The Fiber Connection: How What You Eat Impacts Depression and Anxiety
How important is fiber? What kinds of foods are rich in fiber?
These are important questions to consider, as many people in the U.S. are not getting the recommended daily intake of fiber. Fortunately, there is a wide variety of foods that are rich in fiber. Vegetables, for instance, are an excellent source, including broccoli, Brussels sprouts, carrots, sweet potatoes, spinach, and kale. Fiber can also be found in fruits such as apple skins, pears, berries, bananas, oranges, and avocados. Whole grains, legumes, beans, nuts, and seeds are other great sources of fiber, which is essential for digestive health and numerous other functions in the body.
A 2023 article in Nutritional Neuroscience by Saghafian and his team conducted a systematic review and meta-analysis on the impact of dietary fiber intake on depression and anxiety. The study found that dietary fiber intake was associated with a 10% lower risk of depression in adults and a 57% lower risk of depressive episodes in adolescents. For each 5-gram increase in dietary fiber, the risk of depression was reduced by 5%. This effect was more significant when the fiber came from vegetables, as opposed to sources like cereal or fruit fiber.
Interestingly, women exhibited a more pronounced improvement in mental health symptoms when consuming higher amounts of fiber compared to men. This finding aligns with recent research that explored the relationship between dietary fiber intake and mental health outcomes in a large population of Iranian adults. After adjusting for potential confounders, the study found that participants in the highest quartile of dietary fiber intake had a 33% and 29% lower risk of anxiety and high psychological distress, respectively, compared to those in the lowest quartile. In addition, the study found that women who ate more fiber had a 37% lower risk of depression compared to those who ate less fiber. However, this effect wasn't seen in men. Also, higher fiber intake was linked to a reduced risk of mental health struggles among overweight or obese individuals and a lower risk of anxiety in normal-weight participants. These findings suggest that dietary fiber plays a protective role against various mental health issues, particularly in certain subgroups such as women and individuals with specific weight statuses.
Why is Fiber Helpful for Mental Health? The potential mechanism behind this is that fiber plays a role in modulating the microbiota-gut-brain axis. It increases the production of short-chain fatty acids, which help improve brain function and reduce inflammation. Additionally, fiber can influence gene expression through the gut microbiome, boosting the production of neurotransmitters. Deficiencies in neurotransmitters can exacerbate mental health symptoms. However, by reducing inflammation and boosting neurotransmitter levels, there can be significant improvements in both depression and anxiety.
Aslam, H., Lotfaliany, M., So, D., Berding, K., Berk, M., Rocks, T., Hockey, M., Jacka, F. N., Marx, W., Cryan, J. F., & Staudacher, H. M. (2024). Fiber intake and fiber intervention in depression and anxiety: a systematic review and meta-analysis of observational studies and randomized controlled trials. Nutrition reviews, 82(12), 1678–1695.Saghafian, F., Hajishafiee, M., Rouhani, P., & Saneei, P. (2023). Dietary fiber intake, depression, and anxiety: a systematic review and meta-analysis of epidemiologic studies. Nutritional neuroscience, 26(2), 108–126. https://doi.org/10.1080/1028415X.2021.2020403Saghafian, F., Sharif, N., Saneei, P., Keshteli, A. H., Hosseinzadeh-Attar, M. J., Afshar, H., Esmaillzadeh, A., & Adibi, P. (2021). Consumption of Dietary Fiber in Relation to Psychological Disorders in Adults. Frontiers in psychiatry, 12, 587468. https://doi.org/10.3389/fpsyt.2021.587468Swann, O. G., Kilpatrick, M., Breslin, M., & Oddy, W. H. (2020). Dietary fiber and its associations with depression and inflammation. Nutrition reviews, 78(5), 394–411. https://doi.org/10.1093/nutrit/nuz072