February 24, 2020

expert reaction to study looking at foods and stroke risk

A new study has been published examining the relationships between consumption of different foods and different types of stroke.

Dr Riyaz Patel, Associate Professor and Consultant Cardiologist, and Clinical lead for the CVD Prevention Service, Barts Health NHS Trust, said:

“This is a large study which collected very detailed dietary information on over 400,000 people and followed them to see what illnesses they eventually developed after nearly 13 years.

“The results broadly support existing dietary advice and guidelines around fruit and fibre intake, with the novelty of finding which type of stroke may be more affected by which foods.

“As usual, with association studies like this, we cannot conclude that any specific food type is causing benefit or harm, as many factors relevant to food choices, cooking habits and lifestyle cannot be accounted for even with the most robust statistical efforts.

“The population studied is also not representative for the UK, being mostly white European and predominantly female.

“This is a challenging area of research, with many conflicting studies.  As such, the findings from one study should not be taken in isolation to guide food choices.  Instead, the totality of evidence from all available studies should be looked at, which is what is usually done by national and international bodies when they make dietary recommendations for healthy eating.”

Prof Paul Evans, Professor of Cardiovascular Science, University of Sheffield, said:

“This large clinical study analysed the eating habits of more than 400 000 men and women to investigate the possible link between diet and the risk of stroke, which is a major cause of death and disability.  The authors concluded that the risk of a particular form of stroke, called ischemic stroke, was reduced in individuals that consumed more fruit and vegetables, fibre or certain dairy foods.  There is already strong evidence that healthy eating can protect from heart disease and certain forms of cancer and so the findings from the EPIC cohort further emphasise the importance of a balanced fibre-rich diet in maintaining overall health.

“A major strength of this study is that it captured data from a large cohort of individuals from 9 European countries.  However, although the research has discovered an association between dietary intake and stroke risk, it is possible that the altered stroke risk is not caused by the diet itself but is instead caused by associated socioeconomic or lifestyle factors.  Further research is therefore needed to investigate whether diet has a direct influence on stroke risk.”

Dr Richard Francis, Head of Research at the Stroke Association, said:

“By looking at a large number of people over a long period of time, this study adds insight to what we know about diet and stroke risk.  We know that a healthy balanced diet can reduce the risk of stroke already and this study found different foods were linked with different types of stroke.

“The study asked people to recall what they had eaten in the past and didn’t look at what people actually ate over time, so we can’t say for certain that specific foods had caused their stroke.  Your risk of stroke depends on a number of different things too, such as blood pressure and levels of physical activity.

“Although this research found specific foods may be linked to risk of stroke, it’s better to look at your eating and drinking habits overall.  It is not the case that removing one type of food, such as eggs, from your diet will stop you from having a stroke.  To reduce your risk of stroke, focus on eating a healthy diet, keeping active and monitoring your blood pressure.  If you’re concerned about your stroke risk, talk to your GP.”

Does the press release accurately reflect the science?

Yes – it’s a valid point that we need to address the causes of different types of stroke differently.  The end paragraph addresses the weaknesses in epidemiological studies like this.

Is this good quality research?  Are the conclusions backed up by solid data?

Yes, taking into account the weaknesses cited in the press release – looks like they controlled for other risk factors well (although they didn’t have any info on medications people were taking), their interpretation looks sensible to me.

How does this work fit with the existing evidence?

It adds to what we already know.

Have the authors accounted for confounders?  Are there important limitations to be aware of?

Yes – it’s association not causation, and these are stated at the bottom of the press release.

What are the implications in the real world?  Is there any over speculation?

I’d say it’s over speculation to link specific foods to risk – like eggs, as the measures of intake was only taken once and people’s diets are so variable.

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“Very nice study, even if it’s observational and has all the usual caveats of dietary records which can be imprecise.  That said, the paper adds further support for consuming fibre rich foods including fruit and vegetables as a means lower risks for a range of conditions such as diabetes, heart attacks and now extending nicely to stroke.  Its results will lead me to continue to recommend upping fibre intake to individuals with low such intakes.”

‘The associations of major foods and fibre with risks of ischaemic and haemorrhagic stroke: a prospective study of 418 329 participants in the EPIC cohort across nine European countries’ by Tammy Y.N. Tong et al. was published in the European Heart Journal at 00:05 UK time on Monday 24 February 2020.

DOI: 10.1093/eurheartj/ehaa007

Declared interests

Dr Riyaz Patel: “No disclosures relevant to this topic.”

Prof Naveed Sattar: “No COI.”

None others received.