Fiber is associated with reduced anxiety and depression in observational trials, but not interventional trials Original paper

In this meta-analysis, greater fiber intake was associated with less anxiety and depression in observational studies. However, supplementation with fiber did not reduce anxiety or depression in randomized controlled trials.

This Study Summary was published on February 12, 2024.

Quick Summary

In this meta-analysis, greater fiber intake was associated with less anxiety and depression in observational studies. However, supplementation with fiber did not reduce anxiety or depression in randomized controlled trials.

What was studied?

The association between fiber intake and depression or anxiety in observational studies and randomized controlled trials (RCTs).

This meta-analysis examined the association between fiber intake and validated scores of depression and anxiety in observational studies and RCTs. Subgroup analyses were conducted based on study type, as well as study quality (risk of bias). Among the randomized controlled trials, the roles of dose and fiber type were also assessed.

Who was studied?

A total of approximately 182,045 adults.

The cohorts included adults without known health conditions, older adults, and postmenopausal women, as well as individuals with depression, alcohol use disorder, human immunodeficiency virus (HIV), and gastrointestinal disorders.

How was it studied?

This meta-analysis included data from 32 studies, including 22 observational studies with cross-sectional, longitudinal, and case-control designs, as well as 10 placebo-controlled RCTs.

All of the RCTs examined the effects of supplemental fiber (rather than dietary changes). The trials had parallel or crossover designs and durations of 2 to 8 weeks. All of the fibers were fermentable types such as fructans and galacto-oligosaccharides (GOS). All but one of the studies used doses above 5 grams per day.

What were the results?

Greater intake of fiber was associated with less depression among the observational studies overall, with a small effect size, and among the cross-sectional and longitudinal studies in the subgroup analysis.

Greater fiber intake was also associated with less anxiety (small effect size), based on 3 studies that had that data available.

Among the RCTs, fiber supplementation did not reduce depression in comparison with placebo overall or in the subgroup analyses by risk of bias, supplementation dose, or fiber type.

Anxiety was not reduced by fiber supplementation overall or in the subgroup analyses by risk of bias or supplementation dose. However, supplementation with GOS fiber was associated with a reduction in anxiety (medium effect size.) This finding was based on 3 studies, and the effect was mostly due to 1 study.

This Study Summary was published on February 12, 2024.