The first study, published in the journal Heart, analyzed data from over half a million adults aged in China and found that daily egg consumption may reduce the risk of cardiovascular disease, compared with eating no eggs.
The second study, published recently in The American Journal of Clinical Nutrition, found that, despite conflicting dietary advice, there was no increase in cardiovascular risk factors in people with pre-diabetes or type 2 diabetes from eating up to 12 eggs a week. This intervention study was performed by scientists at the University of Sydney in Australia.
The American Egg Board welcomed the Sydney study’s findings. Rachel Bassler, RD, at the Egg Nutrition Center in Chicago, told FoodNavigator-USA: “It is very promising to see results like this after a year follow-up that the effects remained consistent with the findings in the original 3-month clinical trial conducted by the University of Sydney. Health organizations, like the American Heart Association, have removed previous egg and cholesterol restrictions due to clinical evidence that demonstrates that dietary cholesterol does not raise blood cholesterol levels in healthy people.
“This research adds to that existing body of evidence showing that egg consumption is not detrimental to those with established type 2 diabetes. I should note that other randomized controlled trials are needed for us to fully confirm these findings.”
Half a million Chinese adults
The Heart study assessed data from the China Kadoorie Biobank (CKB) for 512,891 adults aged between 30 and 79 from 10 different geographical areas in China. The scientists, led by Professor Liming Li and Dr Canqing Yu from the School of Public Health at the Peking University Health Science Center, focused their analysis on the 416,213 people who were free of prior cancer, cardiovascular disease (CVD) and diabetes at the start of the study.
During the course of almost 9 years of study, the researchers documented 83,977 cases of CVD, and 9,985 CVD deaths. In addition, they documented 5,103 major coronary events.
The data, which show correlation and not causation, indicated that daily egg consumption (up to one egg/day) was associated with a 26% lower risk of hemorrhagic stroke – the type of stroke with a higher prevalence rate in China than in high-income countries – a 28% lower risk of hemorrhagic stroke death and an 18% lower risk of CVD death.
In addition, there was a 12% reduction in risk of ischemic heart disease observed for people consuming eggs daily (estimated amount 5.32 eggs/week), compared with the ‘never/rarely’ consumption category (2.03 eggs/week).
Commenting on these findings, the Egg Nutrition Center Research's Bassler noted that previous research has demonstrated the positive impact egg intake can have on muscle, weight management and cognition, "but now it’s pointing to eggs’ potential benefit on cardiovascular disease risk as well.
"A new study, which followed nearly half a million individuals, found that daily egg consumption was associated with a 11% lower risk of cardiovascular disease. This study supports a body of evidence demonstrating egg intake may actually lower one’s risk of cardiovascular disease. A 2016 meta-analysis showed daily egg intake may decrease stroke risk by 12%, and other research has indicated that eating eggs may have positive benefits on markers risk factors for heart disease."
“Our findings of the inverse associations implicated that other components from eggs could have a favorable effect on cardiovascular health,” wrote the researchers. “Egg-derived phospholipid can raise HDL levels and enhance HDL function via preferentially incorporating into HDL cholesterol particles, further slowing down the progress of atherosclerosis. Likewise, high-quality egg protein resulted in greater satiety, lower postprandial glycaemia and insulinaemia, and reduced subsequent food intake in healthy and overweight individuals.
“Intake of eggs also increased plasma lutein and zeaxanthin, which play an important role in protecting against oxidation, inflammation and atherosclerosis. Notably, these two carotenoids derived from eggs had higher bioavailability than those derived from vegetables or fruits and promoted carotenoid absorption from other carotenoid-rich foods,” they added.
“The present study finds that there is an association between moderate level of egg consumption (up to 1 egg/day) and a lower cardiac event rate.
“Our findings contribute scientific evidence to the dietary guidelines with regard to egg consumption for the healthy Chinese adult,” concluded the researchers.
Eggs and pre-diabetes or type 2 diabetes
The second study, published in The American Journal of Clinical Nutrition, was conducted by scientists from the University of Sydney in Australia. Led by Dr Nick Fuller, the study built on an early three-month study that aimed to assess the impact of a high-egg (12 eggs per week) or low-egg (less than two eggs per week) diet. The same participants embarked on a weight loss diet for an additional three months, while continuing their high or low egg consumption. For a further six months – up to 12 months in total – participants were followed up by researchers and continued their high or low egg intake.
The data indicated that, regardless of egg consumption, neither groups showed no adverse changes in cardiovascular risk markers and achieved equivalent weight.
“Despite differing advice around safe levels of egg consumption for people with pre-diabetes and type 2 diabetes, our research indicates people do not need to hold back from eating eggs if this is part of a healthy diet,” Dr Fuller said.
“While eggs themselves are high in dietary cholesterol – and people with type 2 diabetes tend to have higher levels of the ‘bad’ low density lipoprotein (LDL) cholesterol – this study supports existing research that shows consumption of eggs has little effect on the levels of cholesterol in the blood of the people eating them,” he added.
The research was supported with a grant from Australian Eggs.
Overall, per capita consumption of eggs in the US is increasing, according to the American Egg Board, with some of this attributed to the protein craze. (Per capita consumption is not a measure of demand. It is a measure of total egg production, less exports, plus imports, divided by the total population.)
Based on figures from the USDA, per capita consumption I n2017 was 279 eggs per person, per year. To put this in a broader context, US egg consumption peaked in the 1940s at around 380 eggs per person per year (more than one a day).
“Associations of egg consumption with cardiovascular disease in a cohort study of 0.5 million Chinese adults”
Authors: C. Qin et al.
The American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.1093/ajcn/nqy048
“Effect of a high-egg diet on cardiometabolic risk factors in people with type 2 diabetes: the Diabetes and Egg (DIABEGG) Study—randomized weight-loss and follow-up phase”
Authors: N.R. Fuller et al.