Myth of the Month: Cholesterol in eggs causes heart disease.
Here we go again with the great egg debate! Today they’re good, the next they’re bad. With the latest egg study, headlines will have you believe that the cholesterol in eggs causes heart disease. So what should you actually believe?
In this Myth of the Month, I’ll be looking at the ‘cracks’ in the latest egg study and the reasons you might consider cutting back.
This is a pretty ‘scrambled’ one – so get your thinking cap on. Or skip to the end for my conclusion!
Note: Before we get going though, I want to clarify that the word ‘egg’ refers to whole eggs. Egg whites are different, as the cholesterol is in the yolk.
About the latest egg study that hit headlines
Back in March, JAMA (Journal of the American Medical Assoc) told us that the more eggs someone eats, the greater the chance they’ll get heart disease or die prematurely of any cause.
Let’s start off by looking at the ‘good’ science of this study:
- results came from a well-known and reputable place (JAMA)
- information from 6 different studies was combined
- there were many participants (almost 30,000 men and women from the US) – we know that with big pools of information, results hold more power as the ‘one-off’ results get lost in the numbers
- people were followed over a long time (average of about 17 years but up to 31) – good because they’re looking at long-term effects of a certain way of eating
- researchers also considered other factors that can have a role in heart disease risk such as: age, exercise, blood pressure, weight, tobacco and alcohol use, medications taken.
- overall diet quality was also considered. But what does that mean? That people’s eating patterns were compared to current policies and food guides, sort of like grading them on following the recommendations.
But despite these strengths, there were plenty of points bringing down the quality of this study, which I’ll get into in a bit.
What the study looked at and what researchers found
According to the eating information that participants gave, people had about 285mg of cholesterol + about 1/3 of an egg per day, on average. Meaning they were having just over 2 eggs per week.
Researchers found that the more cholesterol and/or eggs in a person’s diet, the higher the chance was that the person would have heart diseases or die from any cause when they followed up years later.
They found this to be ‘dose-dependent’ – meaning that as the amounts eaten went up, risks of heart disease and death went up as well. Specifically, they found that for every extra 300mg of dietary cholesterol, heart disease risk went up by 17% and risk of dying from any cause went up by 18%. They also found that for every extra 1/2 egg (over average intakes), risks went up by 6% and 8% respectively.
What struck researchers as most important was that when they adjusted the results to remove the amount of other dietary cholesterol, they saw it was the cholesterol from the eggs that was linked to the increased risks. Based on this, they believe that eggs are the link to heart disease.
But before we get ahead of ourselves, let’s put this into a bit of context.
Why the results should be questioned
Before we come to any conclusions about the current study in question, let’s consider that:
- Scientists generally agree that the amount of cholesterol we eat has little effect on the amount of cholesterol that ends up in our blood
- The 2015-2020 Dietary Guidelines for Americans removed the suggested limit on dietary cholesterol, previously set at 300mg/d or less, stating it isn’t considered a “nutrient of concern for overconsumption” based on available evidence
- There can be a difference between cooking methods of eggs. Fried in butter is obviously different than hard-boiled in terms of nutrition.
- Eating behaviour can be complex – it’s possible that people who eat more eggs may also eat more red meat, smoke and carry extra body weight. They might also eat less fruits, veggies and whole grains. As well, there’s the context of it. Picture someone eating fried eggs on an egg n’ sausage biscuit loaded with saturated fat on their way to work every morning. That’s pretty different than having a hard-boiled or poached egg at home with a side of whole grain toast, some yogurt and a banana.
- Health is complex overall. Researchers considered many other factors about each person but they did not look at stress levels, living environment and social situation. And these can definitely impact heart health outcomes. Again, picture that person going through the drive-thru on their way to their extremely stressful job or at the end of a night shift. How can we tell if it’s the egg breakfast or the job/life stress that took a toll on health?
- While it is true that LDL cholesterol levels can predict heart disease … LDL was actually never tested through these studies. Researchers knew what the LDL level was at the start only. Of course, it’s helpful to know what staring the LDL level was because it could suggest a pre-existing risk for heart disease. But what did the LDL cholesterol look like for the people who had heart disease at the time of follow-up?
A shaky foundation of data
The above points help us see that there are a whole lot of things involved here. With so many factors playing a role in heart disease, it’s a pretty tricky web to untangle when asking what causes what! And it’s hard to test for everything, all at the same time.
But some information should not be optional when it comes to a study like this.
Possibly the most important point to question is the foundation this whole study was build on. Eating patterns and the effect on health over the long run, right?
And how did researchers get this information? ONE diet recall at the beginning of the study.
The diet information collected from people was:
- Self-reported – which usually comes with errors … can you remember what you ate las month? last week? how about yesterday?
- Observational – meaning that results might show some kind of link between dietary cholesterol and heart health but don’t show that eggs cause heart disease
- Limited – they were only asked once what their eating pattern was, at the beginning of the studies. It is very likely that people changed the way they ate over time, especially when we’re talking decades. How can we make a conclusion about how eating X food leads to your chance of getting Y condition if intakes are not actually tracked over the whole time.
