Egg yolks are among the richest food sources of cholesterol, and almost 100 million North American adults have high blood cholesterol levels, signifying increased risk for heart attacks. Most of the cholesterol in your body is made by your liver and less comes from the food that you eat. When you eat cholesterol-containing foods, your liver makes less cholesterol, but dietary cholesterol still can raise blood cholesterol. A recent study analyzed 211 research papers on eggs and found that more than 85 percent of them reported that eating eggs raises blood cholesterol (American J of Lifestyle Med, Dec 11, 2019). However, 49 percent of industry-funded papers further reported conclusions that conflicted with the research results, compared to only 13 percent in research papers not receiving industry funding. In the last ten years, 60 percent of the studies on eggs and cholesterol have been funded by special interest industry groups such as the American Egg Board.
For example, college students who ate two eggs with breakfast for five days each week for 14 weeks had a rise of the harmful blood LDL cholesterol of 15 mg/dl (milligrams per deciliter). An egg contains approximately 186 mg of cholesterol. The authors of the study, which was sponsored by the egg industry, concluded that “an additional 400 mg/day of dietary cholesterol did not negatively impact blood cholesterol,” so a student who has his bad LDL cholesterol rise from a reportedly safe 90 mg/dl to an unsafe 105 mg/dl would not be warned by his doctor that he is now in the dangerous zone for blood cholesterol, even though the current recommendation is to treat everyone with a blood LDL cholesterol greater than 100.
Other Studies on Eggs
The controversy over eggs has been going on for years. See my earlier reports such as:
Eggs Do Not Prevent Heart Attacks and Strokes (from 2018)
The Latest on Eggs (from 2017)
Eggs: New Review of Studies (from 2016)
At the end of this article I have provided a lengthy list of studies on eggs, with particular emphasis on why diabetics may be advised to avoid or limit eggs. Note that in all of these studies, egg yolks are the issue; there is little controversy over eating egg whites or egg white products such as Egg Beaters.
Concerns about Lecithin
Other components of eggs, beyond cholesterol and saturated fat, may be responsible for the frequent association of egg consumption with increased risk for heart attacks. Eggs, meat and milk all contain lecithin, which is broken down into another chemical called choline. Your intestinal bacteria use choline as a source for their energy and then release a breakdown product that is converted by your liver to TMAO (trimethylamine oxide). People with high amounts of TMAO appear to have increased risk for heart attacks. See my report on the Latest Research on TMAO for a full explanation. Researchers at the Cleveland Clinic showed that after eating two hard-boiled eggs, people develop a high rise in blood TMAO levels because lecithin in eggs is converted to TMAO very quickly (N Engl J Med, April 25, 2013; 368:1575-1584). They also showed that the intestinal bacteria produced the precursor of TMAO because giving antibiotics to people and animals before they ate an egg prevented the TMAO from being formed.
Comparing Eggs to Other Breakfast Foods
Sugar and other refined carbohydrates may put you at higher risk for heart attacks and premature death than eating saturated fats and cholesterol in eggs, meat and dairy products. It makes no sense whatever to replace eggs with:
• pancakes covered with sugary maple syrup
• most dry breakfast cereals that are made by grinding whole grains into flour, removing most of the fiber, and adding lots of sugar
• large servings of bakery products such as bagels and muffins
• sausages, bacon and other processed meats, which may increase risk for cancers as well as heart attacks
The healthfulness of your overall diet is far more important than whether or not you eat eggs on occasion (Nutrients, 2015 Sep 3;7(9):7399-420). I believe that most North Americans should limit eggs to about three or four a week. If your bad LDL cholesterol is over 100, or you have heart problems or diabetes, I recommend that you should avoid or severely restrict eggs (Am J Clin Nutr, 2013;98:146-59).
My easy, healthful breakfast is cooked oatmeal, which I flavor with nuts and fruits. Nuts are minimally fattening, even though they contain a lot of fat. Fresh fruits and most dried fruits do not have added sugar, and they provide soluble fiber that helps to prevent a high rise in blood sugar. If you don’t like oatmeal or if you want more variety, other whole grains (such as barley, quinoa or brown rice) can be cooked and served the same way. Diana goes farther afield and eats black beans, chick peas or other legumes for breakfast every day. You do not need to limit yourself to the traditional breakfast foods — you can choose from all of the anti-inflammatory foods.
More studies on whether eggs increase risk for heart attacks:
• A review of 28 studies reported since 2000 showed that compared to people who do not eat eggs, egg eaters have higher blood levels of total cholesterol (5.5 mg/dL) and the bad LDL cholesterol (J Am Coll Nutr, Feb 2018;37(2):99-110).
• A review of six studies of 29,615 adults followed for 17.5 years showed that dietary cholesterol is associated with increased risk for heart attacks, and death from all causes, and each additional half egg consumed per day is associated with an increased risk for heart attacks and death (JAMA, March 19, 2019;321(11):1081-1095). The authors cited previous studies showing how controversial the literature is on whether eggs cause heart attacks.
• In healthy men and women, eating three or more eggs per week was associated with increased size and number of plaques in arteries and the more eggs they eat, the more extensive were the plaques that formed in their arteries (Atherosclerosis, October 2012;224:469–473). However, other authors found no association (Am J Clin Nutr, Mar 2016;103(3):895-901).
• Replacing eggs with plant-based protein led to a 19 percent reduction in death risk (JAMA Internal Medicine, October 2016). This study followed 130,000 men and women for 36 years.
• Ultrasound tests showed that people who eat more than three eggs a week have increased plaques in their arteries compared to those who ate two or fewer eggs a week, even after other risks such as smoking were ruled out (Atherosclerosis, 2012 Oct;224(2):469-73).
Studies suggesting that diabetics and pre-diabetics should restrict eggs:
• Researchers reviewed studies published between 2005 and 2015 and concluded that “up to seven eggs per week can safely be consumed, but in patients with established cardiovascular diseases or type 2 diabetes, only with special emphasis on a prudent diet and proper medical treatment.” (Nutrition, published online September 27, 2017).
• In healthy men and women, no association was found between eating one egg per day regularly and risk for heart attacks and strokes, but for diabetics eating one egg per day was associated with increased risk for heart attacks (Am J Clin Nutr, 2013;98:146–159).
• In healthy men, three or more eggs per week was linked to higher levels of sugar stuck on cells (HbA1C) that measures cell damage from high blood sugar levels, but no increased risk for heart attacks or premature death; and in diabetics, eating three eggs per week was associated with higher blood sugar levels and increased risk of stroke (European Journal of Nutrition, Nov 2, 2017).
• In diabetics, three or more eggs was associated with increased heart attack risk, but in healthy men and women, there was no increased risk (BMJ, 2013 Jan 7;346:e8539).
• In healthy men and women, six eggs or more per week increased risk for diabetes (Diabetes Care, Feb 2009;32(2):295–300).
• Healthy North Americans who eat more than two eggs per week appear to be at increased risk for diabetes, but studies from Spain, France, Finland and Japan showed no increased risk for diabetes (Journal of Clinical Nutrition, Jan 6, 2016).
• A review of 17 studies failed to show increased risk for heart attacks in people who eat eggs (BMJ, January 2013). However, regular egg eaters who are diabetic suffered 150 percent more heart attacks than diabetics who ate eggs sporadically.