Some people hate on eggs due to their high cholesterol and polyunsaturated fatty acid (PUFA) content.
Certain individuals think that PUFAs, specifically linoleic acid, are the cause of the obesity epidemic. I agree with the research that seed and nut oil consumption has sky-rocketed in the last 50 years and that it correlates near perfectly with obesity, metabolic syndrome, etc.
However, they then demonize all foods that contain a fair amount of linoleic acid, such as eggs.
In this article, I want to talk about eggs and their effect on cholesterol, obesity, diabetes, metabolic syndrome, satiety, gut health, etc.
Does consuming eggs have the same side effects as eating highly refined foods soaked in seed and nut oils?
The answer is no and here’s why.
Cholesterol & cardiovascular health
Eggs are the second richest dietary source of cholesterol, with the brain being the highest. However, very few people eat brains, so that makes eggs the most commonly consumed source of cholesterol.
50 years ago cholesterol has been demonized and therefore people have been told to avoid high cholesterol foods and limit egg consumption to no more than 1 per day or even 1 per week.
Why is cholesterol bad?
Because people think that it causes inflammation, causes arterial plague, cardiovascular disease, hypertension, etc.
Eggs and hypertension
It does so by inhibiting ACE. Angiotensin II, produced from angiotensin I by ACE, plays a role in hypertension and insulin resistance by producing reactive oxygen species (ROS), promoting inflammation, vascular stiffness, fibrosis, etc.
Common blood pressure medication inhibits ACE and lowers blood pressure and improves insulin sensitivity.
Eggs and cholesterol
People want to avoid cholesterol because they don’t want to increase their own cholesterol since cholesterol has been demonized.
Within total cholesterol, there are many kinds of lipid particles. Most commonly you have HDL and LDL. On top of that, you also want to look at triglycerides, lp(a), particle number and size, etc.
Total cholesterol is not a good measure for much. You want to look more into the details. Total cholesterol is usually just a sign of a hypo-functioning thyroid and insulin resistance.
“Efficiency of cholesterol absorption additionally seems to vary across human populations, with individuals who are insulin-resistant absorbing less cholesterol then insulin-sensitive counterparts [56,57], regardless of body weight status . However, obese and insulin resistant subjects exhibit increased rates of endogenous cholesterol synthesis, contributing to hypercholesterolemia commonly observed in these populations [56,57,58].” (R)
Let’s talk about HDL and LDL.
Egg consumption increases HDL and LDL equally, thus not altering the ratio. Plus, dietary cholesterol leads to the formation of the large LDL particles that are known to be less atherogenic and reduces the concentration of small LDL, which has been recognized as a highly atherogenic particle for its ability to become oxidized, penetrate the arterial wall and initiate the atherosclerosis process (R).
Additionally, regular egg yolk consumption has been shown to increase plasma HDL-C and increase the mean size of HDL particles in healthy, overweight, and metabolic syndrome populations (R).
Apolipoprotein A-I is the main apolipoprotein of HDL and has strong antioxidant and anti-inflammatory effects. It also aids in the elimination of oxidized lipids thus reducing the production of oxidized LDL (R).
All in all good. It doesn’t change the HDL to LDL ratio and it alters the shape of the LDL molecule, making it less of a problem.
Last but not least, egg consumption, despite containing PUFA, inhibits lipid peroxidation, thus lowering inflammation and atherogenic potential. Lp(a) is a good marker for oxidized cholesterol. If you want to see if eggs are a problem for you, test your lp(a) when you don’t consume eggs, then add 6 eggs to your diet daily for example, and then after 1-2 months, recheck your lp(a) as well as other markers such as fasting glucose, fasting insulin, HOMA-IR, HbA1c, hsCRP, homocysteine, etc, to see if it’s a problem for you.
In summary, egg consumption leads to larger particles and less lipid peroxidation as well as better clearance of oxidized LDL. Conclusion: regular egg consumption doesn’t cause cardiovascular disease and is actually advantageous.
Here is an interesting case study where a 88 year old man consumed 25 eggs daily for roughly 15 years (about 4500 mg cholesterol/day) and had no heart problems and normal plasma cholesterol levels (R).
The body is very good at finding equilibrium. The more cholesterol you eat, the more your body will reduce cholesterol absorption and production and enhance cholesterol excretion.
Eggs & inflammation
Two main reasons why people might think that eggs are inflammatory: cholesterol & PUFA.
I just showed above that cholesterol from eggs is not a problem. The same thing with the PUFA. Eggs are rich in antioxidants, so even though eggs are richer in PUFA than milk or meat, it’s not a problem. If perhaps eggs were refined and made into an oil, it might start to be a problem in large amounts. But when consumed as a whole food, it’s not a problem.
