A new study shows eating more than an egg a day is good for you. It’s yet another sign that cholesterol isn’t as simple as “good” or “bad” 02/15/2021
For centuries, humans all over the world have relied on eggs as a dietary staple (Xiang et al., 2015). Chickens are easy and cheap to keep, and their eggs are a simple way to add protein to any meal. From quiche Lorraine to egg-topped ramen or a classic scrambled egg breakfast, eggs are versatile, delicious, and until quite recently, regarded as highly nutritious.
(Before we go further, we’d be remiss if we omitted classic Vital Choice recipes that combine eggs with seafood, including Potato, Salmon and Spinach Patties with Garlicky Dill Cream, Smoked Salmon and Pesto Scrambled Eggs, or the ever-iconic Maryland Crab Cakes. But we digress.)
In recent generations, Western society has developed a fear of eggs, especially the cholesterol-rich yolks. After scientists raised alarms about cholesterol in the 1950s and 1960s, experts started telling people they should avoid eggs – or stick with the egg whites only - for fear of poor heart health (Keys et al., 1956).
Despite the negative attention, there’s actually ample evidence that eggs, yolks and all, are great for us. And new research is showing that the idea of eggs as harmful may be one of the most pernicious pieces of bad dietary advice in the last 50 years.
In a new study that looks at more than half a century of research on the subject, scientists concluded that people who eat more eggs significantly reduce their risk of coronary artery disease without increasing their broader risk of cardiovascular disease.
To make this distinction clear: Coronary artery disease happens when plaque and inflammation damage the blood vessels that supply the heart. Cardiovascular disease is an umbrella term that covers all types of diseases that affect the heart or blood vessels.
The research was authored by heart health experts at leading U.S. institutions and published in the American Journal of Medicine (Krittanawong et al., 2021).
The finding fits with other recent discoveries that suggest high dietary cholesterol doesn’t necessarily mean high blood cholesterol. (Read More: Cholesterol Picture Gets Clearer.)
Aren’t Eggs Bad for You?
Though it’s often vilified, humans need cholesterol to stay alive. Our bodies create cholesterol naturally, and we also get it from animal products in our diets. Cholesterol is a building block for our body tissues, vital for producing sex hormones, and more.
So, why do we all think cholesterol is bad for us?
Cholesterol is essentially a “vehicle” that allows two types of proteins to travel through our bodies. Doctors usually talk about these two as two different kinds of cholesterol — one “good” and the other “bad.” (Vital Choice reviewed the history in detail in our recent piece Cholesterol Rich Foods Can Be Good for Your Heart.)
LDL, or low-density lipoprotein, is the so-called “bad” cholesterol. Some studies suggest that LDL can clog and harden our arteries, according to the Centers for Disease Control and Prevention. That makes it harder for the body to push blood around, potentially causing heart attacks and strokes. Meanwhile, HDL, the “good” cholesterol, carries that cholesterol to the liver, where our body can flush it out (CDC, 2020).
However, the more scientists research the effects of having high LDL levels, the more they realize it’s a relatively poor heart-risk indicator. A recent study found that most people who have heart attacks actually don’t have high cholesterol levels that would suggest they’re at risk (Hua et al., 2019).
Meanwhile, research into people with low HDL levels has shown that they’re more likely to die of a range of diseases, including cancer (Ko et al., 2016). They also were more likely to have a range of other risk factors, like lower incomes and generally unhealthy lifestyles. And doctors are learning that triglycerides, a kind of fat found in our blood that also hardens arteries, are perhaps a more powerful predictor of heart disease (NIH, 2020).
The emerging conclusion: low HDL and high triglycerides are a better heart-risk indicator than is simply high LDL.
Cholesterol Fears Fade
Meanwhile, as the cholesterol fears fade, it’s becoming clear there are many positive reasons to eat eggs. They’re high in protein, rich in choline — a key nutrient for cell growth — and great for brain function (Zeisel and Costa, 2009).
As a result, until recently, the federal government recommended that people eat less than 300 milligrams of cholesterol per day. An egg holds around 186 milligrams on average, so having a two-egg omelet would throw you over the limit. But there’s been a significant back-and-forth debate over that simple interpretation in recent years. And in 2015, the U.S. government walked back that 300 mg limit, citing a lack of scientific evidence (USHHS, 2015).
