In this meta-analysis, a higher fiber intake was associated with a lower risk of all-cause mortality in participants with cardiovascular disease. Increasing fiber intake also improved blood pressure and blood lipids in participants with cardiovascular disease or hypertension.
A higher dietary fiber intake is generally associated with a reduced risk of many chronic diseases in observational studies and has been shown to improve glycemic control and cardiometabolic risk factors in people with diabetes. However, whether a higher dietary fiber intake improves disease management in people with cardiovascular disease or hypertension had not been determined.
This meta-analysis of 3 prospective cohort studies (including 7,469 participants followed for an average of 8.6 years) and 12 randomized controlled trials (including 878 participants) examined the effect of a high fiber diet in people with cardiovascular disease.
Randomized controlled trials were included if (i) the intervention involved an increase in fiber intake, (ii) the intervention was at least 6 weeks long, and (iii) the participants had either cardiovascular disease or hypertension (i.e., a systolic blood pressure > 130 mmHg). The increase in fiber intake ranged between 5.6 grams and 12 grams per day.
The outcomes assessed in the prospective cohort studies were all-cause mortality and cardiovascular-disease-related mortality. The outcomes assessed in the randomized controlled trials were blood lipids, blood pressure, and fasting blood glucose and insulin.
In the prospective cohort studies, the risk of all-cause mortality was 25% lower in the group who consumed the most fiber compared to the group who consumed the least. Additionally, each 10-gram increment in fiber consumed per day was associated with a 14% lower risk of all-cause mortality, for up to 35 grams per day (data on higher intakes were not available).
In the randomized controlled trials, increasing fiber intake reduced LDL-C by about 18 mg/dL in people with cardiovascular disease, but the certainty of evidence was low. In people with hypertension, increasing fiber intake reduced systolic and diastolic blood pressure by 4.3 and 3.1 mmHg, respectively. Additionally, increasing fiber intake reduced LDL-C by about 11 mg/dL, triglycerides by 17 mg/dL, fasting blood glucose by 8.6 mg/dL, and fasting blood insulin by 3.5 pmol/L. The certainty of evidence for LDL-C and triglycerides was low.
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