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.
However, do these broad strategies cover all types of stroke? Not all strokes are the same, and now, the authors of a new study acknowledge this by zooming in on the association between certain food groups and two subtypes of stroke: ischemic stroke and hemorrhagic stroke.
Tammy Tong, a nutritional epidemiologist at the Nuffield Department of Population Health at the University of Oxford in the United Kingdom, is the first author of the new paper, which appears in the European Heart Journal.
Ischemic stroke is the most prevalent type of stroke, accounting for about 87% of all stroke cases. Ischemic strokes occur when an artery becomes blocked, compromising the supply of oxygen-rich blood to the brain.
Hemorrhagic stroke, on the other hand, occurs when a blood vessel bursts in the brain, and the bleeding damages brain cells.
In their paper, Tong and team explain that previous research has indeed looked at diet and stroke risk. However, they note that this has mostly focused on total stroke risk (which combines ischemic, hemorrhagic, and “unspecified” strokes) or on 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, considering ischemic and hemorrhagic strokes separately.
The study used data from the European Prospective Investigation into Cancer and Nutrition (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 U.K.
As part of EPIC, the participants answered questions about their habitual diet, lifestyle factors, medical history, and sociodemographic characteristics. The researchers clinically followed the participants for an average period of 12.7 years.
During this time, a total of “4,281 incident cases of fatal or nonfatal ischemic stroke, 1,430 cases of hemorrhagic stroke, and 7,378 cases of total stroke (ischemic, hemorrhagic, and unspecified combined)” occurred.
The researchers used statistical tools to estimate hazard ratios over the follow-up period for “ischemic and hemorrhagic stroke associated with consumption of red and processed meat, poultry, fish, dairy foods, eggs, cereals, fruit and vegetables, legumes, nuts and seeds, and dietary fiber.”
Overall, the research found that a higher intake of either fruit, vegetables, fiber, milk, cheese, or yogurt was associated with a lower risk of ischemic stroke but not with that of hemorrhagic stroke.
Specifically, for every additional 200 grams (g) of fruit and vegetables that a person consumed each day, the relative risk of ischemic stroke was 13% lower, and for each 10 g/day of total dietary fiber, the relative risk was 23% lower.
This, explain the authors, is the equivalent of 1.02 fewer cases of ischemic stroke for fruit and vegetables and 1.86 fewer cases for total dietary fiber per 1,000 participants in a 10 year period.
A finer analysis revealed that citrus fruits, hard fruits (such as apples and pears), bananas, fruiting vegetables, and root vegetables lowered the risk, but that leafy vegetables and cabbages did not.
Furthermore, 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.
On the other hand, egg consumption was “positively associated” with a higher risk of hemorrhagic stroke.
In the EPIC study, participants consumed less than 20 g/day of eggs, on average. Each additional 20 g/day of eggs was associated with a 25% increase in the relative risk of hemorrhagic stroke.
The study’s first author comments on the findings, saying, “The most important finding is that higher consumption of both dietary fiber and fruit and vegetables was strongly associated with lower risks of ischemic stroke, which supports 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
In the U.S., the American Heart Association (AHA) recommend four servings of fruit and five servings of vegetables per day.
According to the Food and Drug Administration (FDA), a person should consume 25 grams of fiber a day, based on a 2,000 calorie diet.
First author Tong further comments on what makes this research important and reliable.
She says, “Our study also highlights the importance of examining stroke subtypes separately, as the dietary associations differ for ischemic and hemorrhagic stroke, and is consistent with other evidence, which shows that other risk factors, such as cholesterol levels or obesity, also influence the two stroke subtypes differently.”
The large number of people included in the study and the long follow-up period are further strengths of the study, write the authors, along with the inclusion of major food groups and the statistical adjustment for several important confounders.
However, the analysis is merely observational, meaning that it cannot determine causality between the foods that the participants consumed and the risk of stroke subtypes.
A further limitation of the study is the fact that the collection of dietary data only took place at one point in time. Also, the researchers did not have access to information on medication use, including statins.
Finally, the findings may not be completely generalizable as most participants were white Europeans.