Have you ever experienced stress or anxiety?  While external factors can be beyond our control, we can choose what we put in our bodies every day!  Did you know that what you eat can affect your mood? Diets promoting fruits, vegetables, and whole grains have been found to lessen anxiety and depressive symptoms. Researchers have been focusing specifically on the dietary fiber those foods contain and how it can improve our mood.

What Happens When You Eat Fiber?

The term, dietary fiber, refers to carbohydrates from plants that cannot be digested.  The fiber you consume remains intact and passes through your digestive tract until it reaches your large intestine. There trillions of bacteria residing in your large intestine feed off the fiber, in a process known as fermentation.  The most dominant by-products of fermentation, short-chain fatty acids (SCFAs), are vital to improve your mood.

How Does Fiber Improve Your Mood?

Researchers are working to better understand the connection between fiber and mood.  Clinical studies so far have shown that the SCFAs produce neurotransmitters that activate receptors in your brain and can reduce inflammation.

Gut-Brain Axis

The gut-brain axis is the communication network between your gut microbiota and your brain that runs up the vagus nerve.  This communication signals the SCFA’s to produce the hormones tryptophan and serotonin, as well as the neurotransmitter GABA.

Tryptophan is a precursor to hormone serotonin, which helps regulate your mood.  Because your body do not produce tryptophan, you must get it from your diet or the bacteria in your gut.

Alternatively, GABA is a neurotransmitter, that can be synthesized in our bodies, but is also produced by several bacterial strains in the gut. Scientists have found that if levels of GABA are decreased, anxiety disorders and depression can increase. 

Reduction of Inflammation

Low levels of dietary fiber can result in the development of chronic inflammatory diseases such as colorectal cancer, IBS, and obesity.  Studies have shown that inflammation can lead to depression as well.  The incorporation of fiber into your diet alleviates inflammation in your body by reducing intestinal pH and membrane permeability. The reduction in inflammatory compounds can alter the concentration of neurotransmitters. This, in turn, can reduce your symptoms of depression.

What are Sources of Fiber?

Foods that are considered good sources of fiber are fruits, vegetables, whole grains, legumes (beans, peas, lentils), nuts and seeds.  Processed and refined foods are significantly lower or void of fiber.

According to the Institute of Medicine, fiber recommendation for individuals 50 years old or younger is 38 grams and 25 grams for men and women, respectively.  For those who are 51 years old or older, the recommendation decreases to 30 grams and 21 grams for men and women, respectively.

Focus on increasing the amount of fiber you eat gradually to avoid abdominal bloating and cramping.  Additionally, match your higher intake of fiber with a higher intake of water.  Fiber has the tendency to absorb water, so keeping yourself hydrated will soften your stool and ease overall transit.

How Can You Increase Your Fiber Intake?

• Pick recipes that allow you to incorporate more legumes into your dish. Registred Dietitian Eleanor Baker’s minestrone soup recipe is a great example!
• Choose whole-grain products, instead of refined grains.  At least half of your grains should by whole grains. Try Elevated Dietitian Alyssa Fernandes’ whole wheat berry pancake recipe for a fiber-rich breakfast!
• Search for the words, “whole grain,” “bran,” or “fiber” on the product labeling when grocery shopping.
• When selecting breads, look at the ingredient list and see if whole wheat, whole wheat flour, or another whole grain is listed first.
• When selecting high-fiber cereals, look at the nutrition facts label and choose products with 5 or more grams of fiber per serving.
• Experiment with brown rice, wild rice, barley, whole-wheat pasta, or bulgur wheat.
• Eat five or more servings of fruits and vegetables a day. Eleanor’s summer salmon salad makes this exceptionally easy!

References:

1. Swann OG, Kilpatrick M, Breslin M, Oddy WH.  Dietary fiber and its associations with depression and inflammation.  Nutr Rev.  2019;78(5):394-411.  DOI:10.1093/nutrit/nuz072.
2. Dietary fiber: Essential for a healthy diet.  Mayo Clinic.  https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983.  Accessed June 24, 2020.