Are eggs good for you or not?

We look at the health benefits of eggs -- and the controversy surrounding a new study that suggests egg yolks could be hazardous to your health.

Eggs are bad for you. No, they’re good for you. Now they’re not so good for you? Small surprise we’re so confused about making healthy food choices when studies seem to contradict each other.

What set off the latest debate was a study out of the University of Western Ontario that claimed regularly consuming egg yolks over a long period leads to a greater build up of plaque in the arteries than moderation consumption. To quote lead researcher Dr. David Spence in a UWO press release:

“What we have shown is that with aging, plaque builds up gradually in the arteries of Canadians, and egg yolks make it build up faster — about two-thirds as much as smoking. In the long haul, egg yolks are not okay for most Canadians.”

Yes, you read that right: Researchers compared eating eggs to smoking — and that claim has a lot of people upset. Since the study’s publication, dieticians, doctors, bloggers and the egg industry have been questioning the validity of the study.

Eggs are a hot topic in recent weeks — but should this one study cause us to change our diets?

What we know about eggs

They offer nutrients that benefit our health. The biggest strike against eggs is that they’re high in cholesterol roughly 190-200 mg per large egg — that’s a significant part of the 300 mg daily limit experts say most adults should stay under.

However, there are some good reasons to include them in your diet. They are relatively low in calories at (70-80 per egg), a good source of vitamin B12 and one of the few food sources of vitamin D. You’ll also get modest amounts of folate, riboflavin and vitamin E. They’re low in sodium too: only 55 mg.

Eggs are also high in choline which supports brain development and functioning. They’re a good source of lutein and zeaxanthin which help reduce the risk of age-related macular degeneration and cataracts. Some studies even suggest that people who have higher levels of lutein in their blood tend to have healthier blood vessels.

Eggs increase satiety. When it comes to protein, eggs offer a good amount — 6 g worth — but it’s a complete protein that offers all nine amino acids our bodies can’t make. They also have about 5 g of fat, but only 1.5 g is saturated fat. Together, you’ve got the right mix of nutrients to keep you feeling fuller longer.

Diet plays a smaller role in our cholesterol levels than we think. You might think the more cholesterol we eat, the more shows up in blood — but it’s not so simple. Experts say our diets are responsible for only 20-30 per cent of the cholesterol in our bodies. Our bodies make the other two thirds, and the amount depends on factors such as age, weight, sex and genes.

In addition, it’s saturated fat — not the cholesterol in foods — that is the main culprit. Previous research has shown that saturated fat consumption can increase our  LDL-based cholesterol levels (the “bad” cholesterol) and lower HDL-based cholesterol levels (the “good” cholesterol).

How does this apply to eggs? A handful of studies have found that consuming whole eggs on a regular basis doesn’t lead to an increase in cholesterol levels in the short term. (Though the UWO study’s claims were about the long-term effects.)

Overall dietary habits matter more than individual foods. Experts constantly remind us it’s our overall diet that makes the difference, not loading up on one or two foods. Unfortunately, eggs can get a bad reputation for the company they keep — like bacon and sausage. We have to consider them in context, not in isolation.

No one should load up on eggs, but experts say most healthy adults can include them as part of a healthy diet that’s low in saturated fats and cholesterol. In other words, if you’re going to enjoy eggs, then ease off other dietary sources of saturated fat and cholesterol to balance it. People with certain conditions such as diabetes, high cholesterol levels and high blood pressure should still minimize their egg yolk consumption. (For more information, check out the post in the Harvard Health Newsletter.)

What about Dr. Spence’s claims about the influence of egg industry marketing? There is a large body of research published in reputable health journals — and we should be mindful of who is funding it and if there are any conflicts of interest.

Why the study’s results raise questions

It’s important to remember that this study is just one in a much larger body of research — and it doesn’t necessarily obscure what comes before. Experts have already come out with several critiques of the study:

The limited sample pool. The participants were current cardiovascular patients with an average age of 61 and aren’t representative of the general population. Many commenters have stepped up to say they regularly eat eggs and their cholesterol levels are just fine — like holistic nutritionist Julie Daniluk in her blog post Are eggs dangerous? 

The role of self-reporting. How good is your memory of what you ate for the past decade or more? Surveys and interviews are a necessary part of many studies, but the results rely on the accuracy of people’s responses.

Another issue: it isn’t clear whether people understood to include eggs as an ingredient in foods such as baked goods. The amounts may not be huge, but experts at the American Heart Association say they still count towards your daily cholesterol intake.

Some essential variables were excluded. Remember experiments in science class? You didn’t try to tackle too many questions at once and you had to limit your variables. In this case, important factors like physical activity and diet weren’t included. Even the study’s researchers noted that more research needs to be done.

Correlation does not equal causation. Research involving food can be a tricky area — it’s often hard to prove that a certain food has a certain affect. In this study, researchers found a link that’s worth further investigation, but they can’t say for certain that eggs were responsible for accelerating plaque build up.

If you read the press release, you’ll note that the study’s authors recommended that people at risk for cardiovascular disease should avoid eggs. They didn’t say everyone should drop eggs from their diet.

Experts such as Dr. David L. Katz, director of the Yale Prevention Research Center, also notes that this study was “observational” rather than “intervention”.  In a recent article on the Huffington Post, he explains the true test of whether a food causes a particular issue or not is to remove it from the diet. In this case, would limiting or avoiding egg yolks reduce levels of plaque in the arteries? Would it have a short-term effect? A long-term effect?

Clearly, we haven’t heard the end of the egg debate — and we won’t for some time as new research comes to light.

In the meantime, should you eat eggs — and how many can you safely consume? That’s up to you and your doctor (and cardiologist or dietician, if you have one). As with any published study, experts say it’s a good idea to get some professional advice before you make any changes.

Additional sources: Business Insider Science, The Cleveland Clinic, Eggs.ca, GetCracking.ca, Harvard School of Public Health, Health Canada, the Mayo Clinic, MedicineNet.com, Time Healthland

Photo ©iStockphoto.com/ Stasys Eidiejus

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