For the last two days, we’ve covered the “eggs and cholesterol” controversy. Research on the subject goes back decades, with hundreds – if not thousands – of published studies. Now it’s time to look at the latest research on eggs.
Examining such extensive research teases out a clearer picture of the reality. Although some researchers bias their studies’ designs to achieve their preferred outcome, the astute reviewer should spot potential discrepancies.
Systematic research reviews gather evidence from many published studies into a single report, using statistical methods to create a meta-analysis to summarize the results. Unfortunately, meta-analyses aren’t always exempt from bias-related errors.
With more time, I’d review all 1,800 PubMed studies mentioning eggs and cholesterol. Then I’d visually categorize them as mind-map diagrams.
Because I’m an amateur researcher, my biggest category would probably be titled “HUH?” Its first entry would be this study from the Public Library of Science (PLOS) website. It’s titled:
Schistosoma mansoni immunomodulatory molecule Sm16/SPO-1/SmSLP is a member of the trematode-specific helminth defence molecules (HDMs)
and it includes a discussion of parasite eggs!
Nothing enlightening about our topic there – it’s just one of many, many search results unrelated to the eggs-and-cholesterol debate. After eliminating the irrelevant ones so only pertinent studies remain, I can deduce the best balance of evidence.
This time-intensive approach would most likely require team members more familiar with the studies’ scientific terms than I am. And it would be the most thorough investigative method.
The State of the Latest Research on Eggs and Cholesterol
For today, let’s look at some of the differences between four examples of the most recent extensive studies.
Latest Research on Eggs: Study #1
On February 9, 2021, The PLOS Medicine online journal published a cohort study run by researchers at China’s Zhejiang University.
It collated data gathered from 521,120 US participants in the National Institutes of Health-AARP Diet and Health Study and had a 16-year median follow-up.
The researchers’ goal was to measure associations between their egg and cholesterol consumption and all-cause or specific-cause death. They found that eating whole eggs increased the risk of both.
However, replacing half an egg with “egg white/substitutes or other protein sources” containing less cholesterol lowered the risk of “overall mortality and mortality from major causes, including cardiovascular disease, cancer, and respiratory disease.”
They’re basically saying the problem is with the cholesterol-dense egg yolks.
Latest Research on Eggs: Study #2
On August 31, 2020, the Journal of European Nutrition published this meta-analysis by 10 European and American researchers. Using data compiled from 39 studies, they analyzed the relationship between egg consumption and cardiovascular disease risk.
The nearly 2 million participants included:
- 85,053 with congenital heart disease (CHD)
- 25,103 stroke victims
- 7536 with heart failure
- 147,124 with cardiovascular disease (CVD)
The analysis concluded:
“There is no conclusive evidence on the role of egg in CVD risk… higher-quality studies are warranted to obtain stronger evidence for a possible protection of CVD associated with moderate weekly egg consumption compared to no intake.”
However, it continues:
“… equally, future studies may strengthen the evidence for increased heart failure risk associated with high regular egg consumption.”
In other words, the data showed that “moderate weekly egg consumption” may reduce the risk of cardiovascular disease. But “high regular egg consumption” may lead to a higher risk of heart failure.
They recommend more research on both outcomes, so let’s call that one a draw.
Latest Research on Eggs: Study #3
On May 13, 2020, the American Heart Association Journal published a meta-analysis from China’s Huazhong University of Science and Technology.
Again using US data, the researchers wanted to “identify associations between dietary intakes of eggs and cholesterol and all‐cause and heart disease mortality.”
They used information from the 37,121 participants in the 1999-2014 Data from the National Health and Nutrition Examination Survey, which had a 7.8-year follow-up.
They found “no significant association…between dietary cholesterol intake and heart disease mortality.”
That said, they also associated:
- every 50-mg increase in daily dietary cholesterol intakes up to 250 mg with a lower risk of death from any cause.
- every 50-mg increase in daily dietary cholesterol intake over 250 mg lower risk with a greater risk of death from any cause.
More mixed results!
Latest Research on Eggs: Study #4
This meta-analysis from Northwestern and Duke University researchers appeared in the Journal of the American Medical Association’s March 19, 2019 issue.
The researchers asked, “Is consuming dietary cholesterol or eggs associated with incident cardiovascular disease (CVD) and all-cause mortality?”
They analyzed data collected from 29,625 Americans in six separate cohort studies with an average follow-up of 17.5 years.
“Among US adults, higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner. These results should be considered in the development of dietary guidelines and updates.”
So the Northwestern and Duke team came down firmly on the side of limiting dietary cholesterol and eggs.
Summing It All Up
The two most recent studies (PLOS, 16 years median follow-up) and AHA (7.8 years) came to slightly conflicting conclusions.
- The PLOS study found a strong correlation between eating whole eggs (yolks included) and a higher risk of “overall mortality and mortality from major causes, including cardiovascular disease, cancer, and respiratory disease.”
But the researchers also stated that replacing the yolks with “egg whites/substitutes or other protein sources” could lower the risk of death from the same causes.
- The AHA study concluded that consuming between 50 and 250 mg of dietary cholesterol from any source lowered the risk of death from any cause. Anything over 250 mg raised it.
The 2019 JAMA study (17.5 years) concluded that higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner.
That finding makes sense since cholesterol typically takes decades to accumulate in the arteries. The highest rates usually occur in people in their 50s and 60s.
Finally, the JEN meta-analysis, which included 39 studies but provided no length of follow-up, concluded that we need more studies to determine whether eggs help or hurt us!
My Take Concerning the Latest Research on Eggs
It’s logical that the longer-term studies show a correlation between egg consumption and heart disease because it often takes decades for plaque to build up in the arteries.
The short-term study followed people for less than half the period (7.8 years) as the other two (16 and 17.5 years). It’s therefore no surprise that the short-term study failed to show a negative heart disease correlation – it was too short!
What’s missing from the above research is information on what else the participants ate during the studies! If they were consuming lots of animal-based foods, segregating the eggs’ effects would be tricky.
Suppose you smoked a pack of cigarettes every day. How much statistical difference would having one or two extra once or twice a week make in your risk of developing heart disease?
Not much, at least in the short term!
Looking at all these studies, I believe the most logical conclusion is to proceed with caution when eating eggs. Why would I eat any food when its impact on heart disease is shrouded in controversy?
Not when I can eat a whole-food, plant-based food diet- the only one shown conclusively to reverse heart disease!