The Truth about Cholesterol & Eggs

picture of hard boiled eggs, cut in half, looking like a heart
Figure 1: Contrary to popular belief, eggs (and the cholesterol they contain) are healthy and may promote cardiovascular health. Keep reading to learn more.

Historically, eggs have been given a bad reputation. Websites, new shows and even doctors spread the word that eggs (due to their cholesterol content) are bad and as a result, the cliché is known almost worldwide.

Eggs have been accused of many bad things, but I hope this article will prove to you eggs are safe. In fact, they are better than safe – they promote good health.

How Cholesterol was Linked to Heart Disease

Since the 1950s cardiovascular disease prevention has been a focus in Canada, the United States and the rest of the world. Cardiovascular disease contributes massively to mortality and morbidity rates, not to mention health care spending [1]. Research has focused on identifying causative factors, viable treatment options and disease prevention.  This is where eggs initially got lumped in to this discussion: people thought cholesterol caused atherosclerosis (a type of heart disease) and since eggs are good sources of cholesterol, eggs were suddenly deemed bad. However, as you’ll learn here, cholesterol doesn’t cause atherosclerosis.

It is true cholesterol is present in these atherosclerotic plaques, but its presence does not equate to causation. In fact, dietary sources of cholesterol, such as eggs, have been shown to be heart healthy when part of a well-balanced diet.

Cholesterol and Atherosclerotic Heart Disease

Atherosclerosis (clogged arteries) is rarely spoken about without mentioning cholesterol. People recognize this partnership, but oftentimes fail to understand the true relationship.  The initial ideas about fat and cholesterol

diagram showing healthy artery versus artery with atherosclerotic plaque.
Figure 2: Initially, people looked at the yellow gunk and found cholesterol inside, and attributed atherosclerosis to cholesterol. In reality, there are many contributing factors and several components to this atherosclerotic plaque.

causing atherosclerosis have been disproved. Early research focused on the cholesterol within the gunk rather than the whole disease process. Instead of looking at the gunk, we need to focus on everything else that put the gunk there in the first place. In all actuality, the plaques contain cholesterol along with: monocytes, smooth muscle cells, mast cells, foam cells, dendritic cells and dead cells [2]. These cells will produce cytokines, proteases, pro-thrombotic molecules, vasoactive substances – all of which affect plaque inflammation and vascular function [2].

My point is cholesterol is part of a bigger disease process, yet for decades we focused on the cholesterol. We need to think about the clotting factors, vascular spasms, heart rhythm, and viscosity of the blood, calcium deposition, inflammation and toxins [2]. It is true diet, and the foods you eat play important roles in all of these things, but cholesterol, by itself does not cause these disease processes.

There’s an interesting story about how cholesterol (and fat) got a bad reputation: believe it or not it includes shoddy research and university researchers being paid off. Click here to read how we ended up with the idea cholesterol and fat are bad.

Cholesterol is Actually Important

Functions of Cholesterol

Cholesterol serves many roles in our body and cannot be replaced. Here are just a few important roles of cholesterol:

  • Critical component of cell membranes (helps cell signaling, fluidity of cells, protection of cells)[3]
  • Precursor to all steroid hormones[3]: testosterone, progesterone, pregnenolone, estrogens (estrone & estradiol), aldosterone and more
  • Brain health: 25% of the body’s cholesterol is in the brain [4]. It covers nerve axons, contributes to brain maturation[5], plays a role in sleep [6], as well as learning and memory [4].
  • Precursor to vitamin D [3]

To learn more about cholesterol, including its usefulness and how it can be associated with disease, click here.

Cholesterol and Dietary Recommendations

Until recently, dietary recommendations around the world emphasized the importance of reducing cholesterol. In the past they went as far as providing an upper limit – a certain amount one must never exceed in a day. Organizations such as the American Heart Association and American College of Cardiology were making these recommendations without conclusive evidence [7]. The reason I bring up the American associations first is that these ones are recognized globally. Many nations follow their recommendations and a lot of media and general knowledge is picked up passively by the more outspoken American associations and news outlets.

