1
Eggs: the unsettled debate among scientists
Around the world, the consumption of eggs this decade remains higher than in the last
decade. This increase is seen in particular in developing countries, as the changing diets cause
people to consume a great number of calories from protein sources like poultry meat and eggs.
This popularity might be explained by how convenient eggs seem to be: they’re readily
available, easy to cook, affordable, and packed with protein. Along with its increased
consumption rates over the decades, it has also presented controversies on whether it presents a
threat to your health or not. The controversies seem to focus on its high cholesterol content,
which some studies have linked to an increased risk of heart disease. Other studies have done the
opposite and shown how its consumption is associated with a lower risk of heart disease.
Exploring both sides of this topic makes it possible to better understand why it has been
discussed for years and rethink how to insert eggs into a diet.
“The egg is meant to be something that has all the right ingredients to grow an organism,
so obviously it’s very nutrient dense,” says Christopher Blesso, associate professor of nutritional
science at the University of Connecticut in the US. One of these nutrients is cholesterol, with an
average of 185 milligrams in one egg yolk, which is more than half of the 300 milligrams daily
amount that the US dietary guidelines recommend until recently, which today has changed to
suggest eating as little as possible. This substance can be found in all human body cells and is
essential for making hormones, vitamin D, and digestive compounds. The amount of cholesterol
the human body needs is produced by the liver and intestines, but it can also be found in animal
products. Low-density lipoprotein (LDL) cholesterol, which is transported to arteries and body
2
tissues, is the one usually related to the increased risk of cardiovascular diseases. (Brown)
Understanding how cholesterol works in the human body helps analyze the research related to its
consumption, health risks, and how eggs fit into the issue.
Following on eggs’ known nutritional information and the concern that high cholesterol
presents to human health, a recent study by a group of food engineers from the National
Engineering Laboratory of Intelligent Food Technology and Equipment aimed to examine the
associations of egg and cholesterol intakes with mortality. This study was conducted by using
data from over 500,000 participants and following up after 16 years. Their findings were that the
intake of eggs was associated with higher all-cause, cardiovascular disease, and cancer mortality,
and it was largely influenced by cholesterol intake. Their suggestion was to limit that intake and
replace whole eggs with substitutes or other alternative protein sources for facilitating
cardiovascular health and long-term survival (Zhuang et al.) These shocking results alarmed
other scientists and researchers, who were skeptical about how the study analyzed its data.
One person who was among the skeptics was Riyaz Patel, a consultant cardiologist at
University College London, who said that this study, although well conducted, only adds more
noise to the discussion. Another example was Dr. Walter Willett, a professor of epidemiology
and nutrition at Harvard T. H. Chan School of Public Health, who said, “The study results are
problematic because they only asked people once about their egg consumption, then followed
them for many years without checking to see if their diet had changed. They’re only getting a
snapshot in time.” Moreover, Ada Garcia, a senior lecturer in public health nutrition at the
University of Glasgow, agreed, “The conclusions of this study are overblown; blaming eggs
3
alone for an increased risk of cardiovascular disease is a simplistic and reductionist approach to
the concept of diet and disease prevention.”
This simplistic approach can be rebutted with more data, eggs are the only food high in
cholesterol that are low in saturated fat. “While the cholesterol in eggs is much higher than in
meat and other animal products, saturated fat increases blood cholesterol. This has been
demonstrated by lots of studies for many years,” says Maria Luz Fernandez, professor of
nutritional sciences at the University of Connecticut in the US, whose latest research found no
relationship between eating eggs and an increased risk of cardiovascular disease. Another
explanation is presented by Elizabeth Johnson, research associate professor of nutritional
sciences at Tufts University, who said that the human body’s systems are in place so that, for
most people, dietary cholesterol isn’t a problem, which means that the body can compensate for
the cholesterol consumed. This conclusion was based on a review of 40 studies that Johnson and
a team of researchers did in 2015, and according to them, humans have good regulation when
consuming dietary cholesterol and will make less cholesterol themselves. (Fernandez et al.)
Yet, another compound present in eggs raises controversy: choline, an essential nutrient
similar to B vitamins. While it has proved to help protect against Alzheimer’s disease
(Velazquez) and protect the liver (Corbin and Zaisel), it might also have negative effects. Choline
is metabolized and converted into TMAO, a molecule associated with an increase in
cardiovascular disease. Research that measures egg consumption and TMAO so far has only
found short-time increases in TMAO (DiMarco et al.). The problem is when choline, instead of
being absorbed into the blood, continues to the large intestines where it can be converted to
4
TMAO, but when eating eggs, choline is fully absorbed and doesn’t go to the large intestine,
presenting no risk to heart disease. (Fernandez et al.)
“Despite many years of research, this question about eggs and health has not been
answered, with multiple observational studies over the last few decades showing conflicting
results – some suggesting moderate egg intake is good, while others suggesting it may be bad,”
said Riyaz Patel, a consultant cardiologist at University College London. While researchers are
far from understanding why eggs affect us differently, most recent research suggests they pose no
health risk and are much more likely to provide benefits. Even so, having eggs for breakfast
every day might not be the healthiest option either, at least having a varied diet is recommended.
Whether eggs are good or bad might depend on who is asked, their lifestyle, and their diet.
5
Works Cited
Brown, Jessica. "Are eggs helpful to our health… or a cause of heart disease?" BBC, 23 Apr.
2020.
https://www.bbc.com/future/article/20190916-are-eggs-good-for-you
LaMotte, Sandee. "Are eggs good or bad for you? The truth may be somewhere in between"
CNN, 9 Feb. 2021.
https://www.cnn.com/2021/02/09/health/eggs-good-or-bad-wellness/index.html
Zhuang, Pan et al. “Egg and cholesterol consumption and mortality from cardiovascular and
different causes in the United States: A population-based cohort study.” PLoS Med, 9 Feb
2021.
https://doi.org/10.1371/journal.pmed.1003508
Fernandez, Maria; Melough, Melissa; Chung, Sang-Jin; Chun, Ock. “Association of eggs with
dietary nutrient adequacy and cardiovascular risk factors in US adults.” Public Health
Nutrition, 22(11), 2033-2042. 5 Mar 2019.
Velazquez, Ramon et al. “Maternal choline supplementation ameliorates Alzheimer’s disease
pathology by reducing brain homocysteine levels across multiple generations.” Springer
Nature Limited, 8 Jan 209.
Corbin, Karen; Zaisel, Steven. “Choline Metabolism Provides Novel Insights into Non-alcoholic
Fatty Liver Disease and its Progression.” Curr Opin Gastroenterol, 28 Mar 2012.
DiMarco, Diana et al. “Intake of up to 3 Eggs/Day Increases HDL Cholesterol and Plasma
Choline While Plasma Trimethylamine-N-oxide is Unchanged in a Healthy Population.”
Lipids, Pub Med. 13 Jan 2017