturated fats with 2.0 g monounsaturated fat (MUFA), and 0.7 g polyunsaturated fat (PUFA). Moreover, eggs contain minerals like calcium, iron, magnesium, and phosphorus as well as vitamins. They are nutritious and accessible. (10).
Nevertheless, they have been criticized as a source of dietary cholesterol that increases the risk of cardiovascular disease (CVD).

The tenuous link between dietary cholesterol and cardiovascular disease

Dietary cholesterol has been, for many years, considered a risk factor for cardiovascular disease (CVD). The different dietary guidelines issued by the U.S. government have suggested consuming less than 300 mg per day of dietary cholesterol as a way to prevent heart disease.

However, recent research suggests that this association between CVD and cholesterol may be the result of faulty studies, and poorly designed trials.

Taking dietary cholesterol isolated from its context and placing the blame for CVD on it is a mistake. Research suggests that eating excessive quantities of saturated fat, with too much sugar, and sodium, and not eating enough plant-based fiber are factors that increase the risk of heart disease.

Taking this into consideration, the most recent U.S. Dietary Guidelines (2020-2025) have dropped the strict figure of 300 mg per day, and instead, recommend "that ... dietary cholesterol consumption to be as low as possible."

The American Heart Association has (2) also found that current scientific evidence does support a link between dietary cholesterol and cardiovascular disease, and it concluded that healthy dietary patterns like the Mediterranean diet and the DASH [Dietary Approaches to Stop Hypertension] are a better option to promote heart health. These diets rich in "fruits, vegetables, whole grains, low-fat or fat-free dairy products, lean protein sources, nuts, seeds, and liquid vegetable oils... [are] more likely to improve diet quality and to promote cardiovascular health."

As an example of this recent open-minded attitude towards eggs, the 2022 dietary guidelines issued by AESAN the Spanish Agency for Food Safety and Nutrition, recommend consuming a maximum of 4 medium eggs (53-63 grams each) per week.

Dietary Patterns Matter

Japanese Diet and Eggs

A Japanese study (1) pointed out that the typical Japanese diet is very different from the classic Western diet eaten in America. The Japanese eat more seafood, and vegetables, while Americans consume more beef and processed foods.

Eggs are a good source of protein, and this may have a protective effect on the heart. However, eating eggs increases blood cholesterol levels in both Japanese and Americans, but its impact on cardiovascular health is considerably different (worse in Americans).

This study suggests that "Japanese people may have an extra-reserve against the influence of eggs on cardiovascular risk markers, despite consuming relatively more eggs."

In Japan, eggs provide 50% of the cholesterol intake, with seafood as the second source (21%), and meat comes in third with 18%. In contrast, meat represents 37% of the cholesterol ingested by Americans, followed by eggs with 25%, milk provides 11% and the fats used in grain-based products add up to 18% (pasta, bread, pizza, breakfast cereals, cookies, and biscuits).
In Japan, milk has a 4% share, and grain-based products are less than 4%.

Egg white protein has been tested on humans showing that it decreases total cholesterol and LDL-cholesterol blood concentrations; egg phospholipids may also block cholesterol uptake.

The authors caution that "It seems more important to consider all foods consumed. Indeed, an optimal intake of whole grains, vegetables, fruits, nuts, legumes, dairy, fish, red and processed meat, eggs, and sugar-sweetened beverages showed an important lower risk of CHD, stroke, and heart failure."

The difference in the amounts and composition of nutrients and foods consumed between Japan and the US population may cause a difference in the mortality pattern. There appears to be no robust evidence to avoid egg consumption, as consuming at least one egg daily in Japan may not be similar to the US population. Sugano M, and Matsuoka R., (2020) (1)

Chinese Diet and Eggs

Data from 512,891 adult Chinese aged 30 to 79, and followed up for four years showed (12) that:

• Daily egg consumption had an 11% lower risk of cardiovascular disease compared to non-consumers. Reducing the risk of ischaemic heart disease, hemorrhagic stroke, ischaemic stroke, as well as major coronary events.
• Egg-eaters had an 18% lower risk of dying from CVD and a 28% lower risk of hemorrhagic stroke death compared to non-consumers.

The authors concluded that "Among Chinese adults, a moderate level of egg consumption (up to >1 egg/day) was significantly associated with lower risk of CVD." Interestingly, they pointed out that high-quality egg protein provides a better feeling of satiety, and lowers spikes in blood sugar, reducing the need for eating more food. Eggs contain carotenoids like lutein and zeaxanthin that are antioxidants and protect against inflammation and atherosclerosis. (12)

In another Chinese study, Wu et al. (2021)(3) studied the relationship between cholesterol intake from eggs and other sources and mortality among hypertensive patients. The study included 8,095 participants China Health and Nutrition Survey (CHNS) who were followed up for a mean of 11.4 years. The results were surprising:

• People who consumed more than 7 eggs per week had up to 29% lower mortality compared with patients who did not consume more than 2 eggs per week.
• Only egg cholesterol was inversely associated with mortality (more eggs eaten, lower mortality), as all other cholesterol sources (animal fats, butter, and cheese) had the opposite effect (more intake, higher mortality).

