Spoiler Alert…..If you eat eggs, you are increasing your risk of heart disease.
This statement may catch you off guard due to the extraordinary amount of hype in the media and on the internet about how eggs have no effect on your cholesterol level nor do they lead to increased risk of cardiovascular disease. In short, it is now believed by many people that there is no need to restrict the consumption of eggs. Sadly, this is not true and I hope to show you why.
Back in 1992 a meta-analysis of forty studies performed from 1960 to 1990 showed that cholesterol level in the blood is clearly increased by eating cholesterol-containing foods (1). Other studies told the same story. A randomized double-blind crossover trial involving seventeen lacto-vegetarian college students revealed that adding one extra-large egg a day to their diet for only one week increased their blood LDL-cholesterol by 12%. The amount of dietary cholesterol the students were eating daily before the start of this study was low, about 97 mg, but it increased to 418 mg with the addition of the eggs (2). A study from the University of Pennsylvania Medical School showed that increasing cholesterol in the diet increased total blood cholesterol by 25% on average (3).
Eating eggs not only increases cholesterol levels. It also leads to more cardiovascular disease. The Oxford Vegetarian Study was one of the earlier studies that showed this connection, illustrating that people eating 6 or more eggs per week had a 168% higher risk of dying of heart disease than those eating less than 1 egg per week (4,5). Today there exist more than 200 prospective cohort studies and randomized trials covering more than 2 million participants with 20 million person-years of follow-up that demonstrate consistently that the higher the LDL-cholesterol in the blood, the greater the risk of atherosclerotic cardiovascular disease (the build-up of fatty plaques in artery walls that can increase the risk of heart attacks, strokes and peripheral vascular disease) (6). This body of science is the evidence that supports limits on eating eggs, a process that began during the 1960s and 1970s in many countries as they developed guidelines for heart health.
Aside from the link between eating cholesterol and increased risk of cardiovascular disease, these same studies also uncovered details of how cholesterol is absorbed by the human body. The absorption of cholesterol from food is not a straightforward linear process whereby increasing cholesterol in the diet leads to steadily increasing cholesterol in the blood. It appears that blood cholesterol reaches a plateau level after which much less of it will be absorbed by the body. To put this another way, if a person is eating little to no cholesterol, adding cholesterol from the diet drastically increases the amount of cholesterol that ends up in their bloodstream. On the other hand, the addition of more cholesterol-containing foods by someone eating a standard American diet, which already includes high levels of cholesterol (at least 400 mg daily on average), will result in a much smaller rise in blood cholesterol (1).
Now think about egg producers. They are the ones who stand to lose the most in an environment where eggs are vilified as menacing to health. Egg industries throughout the developed world are large and powerful and of course one of their priorities is the reputation of their product. Thus they have focused much time and effort over the last few decades to bring the egg back into the realm of healthy foods. Many countries even have their own organization for supporting egg farmers, helping them to succeed in marketing more eggs and promoting good news about eggs as a healthy food to the public, health professionals and schools. Examples are the “Egg Farmers of Canada” (also known as the “Canadian Egg Marketing Agency”), the “American Egg Board” and “Australian Eggs”. The tendency of cholesterol absorption to lessen at higher dietary levels has opened opportunities for those who strive to increase the consumption of eggs. Studies can be created that tell only a part of the story, the part that looks like good news for egg eaters.
Let’s look first at examples from the US. In 2005 the American Egg Board supported a study that included 49 healthy adults who began the trial with an average cholesterol level of 5.24 mmol/L, a high-normal cholesterol level common in people eating the standard American diet. Their LDL-cholesterol levels were also high, averaging 3.22 mmol/L. (Ideal LDL-cholesterol level is below 2.6 mmol/L). Remember that people who already have high cholesterol will only absorb reduced amounts of additional cholesterol from their diet. Here’s another bit of information you’ll need to understand this research. The endothelium cells that line our blood vessels are vital for cardiovascular health. They produce nitric oxide whose numerous benefits include regulating the amount of blood flowing to various areas of the body, decreasing inflammation in the cardiovascular system and reducing the stickiness of circulating blood cells thereby lowering the development of atherosclerotic plaques. In this study, the function of the artery lining was determined by looking at the ability of blood vessels to dilate properly. Blood flow through the major blood vessel of the upper right arm was measured using flow-mediated vasodilation (FMD). A decrease in FMD means less blood flow through that artery and is an undesirable outcome. The subjects of this study ate either two eggs or 60 gm of uncooked oatmeal daily for six weeks and then were “crossed over” to the other food choice. Results were also compared to the effects of eating a sausage and egg sandwich (actually a McDonalds Sausage McMuffin). Outcomes showed a slight decrease in FMD after eating either the eggs or the sausage and cheese sandwich and a small increase in FMD after eating the oatmeal. Total cholesterol and LDL-cholesterol blood levels also increased slightly after eating eggs (total cholesterol went from 5.24 to 5.3 and LDL-cholesterol went from 3.22 to 3.34) but were decreased by eating oats (total cholesterol went from 5.24 to 5.01 and LDL-cholesterol went from 3.22 to 3.01). These results were not considered scientifically significant and so the conclusion of the study was that ingestion of two eggs for six weeks had no effect on total cholesterol or LDL-cholesterol blood levels (7).
