Behind the headlines

Does eating an egg reduce my risk of stroke?

egg in eggcup

According to the headlines, if you eat one egg for breakfast you’ll cut your risk of stroke. We investigate whether there’s truth behind this claim.

The study, published in the Journal of the American College of Nutrition, reports that eating up to one egg per day had no noticeable effect on your risk of coronary heart disease (CHD) but was associated with a 12 per cent reduction of stroke risk.

The research

The findings come from reviewing and analysing studies from 1982 to 2014, which evaluated relationships between egg intake and coronary heart disease (including a total of 276,000 people) and stroke (a total of 308,000 people).

They found that having one egg a day, compared to two eggs or less per week was linked to a 12 per cent reduced risk of stroke. The reductions in risk were linked to the two most common types of stroke (ischaemic and haemorrhagic) as well as for fatal stroke.

However, even the researchers themselves said that the study highlights a connection, rather than cause and effect, and more research is needed to understand this link. “It may be possible that those who consume eggs regularly may engage in other favourable dietary and lifestyle habits”, the study paper says.

The research paper says that while a single large egg containing approximately 186 mg of cholesterol, they also contain protein, essential fatty acids, antioxidants, vitamins, and minerals. They are a nutrient-dense food and should be evaluated as a whole, rather than just focusing on one element, such as cholesterol, the researchers said.

The research also relied on self-reported dietary and lifestyle information, which may not always be accurate. 

The research was partially funded by the Egg Nutrition Center, which is part of the American Egg Board, although the researchers say that “design, analysis, writing, and interpretation of study findings were performed independently by the study authors.”

A strength of the research was that it is based on a large number of people, and is based on studies that largely adjusted their data for important factors, such as physical activity, body mass index, and smoking, which could have had changed the results. But two of the studies didn’t adjust for any of these factors, and one only adjusted for people’s age, which makes the result less reliable.

The main study results also excluded specific studies that could be unrepresentative of the wider population.

Eggs are a nutritious food, but you do need to pay attention to how the eggs are cooked and to the trimmings that come with them

The BHF view

Victoria Taylor, Senior Dietician at the British Heart Foundation, said: “This review reinforces previous research that moderate egg consumption does not increase the risk of heart disease in healthy individuals. They can be eaten as part of a healthy diet.

“Eggs are a nutritious food, but you do need to pay attention to how the eggs are cooked and to the trimmings that come with them. For example, poached eggs on wholegrain toast is a much healthier meal than a traditional fry up.

“The fact that eggs can reduce your risk of having a stroke is interesting, however more research is needed to fully understand this association,” she said.

The media coverage

The story got widespread coverage in the national press, such as the Sun, the Mirror, and the Daily Mail.

The Sun stated that “Eating an egg a day ‘keeps STROKE at bay – slashing your risk by 12%’”. This could be over-stating the findings, as the researchers found an association between the two, not a known cause and effect.

In some coverage it was not clear that the scientists reviewed pre-existing research, rather than carrying out a new study, or that it looked at 14 separate research projects that covered 30 years in total. For example, the Telegraph said ‘Scientists looked at research conducted over more than 30 years’. This may be misleading as it sounds like they conducted a 30-year-long research project, when actually the follow-up periods ranged from six years to 26 years.

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