Just when you thought the egg debate was fully cooked, a new study from the University of South Australia suggests that eating an egg a day increases a person’s risk of developing Type 2 diabetes by 60 per cent.

The longitudinal study was based on data from 8545 adults who attended the China Health and Nutrition Survey from 1991 to 2009. The findings are supported by previous population studies in the US and Japan.

The study, conducted in partnership with the China Medical University, and Qatar University, doesn’t prove a causal relationship between eggs and diabetes, more of a concerning association.

But lead researcher Dr Ming Li told The New Daily that the statistical modelling, based on the analysis of nutrition surveys, were “robust” and the conclusions were “plausible.”

Dr Li said the analysis controlled for dietary factors such as processed foods and meat intake, allowing eggs to be reliably targeted.

Dr Ming Li led the study. that found that risky association between eggs and diabetes. Photo: University of South Australia

In a statement, Dr Li said: “What we discovered was that higher long-term egg consumption (greater than 38 grams per day) increased the risk of diabetes among Chinese adults by approximately 25 per cent.

“Furthermore, adults who regularly ate a lot of eggs (over 50 grams, or equivalent to one egg, per day) had an increased risk of diabetes by 60 per cent.”

China as a case study in motion

The 18 years covered by the analysis coincided with a significant lift in prosperity in China, and an associated shift in diet, where a more traditional diet of vegetables and grains was gradually replaced with more unhealthy processed foods, and with more protein, including that from eggs.

It’s this national shift in diet over time that makes the study intriguing – akin to watching a car crash in slow motion – given that egg consumption doubled in China between 1991 and 2009.

But it’s the lift in prevalence of Type 2 diabetes that is staggering. In 1994, according to a 2019 study, 2.5 per cent of the population were estimated to have the disease. By 2009, according to the new study, 11.1 per cent of the population were diabetic.

In Australia, 5.3 per cent of adults had type 2 diabetes in 2017–18, according to self-reported data from the Australian Bureau of Statistics.

So, something is seriously out of whack in China, for sure.

Confused by advice about eggs?

Last year, as The New Daily reported, the Heart Foundation lifted its restrictions on eating full-fat milk, cheese, yoghurt and eggs. You could eat as many eggs as you liked, incorporated into a heart-healthy diet, which means lots of vegetables, whole grains, legumes, fish and poultry.

The trade-off was a reduction in the consumption of red meat.

However, people burdened with high cholesterol or heart disease – and diabetes –  were advised to eat less than seven eggs a week.

A Canadian study published in January found that one egg a day was not linked to risks of heart disease.

A 2018 study led by Dr Nick Fuller from the University of Sydney – funded by a grant from the Australian Egg Corporation – found that eggs might be beneficial for people with diabetes.

Published in the American Journal of Clinical Nutrition, the randomised controlled study compared a high-egg diet (two eggs a day for six days a week) with a low-egg diet (less than two eggs per week) in people with pre-diabetes or type 2 diabetes.

The researchers measured the effect of these diets over three months on cardiovascular and diabetes risk factors.

The study found no significant difference in levels of high-density lipoprotein cholesterol (good cholesterol) between the two groups. Both groups were matched for protein intake, but the high-egg group reported less hunger and greater satiety after breakfast.

“Our research suggests that a high-egg diet – as part of a diet replacing ‘bad’ with ‘good’ fats – can be included safely as part of the dietary management of type 2 diabetes,” Dr Fuller said in a statement at the time.

So what does he make of Dr Li’s study? He said the findings weren’t new – and stressed they showed an association, not a casual link.

Did he find the results interesting? “I find all sorts of research interesting.”

Last year, a Finnish study found consumption of one egg every day seems to associate with a blood metabolite profile that is related to a lower risk of type 2 diabetes. These researchers previously found egg consumption was tied to lower risk of Type 2 diabetes in middle aged men.

They also noted that eggs “remain one of the most controversial foods.”

What other researchers say

In an email responding to questions, Associate Professor Jason Wu, Program Head of Nutrition Science at The George Institute, wrote:

• These types of studies are important, but (they’re) only one piece of the puzzle, because the impact of diet on health is complex and different approaches are needed to complete the picture.
• Studies like the published study generates new hypothesis about possible relationships between foods and disease outcomes, but do not prove causality.
• Data in this field is mixed – we don’t have a clear signal that higher egg consumption is strongly linked to increased risk of diabetes. See here.
• It’s also really important to keep in mind we don’t eat foods in isolation, and the overall dietary pattern matters! If you replace really unhealthy highly processed red meat (sausages for example) with eggs, it is likely beneficial for you.
• Based on current evidence, major dietary guidelines (e.g. from the Heart Foundation of Australia) suggest eggs can form a part of a healthy dietary pattern, that also contain other healthy protein sources such as fish and seafood, beans and lentils, and nuts and seeds.