This trial was followed up by another one in 2010, also supported by the American Egg Board. In this randomized, placebo-controlled crossover trial, forty adults with high blood lipids (including cholesterol) were randomly assigned to eat one of two breakfasts: three medium hard-boiled eggs or a sausage/cheese breakfast sandwich, after which their endothelial function was obtained by looking at their FMD (as in the first study). Four weeks after this initial challenge the participants were randomly placed on a breakfast of either two medium hard-boiled eggs or ½ cup egg substitute for six weeks. It is not at all surprising that the subjects demonstrated impaired endothelial function at the start of the study which remained impaired after the initial meal challenges. “Egg consumption had no effects on endothelial function as compared to sausage and cheese” said the researchers. And no wonder! First of all, these people already had high blood cholesterol levels so adding more to the diet would be expected to have little effect. On top of this, a sausage and cheese breakfast sandwich also contains cholesterol, though not as much as that found in eggs, and is high in saturated fat, both factors with negative effects on the endothelium. More illuminating in this study are the results of the egg vs egg substitute trial. The egg substitute consisted of 99% egg whites and was lower in calories than whole eggs, fortified with vitamins and lacking in cholesterol and fat. Results showed that daily eating of the egg substitute significantly improved endothelial function as compared to whole egg and also lowered total blood cholesterol and LDL-cholesterol. Conclusions of the study stated that “egg consumption was found to be non-detrimental to endothelial function and serum lipids in hyperlipidemic adults, while egg substitute consumption was beneficial.” And this is a study put forward to prove that eating whole eggs is good for health? (8)
Similar studies in Australia were partially funded by Australian Eggs. In 2015 a trial including 140 obese, diabetic participants who were already ingesting well over 300 mg of cholesterol daily were randomly assigned to eat twelve eggs per week or less than two eggs per week for three months. Those in the low-egg group were instructed to match the protein intake of the high-egg group and were encouraged to do this by eating lean meat, chicken or fish for breakfast. To give the investigators credit, the instructional booklet given to the subjects did also mention legumes and reduced-fat dairy products as alternate sources of protein. Study results showed no differences between the two groups in total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides or blood sugar. At the conclusion of the study the researchers stated that “individuals with prediabetes or type-2 diabetes who consumed a high-egg diet for 3 months….. had no adverse changes in circulating lipid profiles compared with participants who consumed a low-egg diet. Therefore, a diet including more eggs than generally recommended may be used safely as part of the nutritional management of this group.” There was no mention of the possible contribution of the cholesterol contained in the animal-based protein added by the subjects eating less than two eggs per week (9,10).
Most threatening of all to truth about eggs and cardiovascular health is that 92% of the trials chosen to be included in the latest meta-analysis of dietary cholesterol and blood levels were those funded by industries that produce products high in cholesterol. This means that the included studies were ones whose methods made it difficult to detect any effect of added dietary cholesterol on blood cholesterol levels (11).
As pointed out earlier, these studies that enjoy so much public attention reveal only part of the story, the portion that means increased profits for the food industry. What is the rest of the story, that which is hidden when researching exclusively people who are already eating a diet high in cholesterol? And where does this leave you? Should you throw caution to the winds and just go ahead and eat all the eggs you want because they don’t appear to raise your cholesterol?
Here are some facts to consider.
Your risk for cardiovascular disease increases as the level of cholesterol in your blood rises (6). Cholesterol from the diet increases the amounts of total and LDL-cholesterol concentrations in the blood as well as the ratios of total cholesterol/HDL and LDL/HDL and these are all established risk factors for coronary heart disease (12,13).
Having a high cholesterol level, even one which is “normal” for people who eat a standard American diet, means your health is in danger. It is not a logical conclusion that it’s okay to eat more high-cholesterol foods just because eating them won’t further increase your cholesterol by very much.
