Eggs are among the most popular foods across the world—even some vegetarians make an exception for them. But how healthy are they, really? Let’s look at what the science says.
Essentially, eggs come with two main concerns: the yolk and the white. The yolk packs a significant amount of saturated fat and approximately 200 mg of cholesterol in a single serving. The white, on the other hand, is almost entirely animal protein, which can put stress on the kidneys—unlike plant-based proteins that are easier on the system.
Think about it: within a single egg lies everything needed to grow a chick—so yes, it’s packed with cholesterol, fat, and dense animal nutrients. Like all animal products, eggs are completely devoid of fiber and complex carbohydrates, two essentials for good health.
It’s widely regarded as healthy, yet it’s essential to see how the U.S. Dietary Guidelines assess it. The 2015 Dietary Guidelines recommend that individuals should eat as little dietary cholesterol as possible while consuming a healthy eating pattern as recommended by the Institute of Medicine (IOM).[1] This advice was reiterated in the 2020-2025 Guidelines[2]—The National Academies recommends that trans fat and dietary cholesterol consumption to be as low as possible without compromising the nutritional adequacy of the diet.
Why the Controversy[3]?
As cited directly in the study published in Journal of the American Heart Association – An important source of the controversy is the role of the food industry in influencing public opinion. It’s the egg industry that manufactures controversy. As noted [4]by the Director of the Stroke Prevention and Atherosclerosis Research Center—“After conviction for false advertising, the industry has spent hundreds of millions of dollars to convince the public, physicians, and policy makers that dietary cholesterol and egg yolk are harmless.”
A meta-analysis of more than 50 randomized controlled trials found that egg consumption significantly increases LDL cholesterol[5].
Decades of research have unequivocally established that high levels of “bad” LDL cholesterol are a leading cause of heart attacks and strokes. Study after study, involving millions of people, shows that LDL builds up in your arteries, causing them to harden and narrow—a condition called atherosclerosis.
Can I Eat Just One Egg a Day?
Backed by the National Institutes of Health and the American Association of Retired Persons, the NIH-AARP Diet and Health Study [6]is one of the largest and most comprehensive prospective studies examining the links between diet, lifestyle, and cancer risk. Covering more than 6 million person-years of data, it found something striking—just swapping 3% of your daily calories from animal protein to plant protein was linked to a 10% lower risk of premature death.
When researchers looked at different sources of animal protein, eggs stood out as the worst. Replacing the same 3% of calories from egg protein with plant protein offered over twice the benefit—about a 20% drop in overall mortality. Even half an egg a day was tied to a 7% higher risk of death from all causes.
Moreover, this conclusion is supported by multiple studies. Six other major U.S. studies [7]found similar patterns—the more eggs people ate, the higher their risk of heart disease and early death. Another study revealed a 4% increase in cancer-related mortality with just one egg per week.
Eggs and Cancer Progression
Researchers at Harvard University conducted a prospective study involving over 1,000 men diagnosed with early-stage prostate cancer, following them for several years to assess the impact of diet on disease progression. The findings revealed that men who consumed even less than one egg per day had approximately double the risk of prostate cancer progression, including metastasis to the bones, compared with those who rarely consumed eggs. Notably, poultry intake was the only dietary factor associated with an even greater risk of prostate cancer advancement.
The Role of Choline
So, what’s in eggs that could be driving this cancer risk? How can less than one egg a day make such a difference? The answer seems to lie in choline—a nutrient that’s especially abundant in eggs[9].
Higher blood levels of choline have been linked to an increased risk of developing prostate cancer in the first place. While well over 3 million men in the US currently live with prostate cancer, not all cases are fatal—the danger arises when the disease spreads or becomes metastatic, significantly reducing survival rates.
Choline, TMAO, and Mortality
In terms of mortality, the same Harvard research team found that men who consumed the most choline from food sources faced a higher risk of dying from prostate cancer. Specifically, those who ate 2½ or more eggs per week had an 81% greater risk of prostate cancer–related death[10] compared to men who consumed fewer eggs.
The choline in eggs, like carnitine in red meat, is converted into a toxin called trimethylamine by the meat-eating bacteria in the gut. The trimethylamine gets oxidized in the liver and becomes trimethylamine N-oxide (TMAO), which appears to increase the risk of heart attack, stroke, and premature death. Per research, higher TMAO is associated with a nearly 50% increase in all-cause mortality risk[11]. Increased levels of TMAO are associated with CVD, psoriatic arthritis, polycystic ovary syndrome (PCOS), cancer (ovarian, colorectal and breast), COPD, dementia, diabetes, pneumonia, kidney failure, etc.
When you eat eggs or meat, your TMAO levels spike within just a few hours. But not all choline-rich foods are created equal. Plant-based sources, like just 2 ounces of pistachios a day or Brussels sprouts, don’t raise TMAO—in fact, they can actually help lower it.
It’s ironic that the egg industry highlights choline as a selling point, even though the average person typically consumes more than enough.
Key Takeaway
Eating eggs may boost prostate cancer risk and raise TMAO, a heart-damaging compound. Plant-based choline, like pistachios or Brussels sprouts, is safer. Most people already get enough choline, so swapping eggs for plant proteins supports better health.
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https://odphp.health.gov/sites/default/files/2019-09/2015-2020_Dietary_Guidelines.pdf ↑
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https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans_2020-2025.pdf ↑
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https://www.ahajournals.org/doi/full/10.1161/JAHA.120.017066 ↑
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https://www.researchgate.net/figure/Forest-plot-of-randomized-controlled-clinical-trials-illustrating-weighted-mean_fig3_342100187 ↑
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https://dceg.cancer.gov/research/who-we-study/nih-aarp-diet-health-study ↑
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https://www.sciencedirect.com/science/article/pii/S2161831323000388?via%3Dihub ↑
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https://www.sciencedirect.com/science/article/pii/S0002916523016878?via%3Dihub ↑
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https://aacrjournals.org/cancerpreventionresearch/article/4/12/2110/49687/Egg-Red-Meat-and-Poultry-Intake-and-Risk-of-Lethal ↑
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