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An egg a day may keep the heart doctor away

Eggs are a rich source of dietary cholesterol and have been given a bad rap in the past because of this. In a world struggling to understand and change the high incidence of raised cholesterol levels and cardiovascular disease, eggs were a natural target for those wishing to live more heart-healthy lifestyles. 

However, eggs contain a wide range of very important nutrients and are eaten by people all over the world. Studies to establish a link between eating eggs and suffering from cardiovascular disease (CVD) have come up with conflicting results and so the relationship remains a subject of debate. 

A 2018 study published in the journal Heart was focused on data from approximately half a million adults in China. The researchers found that those who ate eggs between 3 and 6 times a week had a substantially lower risk of suffering from heart disease, hypertension and stroke compared to those who ate eggs more or less frequently.

Now, a new study has again sought to establish whether eating eggs is harmful or beneficial to our cardiovascular health by considering the role of cholesterol metabolism in the blood. The authors of this study, published in the journal eLife, conducted population-based research exploring how egg consumption affects biochemical markers of cardiovascular health that are found in the blood.

“Few studies have looked at the role that plasma cholesterol metabolism plays in the association between egg consumption and the risk of cardiovascular diseases, so we wanted to help address this gap,” explained first author Lang Pan of Peking University.

For the investigation, the experts selected 4,778 participants from the China Kadoorie Biobank – 3,401 of them had a cardiovascular disease and 1,377 did not. The team then used a technique called targeted nuclear magnetic resonance to measure the levels of 225 different metabolites present in the blood plasma of each of the participants. The researchers identified 24 of these metabolites that were associated statistically with self-reported levels of egg consumption.

Of these 24 metabolites associated with eating eggs, 14 of them were linked specifically to heart disease. The researchers found that participants who ate fewer eggs had lower levels of beneficial metabolites and higher levels of harmful ones in their blood, compared to those who ate eggs more regularly.

In particular, the results of the analysis showed that individuals who ate eggs in moderation had higher levels of a protein in their blood called apolipoprotein A1, a building-block of high-density lipoprotein (HDL), which is also known sometimes as “good lipoprotein.” These individuals had more large HDL molecules in their blood; these are molecules that help clear cholesterol from blood vessels, thereby protecting them from blockages that can lead to heart attacks and strokes.

“Together, our results provide a potential explanation for how eating a moderate amount of eggs can help protect against heart disease,” said study co-author Professor Canqing Yu. “More studies are needed to verify the causal roles that lipid metabolites play in the association between egg consumption and the risk of cardiovascular disease.”

“This study may also have implications for Chinese national dietary guidelines,” added senior author Professor Liming Li. “Current health guidelines in China suggest eating one egg a day, but data indicate that the average consumption is lower than this. Our work highlights the need for more strategies to encourage moderate egg consumption among the population, to help lower the overall risk of cardiovascular disease.”

By Alison Bosman, Staff Writer

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