Studies show that what we know as “normal” cholesterol levels are actually too high. Atherosclerosis is associated with very high LDL levels (greater than 5.2mmol/L) but it is not uncommon even in those with relatively “normal” LDL levels (2.33 to 3.36 mmol/L). In fact the 10% of the population with the highest LDL levels account for only 20% of coronary heart disease events and atherosclerotic plaques are present in 40 to 50% of men and women by the age to 50 (14).
A Canadian study from 2012 found that although atherosclerotic plaques in blood vessels tend to increase as a person ages, tobacco smoking and egg yolk consumption accelerate the formation of these artery-clogging formations by the same magnitude and in the same exponentially increasing pattern (15).
Eating eggs impacts more than just cholesterol level.
A meta-analysis from August 2013 of previous studies encompassing over 320,000 participants showed that eating eggs increases the risk of developing diabetes (16). Another 2013 meta-analysis found that frequent egg consumption was associated with a 42% increase risk in the development of diabetes and, in those that already have diabetes, a 69% higher risk of cardiovascular problems (17).
Coronary artery calcium (CAC), which can be measured by a CT scan, is a potent predictor of coronary artery disease (18). A 2015 study from Korea on over 23,000 men and women found that those who ate seven or more eggs per week suffered an 80% higher risk of dangerously high CAC compared to those eating less than one egg a week (19).
Eggs induce TMAO production due to their high content of choline. Gut bacteria break choline down into trimethylamine (TMA) and the liver transforms the TMA into TMAO (trimethylamine oxidase), a substance that injures the lining of arteries, creates inflammation and increases the build-up of atherosclerotic plaques in blood vessel walls. People with the most TMAO circulating in their bloodstream increase their risk of stroke, myocardial infarction and death by two and a half times. This increase in cardiovascular events remains even after adjustment for traditional risk factors. (20,21,22,23)
It is concerning when a food industry has enough power to overwhelm the truth by ignoring facts and spreading disease-producing advice. Sadly it is often these very same agencies that provide information about food and health for classroom nutrition curriculums and physician education.
It is my hope that this information helps you make a decision about eating eggs in your own life. Eating more eggs is not a prudent decision for health. A better idea is to consider cutting back on the cholesterol-containing foods you are already eating. This means foods that come from animals – all meats including beef, pork, lamb, poultry and fish, dairy products and eggs. And you need have no worries about not getting enough cholesterol. It is not necessary to eat any cholesterol at all. Your body can produce all that it needs.
The consumer of today must be wary about where their information is coming from. It’s time to weigh out the facts and think things out for yourself. If you want to increase your chance of living a long life in robust health choose the foods you eat from the plant kingdom. There is no cholesterol in plant-based foods.
1 Hopkins, P.N. Effects of dietary cholesterol on serum cholesterol: a meta-analysis and review. Am J Clin Nutr. 1992 Jun; 55(6):1060-1070.
2 Sacks, F.M., Salazar, J., Miller, L., Foster, J.M., Sutherland, M., Samonds, K.W., Albers, J.J., Kass, E.H. Ingestion of egg raises plasma low density lipoproteins in free-living subjects. Lancet. 1984 Mar 24; 1(8378):647-649.
3 Mattson, F.H., Erickson, B.A., Kligman, A/.M. Effect of dietary cholesterol on serum cholesterol in man.
Am J Clin Nutr June 1972; 25 (6): 589–594.
4 Appleby, P.N., Thorogood, M., Mann, J.I., Key, T.J.A. The Oxford Vegetarian Study: an overview. Am J Clin Nutr 1999; 70(suppl): 525S–531S.
5 Mann, J., Appleby, P., Key, T., Thorogood, M. Dietary determinants of ischaemic heart disease in health conscious individuals. Heart. 1997 Nov; 78(5): 450–455.
6 Ference, B.A., Ginsberg, H.N., Graham, I., Ray, K.K., Packard, C.J., Bruckert, E., Hegele, R.A., Krauss, R.M., Raal, F.J., Schunkert, H., Watts, G.F., Borén, J., Fazio, S. et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. Eur Heart J. 2017 Aug 21; 38(32):2459-2472.
7 Katz, D.L., Evans, M.A., Nawaz, H., Njike, V.Y., Chan, W., Comerford, B.P., Hoxley, M.L. Egg consumption and endothelial function: A randomized controlled crossover trial. Int J Cardiol .2005 99(1):65 – 70.
8 Njike, V., Faridi, Z., Dutta, S., Gonzalez-Simon, A.L., Katz, D.L. Daily egg consumption in hyperlipidemic adults–effects on endothelial function and cardiovascular risk. Nutr J. 2010 9:28.