According to this 2020 meta-analysis, egg consumption did not affect hs-CRP, IL-6, and TNF-α (markers of inflammation). “Overall, this meta-analysis revealed that egg consumption had no significant effect on serum biomarkers of inflammation in adults.” (R). Egg consumption in most of the studies in the meta-analysis was around 1-3 eggs per day.
These studies found that:
- Adding eggs to a carbohydrate-restricted diet decreased plasma CRP and increased plasma adiponectin compared to a carbohydrate-restricted diet without eggs (R).
- Consuming three eggs per day for 12 weeks resulted in a reduction in plasma CRP and an increase in adiponectin in overweight men; changes which were not observed with yolk-free egg substitute (R).
- Egg consumption improves circulating plasma inflammatory markers in adults with metabolic syndrome, such as TNF-α and serum amyloid A (R).
- 2 eggs daily added to a plant-based diet lowered malondialdehyde (MDA), which is a marker of lipid peroxidation (R).
Choline and inflammation
Eggs and liver are the richest sources of choline.
Choline isn’t just necessary for neurotransmitter synthesis and brain health, but also for the transportation of fat out of the liver (protecting against fatty liver) and lowering inflammation (R).
“Dietary choline intake has been shown to be inversely associated with serum inflammation markers in healthy adults.” (R)
Eggs and gut inflammation
You might have heard of the gut-brain axis. By now there is a gut-everything else axis. Meaning, the gut-skin axis, gut-liver axis, gut-thyroid axis, etc.
Inflammation in the gut contributes to diabetes, cardiovascular syndrome, hypertension, etc.
Long-term oxidative stress in the gastrointestinal tract can lead to chronic intestinal disorders (and other health disorders). Food anti-oxidants, such as those found in eggs, can have protective effects. Eggs contain many antioxidant compounds, such as vitamins, carotenoids, minerals, and trace elements as well as major egg-white proteins such as ovotransferrin, ovomucoid and ovomucin hydrolysates and derived peptides, and egg yolk-proteins including phosvitin (R).
Other powerful compounds in eggs that can help to reduce gut inflammation include:
- Lysozyme. “In a colitis porcine model, lysozyme was demonstrated to significantly protect animals from colitis and reduce the local expression of pro-inflammatory cytokines while increasing the expression of the anti-inflammatory mediators .” (R)
- Egg-white pleiotrophin, play a pivotal role in the generation and resolution of inflammatory responses. (R)
- Choline administration to mice has been shown to significantly reduce plasma TNFα and enhance survival in response to an endotoxin challenge (R). Choline seems to act through nicotinic acetylcholine receptor subunit α7 (α7nAChR) activation, which has a tonic inhibitory effect on immune cell inflammatory responses.
- Immunoglobulin Y (IgY) – immunoglobulin Y (IgY) in medicine has additionally shown promising results in promoting passive immunity against a variety of pathogens in the treatment of conditions such as colitis, influenza, and infection of Clostridium botulinum, Staphylococcus aureus, Candida albicans, and Helicobacter pylori (R).
- Phosphatidylcholine – Individuals with ulcerative colitis have lower levels of phosphatidylcholine in the gastrointestinal mucus layer, and supplementation of phosphatidylcholine has positive clinical outcomes, by lowering inflammation and protecting against endotoxins (R).
- Egg yolk peptide treatment increased GSH and gamma-glutamylcysteine synthetase mRNA expression and activity, significantly increased antioxidant enzyme activities, in particular catalase and glutathione S-transferase activities, and reduced protein and lipid oxidation in the duodenum, jejunum, ileum, and colon (R).
- Egg antimicrobials in edible parts are essentially concentrated in egg white and the vitelline membrane. Depending on the protein considered, these antimicrobials may exhibit antibacterial, antiviral, antifungal, or antiparasitic activities (R).
Eggs and TMAO
The supposed increase in TMAO from food is a big concern for certain people since fasting plasma concentration of TMAO has been shown to be a risk factor for cardiovascular disease.
TMAO is produced when someone eats choline or carnitine, which is then converted to TMA in the gut, and then transformed to TMAO in the liver.
However, studies have not shown a consistent link between the dietary intake of eggs and long-term fasting TMAO concentrations. Egg consumption might increase TMAO acutely, but not chronically. A similar example is uric acid. Acute increases in uric acid are good, but chronically elevated uric acid (in the presence of insulin resistance and inflammation) might cause gout and other problems (article on this).
