Niha Zubair, Arivale Clinical Research Scientist, PhD
[Arivale Hot Topics address health stories currently in the news. The Arivale Clinical Team’s commentary on these news articles is not a review of the scientific evidence, nor an endorsement of a specific study, and is not meant as official medical opinion.]
Cardiovascular disease is one of the leading causes of death and disability worldwide. We know blood cholesterol levels play an important part in the development of cardiovascular disease, however, whether foods high in dietary cholesterol, specifically eggs, contribute to the development of cardiovascular disease is less clear.
Much previous thinking held that because egg yolks contain a lot of cholesterol, and high levels of LDL – or bad – cholesterol in the blood increase the risk of cardiovascular disease, avoiding eggs was best.
But, previous studies have shown it’s actually saturated and trans fat, rather than cholesterol per se, that most increases the risk of cardiovascular disease. And now, the new study shows eating eggs may actually be linked to a reduced risk of cardiovascular disease.
From 2004 to 2008, researchers asked over half a million people between the ages of 30 and 79 in China about their egg consumption. The participants were free of cardiovascular disease, as well as cancer and diabetes. Approximately 13 percent of participants said they ate eggs daily; approximately 9.1 percent said they never or very rarely ate eggs. Researchers tracked participants to monitor their cardiovascular health for an average of nine years afterward.
Here’s what researchers found in participants who said they ate eggs daily compared to those who said they never or very rarely ate eggs:
- 26 percent lower risk of bleeding-related stroke
- 10 percent lower risk of clot-based stroke
- 11 percent lower risk of heart disease
- 18 percent lower risk of dying from heart disease during the study period
These effects were seen after accounting for potential factors that could influence egg consumption and cardiovascular disease, such as income, body mass index, dietary pattern, and sex.
Overall, the study finds there’s an association between moderate egg consumption and a lower rate of cardiovascular events. The study doesn’t delve into how or why this association occurs.
The Time article speculates on a few reasons why eggs might be protective for the heart. One reason they cite is that “while eggs may be high in total cholesterol, much of that is due to their high HDL, or good cholesterol.” This is not true. Eggs are high in dietary cholesterol but don’t contain any high-density lipoprotein, or HDL cholesterol. Actually, no foods contain HDL cholesterol! HDL cholesterol is created by the body and is called “good cholesterol” because it helps remove other forms of cholesterol from your bloodstream. Some studies do suggest egg consumption may increase your body’s production of HDL.
As with any study, there are some limitations. Assessing dietary intake is a tricky task. Participants (and people in general) are not always great at remembering what they ate, especially if they have to remember from a while back. Also, participants may answer a question based on their beliefs of what is or isn’t healthy. A specific limitation to this study is that habitual egg consumption was collected once at the beginning of the study and might not reflect dietary habits over the follow-up years.
Another note of caution is the generalizability of this study. The study was conducted in a Chinese population that was free of cardiovascular disease, cancer, and diabetes from 10 survey sites across China. The genetic makeup, dietary habits, and lifestyle and environmental characteristics unique to this population may play a part in why a beneficial association with egg intake and heart health was observed. It’s unclear if we would see such an association in other populations.
That being said, eggs can be part of a heart-healthy and well-balanced diet.
While one egg yolk has 200mg of cholesterol – making it one of the richest sources of dietary cholesterol – it’s important to distinguish between dietary cholesterol and cholesterol in the blood, which are not strongly correlated. Because of this, the American Dietary Guidelines in 2015 removed its prior recommendation to limit consumption of dietary cholesterol.
While there’s no conclusive science on exactly how many eggs one should eat a day, it seems that – for people who are generally healthy – eating an egg a day can be safe and may even have some benefit. Some evidence suggests that for individuals with diabetes or heart disease, it might be best to limit egg consumption to a few times a week.