This study suggests that eggs have a protective effect due to their low saturated fatty acids content and high levels of choline, carotenoids, vitamins, and minerals. On the other hand, cholesterol found in other sources (dairy, red meat, pork, cheese) has a substantial amount of saturated fat besides cholesterol, and this may be the cause of the higher CVD risk.

People should not be too concerned about cholesterol consumption from egg yolks; at least, due to eggs as an economical and nutrient-rich food, consuming one egg per day is appropriate and beneficial for persons with hypertension. However, imposing a limit on the dietary cholesterol consumption from non-eggs such as red meat should keep forward. Wu et al. (2021)(3)

An Australian study on eggs

A randomized study conducted in Australia followed 128 subjects with type-2 diabetes or prediabetes for one year. They all followed a calory-restricted diet that replaced saturated fats for MUFA and PUFA monounsaturated and polyunsaturated fats, but one group consumed at least 12 eggs per week, eating 2 eggs for breakfast 6 days per week. The control group didn't eat eggs, instead, they consumed lean animal protein or low-fat dairy and legumes for breakfast.

The high-egg diet did not cause any negative outcomes regarding blood levels of HDL, LDL, total cholesterol, triglycerides, inflammatory and oxidative stress markers, or those linked to diabetes or prediabetes (fasting glucose, HbA1c, adiponectin, and 1,5AG).

Our findings suggest that a high-egg diet is safe for those with T2D—just as for the general population—without adverse consequences for cardiovascular risk factors... It is safe for persons at high risk of T2D and those with T2D to include eggs, an acceptable and convenient food source, in their diet regularly. Fuller, Nicholas R et al., (2018) (11)

Eggs may have a protective effect; the authors noticed that homocysteine concentration in the high-egg group participants was lower; homocysteine is a risk factor for CVD and they suggest that choline from the egg diet increased their betaine production, lowering homocysteine. Interestingly, participants were also instructed to replace foods containing saturated fats with foods containing monounsaturated and polyunsaturated fats to improve diet quality. This could also have exerted a beneficial effect on health markers.

Cholesterol plus Saturated Fats is the real problem

Soliman GA., (2018) (5) notes that cholesterol-rich foods are "also high in saturated fatty acids and thus may increase the risk of CVD due to the saturated fatty acid content. The exceptions are eggs and shrimp."

Soliman pinpoints high-cholesterol sources such as "beef (untrimmed and with marble), natural cheese, and butter [that] may increase the risk of CVD due to the saturated fatty acid content."

Are Eggs Bad For You?

There are many studies that suggest a negative effect of egg consumption on human health. This section describes some of them, but as you will see, the link is not strong.

Li MY, Chen JH, Chen C, and Kang YN., (2020) (10) reviewed 17 randomized trials investigating egg intake in healthy populations. They found that those consuming more eggs had a higher LDL cholesterol to HDL cholesterol ratio, and a higher level of LDL cholesterol, but it did not increase the HDL cholesterol levels. The authors pointed out that they could not identify which other foods accompanied the eggs in the trials they reviewed, acknowledging that different background diets may have influenced the results.

Darooghegi Mofrad et al., (2022) (9) reviewed 55 studies with data from over 2,772,000 subjects to investigate the association of eggs and mortality.

These included 27 studies with 1,153,367 participants; the Relative Risks from these studies "did not provide evidence for an association between egg consumption and all-cause mortality".

However, analysis of 28 studies showed that "each additional egg per day was associated with a 7% higher risk of all-cause mortality... one egg per day had no association with all-cause mortality, while the consumption of more than 1 egg per day (~1.5 eggs/day) was associated with an increase in all-cause mortality." Which sounds reasonable.

The data for eggs and CVD mortality, involved 16 cohort studies with 1,479,181 participants however, the authors did not find a link between eggs and CVD mortality.

They did find that an overall high cholesterol intake was associated with an all-cause death rate. Suggesting perhaps that other dietary sources of cholesterol may be to blame.

For cancer, those eating more eggs had a 13% higher risk of cancer mortality, however, they pointed out that "there was notable heterogeneity and the significant association [of egg intake with cancer] was not observed in several studies" and that "the intake of red meat and processed meat, known as rich sources of cholesterol, was positively associated with the risk of cancer mortality."

The TMAO controversy

Spence (2016) (8) concedes that "the US diet is so bad that in Americans, it is difficult to show harm from egg consumption... fewer than 10% of Americans eat a healthy diet."

