First Stroke Risk Reduced With High Fiber Intake

Persons who eat a high-fiber diet experience a lower risk of first-time stroke, according to a new meta-analysis that supports current guidelines to increase fiber consumption.

“Physicians should be aware that, on average, intakes of dietary fiber in the United States are much lower than recommended goals-about half of what is advised. Reaching the fiber goal is likely to have many health benefits. We think that reducing the long-term stroke risk should be added to that list,” lead author Dr Victoria J. Burley, Senior Lecturer in Nutritional Epidemiology at the School of Food Science and Nutrition at the University of Leeds, Yorkshire, United Kingdom, told ConsultantLive.

Using data from 8 large studies conducted around the world, British researchers found that within the usual range of fiber intakes (from about 10 to 30 g/d), the more fiber persons eat, the lower the risk of stroke. For each 7 g/d increase, the risk of stroke was reduced by 7%.

“To our knowledge, this is the first time this analysis has been done,” said Dr Burley. “This sounds like a small reduction in risk, but because stroke affects so many people, lowering risk by 7% could potentially impact many thousands of individuals.”

The study participants had not previously experienced a stroke, so the results are relevant only to persons with no previous stroke history, Dr Burley noted. “The dose response curve was linear. The 7% reduction was similar in people eating 10 grams of fiber per day and those eating 20 grams per day. However, data points were sparse above about 25 grams per day because fewer people eat those higher amounts of fiber. We can’t say with certainty that we would see the same 7% risk reduction at intake levels well above the recommended amounts.”

Four studies also examined the particular risk of ischemic stroke, which appeared less common with higher total dietary fiber intake in 2 of these studies. Three studies also assessed the particular risk of hemorrhagic stroke, but in these studies the link with dietary fiber intake was less conclusive.

Fiber probably affects stroke risk factors through a variety of mechanisms, including reducing inflammation, energy intake (high-fiber foods tend to satisfy hunger for fewer calories), and the enterohepatic circulation of cholesterol, Dr Burley said.

Unprocessed higher-fiber foods (fruits, vegetables, whole grains, nuts, seeds, and legumes) also are naturally rich in other biologically active components, such as flavonoids, antioxidants, and minerals, that may also have an impact on lowering blood pressure.

“We can’t be sure that the effect we have found on reducing stroke risk isn’t a surrogate effect for a generally healthy lifestyle,” Dr Burley said, “although all of the studies had made statistical adjustments for other lifestyle habits, such as smoking, obesity, and untreated high blood pressure.”

Recommendations of wholesale changes in the diet often are not necessary, Dr Burley noted. “Just substituting refined carbohydrates with the higher-fiber, less refined versions, as well as aiming for 5-a-day intake of fruits and vegetables, will take the average patient a long way toward achieving fiber goals.”

The researchers reported their results online on March 29 in the journal Stroke.