Everyone knows that dietary fiber is essential for digestive health, and that fiber-rich diets reduce the risk of cardiovascular disease. A new cross-sectional analysis of data from more than 4,600 Americans indicates that high intake of dietary fiber may also lower the risk of peripheral artery disease (PAD).
Researchers at the Shenzhen Clinical Research Centre for Geriatrics, Guangdong, China, studied ankle-brachial pressure index data, applying univariate and multivariate logistic regression analysis to identify variables associated with PAD. The data were from the US National Health and Nutrition Examination Surveys (NHANES).
The 4,628 participants included in the analysis included a large percentage of high-risk individuals: roughly half had been previously diagnosed with cardiovascular disease, 85% were dyslipidemic, and 33% had type 2 diabetes. All of the subjects had hypertension.
A total of 471 subjects (10.2% of the cohort) had PAD, based on their ankle-brachial pressure index measurements.
“After adjusting for confounding factors, a decreased risk of PAD was observed in hypertensive patients with dietary fiber intake greater than 21 g per day,” reported lead investigator Yingnan Liu. The risk of PAD was approximately 33% lower among those with fiber intake over 21 grams compared with those eating less than that amount of fiber. The study was published in the Journal of Health, Population, and Nutrition, in August.
The risk of PAD was approximately 33% lower among those with fiber intake over 21 grams compared with those eating less than that amount of fiber.
Notably, Liu and colleagues observed an even greater PAD risk reduction of 77% in subjects who were under 60 years of age, and a reduction of 67% in those with normal lipid profiles. This suggests that increased fiber intake is beneficial for the peripheral vasculature, not only for people who already have advanced cardiometabolic conditions, but for those who are still relatively young and healthy.
There was also an impressive 50% PAD risk reduction associated with fiber intake over 21 grams, in a subgroup of hypertensive but non-diabetic subjects.
Though it doesn’t generally get as much attention as coronary artery disease, PAD is a significant global health problem, Liu and colleagues write. It affects roughly 10% of the global population, especially people over the age of 70. As in the coronary arteries, atherosclerosis is the primary culprit causing peripheral artery occlusion.
Several studies have suggested that blood pressure is closely related to the risk of PAD, and that hypertension increases the risk of PAD. It also seems to be true that PAD is associated with left ventricular hypertrophy, increased risk of cardiovascular events, and increased risk of all-cause mortality and cardiovascular mortality in hypertensive people.
The Shenzhen researchers controlled for a wide spectrum of potentially confounding variables including: age, education level, race, smoking and alcohol history, physical activity level, BMI, dyslipidemia, and diabetes.
Given that this is a cross-sectional analysis, not a prospective intervention trial, it is not possible to definitively prove a causal relationship between dietary fiber intake and reduced PAD. But the associations described by Liu and colleagues are robust, and they hold up across multiple subgroups.
The Liu study takes on added significance when viewed in light of other recent studies and systematic reviews showing that higher fiber intake is associated with lower risk of CVD and coronary heart disease; and improved glucose/insulin regulation.
The term “dietary fiber” includes both insoluble fibers like cellulose, hemi-celluloses and lignin, as well as soluble fibres include pectins, β-glucan and hydro-colloids. Since all of these substances are plant-derived, measurements of fiber intake in epidemiological studies like Liu’s are really indicators of the degree to which someone is incorporating fruits, vegetables, and grains in his or her diet.
One need not gorge on fiber-rich foods or fiber supplements in order to obtain the cardiovascular benefits indicated by the study.
While current guidelines recommend that adults eat between 25 to 30 grams of fiber daily, the reality is that the average in the US is 15 grams daily—roughly half the recommended amount.
The 21-gram threshold used in the Liu study is actually lower than the current recommendation. This suggests that one need not gorge on fiber-rich foods or fiber supplements in order to obtain the cardiovascular benefits indicated by the study. 21 grams is still on the low side of “healthy.”
“More attention should be paid on the quality of diet in hypertensive people,” write Liu and colleagues. They suggest that it makes sense to include recommendations for fiber-rich diets in both CVD prevention and treatment programs, and called for fiber intervention trials to test whether increasing fiber intake will translate into reduced incidence of PAD.
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