Just to give you a sense of what a ‘diet recall’ can look like in real-life. When I was in university, I participated in a research study looking at calcium intakes. Part of the information they wanted from me was a list of what I had eaten in the previous week. Picture this: I was a student, living on my own and cooking for myself. I ate the same thing for 5 days straight! That week I had made a huge (time-saving) stir-fry … that I was utterly sick of by Friday by the way. Now imagine this was the only eating information the researchers had collected. I clearly have not eaten the same way in the 15 years since then.
Results are only as good as the data
So that leaves us with with the researchers’ findings that eggs are linked to heart disease risk … but on some pretty shaky assumptions.
- neither eating patterns nor LDL tests were tracked along the way
- some well-proven risks for heart disease were not accounted for, including stress
Going back to my example above, could any conclusion really be made about how that tofu stirfry back in my student days lead to my current health??
After we look at all of the above, there’s one thing left to point out. The increased risk they found was considered modest … not even significant.
Interestingly, this was discussed by Dr. J. Wilkins, one of the researchers on the team, during his interview with JAMA Network last week. If you want to learn more about the study from an insider’s view, read the interview for yourself (see references below).
Eggs can be a delicious and nutrition-packed addition to your eating pattern. But, the jury really does remain out as there have been conflicting results over the years. So to err on the side of ‘the unknown’, some recommendations say to cut back. For some people, cutting back on eggs is not a problem. While for others, it’s a big deal!
Because the role of RDs is to help individuals make the best choices for their own life, it depends on who you talk to as to what they’ll recommend.
For example, speak to an RD who works with those eating mostly plant-based diets and they would likely say ‘if you choose to include eggs, there’s little harm since your unhealthy fat intakes are probably fairly low’. Speak to an RD who works with people lowering their blood cholesterol levels and they might say ‘let’s try eating less eggs and see what happens to your bloodwork’. Speak to an RD who works with someone who just loves eggs and doesn’t want to cut back and they might say ‘well let’s find other ways to decrease your risks’.
Having said that, we can probably agree that in general, there is little risk for most people when they’re eating eggs everyday.
It’s important to remember that when recommendations are made, they’re for whole populations. On an individual level, some people respond differently – some people convert the cholesterol they eat into blood cholesterol more easily than others, and at least part of this is related to genetics.
The research team for this latest study concluded that health guidelines and polices should be updated. However, there is not yet enough new information to come up with a ‘safe’ number of eggs to eat for everyone.
There are some people though who could re-think how often they have eggs.
How many eggs can you eat a day?
Let’s just take a moment to review what some health organizations are saying about eggs:
The American Heart Association says it can be considered just fine for generally healthy people to include 1 whole egg/day or 2 egg whites/day if they want to include eggs in their eating pattern.
A landmark study in the Canadian Journal of Diabetes stated: “Results from randomized controlled trials suggest that consumption of 6 to 12 eggs per week, in the context of a diet that is consistent with guidelines on cardiovascular health promotion, has no adverse effect on major CVD [cardiovascular disease] risk factors in individuals at risk for developing diabetes or with type 2 diabetes.” (Can J Diabetes, 2017)
At the same time though, standard practice tells us that people with diabetes, existing heart disease and dyslipidemia (elevated LDL, TG and/or decreased HDL cholesterols) should limit dietary cholesterol to 200mg/day or less (1 egg/week) to reduce CVD events (PEN). This is based on observations of people with diabetes as well as the cholesterol levels in healthy populations. It also accounts for some people possibly having increased LDL more easily when cholesterol intakes are >200mg.
Neither the 2019 Canada’s Food Guide nor the 2015 Dietary Guidelines for Americans have recommendations to limit cholesterol to specific amounts.
Yet Dr. Wilkins said there’s moderately more risk for people who ate 3-4 eggs per week and who did not have low LDL-cholesterol at the start of the study (not counting those on meds to bring LDL down). And as he pointed out in his interview, people with ‘not low’ cholesterol is different from having high cholesterol.
Is your head spinning yet?
Basically there is no one right answer for everyone. When making any kind of recommendation to people, I prefer to talk about what the possible risks are with any given dietary advice and have them deicide which, if any, risks they are willing to take.
Are eggs bad for YOU?
People who eat eggs and other high-cholesterol foods regularly can consider cutting back.
As I mentioned, some people are choosing to take the side of caution and look at this as an ‘unknown’. Whether eggs lead or heart disease or even increase LDL cholesterol is still up in the air. It hasn’t been conclusively seen as harmful … but might not be beneficial either. At this point, the question for some people is how important is it to them to eat eggs?
Despite the possible flaws of this study, it does suggest that there may be some extra risk if you eat more cholesterol and/or eggs than an average person. Remember this was about 300mg cholesterol and 1/2 an egg daily per person in the US.
What might that look like? If you’re eating 2 or more egg yolks per day, you could consider cutting back and/or taking another look at other ways you’re helping your heart.
Eating for heart health
Whether you choose to watch the number of eggs you eat or not, there are ways you can lower your risk of heart disease. Here are a few ideas:
- Swap saturated and trans fats for more heart healthy fats including avocado or olive oil.