Nevertheless, he supports the notion that eggs increase CVD risk; he points out that one large egg yolk contains 237 mg of cholesterol and that the phosphatidylcholine (lecithin) in egg yolk leads is converted by the microbes in the gut into trimethylamine (TMA) which the liver then oxidizes into trimethylamine n-oxide (TMAO); it is then transported to tissues or excreted into the urine. He points out that TMAO causes the buildup of plaque, or atherosclerosis, in mice.

TMAO and eggs

However, there are conflicting views on the role of TMAO and plaque as many factors have to be taken into account. It isn't a straightforward association.

The transformation of choline found in eggs into TMA depends on the type of gut microbiota (Firmicutes and Proteobacteria) in each individual, and to make things even more complex, these microbes are influenced by the type of diet that each person eats.

Vegans and vegetarians have been reported to have lower TMAO than meat eaters.

It is also possible that choline in its phospholipid form, as found in eggs, may not easily be transformed to TMA in the gut, in comparison to other free forms of choline. Phosphatidylcholine is mostly absorbed in the upper gastrointestinal tract leaving less choline available for the TMA-producing gut microbes, which are concentrated in the lower intestinal tract, who thrive on other forms of choline. (6)

Many processed foods also contain lecithin, which is added as an emulsifying agent in gravies, salad dressings, soups, mayonnaise, ice creams, and margarine just to mention a few.

Another factor to consider is that people with health issues (gastrointestinal, liver, gall bladder, and pancreatic diseases) may in fact produce higher levels of TMAO in response to egg consumption due to a failure to absorb the phosphatidylcholine in their small intestine leaving a greater availability for the TMA-producing gut microbes in the colon. (6)

Interestingly, eating red meat (but not white meat) increases TMAO which in this case is produced by the gut microbiome from L-carnitine, but not from the choline found in it. (7) suggesting that a "whole-diet" viewpoint should be taken into account, and not only a focus on eggs.

Studies have shown that " egg consumption is considered not to associate with plasma levels of TMAO, ... plasma TMAO concentration is more strongly affected by intraindividual variation, probably reflecting the difference in gut microbiota composition." (1)

Furthermore, TMAO is but one of many factors that can influence atherosclerosis and its complications.

Andersen CJ. et al., (2023) (4) conducted a 16-week random trial with different types of egg intakes and found that:

• Eating 3 whole eggs per day for 4 weeks increased serum choline and betaine without altering TMAO.
• Whole eggs also reduced blood markers associated with insulin resistance.

The intake of whole eggs improved the nutrient density of the diet in various aspects while additionally improving choline status, HDL profiles, blood amino acid profiles indicative of T2DM risk..., hematocrit, and platelet counts... these findings suggest that, in a young healthy population, whole egg intake confers mostly beneficial changes in global clinical profiles. Andersen CJ. et al., (2023) (4)

Adding Eggs to Your Healthy Diet

When thinking about eggs we usually evoke them as fried or scrambled, but there are healthier ways to add them to your balanced diet.

Poached on a slice of whole grain bread with a side of beans and grilled tomatoes (packed with lycopene).

Hard-boiled, sliced, topped with protein-rich Greek yogurt, chopped onion and celery, salad greens, and a dash of extra virgin Olive Oil.

Stir-fried (by cracking an egg into a hot wok) with kale, cabbage, and soybean sprouts. The fiber and plant-based antioxidants will combine well with the egg's carotenoids.

For animal welfare reasons, choose free-range chicken eggs.

Closing Comments

Over the past decade, research has shown that nutrients shouldn't be taken in isolation but considered in a holistic manner, as part of a diet, with many nutrients and ingredients interacting with a person. For over a century, the focus has been the opposite, where food was dissected into individual isolated compounds, some of which were subjected to intense research to identify the cause of a disease in one nutrient.

Saturated fats and cholesterol have all been subjected to nutritional reductionism and degraded, while fiber has been promoted and sugar (used to replace "evil" fats) has been ignored, perhaps due to an efficient industry lobby.

Only now is science looking into the Western diet, however, its message is still reductionist: "Eat less salt, and fat" instead of "Eat less ultra-processed foods."

In this context, this article shows that eggs, as a nutrient, are much more than cholesterol. Eggs contain proteins, minerals, and carotenoids and are a healthy nutrient in combination with a balanced diet that includes minimally processed foods, fresh vegetables, fruit, fish, poultry, legumes, olive oil, nuts, seeds, and whole grains.

Egg cholesterol may be problematic, but only if it is part of a typical Western diet, with sugary beverages, highly processed ingredients, refined sugars, and carbohydrates, beef, and hardly any fruits and vegetables. It is the Western diet with its ultra-processed foods that promotes gut dysbiosis, insulin resistance, weight gain, and obesity, and ultimately increases the risk of CVD and cancer.