First eggs are bad. Then they’re OK. Now they’re bad again. Nutrition Diva puts the latest study on eggs and cholesterol in perspective (and provides solid, scientifically-based advice without the hype).
First eggs are bad. Then they’re OK. Now they’re bad again. Nutrition Diva puts the latest study on eggs and cholesterol in perspective (and provides solid, scientifically-based advice without the hype).
Nutrition Diva is hosted by Monica Reinagel, MS, LDN. Transcripts are available at Simplecast.
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In last week’s Nutrition Diva podcast, I talked about the potential benefits of omega-3 eggs. Ironically, shortly before that episode was released, a new study came out that was widely covered in the media, finding that people who ate more than a few eggs a week had an increased risk of heart disease and death.
This headline wouldn’t have raised any eyebrows 20 years ago, when we firmly (but falsely) believed that eating foods that contained cholesterol would contribute to high blood cholesterol and heart disease risk.
But in 2016, the Dietary Guidelines for Americans officially removed cholesterol from the list of nutrients that we need to worry about limiting. This was based on an accumulating stack of epidemiological evidence finding no clear link between dietary cholesterol and heart disease risk.
In addition to these observational studies, there have also been controlled diet studies which are able to provide more reliable information about cause and effect. Most of these found that diets containing more cholesterol did not increase heart disease risk factors compared to similar diets that were lower in cholesterol.
All of this evidence ultimately led the USDA to take cholesterol off the list of nutrients of concern. This decision was not an impulsive one. In fact, many in the health and nutrition community felt that it took the USDA 10 or 20 years longer than it should have to let eggs and cholesterol off the hook.
When this latest study hit the newswire, dozens of concerned Nutrition Diva listeners reached out to me for comment. And I totally sympathize with those of you who feel jerked around. First eggs are bad. Then they’re fine. Now they’re bad again. So let me try to put this latest headline in perspective.
These findings weren’t actually about eggs. They were about cholesterol.
The first thing you need to know about this study is that the increase in risk was pretty modest. Overall, 18% of the people the researchers followed developed heart disease over the course of a couple of decades. Of those who had more cholesterol in their diets, 21% developed heart disease. So, according to this study, if you have a low cholesterol diet, your risk of developing heart disease is just under 1 in 5. If you have a high cholesterol diet, your risk is just over 1 in 5.
The second thing you need to know is that these findings weren’t actually about eggs. They were about cholesterol. The analysis found that those consuming more than 300 mg of cholesterol a day had an increased risk of heart disease. They also found an increased risk among those eating more than 3 eggs a week. But the association between egg consumption and heart disease disappeared when they adjusted for cholesterol consumption. It wasn’t eggs per se that was increasing the risk, it was the cholesterol.
Most of the cholesterol we take in comes from meat, poultry, fish, and dairy products. Eggs account for only 25% of the cholesterol in the typical diet. The conclusion that it’s only safe to consume 3-4 eggs a week is based on the assumption that you are also eating meat, poultry, fish, and/or dairy products on a daily basis. And that may or may not be true for you. If you don’t eat meat, for example, then you could eat a dozen eggs a week.
But is this association between cholesterol and heart disease even real? This latest study was a meta-analysis of six observational studies. In each of these studies, they asked a big group of people about their diet. Then they followed them for decades to see what sort of health problems they developed. Then they crunched the data to look for associations between their diet and their health.
But this is not the first time researchers have crunched this type of data. One big question is why this latest study found a link between cholesterol and heart disease when so many previous analyses did not? The authors argue that they did a better job adjusting for variables such as smoking, drinking, exercise habits, and other aspects of diet.
Keep in mind that these dietary surveys were done between 1985 and 2005. This was still during a time when people were counselled to limit eggs and cholesterol. So those who were eating a lot of eggs may not have been particularly concerned about nutrition. And that may have spilled over into other aspects of their lifestyle. Indeed, that those who ate the most eggs were more likely to be smokers, more likely to have diabetes, and had lower diet quality over all.
But there’s something else about this study that strikes me as even more problematic. The researchers only asked the subjects about their typical dietary patterns once, at the beginning of each study. They continued to gather data about their health for anywhere from 10 to 30 years. But they assumed that people continued to eat the same way the whole time.
The researchers only asked the subjects about their typical dietary patterns once...continued to gather data for 10-30 years...and assumed that people continued to eat the same way the whole time.
Let me just ask you: Has your diet changed at all over the last 10 years? Mine sure has. We are likely to modify our diets as we go through life in response to evolving research, or a change in our own health, or any number of other influences, including our family, friends, and popular culture.
Let’s say one of these subjects started out as a healthy 49-year-old who reported eating a dozen eggs a week. Two years later at a routine physical, his doctor finds that he has elevated cholesterol. It’s the 90s, so he’s given the standard advice. He starts avoiding eggs and eating a low fat diet, one that’s a lot higher in carbohydrates. Twelve years later, when he’s 63, he has a heart attack. By this point, he’s been eating nothing but egg whites for 12 years. But in this analysis, he’d still be counted as someone who eats a dozen eggs a week and developed heart disease.
Another participant might have been a health-conscious 50-year-old who follows nutrition news avidly. At the time the study begins in 1988, she reports eating 2-3 eggs a week, in line with current recommendations. But over the years, she sees more and more research questioning the relationship between cholesterol and heart disease. Meanwhile, she’s reading a lot about the benefits of higher protein diets. As a result, she starts eating more eggs. At 65, she’s eating 8-10 eggs a week and is heart-disease free. But in this analysis, she’d be counted as someone who eats very few eggs and doesn’t have heart disease.
I actually think it’s pretty unlikely that people’s egg consumption remained constant over the course of these decades and that makes it hard for me to put much confidence in these associations.
In my opinion, when it comes to your risk of heart disease, the amount of cholesterol in your diet plays only a minor role compared to the your overall diet quality and lifestyle. It comes down to the three questions I always ask: How much are are you eating? What are you eating it with? What would you be eating if you weren’t eating that instead?
If you’re replacing your breakfast pastry with a couple of eggs, or your afternoon candy bar with a hard-boiled egg, or your hamburger with a vegetable frittata, I think those eggs are doing a lot more good than harm.
Obviously, it’s possible to overdo just about anything. I’m not suggesting that it’s a good idea to be eating half a dozen eggs every day. But I don’t think you need to limit yourself to 3 eggs a week either. Personally, I feel perfectly comfortable consuming a dozen eggs a week and this study doesn’t change that.