by Carol L. Cheatham, Ph.D.
Associate Professor, Psychology and Neuroscience
UNC Nutrition Research Institute
April 18, 2019 – How are we expected to make healthy choices about food when the headlines are so confusing? We all suffer whiplash when we read butter is bad, then butter is good; when red meat is bad, then red meat is good; when red wine is good, and then it is bad….so, what is the headline du jour? Once again, eggs are reported to be bad for you due to their cholesterol content.1 How concerned should we be when we all know the egg has had a tumultuous relationship with science?2
Well, that depends. What other foods do you eat? Is your diet laden with high fat and high sugar foods? Do you have the genetic make-up that means you are sensitive to cholesterol? Many factors go into whether or not you, as an individual, will develop heart disease. Cholesterol is not singularly evil, and actually, it serves many noble purposes in the human body. In fact, if it is not consumed in appropriate quantities, the human body will manufacture it.3 Bottom line – we need cholesterol to live.
So, what is the issue? A recent report in the Journal of the American Medical Association (JAMA), a highly respected scientific journal, sets forth the conclusion that eating eggs increases risk for cardio-vascular disease and in general, death.4 The study is very detailed and involved data from almost 30,000 participants from six different samples. The scientists used all the proper techniques and controls. They even controlled for the diet as a whole. Their conclusion should be solid, right?
Answer this for me – how many times in the past 6 months have you eaten eggs? This question is what you would answer if you completed a food frequency questionnaire (FFQ), which is a method of collecting diet data. Even though FFQs serve an important purpose in nutrition research, the data are subject, as you can imagine, to the fallibility of memory: as humans, our memories are just not that reliable (which is how I have been able to build a career studying memory). In the JAMA report, the answer to this one FFQ question was found to be associated with whether or not one had developed cardio-vascular disease as much as 31 years later. As mentioned, the statistics controlled for other lifestyle factors, but the fact remains, the data are only correlational (which if you remember high school science, does not mean causation) and depend solely on an unreliable memory dump. To contrast, in a similar correlational study published in JAMA in 1999 with data from over 117,000 people, it was reported that healthy people could eat an egg a day without any change in cardio-vascular disease risk.5 Bottom line – correlation provides us clues about what experimental research might be useful, but it does not equal causation.
Okay, so what if we do the experiment and assign people randomly to eat eggs or not to eat eggs? This type of a study (randomized controlled trial or RCT) will allow us to determine causation. Many studies have been completed, and a complete review is beyond the scope of this article; here are the results of a representative study.6 Participants ate 3 eggs a day for four weeks and had their cholesterol assessed. The results showed an improvement in HDL (the “good” cholesterol) function and an improvement in LDL size. As a bonus, plasma antioxidant content was also increased, because the egg contains several nutrients that are amazingly good for the body and brain. As further evidence, another group completed a meta-analysis of the egg research up to that point (2013) and concluded that eggs are not related to an increased risk in cardio-vascular disease, unless the consumer is diabetic.7 Thus, the egg is a great addition to a diet for healthy individuals.
On a personal note, I purposefully ate a dozen eggs a week for 4 weeks to see what effect it would have on my cholesterol in preparation for a study in which I was going to ask women to eat 5 eggs a week.8 This egg experiment only increased my HDL – which is good. My LDL remained stable and my triglycerides decreased. In addition before starting research with the egg in my lab, I researched the egg very carefully and am satisfied that it is a very nutritious and safe food.
So, don’t be too concerned about eating eggs unless you know you are one of the 3 in 1000 people that are sensitive to cholesterol or unless you are unhealthy to start. If you can, buy eggs from a farm that allows the chickens to roam free and eat their natural diet or that feeds them seeds that will increase the fatty acids in the egg (fatty acids are good for your heart). The fatty acids, choline, and lutein found in eggs are phenomenally good for you. In fact, I believe that eggs are the perfect food for brain development and function.
- For synopsis of the headlines, see https://khn.org/morning-breakout/so-eggs-are-bad-again-new-study-offers-link-between-eggs-increased-risk-of-heart-disease/
- For review of the egg timeline see https://www.cnn.com/2019/03/27/health/eggs-good-or-bad-where-do-we-stand/index.html
- For more information in layman’s terms see https://en.wikipedia.org/wiki/cholesterol
- Zhong, V. W., et al. (2019). Associations of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. JAMA 321(11): 1081-1095.
- Hu, F. B., et al. (1999). A prospective study of egg consumption and risk of cardiovascular disease in men and women. JAMA 281(15): 1387-1394.
- DiMarco, D. M., et al. (2017). “Intake of up to 3 Eggs per Day Is Associated with Changes in HDL Function and Increased Plasma Antioxidants in Healthy, Young Adults.” J Nutr 147(3): 323-329.
- Shin, J. Y., et al. (2013). Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr 98(1): 146-159.
- For the ICAN study, go to www.cheathamlab.com and click on “Projects”
Post: April 18, 2019