- Cook eggs by poaching or hard-boiling rather than using a lot of butter to fry them. You can also fry or scramble in a non-stick pan or use a vegetable-oil based margarine in place of butter.
- If you choose to cut back on eggs, mix a whole egg in with egg whites to reduce the number of yolks you’re eating.
- Be sure to include foods with heart-healthy fibre, such as oatmeal.
- Increase fruits and vegetables.
- Cut back on red meat.
- Include physical activity in your life, in a way that’s safe and comfortable for you.
But just tell me – are eggs good or bad?
So we’re back to the beginning of the great egg debate. Recommendations from health groups haven’t changed at this point with this new information. Eating more fruits and vegetables, lean proteins and whole grains continues to be a cornerstone of an overall healthy eating pattern. As does limiting refined sugars, unhealthy fats and salt.
Singling out foods as being ‘good’ or ‘bad’ is also not really helpful. For many, eating eggs is a cost-effective and enjoyable way to get a lot of nutrition in a small package! Eggs contain a day’s worth of vitamin B12, 6g of protein as well as calcium, vitamin D, folate, zinc and iron and are relatively low in calories. They have important nutrients, lutein and zeaxanthin, that are known to lower risk of cataracts and macular degeneration. Being versatile, quick and easy, eggs are a great choice for many people.
News stories such as the ones about this egg study can make people feel guilty about their food choices. And when that happens, people turn away from the food in question … toward choices that may be even less healthy.
At the end of the day, paying attention to your heart health means more than just watching the number of eggs you eat. Having said that, there are things we know are good for us. There are things we aren’t sure about and should proceed with caution. And there’s the stuff we know isn’t good for us.
It seems like eggs continue to sit into the grey-zone of uncertainty. Choosing to eat eggs or not is a very individual decision and based on many factors, as I’ve already talked about.
Does the cholesterol in eggs cause heart disease?
Health can be a complex thing to untangle and usually there are no one-size-fits-all or black-and-white answers.
For me, saying the cholesterol in eggs causes heart disease is not accurate. Cause-and-effect was not something this study could clearly point out.
Does that mean everyone should just eat eggs all day? Probably not … but for many reasons, not just because of this study.
My question to you then is, rather than focus on one food that might (or might not) be a problem … how will you add in foods and other lifestyle habits that are known to help your heart?
If you’re looking to learn more about how to eat well to live well with your heart health, find out more about my
Nourish your Heart program. Lower your cholesterol, blood pressure and worries about your heart’s health.
In this program we talk about how to eat for heart health … but it’s so much more! Find out the places to focus your energy when making changes, how to use the info in YOUR real life and get support from a group as well as Angela throughout. Learn more about the program and find out when the next session is open for registration.
Associations of Dietary Cholesterol or Egg Consumption With Incident Cardiovascular Disease and Mortality. Victor W. Zhong,Linda Van Horn,Marilyn C. Cornelis, et al. JAMA. 2019 Mar 19; 321(11):1081-1095. doi: 10.1001/jama.2019.1572. Accessed abstract via PubMed May/19.
expert reaction to study looking at eggs cholesterol and heart disease. Science Media Centre website: http://www.sciencemediacentre.org/expert-reaction-to-study-looking-at-eggs-cholesterol-and-heart-disease/. Accessed May/19
CVD Practice Guidance Toolkit. Practice Evidence-Based Nutrition (PEN) website, subscription required. Accessed April/19.
Are Eggs good for you or Not? American Heart Association website: https://www.heart.org/en/news/2018/08/15/are-eggs-good-for-you-or-not?s=q%253Degg%252520consumption%252520in%252520cardiovascular%252520disease%2526sort%253Drelevancy. Accessed May/19.
Impact of Egg Consumption on Cardiovascular Risk Factors in Individuals with Type 2 Diabetes and at Risk for Developing Diabetes: A Systematic Review of Randomized Nutritional Intervention Studies. Richard C, Cristall L, Fleming E, et al. Can J Diabetes. 2017 Aug; 41(4):453-463. doi: 10.1016/j.jcjd.2016.12.002. Epub 2017 Mar 27. Accessed abstract via PubMed May/19.
A couple of helpful articles I came across:
Are Eggs Good or Bad for You? How you Should Interpret this Latest Study. Forbes.com. https://www.forbes.com/sites/brucelee/2019/03/16/are-eggs-good-or-bad-how-you-should-interpret-this-latest-study/#55314d346525. Accessed May/19
Study puts eggs and dietary cholesterol back on the radar. JAMA Network website: https://jamanetwork.com/journals/jama/fullarticle/2733396?widget=personalizedcontent&previousarticle=2728487. Accessed May/19
Angela Hubbard is a Registered Dietitian (RD) and Certified Diabetes Educator (CDE) with 10 years experience working in the field of nutrition. Her work focuses on helping people take back control of their health & weight … before it feels like their health controls their life. In her off time she loves swapping recipes, creating and exploring Northern BC life with her young family.