After decades of the old guidelines, in 2015, new American guidelines were introduced. The emphasis for heart health shifted from avoiding cholesterol to limiting sugar intake [8]. The advisory panels stated “available evidence shows no appreciable relationship between consumption of dietary cholesterol and serum (blood) cholesterol. Cholesterol is not a nutrient of concern for overconsumption” [8].

Doctors had long assessed heart health on a cholesterol number, particularly LDL (what they deem to be ‘bad’ cholesterol). These new guidelines advise doctors to assess other factors and “physicians now have to shift their thinking away from only looking at cholesterol levels” [8]. For more information about interpreting cholesterol blood tests, please click here.

It should be noted, that Canadian guidelines recommended limiting cholesterol but never gave an upper limit. Beyond that, the general message was the same as the American Guidelines – cholesterol was always presented in a negative light and we were told to avoid it. Much of our ‘medical advice’ comes from American sources and media, so many Canadians had also adopted an ultralow low fat and low cholesterol diet [9].

Dietary Cholesterol

Two Sources of Cholesterol

The concentration of serum (blood) cholesterol is regulated by two sources of cholesterol. The first pathway is called the endogenous pathway; where cholesterol is made inside the liver and sent out into the blood (packaged in the molecules VLDL or LDL). The second pathway is the exogenous pathway; where cholesterol is obtained from dietary sources such as eggs [10]. Figure 3 simplifies this concept. As you can see, the majority of the circulating cholesterol from the blood is made in the liver, where the rest is obtained through diet.

picture depicting sources of cholesterol which include the liver and diet
Figure 3: The majority of blood (serum) cholesterol is coming from the liver. Dietary cholesterol accounts for some, but not as much as we were led to believe.

Dietary Cholesterol Does Not Need to Be Avoided

For years, we had been told to avoid high-cholesterol foods such as eggs for heart health, but this has since been disproven. A lot of evidence has accumulated over the past 2-3 decades which indicates dietary cholesterol is not a factor influencing blood cholesterol levels in the general population [11]. In other words, eating cholesterol usually doesn’t affect blood cholesterol. Although these findings weren’t reflected in nutrition guidelines for the longest time, finally, in 2015, a top nutrition advisory committee confirmed we no longer need to be concerned about high cholesterol foods. This advice has finally found its way into the current guidelines.

All the meta-analyses and carefully controlled studies reported since 1993 estimate that a decrease of 100 mg dietary cholesterol results in decrease of plasma cholesterol of 0.05 mmol/L [11]. On a population basis this change is relatively insignificant considering that it represents approximately 1% of the average population plasma cholesterol concentration [11].

If you’re confused about how we went from thinking cholesterol was bad to all of a sudden thinking its good – please click here to read about how those initial studies lead us down the wrong path.

So now hopefully you understand: Eating cholesterol is not dangerous. Let us focus on eggs specifically.

What’s in an Egg

Eggs are actually nutrient dense and rich in essential amino acids. It is true; eggs are one of the most cholesterol containing foods [12], but remember, cholesterol is not a bad thing itself.

picture of an egg cut in half, with information about minerals and vitamins found within
Figure 4: Eggs are a nutrient dense food. Their yolks are packed with a lot more than cholesterol.

Cholesterol

Eggs contain about 141 mg to 234 milligrams of cholesterol, depending on size [7]. The old US guidelines used to recommend limiting daily cholesterol to 300 mg per day [7] (now this upper limit has been removed). Since cholesterol is vital to health, our body will make as much as it needs. On average, we need about 1000 mg a day and the liver will make the difference. If you got 200 mg through diet, the liver would make about 800 mg [13].