Controlled intervention studies feeding 2-3 eggs per day have not shown increases in TMAO concentrations on average (R). In comparison, people who eat more fish have on average higher TMAO than people who consume less fish and more eggs. And fish is not associated with CVD. So why is the increase in TMAO from eggs a problem, if it’s not from fish? It isn’t.
Blood sugar control and egg consumption
Insulin resistance is another risk factor for cardiovascular disease.
Eggs have been shown to improve insulin sensitivity through a variety of mechanisms, such as:
- Inhibition of α-glucosidase, an enzyme that breaks down carbohydrates, thus reducing glucose absorption. Maybe anti-diabetic drugs work through the same mechanism. The peptide KLPGF is the most potent one, which was shown to have comparable potency as acarbose (R).
- Inhibition of DPP-4, which degrades incretin hormones such as glucagon-like peptide 1 (GLP-1). GLP-1 has anti-diabetic effects by promoting insulin secretion from pancreatic β-cells, preserving β-cell proliferation and regeneration, and inhibiting glucagon production (R, R).
In a study that involved 2394 adults from Newfoundland, the dietary choline intake was negatively associated with blood concentrations of fasting glucose and insulin and HOMA-IR with age, total calorie intake, and physical activity level being controlled (R).
According to this study, 3 eggs per day has been shown to improve insulin sensitivity in individuals with metabolic syndrome (R).
Other benefits of egg consumption
- Increase muscle strength (R) and potentially muscle growth as well since it contains several nonprotein nutrients that could possess anabolic properties (e.g., microRNAs, vitamins (vit A (R) and D (R)), minerals (zinc), lipids (palmitic acid stimulate mTOR (R)), phosphatidic acid and other phospholipids.
- Increase testosterone. This study found that consuming 3 whole eggs (compared to consuming 6 egg whites) for 12 weeks increased testosterone by 240ng/dl vs 70 in the egg white group (R).
- Protect against oxidative stress in the brain, eyes, skin, liver, testes and fat tissue by providing powerful anti-oxidants, such as lutein and zeaxanthin (R).
- Prevent the drop (or at least a significant drop) in vit D during wintertime (R).
- Provide lots of nutrients. Just 2 eggs daily provide 10% to 30% of the vitamin requirements for humans (R).
- Optimize muscle function. Acetylcholine is necessary for muscle firing and movement.
- Optimize neural and cellular health. The phospholipids phosphatidylcholine and sphingomyelin, the forms of choline mostly present in the body, are integral to the structural integrity of cell membranes and are required for myelin sheets.
- Total choline intake at 187.06-399.50 mg/day reduces the risk of low cognitive function by approximately 50% compared to intake at <187.6 mg/day. (R)
- This prospective study suggests that egg consumption is associated with a reduced risk of dementia, and specifically Alzheimer’s disease (R).
- Choline helps to keep the liver lean. In humans, a single-nucleotide polymorphism in the PC-synthesizing enzyme, phosphatidylethanolamine N-methyltransferase (PEMT), is associated with a greater risk for non-alcoholic fatty liver disease (NAFLD) (R).
- Choline is necessary for bile acid formation. Low choline intake can lead to bile stones.
- Promote satiety. Eggs at breakfast results in lower ghrelin and better satiety (R).
- Reduce mortality. “consuming more than seven eggs per week was related to 29% lower mortality among the hypertensive patients compared with the consumers with not more than two eggs per week [hazard ratio (HR): 0.71; 95% CI: 0.59-0.85; P < 0.001]. Similarly, the egg-sourced cholesterol intake was inversely associated with mortality.” (R)
Best ways to have eggs
2 things of importance here.
Heat treatment of the eggs (cooking) oxidizes some of the anti-oxidants, free aromatic amino acids, PUFA and cholesterol. However, the amount being oxidized is small (around 1-2%) and doesn’t change the benefits of the egg (R, R, R).
Secondly, storing the egg also enhances the oxidation of lipids and cholesterol (R). Getting fresh eggs would be best. However, if you can’t get eggs straight from the cloaca (the hole that does it all), then don’t sweat it. Don’t make perfect the enemy of good.
All of the studies mentioned above used non-organic, grain-fed, store-bought eggs that were heat treated. And they showed benefits!
I’m not a big fan of cooked eggs, I get nauseous if I eat too many, but I have no issue using them raw in smoothies.
My favorite recipe:
- 3-6 whole eggs
- 1-2 cups whole milk
- 1 heaped tsp PB2
- 2 tbsp honey/maple syrup
- Optional: fruit of choice
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