That’s helped eggs make something of a comeback among dietary experts. Yet a few studies suggesting a link between high cholesterol and heart problems have kept those concerns alive. And that’s why this latest research cast such a wide net in its attempt to find a more conclusive answer to the question of whether or not eggs are good for us.
“Although there is no direct evidence that egg consumption can lead to elevated cholesterol levels, the American Heart Association Dietary Guidelines Revision 2000 recommended to the public that they consume [less than] 300 mg/day of cholesterol to minimize the elevation of blood cholesterol,” the team wrote in their paper (Krittanawong et al., 2021).
Eggs Reduce Cardiovascular Disease Risk
The researchers hoped that by diving deep into the past half-century of research, they could finally illuminate if there was truly a cause-and-effect connection between heart problems and eggs.
The authors looked at nearly two dozen studies dating as far back as 1966. Altogether, the research encompassed the health and diets of 1.4 million people, and included more than 150,000 cardiovascular disease events (Krittanawong et al., 2021).
‘[Our analysis] identified no significant association between egg consumption and risk of cardiovascular disease events, but we found that egg consumption (more than one egg per day) is associated with a reduction in coronary artery disease risk,” the authors wrote.
In other words, eating eggs didn’t lead to heart attacks — in fact, they helped improve heart health.
Their finding isn’t the only one to reach similar conclusions by looking back at decades of research. Eight other meta-analyses — where researchers look at the combined data from multiple studies — also found that there wasn’t any significant link between cardiovascular disease events and how many eggs people ate.
Moons Over My Hammy
Yet even the past few years have seen headlines from major outlets suggesting the opposite. For example, in 2019, The New York Times reported on a study that found every additional half egg eaten per day increased the chance of cardiovascular disease by six percent (Zhong et al., 2019).
So why are other studies still sometimes finding a link between eggs and heart problems? According to the American Heart Association, part of the problem may be that people don’t usually eat just eggs. Carb-rich breads with jam toppings and sugary fruit juices are often paired with eggs. And it’s common to fry eggs in cheap, unhealthful cooking oils such as one of the “Hateful Eight” identified by Dr. Cate Shanahan.
So, maybe it wasn’t the eggs boosting heart disease risk — it was the abundant carbs and inflammatory seed oils eaten with those eggs.
The Mayo Clinic’s advice lines up with that recommendation. People can eat an egg every day without worrying about increasing their chances of heart disease, Doctor Francisco Lopez-Jimenez writes on the medical center’s website.
And that kind of egg consumption also has some serious benefits. Lopez-Jimenez points out that regularly eating eggs appears to lower the risk of strokes, as well as macular degeneration, a serious eye condition that can cause blindness. That puts eggs up there with wild-caught salmon and shellfish among foods that can improve heart and overall health. They’re both rich in vitamins, nutrients and healthy fats that can help blood flow and even lower triglycerides. Eating an omelet with salmon may be a delicious and effective way of helping your heart.
So, don’t feel bad the next time you crack an egg into the pan as you take your first sips of morning coffee. You’re likely doing your heart a favor.
Chicken domestication in China 10,000 years ago. Hai Xiang, Jianqiang Gao, Baoquan Yu, Hui Zhou, Dawei Cai, Youwen Zhang, Xiaoyong Chen, Xi Wang, Michael Hofreiter, Xingbo Zhao. Proceedings of the National Academy of Sciences. Dec 2014, 111 (49) 17564-17569; DOI: 10.1073/pnas.1411882111
Keys A, Anderson T, Mickelsen O, Adelson S, Fidanza F. Diet and Serum Cholesterol in Man: Lack of Effect of Dietary Cholesterol. OUP Academic. https://academic.oup.com/jn/article-abstract/59/1/39/4722525. Published May 1, 1956.
Centers for Disease Control and Prevention. LDL & HDL Cholesterol: "Bad" and "Good" Cholesterol. (Updated January 30, 2020) https://www.cdc.gov/cholesterol/ldl_hdl.htm
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High blood triglycerides. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/high-blood-triglycerides. Accessed Feb. 8, 2020.
Zeisel, Steven H, and Kerry-Ann da Costa. “Choline: an essential nutrient for public health.” Nutrition reviews vol. 67,11 (2009): 615-23. doi:10.1111/j.1753-4887.2009.00246.x
U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at https://health.gov/our-work/food-nutrition/previous-dietary-guidelines/2015.
Zhong VW, Van Horn L, Cornelis MC, et al. Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality. JAMA. 2019;321(11):1081–1095. doi:10.1001/jama.2019.1572