Few foods have been as vilified as the “incredible, edible egg.” But why would such a simple, natural food be so maligned? There’s really one main reason—eggs, in particular yolks, are a fairly significant source of dietary cholesterol.
Cholesterol gets a bad rap due to its link to heart disease, but your body actually needs a certain amount of it to function properly. Cholesterol is a structural component in each and every cell in the body. It is the precursor to steroid hormones, which help in the regulation of blood sugar, blood pressure, mineral balance and many other important body processes. Cholesterol is also the precursor to the sex hormone pregnenolone, which is then converted to progesterone, testosterone or estrogen.
In addition, cholesterol plays a role in digestion.
In general, your liver and other cells make about 75 percent of the cholesterol in your body. The other 25 percent comes from the foods you eat. Decades ago, when experts started warning Americans about the dangers of high cholesterol and its link to heart disease, eggs took a beating. The belief was that high-cholesterol foods surely must raise blood cholesterol, therefore increasing the risk of heart-related problems.
Lots of studies have since disproven this notion, but even today, science still can’t come to a concrete agreement over eggs. On one hand, you have the recent study published in the journal Atherosclerosis that concluded that the consumption of egg yolks is nearly as dangerous as smoking cigarettes.1 But the results of this study completely contradict a solid body of research that puts eggs in a much more favorable light.
So which is it? Are eggs good or bad for you? Let’s take a look at both sides of this debate.
The Cholesterol Conundrum
In the most recent negative study published on eggs, researchers found that the plaque in the arteries of patients who consumed three or more egg yolks per week was significantly higher than in those who consumed two or less egg yolks per week. To put this in perspective, researchers said that eating egg yolks increases plaque buildup about two-thirds as much as smoking.1
To come to this conclusion, they followed 1,231 heart patients who had high blood pressure or had experienced a stroke, or who had a family history of high blood pressure or heart disease. These patients filled out questionnaires about their diet, medications and certain lifestyle habits (including their egg yolk consumption and whether or not they smoked). Researchers also took into account the patients’ cholesterol levels, blood pressure, body mass index and diabetes status.
However, they did not account for other factors that are very important indicators of heart disease risk, including sugar consumption,2 larger waist circumference3 and exercise habits.
Furthermore—and most notably—the study only included patients with existing cardiovascular issues; in other words, those who had a much higher risk than the average population. For that reason alone, any number of issues could have contributed to the buildup of their arterial plaque, yet researchers isolated this single food and denounced it as the cause of the problem.
Of course, this isn’t the first study—just the latest—to raise a red flag about eggs and cholesterol levels. In one study published in the American Journal of Clinical Nutrition, researchers advised reducing the consumption of eggs because “dietary cholesterol raises the ratio of total to HDL cholesterol and therefore adversely affects the cholesterol profile.”4 However, while cholesterol ratios can be a useful monitoring tool, the American Heart Association actually recommends that doctors use the absolute numbers for HDL and total cholesterol, rather than ratios, to plan out the best patient care.5 In the grand picture, ratios don’t matter as much.
The Other Side of the Cholesterol Debate
While it’s clear that some experts in the medical community believe that eggs (mainly yolks) are detrimental and should be avoided, there is a whole other side to this argument—a side that touts eggs as one of the best sources of various nutrients, and perhaps a near-perfect natural food, regardless of its high cholesterol content.
One large egg contains about 185 mg of cholesterol,6 almost all of which resides in the yolk. Fortunately, despite the previous negative studies, strong research shows that, for most people, cholesterol in food has a much smaller influence on blood levels of total and LDL cholesterol than originally thought, and actually has a positive effect on HDL—the more protective form of cholesterol.
In one published review, the lead researcher noted that 70 percent of the population experiences little to no alterations in plasma cholesterol from eating eggs.7 In those who do experience a slight increase, it’s not only on LDL, but HDL as well. And, as we’ve learned, the more HDL you have, the better.
Furthermore, the researcher noted that egg intake shifts the pattern of LDL cholesterol in the blood from B to A particle size. People with LDL cholesterol pattern A have larger, more buoyant cholesterol particles, and are more likely to have healthier LDL, HDL and triglyceride levels.
People with pattern B, on the other hand, have small and dense LDL particles, which are strongly associated with high LDL and triglycerides, low HDL and an increased risk for heart problems. These smaller particles are more dangerous because they can easily squeeze between cells to reach the artery walls, settle in and cause blockages.
