Does eating more fiber reduce the risk of dying? Original paper

In this meta-analysis of prospective cohort studies, higher fiber intakes were associated with a reduced risk of mortality from all causes, cardiovascular disease, and cancer.

Whether fiber intake is associated with the risk of (i) all-cause mortality, (ii) cardiovascular disease (CVD) mortality, or (iii) cancer mortality.

A total of 1,613,885 participants.

A meta-analysis of 28 prospective cohort studies was performed. Fourteen studies were conducted in Europe, 7 in the United States, and 7 in Asia. The follow-up duration ranged from 5 to 40 years. Most of the studies assessed dietary intake using a food frequency questionnaire and adjusted their results for the following confounders: age, sex, BMI, smoking status, alcohol drinking, educational status, physical activity, and energy intake.

In addition to total fiber intake, analyses were conducted to determine the relationship between the consumption of certain fiber subtypes — cereal, vegetable, fruit, legume, soluble, and insoluble fiber — and mortality risk.

Data comparing the group with the highest fiber intake to the group with the lowest fiber intake were obtained from each study. Dose-response analyses were also conducted to estimate the effect of each 10-gram and 5-gram increase in the daily intakes of total fiber and each fiber subtype.

Compared to lower total fiber intakes, higher total fiber intakes were associated with a 17%, 21%, and 15% lower risk of all-cause mortality, CVD mortality, and cancer mortality, respectively.

According to the dose-response analyses, each 10-gram increase in total daily fiber intake (up to 40 grams) was associated with a 15%, 20%, and 10% lower risk of all-cause mortality, CVD mortality, and cancer mortality, respectively.

A higher intake of each fiber subtype was associated with a reduced risk of all-cause mortality (with the exception of fruit fiber), a reduced risk of CVD mortality, and a reduced risk of cancer mortality (with the exception of fruit fiber, legume fiber, and soluble fiber).

Among fiber subtypes, higher intakes of insoluble fiber were associated with the greatest reductions in all-cause and CVD mortality (−23% and −26%, respectively), compared to lower intakes. However, the dose-response analyses indicated that higher intakes of soluble fiber were associated with the greatest reductions in all-cause and CVD mortality: each 5-gram increase in total daily intake was associated with a 23% lower risk of all-cause mortality (up to 10 grams per day) and a 34% lower risk of CVD mortality (up to 16 grams per day).

There were a smaller number of studies included in the analyses for cancer mortality than for all-cause mortality and CVD mortality. Furthermore, for the analyses for fiber subtype and cancer mortality, there were generally only 2 to 3 studies included in each analysis. Thus, we have less confidence in the results for cancer mortality than the other outcomes.