9 Fuller, N.R., Caterson, I.D., Sainsbury, A., Denyer, G., Fong, M., Gerofi, J.,Baqleh, K., Williams, K.H., Lau, N.S., Markovic, T.P. The effect of a high-egg diet on cardiovascular risk factors in people with type 2 diabetes: the Diabetes and Egg (DIABEGG) study—a 3-month randomized controlled trial . American Journal of Clinical Nutrition April 2015; 101(4): 705–713.
10 Fuller, N.R., Sainsbury, A., Caterson, I.D., Denyer,G., Fong, M., Gerofi, J.,Leung, C., Lau, N.S., Williams, K.H., Januszewski, A.S. et al. Effect of a high-egg diet on cardiometabolic risk factors in people with type 2 diabetes: the Diabetes and Egg (DIABEGG) Study—randomized weight-loss and follow-up phase. American Journal of Clinical Nutrition June 2018; 107(6): 921-931.
11 Griffen, J.D., Lichtenstein, A.H. Dietary Cholesterol and Plasma Lipoprotein Profiles: Randomized-Controlled Trials. Curr Nutr Rep. Dec 2013 ; 2(4): 274–282.
12 Kinosian, B., Glick, H., Preiss, L., Puder, K.L. Cholesterol and coronary heart disease: predicting risks in men by changes in levels and ratios. J Investig Med. 1995 Oct; 43(5):443-450.
13 Weggemans, R., Zock, P.L. Dietary cholesterol from eggs increases the ratio of total cholesterol to high-density lipoprotein cholesterol in humans: A meta-analysis. Am J Clin Nutr June 2001; 73(5 :885-891.
14 O’Keefe, J.H., Cordain, L., Harris, W.H., Moe, R.M., Vogel,R. Optimal low-density lipoprotein is 50 to 70 mg/dl: Lower is better and physiologically normal. J Am Coll Cardiol June 2004; 43(11): 2142-2146.
15 Spence, J.D., Jenkins, D.J., Davignon, J. Egg yolk consumption and carotic plaque. Atherosclerosis. 2012 Oct; 224(2): 469-473.
16 Li, Y., Zhou, C., Zhou, X., Li, L. Egg consumption and risk of cardiovascular diseases and diabetes: a meta-analysis. Atherosclerosis. 2013 Aug; 229(2):524-530.
17 Shin, J.Y., Xun, P., Nakamura, Y., He, K. Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr. 2013 Jul; 98(1):146-159.
18 McClelland, R.L., Jorgensen, N.W., Budoff, M., Blaha, M.J., Post, W.S., Kronmal, R.A. et al. Ten-Year Coronary Heart Disease Risk Prediction Using Coronary Artery Calcium and Traditional Risk Factors: Derivation in the Multi-Ethnic Study of Atherosclerosis with Validation in the Heinz Nixdorf Recall Study and the Dallas Heart Study. J Am Coll Cardiol. 2015 Oct 13; 66(15): 1643–1653.
19 Choi, Y., Chang, Y., Lee, J.E., Chun, S., Cho, J., Sung, E., Suh, B.S., Rampal, S., Zhao, D., Zhang, Y., Pastor-Barriuso, R., Lima, J.A., Shin, H., Ryu, S., Guallar, E. Egg consumption and coronary artery calcification in asymptomatic men and women. Atherosclerosis. 2015 Aug; 241(2): 305-312.
20 Koeth, R.A., Wang, Z., Levison, B.S., Buffa, J.A., Org, E., Sheehy, B.T., et al. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Nature Medicine. May 2013; 19 (5): 576–585.
21 Tang, W.H.W., Wang, Z., Levison, B.S., Koeth, R.A., Britt, E.B. et al. Intestinal Microbial Metabolism of Phosphatidylcholine and Cardiovascular Risk . N Engl J Med 2013; 368:1575-1584
22 Mente, A., Chalcraft, K., Ak, H., Davis, A.D., Lonn, E. et al. The Relationship Between Trimethylamine-N-Oxide and Prevalent Cardiovascular Disease in a Multiethnic Population Living in Canada. Can J Cardiol. 2015 Sep; 31(9):1189-1194.
23 Miller, C.A., Corbin, K.D., da Costa, K.A., Zhang, S., Zhao, X., Galanko, J.A., Blevins, T., Bennett, B.J., O’Connor, A., Zeisel, S.H. Effect of egg ingestion on trimethylamine-N-oxide production in humans: a randomized, controlled, dose-response study. Am J Clin Nutr. 2014 Sep; 100(3):778-786.