These study results were later confirmed in a 2008 study that looked at the effects of increased dietary cholesterol and weight loss. Results showed that, although dietary cholesterol increased in the egg-fed group from 278 mg to 582 mg after six weeks, the concentration of LDL cholesterol decreased in both the egg-fed and non-egg-fed groups at 12 weeks, and there were no significant changes in LDL particle size either. These researchers concluded, “An increased intake of dietary cholesterol from two eggs a day does not increase total plasma or LDL cholesterol when accompanied by moderate weight loss.”8
Of course, no discussion about high cholesterol is complete without acknowledging its role in cardiovascular disease and stroke. The good news is that studies have also confirmed that eggs do not increase the risk of either of these conditions.
In one study published in the Journal of the American Medical Association, researchers followed more than 37,000 men and 80,000 women for 14 years and found no evidence of significant association between eating eggs and the risk of cardiovascular disease or stroke in either sex. They concluded that eating one egg a day does not have an impact on either condition in healthy adults.9
Another study published several years later had similar results. Following 9,734 men and women over 20 years, researchers discovered that those who ate six or more eggs per week did not have any greater risk of stroke or cardiovascular disease.10
In both studies, higher egg consumption did seem to increase cardiovascular disease risk among diabetics, which warrants further study. But overall, even comprehensive reviews of all the data available on this topic seem to have the same conclusion: Making a blanket statement that the general population should limit egg consumption to prevent cardiovascular disease or stroke is simply not warranted.11
Nutrients Galore
With all of this focus on cholesterol, most people don’t even realize that eggs are jam-packed with vitamins, minerals, protein and healthy fats. While the protein exists mainly in the egg white, the yolk houses most of the other beneficial nutrients.
Specifically, egg yolks are a great source of vitamin A (a whopping 270 IU),6 folate, calcium and carotenoids like zeaxanthin and a highly bioavailable form of lutein, both of which are important for eye health.12
Additionally, two egg yolks provide roughly 250 mg of choline6—half of the recommended daily intake for women who are pregnant or breastfeeding.13 Choline is critical for healthy fetal development and helps to prevent brain and neural tube defects.14 Choline also helps the adult brain function by ensuring the proper firing of neurotransmitters.
Finally, egg yolks are an excellent source of heart-friendly monounsaturated fats and omega-3 essential fatty acids. One egg yolk provides about 40 mg of total omega-3s.15 (Heart-protective nutrients contained in a food that has been derided as heart disease-promoting. Ironic, isn’t it?)
Smart Nutrition on Every Level
Given the research, we feel that egg consumption is not only okay, but even healthful, for the majority of people. If you have concerns with diabetes, then discuss your consumption with your physician, but overall, there is no reason for a healthy adult or child to avoid eggs for fear of developing high cholesterol or heart problems. The most comprehensive, long-term research just doesn’t support that idea.
When buying eggs, make sure they come from free-range chickens that are able to eat insects, grass, leaves, grubs and other items found in nature, rather than commercial feed. The chickens’ consumption of insects, in particular, naturally increases the essential fatty acid content of the egg, making them even more nutritious for you.
References:
1. Spence JD, et al. Atherosclerosis. 2012 Oct;224(2):469-73.
2. Howard BV and Wylie-Rosett J. Circulation. 2002;106:523-27.
3. Hans TS, et al. BMJ. 1995 Nov 25;311(7017):1401-5.
4. Weggemans RM, et al. Am J Clin Nutr. 2001 May;73(5):885-91.
5. American Heart Association. www.heart.org/HEARTORG/Conditions/Cholesterol/AboutCholesterol/What-Your-Cholesterol-Levels-Mean_UCM_305562_Article.jsp.
6. www.incredibleegg.org/health-and-nutrition/egg-nutrients/nutrient-chart.
7. Fernandez ML. Curr Opin Clin Nutr Metab Care. 2006 Jan;9(1):8-12.
8. Harman NL, et al. Eur J Nutr. 2008 Sep;47(6):287-93.
9. Hu FB, et al. JAMA. 1999 Apr 21;281(15):1387-94.
10. Qureshi AI, et al. Med Sci Monit. 2007 Jan;13(1):CR1-8.
11. McNamara DJ. J Am Coll Nutr. 2000 Oct;19(5Suppl):540S-48S.
12. Chung HY, et al. J Nutr. 2004 Aug;134(8):1887-93.
13. www.cholineinfo.org/pdf/you_your_patients/JADACholineFactSheet.pdf.
14. Zeisel SH. Annu Rev Nutr. 2006;26:229-50.
15. Nutrition Data. http://nutritiondata.self.com/facts/dairy-and-egg-products/113/2.
http://www.wholehealthinsider.com/newsletter/2012/december/up-for-debate-are-eggs-bad-for-you/