Vitamins and Minerals

Fat soluble vitamins A, D, E and K as well as B vitamins (B1, B2, B3, B6 and B12) are found in whole eggs. Trace minerals such as calcium, iron, phosphorus, zinc, magnesium, copper, manganese, selenium, and potassium are also plentiful in eggs [7], [14].

As you’ll soon see, cholesterol itself can be considered heart healthy. In addition to cholesterol, eggs have other heart-healthy antioxidants such lutein and zeaxanthin which may protect against lipid peroxidation [7]. They are also one of the few natural food sources of choline, which has protective roles against both cardiovascular and liver disease [7].

Protein

Like many animal based products, eggs are considered a complete protein source. What makes a protein source complete is the presence of all nine essential amino acids at proportions required by humans. Eggs deliver about 6 grams of protein per egg, with almost half of that coming from the yolk.

Research on Eggs

Old, Outdated Research

Since the 1970’s eggs had always been associated with higher risk of cardiovascular disease. Those initial studies were based on observational studies [12], a research method from which causation is impossible. More scientifically sound research has shown there to be no causal effect of eggs in cardiovascular disease [12].

There are many specific patient populations, all of whom eggs have been studied specifically. It’s reaffirming to tell patients and doctors alike, that eggs have actually been researched on particular disease processes.

Below, I will mention terms such as LDL-C, HDL-C, total cholesterol, cholesterol ratios and other terms. Please click here to read about Lab Tests and how to interpret these numbers.

Egg Consumption in Healthy Individuals

Studies looking at healthy individuals showed 3 eggs a day didn’t affect blood cholesterol at all [7], [15]. The best news is, the eggs did improve HDL, increase plasma antioxidants, increased plasma choline levels and favored less atherogenic LDL particle profiles [7], [15]. All of these are good outcomes!

Egg Consumption in Individuals at High Risk for Cardiovascular Disease

This is determined by a combination of factors, including: hypertension, diabetes, dyslipidemia, age and family history.

One study looked at people with high risk of cardiovascular disease. Half the people were given 2 whole eggs a day, while the other half were given cholesterol-free egg substitute. The trial lasted only 1 month. The findings showed that eggs improved cholesterol profiles [7], whereas the cholesterol-free egg-substitute did not. Total cholesterol in the egg group did go up, but HDL went up and the LDL profile favored the less dangerous, large buoyant LDL particles [7]. Again, the egg group showed favorable outcomes.

Egg Consumption in Diabetics

A systematic review, looking at multiple studies on diabetic patients, those with prediabetes, insulin resistance or metabolic syndrome have found that egg consumption did not affect cardiovascular risk factors [16]. Studies have looked at consuming from 6-12 eggs per week and found no impact on plasma concentrations of total cholesterol, LDL, triglycerides, fasting glucose, insulin or c-reactive protein. To further show eggs’ importance in this population, 66% of the studies looked at showed an increase to HDL, showing its protective effects on heart health [16]. Nutrition advice for diabetics and anyone else with blood sugar dysregulation should encourage eggs, but they should be part of an otherwise healthy diet in the context of cardiovascular and diabetic health promotion.

Furthermore, egg consumption has no link to causing diabetes [17] or inducing blood sugar dysregulation in non-diabetic individuals. Studies have been done on overweight and obese patients and consuming 3 eggs a day for 12 weeks did not impair glucose metabolism [18]. The same is true for healthy, individuals – eggs do not negatively affect glucose or insulin concentrations [7].

Egg Consumption in Obese, Diabetic Individuals

Studies have looked at 3-egg breakfast versus bagel based breakfast in obese diabetics. The eggs proved to be advantageous in helping HDL-C and having no effect on the bad LDL-C [19]. This experiment was done in the context of a calorie restricted diet to promote weight loss. To further prove eggs efficacy, eggs also proved to enhance fat loss versus the bagel breakfast [19].

In another study, looking at how many eggs to eat, it was found that eating anywhere from 2-4 eggs a day increased HDL-C and had favorable effects on LDL-C. This study lasted 4 weeks [20].

