How different diets affect the risk of various types of stroke

A new study examines the associations between certain foods and the risk of either an ischemic or hemorrhagic stroke. The in-depth findings provide nuanced insights into which foods are associated with a lower risk of various stroke types.

Higher fruit and vegetable intakes can lower the risk of ischemic stroke.
Higher fruit and vegetable intakes can lower the risk of ischemic stroke.

Stroke is a major cause of mortality in the United States, with the condition being responsible for 1 in every 20 deaths each year. According to the Centers for Disease Control and Prevention (CDC), more than 795,000 people in the U.S. experience a stroke every year, and 140,000 die as a result.

In this context, strategies for preventing stroke are of the utmost importance.

Exercising more, quitting smoking, eating more fruit and vegetables, and avoiding foods high in cholesterol — such as cheese, burgers, and some desserts— are only some of the well-known ways to improve cardiovascular health and keep the risk of stroke to a minimum.

Do these broad strategies however cover all stroke types? Not all strokes are the same, and now a new study’s authors acknowledge this by zooming in on the association of certain food groups with two stroke subtypes: ischemic stroke and hemorrhagic stroke.

Tammy Tong, a nutritional epidemiologist at the University of Oxford, UK’s Nuffield Department of Population Health, is the first author of the new paper that appears in the European Heart Journal.

The need for new research

Ischemic stroke is the most prevalent type of stroke, representing about 87 percent of all cases of stroke. Ischemic strokes occur when an artery becomes blocked, and the supply of oxygen-rich blood to the brain is compromised.

On the other side, hemorrhagic stroke happens when a blood vessel bursts in the brain, and the bleeding kills the brain cells.

Tong and team demonstrate in their paper that earlier research has indeed looked at the danger of diets and strokes. They note, however, that this has focused mostly on total risk of stroke (which combines ischemic, hemorrhagic, and “unspecified” strokes) or ischemic stroke, as this type tends to occur more often.

So, the authors set out to examine the associations between dietary intake — focusing on major food groups and fiber — and stroke, separately considering ischemic and hemorrhagic strokes.

Studying different foods and stroke types

The study used data from EPIC, a large cohort of more than 418,329 people from nine European countries: Denmark, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the United Kingdom.

The participants responded to questions about their usual diet, lifestyle factors, medical history and sociodemographic characteristics as part of EPIC. Clinically, the researchers tracked the participants over an average 12.7 year period.

A total of “4,281 instances of fatal or non-fatal ischemic stroke, 1,430 cases of hemorrhagic stroke and 7,378 cases of total stroke (ischemic, hemorrhagic, and unspecified combined)” occurred during this time period.

The researchers used statistical tools to estimate hazard ratios over the follow-up period for “ischemical and hemorrhagic stroke associated with the intake of red and processed meat, poultry, fish, dairy products, eggs, cereals, fruit and vegetables, legumes, nuts and seeds, and dietary fibre.”

Eggs may raise hemorrhagic stroke risk

Overall, the research found that a higher intake of either fruit, vegetables, fibre, milk, cheese, or yogurt was associated with a lower risk of ischemic stroke but not with hemorrhagic stroke.

Specifically, the relative risk of ischemic stroke was 13 percent lower for every additional 200 grams (g) of fruit and vegetables a person consumed each day, and the relative risk of total dietary fiber was 23 percent lower for every 10 g / day.

This, the authors explain, is the equivalent of 1.02 fewer ischemic stroke cases for fruit and vegetables, and 1.86 fewer cases for total dietary fiber per 1,000 participants over a 10-year period.

A finer analysis revealed that the risk was reduced by citrus fruits, hard fruits (such as apples and pears), bananas, fruiting vegetables, and root vegetables but not by leafy vegetables and cabbages.

In addition, 200 g / day of milk was associated with a 5% lower relative risk of ischemic stroke, 100 g / day of yogurt with a 9% lower relative risk and 30 g / day of cheese with a 12% lower relative risk, respectively.

On the other hand, the use of eggs was “positively associated” with an increased risk of hemorrhagic stroke.

Participants consumed less than 20 g / day of eggs an average in the EPIC study. A 25 per cent increase in the relative risk of hemorrhagic stroke was associated with each additional 20 g / day of eggs.

Some foods lower ischemic stroke risk

The first author of the study reflects on the findings, stating, “The most important finding is that higher dietary fiber and fruit and vegetables intake are strongly associated with lower ischemic stroke risks, which support current European guidelines.”

“The general public should be recommended to increase their fiber and fruit and vegetable consumption, if they are not already meeting these guidelines.”

– Tammy Tong, first author

The American Heart Association (AHA) recommends four fruit portions and five vegetable portions per day in the US.

According to the Food and Drug Administration (FDA), based on a 2,000-calorie diet, a person will consume 25 grams of fibre a day.

Some study strengths and limitations

First author Tong focuses further on what makes this work so relevant and accurate.

She says, “Our study also highlights the importance of examining stroke subtypes separately, since the dietary associations differ for ischemic and hemorrhagic stroke, and is consistent with other evidence that other risk factors, such as cholesterol levels or obesity, also affect the two stroke subtypes differently.”

The large number of people included in the research and the long follow-up duration are further strengths of the analysis, the authors write, together with the inclusion of large food groups and the statistical correction for several significant confounders.

The analysis, however, is mere observational, meaning it can not determine causality between the foods consumed by the participants and the risk of stroke subtypes.

A further drawback of the analysis is the fact that dietary data were only obtained at one point in time. The researchers have lost access to information about the use of medications, including statins.

Finally, the findings may not be fully generalizable since the majority of participants were white Europeans.

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