New research has been released which reaffirms that eating eggs does not pose a risk of cardiovascular disease.
For many years it was believed that cholesterol in eggs could lead to high blood pressure and heart disease, but research over recent years has dispelled this concern.
Last year, however, a US study again raised concerns by suggesting that adults who ate more eggs and dietary cholesterol had a significantly higher risk of cardiovascular disease.
The study, at the Feinberg School of Medicine, suggested that people should reduce their consumption of eggs and red meat.
“Our study showed if two people had exact same diet and the only difference in diet was eggs, then you could directly measure the effect of the egg consumption on heart disease,” said co-corresponding study author Norrina Allen, PhD.
“We found cholesterol, regardless of the source, was associated with an increased risk of heart disease,” she said.
However, new work published in the medical journal The BMJ said there was no evidence that moderate egg consumption was linked to cardiovascular disease.
The study was led by Dr Jean-Philippe Drouin-Chartier at the Department of Nutrition at Harvard.
"The results from our cohort study and updated meta-analysis show that moderate egg consumption (up to one egg per day) is not associated with cardiovascular disease risk overall," the study team concluded.
"Findings were consistent across multiple participant and study characteristics except for geographical region. We found that egg consumption was associated with a slightly lower cardiovascular disease risk among Asian cohorts.
"However, mean egg consumption in the three US cohorts in our study and in cohorts included in the meta-analysis was relatively low.
"This consumption level should be taken into account when interpreting our results because most participants consumed one to less than five eggs per week, and relatively few participants consumed at least one egg per day."
Researchers looked at data from three large US studies - the Nurses’ Health Study (NHS), the NHS II, and the Health Professionals’ Follow-Up Study (HPFS).
These included 83,349 female nurses aged 30-55; 90,214 female nurses aged 25-44; and 42,055 male health professionals aged 40-75, respectively, who were free of CVD, type 2 diabetes, and cancer at the start of the study.
The researchers said in their report that eggs were a major source of dietary cholesterol, but were also an affordable source of high quality protein, iron, unsaturated fatty acids, phospholipids, and carotenoids.
Because of the cholesterol content in eggs, they said, the association between egg intake and cardiovascular disease risk had been a topic of intense debate in the past decade.
Many prospective studies on the association between egg intake and cardiovascular disease risk had provided conflicting findings.
Some studies had reported no association between egg intake and risk of cardiovascular disease, some had reported a higher risk and others had reported an inverse association with cardiovascular disease events or subclinical measures.
Even meta-analyses of prospective studies on egg consumption and cardiovascular disease risk did not provide consistent results and created further confusion, they said.
In their new study, the scientists examined the association between egg intake and incident cardiovascular disease by using repeated measures of diet over up to 32 years of follow-up, with detailed control of dietary and other potential confounders.
They said that the results from the three cohorts they studied and from their updated meta-analysis showed that moderate egg consumption was not associated with cardiovascular disease overall and was associated with potentially lower cardiovascular disease risk in Asian populations.
In 2018, a huge study in China suggested that eating eggs could reduce the risk of heart disease.
Half a million people were recruited for research looking into the associations between egg consumption and cardiovascular disease (CVD), ischaemic heart disease (IHD), major coronary events (MCE), haemorrhagic stroke and ischaemic stroke.
A team including Canqing Yu, an associate professor in the Peking University School of Public Health in Beijing, concluded: "Our findings suggested that daily egg consumption (<1 egg) was associated with lower risk of CVD, IHD, MCE, haemorrhagic stroke and ischaemic stroke among Chinese middle-aged adults.
"Our findings contribute scientific evidence to the dietary guidelines with regard to egg consumption for the healthy Chinese adult."
For many years organisations like the British Heart Foundation and other international bodies involved in promoting a healthy heart recommended that consumers should restrict the number of eggs they ate.
More recent scientific research has reversed this train of thought. In 2015 the British Heart Foundation said that eating eggs should no longer be seen as a heath risk.
Advice to restrict egg consumption was dropped in the United States, too, and other countries around the world, as research started to identify more and more benefits of eating eggs. The research has led to eggs being seen as a superfood.
One large egg provides varying amounts of 13 essential vitamins and minerals, including nutrients that are not found abundantly in other foods, including vitamin D and choline.
Lutein and zeaxanthin, which are present in egg yolk, are antioxidants that may prevent macular degeneration and consequent age-related blindness.
Whilst eggs contain only small amounts of these nutrients, research shows that lutein and zeaxanthin from eggs may be more bioavailable, or better used by the body, than from more concentrated sources like supplements.
A study published in Food and Function found that daily consumption of egg yolks was associated with increases in plasma lutein, zeaxanthin and beta-carotene in people with metabolic syndrome.
There is evidence that eggs can lower breast cancer risk, lower the risk of age related eye disease and lower muscle loss. Scientists say that an egg is an important source of choline.
Studies have shown that choline is needed for optimal foetal brain development, it reduces neural tube risk and lowers inflammation markers. Eating eggs can replace what appears to be a shortage of choline in the diet.