Egg Consumption in Patients with Metabolic Syndrome

Metabolic syndrome is characterized by a combination of dyslipidemia, impaired endothelial function and vascular stiffening [7]. These patients typically have dyslipidemia, hypertension and diabetes and are known to have a high risk of cardiovascular events. These are the typical patients being told to avoid eggs at all costs. Well research shows otherwise.

In one study with 2 eggs a day for breakfast, it was found no negative effect on endothelial function (assessed by flow mediated dilation) in obese individuals with metabolic syndrome, proving to have no detriment to vascular health [21].

Another study provided 3 eggs a day and that proved to improved inflammatory markers (CRP, TNF-a). They compared it to cholesterol-free egg substitute – which had no such effect [7].

Eggs Consumption and Stroke Risk

Stroke is the 4th leading cause of death and is often associated with suboptimal diet. Although having too much cholesterol is a risk factor, a big study called NHANE-1 found that eating more than 6 eggs a week did not increase risk for stroke [22].

Egg Consumption and Overeating

In addition to the improvements in cholesterol profiles mentioned above, eggs have also been shown to help with satiety (the feeling of fullness) after a meal. Those having eggs for breakfast versus oatmeal showed improved satiety – meaning they were less likely to snack and overeat throughout the rest of the day [7], [23].

Controversies That Still Loom

TMAO

Trimethylamine N-oxide (TMAO) is an amino oxide that some research has linked to heart disease [24]. TMAO is produced by gut bacteria, when the bacteria metabolize dietary choline, betaine and carnitine. Foods rich in choline, betaine and carnitine are considered TMAO-producers [24] and some argue any foods containing these would lead to increased risk of heart disease. Eggs are in fact rich in choline.

The relationship between food and TMAO is still quite confusing. There is some research showing 2 eggs a day increases TMAO [7] and other research showing up to 3 eggs causes no change in TMAO levels [25]. Furthermore, fish is known to be the richest source TMAO and actually has protective effects against cardiovascular disease.

Take home message on TMAO is that it’s a complicated, poorly understood phenomenon. The gut plays a huge role and there are complex relationships between the gut and measuring bacterial metabolites. We have to consider the host genetics, host diet and other unknown factors [24].

For now there isn’t enough conclusive evidence to make judgements about TMAO [7], [24].

For more information on TMAO, please click here.

Hyper-Responders

As I mentioned above, most people experience little or no change in plasma (blood) cholesterol concentration from dietary cholesterol. In other words, most people eat eggs and nothing significantly changes in their cholesterol values [7].

Hyper-responders are the minority of people (about 20%) who do experience a change in plasma (blood) cholesterol. However, the increase tends to be both HDL and LDL lab values. This equates to the same cholesterol ratio. As you may know, the ratio between HDL and LDL is the most important predictor for heart health. For more information on the ratios and all the other lab values such as LDL cholesterol and HDL cholesterol please click here.

Take Away Message on Cholesterol and Eggs

Eggs can be part of a healthy diet. All of the studies I referenced in this article were done on humans, and prove eggs (and their cholesterol) are likely not a driving force behind cardiovascular disease.

Eggs can be safely eaten as part of a healthy diet – in healthy populations all the way down to those with atherosclerosis, hypertension and diabetes.

It’s true eggs increase dietary cholesterol, but has insignificant effect on serum (blood) cholesterol and cardiovascular events. Studies have shown up to 3 eggs a day to be beneficial to health, and this is a number I recommend to most patients who want to incorporate eggs back into their diet.

 

Works Cited

About the Author

picture of me, johann de chickera, naturopathic doctor

I'm Johann de Chickera, a Naturopathic Doctor, practicing in Ontario, Canada. My clinical practice relies on keeping up with the most up-to-date research and continued education. This blog serves as a way to provide others with a compilation of everything I've learned along the way. Please click here if you're local and want to see me in practice.