Current Research About Eating Eggs. What Science Actually Says

I’m a nutritionist geek who has spent thousands of hours researching and reading scientific studies in various journals. There is still so much yet to be learned about both health and nutrition.
Understandably, there are mixed perspectives on whether or not eggs cause heart disease, which I’ll explain in this article.
In my opinion, based on my research, I believe eggs are very healthy food and do not cause heart disease as long as they are a part of a low-fat diet with limited red meat.
I’ll make a science-based case in this article on why I think eggs are a superfood and why I believe eggs may improve heart health.
But first, my disclaimer:
I am not a doctor. I’m not preventing, diagnosing, treating, curing, or managing any disease or condition. Your health is between you and your doctor.
Before we talk about heart health, consider some of the powerful nutrients eggs offer for overall health. Eggs are a good source of:
protein, with one egg providing 6.3 grams
vitamins, such as B2 (riboflavin), B5 (pantothenic acid), B12 (cobalamin), biotin, choline, folate, vitamin A and vitamin D
omega-3 and omega-6
minerals such as iodine, selenium, phosphorus, and zinc
carotenoids, such as lutein and zeaxanthin (important for eye health)
cholesterol
While we tend to look at cholesterol as a bad thing, it might surprise you that cholesterol is very important for overall health. Our body needs to make vitamin D, bile, and steroid hormones progesterone, estrogen, and testosterone.
Contrary to popular belief, there is little evidence that dietary cholesterol leads to cardiovascular disease.
In fact, most of the cholesterol found in our blood is made by the liver.
One of the challenges in studying dietary cholesterol in heart disease is that certain dietary sources of cholesterol also happen to be high in saturated fat, trans fats, or iron, all associated with high blood cholesterol.
It was already verified in 1951 that a high-fat diet raises cholesterol.
Eggs happen to be low in saturated fats.
However, eggs are often cooked and eaten with other foods that are high in saturated fat. This may be an issue if the entire diet is high in fat.
Diets that are very high in fat change the gut microbiome, increasing risk factors for cardiovascular disease.
Let’s now look at three blood markers doctors look at in heart disease and see how those are impacted by egg consumption.
1. Cholesterol
There are two types of cholesterol — high-density lipoproteins, also known as HDL, and low-density lipoproteins called LDL.
LDL can be further broken down into sizes, such as very low-density lipoproteins or VLDL for short.
LDL and VLDL are considered “bad” because they build up in the arteries, leading to plaque build-up, thus affecting blood flow. This plaque can harden and lead to cardiovascular disease.
HDL is considered to be “good cholesterol” and is associated with heart health.
The American Heart Association says:
HDL cholesterol can be thought of as the “good” cholesterol because a healthy level may protect against heart attack and stroke.
HDL carries LDL (bad) cholesterol away from the arteries and back to the liver, where the LDL is broken down and passed from the body.
Egg intake on a normal fat diet increases HDL levels.
A 12-week study of 56 healthy adults found that an additional egg per day on a normal fat diet significantly raised their HDL.
Another study involving 24 healthy adults that added two boiled eggs to their diet for 6 weeks increased HDL levels by 10%.
Other studies also show that egg consumption increases in HDL.
2. Homocysteine
High homocysteine levels are a risk factor for heart disease.
In a rat model, it was found that eggs may actually prevent high homocysteine levels.
A study from Iowa State University looked at various protein sources in relationship to homocysteine. They found that an egg white is a very high-quality protein with a balanced methione and cysteine profile, making it an effective protein in preventing homocysteine accumulation.
The same study also looked at the egg yolk, which contains choline. Choline breaks down into betaine, which is an important methyl group that remethylates homocysteine.
They go on to say that whole eggs represent an excellent food choice in managing homocysteine.
3. Trimethylamine N-oxide (TMAO)
High TMAO levels are associated with heart disease. Research at the Cleveland HeartLab found that “TMAO can powerfully predict risk for heart attack, stroke, and death in patients who otherwise appear healthy.”
Bacteria in the gut make a compound called TMA. This gets absorbed into the bloodstream, goes to the liver, and then converts to TMAO.
Many studies say that egg consumption increases TMAO levels, and studies that say eggs do not.
Which is right? Well, it depends.
This is because gut microbes create TMA from choline, and eggs have a lot of choline. But it also takes the amino acid carnitine. Both carnitine and choline are found in high quantities in red meat.
People who eat red meat have 3 times the level of TMAO in their blood than those who eat a diet rich in either white meat or mostly plant-based proteins.
An article in Harvard Health says:
… the more red meat you eat, the more of these meat-eating bacteria your body produces in your gut. Exposure to red meat changes the gut flora. “It essentially grows more microbes that can metabolize meat,” says Dr. Manson.
If a long-term vegetarian without high levels of these microbes inside their body eats red meat, they will not initially be able to synthesize TMA in the gut or convert it to TMAO in the liver. That means they likely won’t have the high TMAO levels seen in people who regularly eat red meat — at least not at first. But if they continue to eat red meat, over time their bodies could develop more of the microbes that produce TMA, and their TMAO levels would likely rise, says Dr. Manson. Research has also linked some types of fish to higher TMAO levels, but fish have other health benefits that may offset the risk, says Dr. Manson. Poultry, eggs, and dairy foods don’t appear to have the same effect on TMAO levels as red meat and fish, she says.
Supplementing with carnitine increases TMAO levels as well.
And although eggs increase choline levels, it does not increase TMAO as carnitine does.
In a study of overweight postmenopausal women, whole egg consumption increased plasma choline levels but did not increase TMAO levels.
So although eggs contain choline, an ingredient in TMAO, it is the carnitine found in red meat or supplements that actually increases the number of bacteria that create TMA from choline and carnitine. Carnitine increases the overall production of TMAO.
So how many eggs can one eat?
A study among Chinese adults found that up to 1 egg per day was significantly associated with a lower risk of cardiovascular disease.
There is even a case study of an 88-year-old who ate 25 eggs per day and still had normal cholesterol levels.
In my opinion, it’s safe to eat as many eggs as you want per day, as long as the overall diet is relatively low in saturated fats and red meat.

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