Dec 02

How increasing fibre intake can help treat depression

There is an increasing abundance of research confirming an association between diet and mental health conditions such as depression. Overall, the evidence indicates that eating a healthier diet is associated with a reduced prevalence of depression, and there are a few studies showing dietary interventions can improve mood in people with depression [1,2].

An increased fibre intake, which usually occurs following dietary improvements, may be an important factor associated with these positive findings. Dietary fibres are nondigestible carbohydrates that originate from plant sources. They cannot be digested by humans and therefore pass through the digestive tract, where they are partially or completely fermented by trillions of intestinal bacteria.

In a recent review, it was revealed that there are several studies demonstrating a relationship between the intake of dietary fibre and depression. Although not entirely consistent, results from observational studies have shown that a greater intake of dietary fibre is associated with lower depressive symptoms [3].

In this paper, it was reported that there are several ways fibre may have beneficial effects on depression. Some of these mechanisms are listed below:

  • Reducing inflammation – on the whole, people with depression have higher levels of inflammation in their body (as measured by blood tests for inflammation including c-reactive protein and interleukins). Excess or chronic inflammation can have damaging effects on our brain and can alter several physiological processes associated with mood and mental health. This includes altering levels of mood-enhancing neurotransmitters such as serotonin, dopamine, and GABA. Inflammation can also alter levels of our stress hormone, cortisol. There are several studies confirming an increased intake of dietary fibre is associated with reduced inflammation. Thereby, through its anti-inflammatory effects, fibre can have a positive influence on all the previously-mentioned processes, resulting in improved mental health.
  • Increasing the production of short-chain fatty acids (SCFAs) – SCFAs are produced by bacteria when they ferment dietary fibre. There is now an abundance of evidence confirming SCFAs have an important role in the maintenance of health and the prevention of disease [3]. Although research is still preliminary, there is some evidence to suggest people with depression have lower levels of SCFAs [4]. In an animal study, the administration of the three most abundant SCFAs (acetate, butyrate and propionate) was shown to alleviate symptoms of depression [5]. Increasing SCFAs may have beneficial effects on mood due to their anti-inflammatory effects, role in energy production, ability to alter the production of neurotransmitters, cortisol-lowering effects, and ability to increase the production of proteins that can increase neuroplasticity (e.g., brain-derived neurotrophic factor).
  • Increasing the production of mood-lifting neurotransmitters – through its effect on intestinal microbiota, fibre can increase the availability of neurotransmitters such as serotonin and GABA. Low levels of serotonin are found in people with depression and anxiety. GABA is also an important neurotransmitter linked with anxiety disorders and many anti-anxiety drugs work by altering GABA.
  • Improving overall health and wellbeing – eating a high-fibre diet is associated with reduced diseases including obesity, cardiovascular disease, diabetes, etc. There is a high co-morbidity between depression and these diseases. By potentially reducing the prevalence or severity of these diseases, improved physical and mental health will occur.

This evidence suggests that increasing fibre intake can potentially be an effective treatment for depression and other mental health disorders. While further research is required, there is some research that supports this claim. For example, in a randomised-controlled trial in women with type 2 diabetes, supplementation with a resistant dextrin (NUTRIOSE®) for 8 weeks was associated with significant reductions in inflammation, cortisol and depressive/anxiety symptoms [7]. In a review paper, it was also concluded that in participants who increased their intake of the fibres, fructooligosaccharide and galactooligosaccharide to greater than 5 grams a day, had improvements in anxiety and depression symptoms [8].

While further research is required, increasing fibre intake can be a potential way to treat or prevent depression. This can occur by increasing the consumption of foods high in fibre (e.g., fruits, vegetables, and whole grains) and/or by supplementing the diet with specialised fibre supplements.

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References

  1. Jacka FN, et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med. 2017 Jan 30;15(1):23.
  2. Parletta N, et al. A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutr Neurosci. 2019 Jul;22(7):474-487.
  3. Swann, O.G., et al Dietary fibre and its associated with depression and inflammation. Nutri Rev. 2019. nuz072
  4. Tan J, et al. The role of short-chain fatty acids in health and disease. Adv Immunol. 2014;121:91-119.
  5. Skonieczna-Żydecka K, et al. Faecal Short Chain Fatty Acids Profile is Changed in Polish Depressive Women. Nutrients. 2018 Dec 7;10(12). pii: E1939.
  6. van de Wouw M, et al., Short-chain fatty acids: microbial metabolites that alleviate stress-induced brain–gut axis alterations. J Physiol. 2018;596(20):4923–4944.
  7. Farhangi MA, et al. A randomized controlled trial on the efficacy of resistant dextrin, as functional food, in women with type 2 diabetes: Targeting the hypothalamic-pituitary-adrenal axis and immune system. Clin Nutr. 2018 Aug;37(4):1216-1223.
  8. Taylor AM and Holscher HD. A review of dietary and microbial connections to depression, anxiety, and stress. Nutr Neurosci. 2018 Jul 9:1-14.
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